McGraw-Hill Specialty Board Review

RADIOLOGY

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Editor

Cheri L. Canon, MDProfessor of Radiology

Senior Vice Chair for OperationsDirector, Division of Diagnostic Radiology

Chief, Gastrointestinal RadiologyUniversity of Alabama at Birmingham

Birmingham, Alabama

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McGraw-Hill Specialty Board Review

RADIOLOGY

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This book is dedicated to Malcolm, Olivia, and Evan, for their love and endless patience,

and

To Heather, who is my balance between work and family,

and

To Bob Koehler for his wisdom, enthusiasm, and above all else, his friendship.

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vii

Contributors xiiiPreface xixAcknowledgments xxi

Section ICENTRAL NERVOUS SYSTEM

1 Technical Aspects of CNS Imaging 1Joseph C. Sullivan III

2 Brain and Spine Anatomy 4Surjith Vattoth and Joseph C. Sullivan III

3 Developmental Disorders 16Surjith Vattoth and Joseph C. Sullivan III

4 Cerebrovascular Anatomy 28Asim K. Bag and Joseph C. Sullivan III

5 Stroke and Cerebrovascular Diseases of the Brain 37Ahmed Kamel Abdel Aal and Joseph C. Sullivan III

6 Intracranial Aneurysms and Vascular Malformations 46Ahmed Kamel Abdel Aal and Joseph C. Sullivan III

7 Head Trauma 53Ahmed Kamel Abdel Aal and Joseph C. Sullivan III

8 Spine Trauma 59Joseph C. Sullivan III

9 Central Nervous System Neoplasms 63Asim K. Bag and Joseph C. Sullivan III

10 Intracranial Infections 77Ahmed Kamel Abdel Aal and Joseph C. Sullivan III

11 Neurodegenerative and White Matter Diseases 87Ritu Shah and Joseph C. Sullivan III

12 Sella and Parasellar Pathology 94Joseph C. Sullivan III

CONTENTS

viii CONTENTS

13 Face and Neck Anatomy 99Surjith Vattoth and Joseph C. Sullivan III

14 Head and Neck Pathology 114Asim K. Bag and Joseph C. Sullivan III

15 Spinal Cord Pathology 133Joseph C. Sullivan III

Section IIPULMONARY

16 Normal Anatomy and Variants 139John C. Texada and Satinder P. Singh

17 Thoracic Imaging 149John C. Texada and Satinder P. Singh

18 Congenital Thoracic Anomalies 159John C. Texada and Satinder P. Singh

19 Airway Diseases 170John C. Texada and Satinder P. Singh

20 Pulmonary Infection 181John C. Texada and Satinder P. Singh

21 Noninfectious Inflammatory Diseases 192John C. Texada and Satinder P. Singh

22 Interstitial Lung Disease 203Ian Malcolm and Satinder P. Singh

23 Pulmonary Neoplasms 209Jonathan W. Walter, Ian Malcolm, and Satinder P. Singh

24 Pneumoconioses 219John C. Texada and Satinder P. Singh

25 Pulmonary Edema 226John C. Texada and Satinder P. Singh

26 Pulmonary Arterial Hypertension 235Ian Malcolm and Satinder P. Singh

27 Radiation-Induced Lung Changes 242John C. Texada and Satinder P. Singh

28 Mediastinal Masses 245Satinder P. Singh

29 Pleural Diseases 254Satinder P. Singh

30 Atelectasis 266Satinder P. Singh

31 Diaphragmatic Diseases 269John C. Texada and Satinder P. Singh

32 Chest Trauma 273Ian Malcolm and Satinder P. Singh

33 Drug-Induced Lung Toxicity 280John C. Texada and Satinder P. Singh

CONTENTS ix

Section IIICARDIAC

34 Cardiac MRI Technique 289Satinder P. Singh

35 Cyanotic Congenital Heart Disease 291Satinder P. Singh

36 Acyanotic Congenital Heart Disease 299Satinder P. Singh

37 Valvular Heart Disease 306Satinder P. Singh

38 Ischemic Heart Disease 310Satinder P. Singh

39 Cardiac and Pericardial Tumors 317Satinder P. Singh

40 Pericardial Disease 321Satinder P. Singh

41 Cardiomyopathy 325Satinder P. Singh

42 Cardiac Surgeries 330Satinder P. Singh

43 Aortic Diseases 334Satinder P. Singh

Section IVGASTROINTESTINAL TRACT

44 GI Tract Contrast and Technique 343Cheri L. Canon

45 Esophagus 344Cheri L. Canon and Sanjiv K. Bajaj

46 Stomach 353Sanjiv K. Bajaj and Cheri L. Canon

47 Small Bowel 361Sanjiv K. Bajaj and Cheri L. Canon

48 Colon and Rectum 369Sanjiv K. Bajaj and Cheri L. Canon

49 Appendix 376Camden L. Hebson and Cheri L. Canon

50 Imaging of the Liver 379Allen B. Groves and Lincoln L. Berland

51 Biliary System 387Desiree E. Morgan

52 Spleen 398Andrew S. Ferrell, Katherine P. Lursen, and Robert E. Koehler

x CONTENTS

53 Pancreas 405Desiree E. Morgan

54 Peritoneal Cavity and Abdominal Wall 417Bhavik N. Patel, Sanjiv K. Bajaj, and Cheri L. Canon

Section VGENITOURINARY TRACT

55 Intravenous Contrast Agents and Reactions 429Philip J. Kenney

56 Kidneys 441Michelle M. McNamara and Mark E. Lockhart

57 Ureters 448Heather L. Haddad and Mark E. Lockhart

58 Urinary Bladder 452Heather L. Haddad and Mark E. Lockhart

59 Adrenal Glands 457Mark E. Lockhart and Mark D. Little

60 Male Reproductive System 463Therese M. Webe and Heather L. Haddad

61 Female Reproductive System 471Heather L. Haddad and Therese M. Weber

Section VIULTRASOUND

62 Ultrasound Physics 483Kenneth Hoyt and Franklin N. Tessler

63 Abdominal Ultrasound 493Franklin N. Tessler

64 Female Pelvic Ultrasound 507Arthur C. Fleischer and Robert S. Morrison III

65 Obstetrical Ultrasound 512Rochelle F. Andreotti, Reagan R. Leverett, and Libby L. Shadinger

66 Vascular Ultrasound 528Mark E. Lockhart and Heather L. Haddad

67 Scrotum 532Michelle L. Robbin and Victoria E. Kraft

68 Thyroid, Parathyroid, and Neck Ultrasound 540Mark D. Little and Franklin N. Tessler

Section VIIMUSCULOSKELETAL SYSTEM

69 Musculoskeletal Anatomy and Basic Physiology 549Andrew S. Ferrell and Matthew C. Larrison

CONTENTS xi

70 Musculoskeletal Trauma 555Roderick F. Biosca Jr. and Matthew C. Larrison

71 Infection 564James S. Spann Jr. and Robert Lopez-Ben

72 Bone Tumors and Tumorlike Conditions 572Matthew C. Larrison and Gregory S. Elliott

73 Arthropathies 581Mark Sultenfuss and Robert Lopez-Ben

74 Endocrine and Metabolic Bone Disease 587Michael A. Bruno and Robert Lopez-Ben

75 Hematopoietic and Miscellaneous Musculoskeletal 593DisordersBhavik N. Patel, Joshua P. Smith, Matthew C. Larrison,and Gregory S. Elliott

Section VIIIBREAST RADIOLOGY

76 Breast Anatomy and Imaging Modalities 601Heidi R. Umphrey, Cheryl R. Herman, and David E. Hogg

77 Breast Screening and Breast Imaging Reporting 607and Database System (BI-RADS) LexiconHeidi R. Umphrey, Cheryl R. Herman, and David E. Hogg

78 Evaluation of Breast Masses 612Heidi R. Umphrey, Cheryl R. Herman, and David E. Hogg

79 Evaluation of Breast Calcifications 620Heidi R. Umphrey, Cheryl R. Herman, and David E. Hogg

80 The Surgically Altered Breast 623Heidi R. Umphrey, Cheryl R. Herman, and David E. Hogg

Section IXINTERVENTIONAL RADIOLOGY

81 Diagnostic Arteriography 627Heidi R. Umphrey and Baljendra S. Kapoor

82 Arterial Interventions 640Anne F. Fitzpatrick and Souheil Saddekni

83 Venous Disease 649Karthikram Raghuram, Kay M. Hamrick, and Jeffrey R. White

84 Abdomen and Liver 659Kok C. Tan and Souheil Saddekni

85 Gastrointestinal and Biliary Disease and Intervention 666Kay M. Hamrick and Emily R. Norman

86 Genitourinary 674Rachel F. Oser

xii CONTENTS

87 Pulmonary Angiography and Intervention 682Ahmed Kamel Abdel Aal and Bao T. Bui

88 Spine Intervention 691Shyamsunder B. Sabat and Edgar S. Underwood

89 Principles of Tumor Ablation 697Clinton R. Smith and Edgar S. Underwood

Section XNUCLEAR RADIOLOGY

90 Radiation Safety, Instrumentation, and Quality Control 707Jon A. Baldwin and Kok C. Tan

91 Skeletal Nuclear Medicine 721Pradeep G. Bhambhvani

92 Pulmonary Scintigraphy 732Pradeep G. Bhambhvani

93 Nuclear Medicine: Gastroenterology 739Sibyll Goetze

94 Genitourinary Nuclear Medicine 749Jon A. Baldwin

95 Central Nervous System Scintigraphy 759Jon A. Baldwin

96 Nuclear Cardiology 767Sibyll Goetze

97 Thyroid and Parathyroid Scintigraphy 778Sibyll Goetze

98 Oncology 788Pradeep G. Bhambhvani and Sibyll Goetze

99 Laboratory Nuclear Medicine and Molecular Imaging 799Jon A. Baldwin

Section XIPEDIATRIC RADIOLOGY

100 Pediatric Musculoskeletal System 811Brenton D. Reading and Robert P. Nuttall

101 Pediatric Chest 822Richard S. Martin and Christopher J. Guion

102 Pediatric Cardiovascular Disease 829Eric J. Howell

103 Pediatric Gastrointestinal Tract 837Martha M. Munden and Daniel W. Young

104 Pediatric Genitourinary Tract 849Jeremy T. Royal and Stuart A. Royal

105 Pediatric Neuroimaging 859Shyamsunder B. Sabat and Yoginder N. Vaid

Index 873

xiii

Ahmed Kamel Abdel Aal, MD, MScClinical InstructorDepartment of RadiologyChief of Vascular and Interventional RadiologyUniversity of Alabama at Birmingham, VAMedical CenterBirmingham, Alabama

Rochelle F. Andreotti, MDAssociate Professor of Clinical RadiologyAssistant Professor of Obstetrics andGynecologyDepartment of Radiology and RadiologicalSciencesVanderbilt University Medical CenterNashville, Tennessee

Asim K. Bag, MDFellow Department of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

Sanjiv K. Bajaj, MDResident PhysicianMallinckrodt Institute of RadiologySt. Louis, Missouri

Jon A. Baldwin, DO, MBSAssistant Professor of RadiologyDivision of Nuclear MedicineProgram Director, Nuclear Medicine ResidencyProgramUniversity of Alabama at BirminghamBirmingham, Alabama

Lincoln L. Berland, MD, FACRProfessor of RadiologyVice-Chairman for Quality Assurance andPatient SafetyChief, Body CT and 3D LaboratoryUniversity of Alabama at BirminghamBirmingham, Alabama

Pradeep G. Bhambhvani, MDAssistant Professor of RadiologyDivision of Nuclear MedicineUniversity of Alabama at Birmingham Birmingham, Alabama

Roderick F. Biosca Jr., MDResidentDepartment of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

Michael A. Bruno, MS, MDAssociate Professor of Radiology & MedicinePenn State University College of MedicineDirector of Quality Management ServicesThe Milton S. Hershey Medical CenterHershey, Pennsylvania

Bao T. Bui, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

CONTRIBUTORS

xiv CONTRIBUTORS

Cheri L. Canon, MDProfessor of RadiologySenior Vice Chair for OperationsDirector, Division of Diagnostic RadiologyChief, GI RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Gregory S. Elliott, MDX-Ray Associates of LouisvilleLouisville, Kentucky

Andrew S. Ferrell, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Anne F. Fitzpatrick, MDFellowVascular and Interventional Department of RadiologyUniversity of Alabama at Birmingham HospitalBirmingham, Alabama

Arthur C. Fleischer, MDProfessor of Radiology and RadiologicalSciencesProfessor, Department of Obstetrics andGynecologyVanderbilt University Medical CenterNashville, Tennessee

Sibyll Goetze, MDAssistant Professor of RadiologyDivision of Nuclear MedicineUniversity of Alabama at BirminghamBirmingham, Alabama

Allen B. Groves, MDFellowAbdominal Imaging Department of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

Christopher J. Guion, MDClinical Professor of Radiology and PediatricsUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

Heather L. Haddad, MDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Kay M. Hamrick, MDAssociate Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Camden L. Hebson, MDChief ResidentDepartment of PediatricsEmory University Atlanta, Georgia

Cheryl R. Herman, MDAssistant Professor of RadiologyMallinckrodt Institute of Radiology atWashington UniversitySt. Louis, Missouri

David E. Hogg, MDAssistant Professor of RadiologyMedical Director Outpatient Radiology University of Alabama at BirminghamBirmingham, Alabama

Eric J. Howell, MDClinical Assistant Professor of Radiology andPediatricsUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

Kenneth Hoyt, PhDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

CONTRIBUTORS xv

Baljendra S. Kapoor, MDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Philip J. Kenney, MDProfessor and Chair of RadiologyUniversity of Arkansas for Medical ScienceLittle Rock, Arkansas

Robert E. Koehler, MDProfessor Emeritus of RadiologyUniversity of Alabama School of MedicineBirmingham, Alabama

Victoria E. KraftUndergraduateUniversity of ChicagoChicago, Illinois

Matthew C. Larrison, MDAssistant Professor of RadiologyProgram Director, Musculoskeletal FellowshipUniversity of Alabama at BirminghamBirmingham, Alabama

Reagan R. Leverett, MDInstructorWomen’s Imaging FellowDepartment of RadiologyVanderbilt University Medical CenterNashville, Tennessee

Mark D. Little, MDClinical Instructor of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

Mark E. Lockhart, MD, MPHAssociate Professor of RadiologyChief, Genitourinary RadiologyProgram Director, Abdominal ImagingFellowshipUniversity of Alabama at BirminghamBirmingham, Alabama

Robert Lopez-Ben, MDAssociate Professor of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

Katherine P. Lursen, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Ian Malcolm, MDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Richard S. Martin, MDClinical Assistant Professor of Radiology and PediatricsUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

Michelle M. McNamara, MDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Desiree E. Morgan, MDProfessor of RadiologyVice Chair for Clinical ResearchChief, Body MRIMedical Director, MRI University of Alabama at BirminghamBirmingham, Alabama

Robert S. Morrison III, MD, MSResidentDepartment of Radiology and RadiologySciencesVanderbilt University Medical CenterNashville, Tenessee

Martha M. Munden, MDAssociate Professor of Radiology and PediatricsUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

xvi CONTRIBUTORS

Emily R. Norman, MDResidentDepartment of RadiologyUniversity of Alabama at Birmingham HospitalBirmingham, Alabama

Robert P. Nuttall, MD, PhDClinical Assistant Professor of Radiology andPediatricsUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

Rachel F. Oser, MDAssociate Professor of RadiologyProgram Director, Vascular and InterventionalRadiology FellowshipUniversity of Alabama at BirminghamBirmingham, Alabama

Bhavik N. Patel, MDResidentDepartment of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

Karthikram Raghuram, DNB, MDAssistant ProfessorSection of Neuroradiology and InterventionalNeuroradiologyWest Virginia University

Brenton D. Reading, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Michelle L. Robbin, MD, FACRProfessor of RadiologyChief of UltrasoundUniversity of Alabama at BirminghamBirmingham, Alabama

Jeremy T. Royal, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Stuart A. Royal, MS, MD, FACRClinical Professor and Chief of Radiology andPediatricsUniversity of Alabama at BirminghamRadiologist-in-Chief, PediatricsChildren’s Health System of AlabamaBirmingham, Alabama

Shyamsunder B. Sabat, MDFellowNeuroradiologyDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Souheil Saddekni, MD, FSIR, FAHAProfessor of RadiologyChief of Vascular and Interventional RadiologyCo-Medical Director, Heart and Vascular CenterUniversity of Alabama at BirminghamBirmingham, Alabama

Libby L. Shadinger, MDInstructorDiagnostic RadiologyVanderbilt University Medical CenterNashville, Tennessee

Ritu Shah, MDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Satinder P. Singh, MD, FCCPAssociate Professor of RadiologyChief Cardiopulmonary RadiologyDirector, Cardiothoracic CTUniversity of Alabama at BirminghamBirmingham, Alabama

Joshua P. Smith, MDResidentDepartment of RadiologyUniversity of Alabama at Birmingham Birmingham, Alabama

CONTRIBUTORS xvii

Clinton R. Smith, MDFellowVascular and Interventional RadiologyDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

James S. Spann, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Joseph C. Sullivan III, MDAssistant Professor of NeuroradiologyResidency Program DirectorUniversity of Alabama at BirminghamBirmingham, Alabama

Mark Sultenfuss, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Kok C. Tan, MD, FRCR (UK)FellowInterventional Radiology and Nuclear MedicineDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Franklin N. Tessler, MD, CMProfessor of RadiologyVice Chair for Radiology InformaticsChief of Body ImagingUniversity of Alabama at BirminghamBirmingham, Alabama

John C. Texada, MDFellowCardiothoracicDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Heidi R. Umphrey, MD, MSAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Edgar S. Underwood, MDAssistant Professor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Yoginder N. Vaid, MBBS, DMRD, MDClinical Professor of Pediatrics and DiagnosticRadiologyUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

Surjith Vattoth, MD, DMRD, DNB, FRCRFellowVascular and Interventional RadiologyDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Jonathan W. Walter, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Therese M. Weber, MDProfessor of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Jeffery R. White, MDResidentDepartment of RadiologyUniversity of Alabama at BirminghamBirmingham, Alabama

Daniel W. Young, MD, FACRClinical Professor of Radiology and PediatricsUniversity of Alabama at BirminghamChildren’s Health System of AlabamaBirmingham, Alabama

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xix

In recent years, there has been a paradigm shift in learning, specifically themanner in which information is gathered and ingested. This is particularly no-table in subject matter that covers great breadth or is rapidly evolving, such asmedicine, and more specifically, diagnostic imaging. Students and residents(and for that matter, practicing radiologists) quickly turn to the Internet to“Google™” unknown factoids, rapidly gathering information, in many caseswithout source validation. This has created silo learning where tidbits of infor-mation are immediately collected, answering the one specific question of con-cern. However, there is little depth or longevity afforded with this learningprocess, which in many cases does not drill down to the anatomic or patho-physiologic fundamental principles. As a result, there is a lack of complete un-derstanding, or even worse, misunderstanding, and the information is oftenretained only long enough to address the question at hand.

This book is an attempt to address the silo learning afforded by the Internet.It is organized according to 10 subspecialties and includes overviews of imag-ing-based physics for ultrasound, MRI, and nuclear medicine. Content centerson the fundamentals of anatomy and pathophysiology with concise relevant im-aging correlation. This, however, is not a text emphasizing image interpretation,as there are countless other references that do this quite well. At the end of eachchapter, the reader is challenged with a set of questions written in single bestanswer, multiple-choice format. Detailed discussions of the answers enhanceand enforce the reader's learning experience.

The goal of this text is to provide a firm foundation for learning and refer-ence during residency training, and through lifelong learning. Its intent is tolink together common concepts while presenting often complex material in asimple, straight-forward manner, hopefully balanced with enough depth so thatfundamental concepts are reinforced so as to avoid piecemeal or silo learning.

PREFACE

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xxi

I am indebted to the contributing authors for their knowledge, insight, and per-severance. Their expertise has proven invaluable.

I would also like to thank Beth Parker, my assistant, for endless hours of ed-iting and overall coordination of this project. Additionally, thanks goes toRachel Metcalf, Toni Braddy, Brittany Harris, and Pat Moore for their supportand to Tony Zagar for his illustrations. He has drawn clear, understandable fig-ures despite my ambiguous and often conflicting instructions.

Finally, a note of appreciation goes to my fellow members of the AbdominalImaging Section at the University of Alabama at Birmingham, Department ofRadiology. Without your support and encouragement, this book would havenever happened. It is a real pleasure to work with you each and everyday.

ACKNOWLEDGMENTS

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1 TECHNICAL ASPECTS OFCNS IMAGINGJoseph C. Sullivan III

Imaging used to evaluate the brain, head and neck, andspine primarily incorporates volume acquisition imag-ing, mainly CT and MRI. Conventional radiography re-mains useful in central nervous system (CNS) evaluationprimarily in the realm of prescreening for indwellingmetal foreign bodies and implants in patients undergoingMRI and initial imaging in an emergency setting.

CT

CT uses an x-ray transmission algorithm to mathemati-cally reconstruct a cross-sectional image of the body fromrelative amounts of x-ray transmission. As the gantry ofthe CT scans spins around the patient, a narrow beam ofx-rays is emitted to an associated row of rotating detec-tors on the opposite side of the gantry. Relative transmis-sion is calculated and a cross-sectional image is createdvia computer algorithm. The use of multirow detectorswith CT has nearly eliminated conventional (nonhelical)CT, as the speed at which helically acquired CT is nowobtained allows for increased areas of coverage withoutbreath-hold or with shorter breath-hold times. High-detailthree-dimensional imaging can be obtained via postpro-cessing. Additionally, the larger number of detectors andoverlap of the spiral acquisition nearly eliminates misreg-istration and volume-averaging artifacts.

The display of data with CT is a computer-based pixelassignment relative to water densities, Hounsfield unit(HU). This scale, named for Sir Godfrey Hounsfield as-signs increasing HU to higher density materials with wa-ter being O. Therefore, fat and air have negative HU andbone is highly positive. Brain parenchyma and even CSF,

which is slightly more dense than water, have HU some-where between that of water and bone.

The basis of the display of this data is relative to thevalue given to each pixel and the display algorithm that ischosen. The midlevel, or area of interest based on tissuedensity, is the selected window level. A window widthencompassing this level increases or decreases the sur-rounding variation of shades of gray displayed. There-fore, to evaluate a specific portion of the anatomy, thewindow is narrowed to a particular width to include thedesired surrounding tissues. Therefore, multiple differentwindow-width and window-level settings are used toevaluate for parenchyma (approximately 35–40 HU),blood (approximately 60–70 HU in a normal patient),bone (2000 HU or greater). Dedicated narrow windowsare necessary to evaluate for stroke, specifically lookingfor edema within the parenchyma (25–40 HU); “sub-dural window” employs more of a soft-tissue window.

Image data can be reviewed in multiple ways and dif-fering planes, allowing for increased information with-out subjecting the patient to additional radiation. Itshould be considered, however, that the imaging tech-nique should be tailored for the specific clinical indica-tion. Higher kVp provides improved resolution for moredense material such as bone, versus increased mA togive better resolution of soft tissue.

Ever-increasing multidetector helical acquisition andappetite for improved anatomical resolution must bebalanced with risks of increased radiation dosage, par-ticularly in those who are more susceptible to the ad-verse effects of radiation, that is, infants and children.

CT images are obtained with x-rays and are thereforesubject to beam hardening and streak artifacts. As abeam of photons passes through a particular section ofanatomy, it is attenuated so that the higher kVp photonsare transmitted and registered by the detector on thecontralateral side. This results in a misinterpretation bythe detector that there was higher transmission than ac-tually occurred, in turn calculated by the computer as anarea of low density, thus lower HU. Streak artifact oc-curs when there are edges of sharp density delineation

Section 1

CENTRAL NERVOUS SYSTEM

1

2 SECTION 1 • CENTRAL NERVOUS SYSTEM

between adjacent objects. As the computer sees the largevariation in x-ray attenuation, it misinterprets these re-gions and produces a “star” or a multistreak artifact as thegantry rotates around this interface. Motion artifact oc-curs when structures change position within the field ofview as acquisition of the object changes position relativeto the gantry. As the gantry encircles the patient, thiscauses a misregistration of the object in the field. Thismay be secondary to normal physiological motion in thecase of heartbeat, respiration, vessel pulsation, or bowelgas peristalsis. Although CT scanners have improved intheir speed of acquisition to the point this can be nulled oreven gated, patient motion remains a continuing problem.

MRI

MRI is a completely different form of volume acquisi-tion. There are different tissue characteristics based on itsprotons, resulting in differing T1 and T2 relaxation times.The T1 relaxation time is the time it takes for a tissue tobecome magnetized, while T2 indicates the time for lossof this magnetization. These differing relaxation times arelocalized within the field of the magnet depending onsmall variations in the radiofrequency applied and re-ceived by tailored antennas known as coils. Tissue withina field of localization may not remain within that field ormay pass into that field under normal physiological con-ditions. Specifically, blood flow may demonstrate a flowvoid as blood flows through a blood vessel into and out ofa magnetized field. Also, in variation with CT, which isacquired in a cross-sectional anatomic demographicplane and reconstructed via postprocessing, MRI can beacquired in multiple planes as the data is acquired volu-metrically and presented in planes based on frequency en-coding, corresponding to the x-axis, and phase coding, y-axis. Respectively, slice location is determined by slightvariations and the gradient intensity along the z-axis.

MR is obtained in multiple varied sequence acquisi-tions, the primary of which is a spin echo pulse sequence.Standard T1- and T2-weighted images are created using ashort time of repetition and time of echo versus longertimes, respectively. Proton density sequences use a combi-nation of long repetition time and short echo time, allow-ing for accentuation of hydrogen density differences be-tween tissues. Variations of spin echo, called multiple spinecho, allow for the reduction of image acquisition time,typically referred to as fast-spin or turbo-spin echo. Thetrade-off is degradation of signal intensity and increasedfat intensity on T2-weighted imaging. Fat-suppressiontechniques are often used to counter this effect and/or toallow for detection of underlying fluid latent pathology.Inversion recovery pulse sequences emphasize differencesbetween T1 relaxation times as a delayed time of inversionis added to the time of repetition and time of echo; tissues

with short T1 relaxation times such as fat are suppressedand tissues with an unexpected high water content (pathol-ogy) are accentuated. Fat-suppression techniques attemptto similarly depress the short T1 signal of fat; however,these are highly sensitive to magnetic field inhomogeneity,and do not work well with low field magnet strength. Fatsuppression is performed using a saturation pulse at a res-onant frequency of fat applied to each imaging plane. Al-though this is limited by its sensitivity for field inhomo-geneity, this is better for use with postcontrast techniquethan those of inversion recovery as the latter suppresses alltissues with short T1 including those that may enhance af-ter the administration of gadolinium. Echo planar imagingincorporates fast MR techniques for multislice studieswith single radiofrequency excitation. It decreases motionartifact and continues to show improvement in high-reso-lution techniques such as blood perfusion and functionalMR. Gradient recall echo imaging pulse sequences em-ploy multiple short flip angles of less than 90 degrees todecrease the time taken to recover a signal. This, however,creates sensitivity to imperfections in the magnetic fieldfrom short T2 relaxation times, also known as T2 star.

Safety of the patient is the foremost concern. Ferro-magnetic and magnetic susceptibility of implants, per-sonal items carried by the patient, and support devices in-advertently taken into the field of the magnet must all beconsidered with each patient. Furthermore, althoughsome implants may not have ferromagnetic components,the components of those implants should be carefullyevaluated as wires or loops in a magnetic field can gener-ate electric current. Such radiofrequency current cancause burns or false activation or failure of the implant.The strength of the magnet must also be considered asvariations in magnetic field strength can have variable ef-fects on all such devices. Some implants, although con-sidered compatible with MR, may demonstrate artifactsassociated with disruption of the magnetic field. This im-plies the object has some ferromagnetic quality. Thesafety considerations and compatibility of implants farexceeds the content of this text and should be consideredon an individual case-by-case basis.

Motion artifacts in MR are also more prevalent thanCT secondary to the longer acquisition time. Multipletechniques such as shorter acquisition time and com-puter reregistration are used for motion correction.

MYELOGRAPHY

Myelography is a useful tool in those who cannot be im-aged adequately or safely with MRI. Although it is notnearly as prevalent as it once was, indications for andusefulness of myelography remain. A lumbar puncture isperformed and once a spinal needle is advanced into thethecal sac, at a level that is deemed safe, the stylet is

CHAPTER 1 • TECHNICAL ASPECTS OF CNS IMAGING 3

retracted. Upon the spontaneous return of cerebrospinalfluid, contrast media is carefully injected under direct vi-sualization. Spot fluoroscopic imaging obtained at thetime of contrast placement can reveal significant patho-logic information by assessing contrast flow. Keeping inmind that all sections of the spinal thecal sac can usuallybe evaluated from a single puncture, it should be remem-bered that the density and amount of contrast materialgreatly varies based upon the clinical question at hand.Careful attention to the location of the contrast in thethecal sac, as this can have clinical side effects basedon misplacement and/or its extension into the skullbase, and the puncture site, as symptoms of skull-based headaches from cerebrospinal fluid leaks can bedetrimental to the patient, must be demonstrated.

Myelographic imaging remains limited in that it onlycan delineate those things within the thecal sac or that im-press upon the thecal sac but not pathology within the corditself. However, in the patient in whom an MRI is con-traindicated, localization of cord swelling or impressionupon the cord or other neuroelements may be key to thesurgical planning. Further usefulness of myelography isseen with postsurgical patients who have hardware thatmay not be tolerated in a magnetic field or may create ar-tifacts to the point that evaluation of the adjacent neuralelements may be precluded. Provided that the postmyelo-graphic CT does not have substantial artifacts to limit itsuse, it must be remembered that the acquisition of fluoro-scopic spot film at the time of actual myelography can givealmost as much information as the postmyelographic CT.

SUGGESTED READING

Arena L, Morehouse H, Safir J. MR imaging artifacts that simu-late disease: how to recognize them and eliminate them. Radi-ographics. 1995;15:1373-1394.

Association of University Radiologist. Abstracts from contrastmedia research symposium. Acad Radiol. 2005;12:S2-S85.

Frush D et al. Computed tomography and radiation: understand-ing the issues. J Am Coll Radiol. 2004;1:113-119.

Kanel E, Borgstede J, Barkovich A. American College of Radiol-ogy white paper on MR safety. Am J Roentgenol. 2002;178:1335-1347.

McNitt-Gray M. Radiation dose in CT. Radiographics. 2002;22:1541-1553.

Nguyen G et al. Adequacy of plain radiography in the diagnosisof cervical spine injuries. Emerg Radiol. 2005;11(3):158-161.

Pomper M et al. New techniques in magnetic resonance imagingof brain tumors. Neuroimaging Clin N Am. 2001;11(3):501-525.

Thompson M et al. Increased contrast, high spatial-resolution,diffusion-weightd, spin-echo, echo-planar imaging. Radiology.1999;210:253-259.

White M. Cervical spine-magnetic resonance imaging techniquesand anatomy. Magn Reson Imag Clin N Am. 2000;8:453-469.

QUESTIONS AND ANSWERS

1. What is the result when decreasing CT slice thick-ness with all other factors constant?A. Decreased radiation to the patientB. Decreased noiseC. Decreased resolutionD. Decreased tube heatingE. Decreased motion sensitivity

ANSWER: C. Resolution is decreased in the useof thinner slices if all other factors remain thesame (unless kVp and/or mA are increased). Asmoothing algorithm may be used to make the im-ages more pleasing which may further limit sensi-tivity to subtly pathology. Radiation to the patientwill increase unless kVp and/or mA is decreased.Tube heating therefore is also increased. Thelonger scan acquisition time increases risk for mo-tion artifact.

2. Which one of the following artifacts is correctlypaired with its modality?A. Beam attenuation–MRIB. Ring down–CTC. Streak–MRID. Aliasing–MRIE. Partial-volume averaging–radiograph

ANSWER: D. Aliasing is also known as wrap-around artifact. Ring down occurs with ultrasound.Beam attenuation can occur with any radiation-dependent imaging. Streak artifact occurs on CTat interfaces or secondary to motion at these inter-faces.

3. What is an imaging benefit of CT versus conven-tional radiography?A. Decrease in artifactsB. Improved resolutionC. Decreased noiseD. Decreased contrast thresholdE. All of the above

ANSWER: D. CT is able to detect lower-contrastdifferences between tissues than conventional radi-ography. Radiography has fewer artifacts, betterline pair resolution, and less noise than CT.

4. What is the basic measure of tissue variation inMRI?A. K-spaceB. MatrixC. NEXD. Proton densityE. Proton rotation

4 SECTION 1 • CENTRAL NERVOUS SYSTEM

ANSWER: D. The variability of T1 and T2 is pri-marily dependent on the differing density of protonsin tissue. K-space is the image space from which animage is calculated from related to the area that isbeing imaged. The matrix is the rows and columnthat determine the resolution. NEX is the square rootof the number of acquisitions and is related to signalnoise. The spin of the protons allows the proton togive off signal as they align and precess in the field.

5. On MRI, what primarily affects the Larmor fre-quency?A. Strength of the magnetic fieldB. Orientation of the magnetic fieldC. Location within isocenter of the magnetic fieldD. Shimming of the magnetic fieldE. Bore size of the magnet

ANSWER: A. Strength and isotope are the primarycontributors to the Larmor frequency. Although lo-cation within a magnetic field cause a decrease instrength, this should occur while remaining withinthe isocenter.

6. Why are hydrogen (protons) molecules the idealisotope for MRI?A. High spin densityB. High tissue densityC. High NMR sensitivityD. High abundanceE. All of the above

ANSWER: E. Spin and tissue density are the samething. Protons have a high NMR sensitivity and arehighly abundant in tissue as water.

7. What is the Hounsfield unit a measure of?A. Proton densityB. Tissue densityC. Spin densityD. Hemoglobin densityE. Bone density

ANSWER: B. Density of tissue is measured inHounsfield units (HU). Water is 0 HU. Those tis-sues less dense than water are given negative num-bers, and those tissues more dense than water arepositive, respectively.

8. How does increasing image noise impact an imag-ing study?A. Increased artifactsB. Increased blurC. Increased image distortionD. Decreased low-contrast resolutionE. Increased radiation to the patient

ANSWER: D. Increasing noise makes it more diffi-cult to resolve images at lower contrast.

9. What modality has the best native resolution?A. MRIB. CTC. Conventional radiographyD. Ultrasound

ANSWER: C. Although modern CT scannershave improved their resolution capabilities sub-stantially, the line pair resolution for conventionalradiography continues to have the best inherentresolution.

10. Image resolution is a direct measure of what?A. Low-contrast objectsB. High-contrast objectsC. Anatomical detailD. Noisy images

ANSWER: C. Resolution measures blurring asso-ciated with clarity of anatomical detail.

11. Of the following, what factor has the most signifi-cant effect on the majority of artifacts?A. Matrix sizeB. Gradient strengthC. Magnetic field orientationD. Magnet strengthE. NEX

ANSWER: D. As magnet strength increases, thesusceptibility and their respective artifacts also in-crease. Only motion artifacts may decrease withhigher magnet strengths if additional parametersare constant.

2 BRAIN AND SPINEANATOMYSurjith Vattoth and Joseph C. Sullivan III

BRAIN ANATOMY

SCALP

The scalp consists of five layers: skin, connective tissue,aponeurosis, loose connective tissue, and pericranium. OnT1-weighted images, scalp is hyperintense because of thefatty components.

CHAPTER 2 • BRAIN AND SPINE ANATOMY 5

The skin is attached to the third layer by fibroussepta, so that all three layers move together.

The second layer consisting of fibroadipose tissuelodges the blood vessels of scalp derived mainly from theexternal carotid artery and cutaneous sensory nerve sup-ply derived from the second and third cervical nerves(the first cervical has no cutaneous branch) and from thetrigeminal nerves, with the vessels attached to the fi-brous septa. Wounds of the scalp bleed profusely be-cause the vessels, being attached to fibrous septa, cannotretract and constrict. Posteriorly, the skin up to the ver-tex is supplied by the greater occipital and third occipi-tal nerves (posterior primary rami of C2 and C3), whilethe skin behind the ear is supplied by the lesser occipitalnerve (anterior primary rami of C2). The third layer con-sists mainly of galea aponeurotica, frontalis muscle an-teriorly, and occipitalis muscle posteriorly. The fourthlayer is loose areolar connective tissue between the up-per three layers that move together and the periosteumof the skull vault. The periosteum or pericranium on theouter surface of the calvarium is continuous with that ofthe inner surface at the sutural connections between thebones of the skull.

CALVARIUM

The cranium consists of calvarial vault, base of skull,and facial skeleton. The calvarial vault is composed offrontal bone, paired parietal bones, squamous occipitalbone, and paired squamous temporal bones. The coronalsuture separates the frontal bone from the two parietalbones; the metopic suture seen in neonates separates thefrontal bones in the midline which fuses later in life.The sagittal suture separates the two parietal bones, andthe lambdoid suture separates the occipital bone fromthe two parietal bones.

On T1-weighted images, the calvarium is seen as hy-perintense, fatty marrow, lined on inside and outside bylow signal inner and outer tables of skull, respectively.The evaluation of the calvarial signals on the T1-weighted image is important to assess for marrow infil-trative disorders.

The base of skull and facial skeleton will be dealtwith Chapter 13.

MENINGES

The dura (pachymeninges), arachnoid, and pia mater(combinedly called the leptomeninges) form the threemeningeal layers covering the brain.

The dura mater has two layers, a superficial layer,which forms the periosteum of the inner skull and a deep

layer, which forms the dura mater proper. The dura sepa-rates into two layers at dural reflections, two main duralreflections being falx cerebri and tentorium cerebelli.

The potential extradural or epidural space lies be-tween the skull and dura and is seen as a biconvex spacewhen collections or hematoma develops in this space.Epidural collections do not cross sutures, but may crossthe midline. Epidural hematomas usually develop be-cause of arterial bleeding from injury to the skull. Thesubdural space is a potential space between the dura andthe arachnoid and the subdural collections have a con-cavo–convex appearance. Subdural collections cross su-tures, but do not cross the midline. Subdural hematomasoccur because of bleeding from the torn bridging veinsin the subdural space.

Arachnoid lies inner to the dura and like the duradoes not invaginate into the sulci. The subarachnoidspace contains CSF and lies between the arachnoid andpia mater. The arachnoid villi are CSF reabsorbingendothelial-lined granulations of arachnoid and sub-arachnoid space extending into the dural sinuses.

Pia, which is the innermost meningeal layer, unlikethe other two layers, invaginates into the sulci. It followsthe penetrating cortical arteries into the brain to form theperivascular spaces also known as Virchow-Robinspaces. The subpial space is a potential space betweenthe pia mater and the glia limitans of cortex.

PRACTICAL APPROACH TO IDENTIFICATION OF SULCI AND GYRI

First, at the top axial images, identify the anteroposteri-orly oriented superior frontal sulcus joining the trans-versely oriented precentral sulcus. The premotor cortexof the frontal lobe lies anterior to this precentral sulcus.The central sulcus or Rolandic fissure, which separatesthe frontal and parietal lobes, is the next transverselyoriented sulcus lying immediately posterior to precen-tral sulcus. The motor cortex of the frontal lobe lies be-tween the central sulcus and precentral sulcus. The in-verted omega or horizontal epsilon shaped posteriorlydirected knob on the central sulcus/gyrus designates themotor cortex controlling hand function. The motor cor-tex for facial muscles lies lateral to the hand knob andthe leg area lies medially in a parasagittal location. Thesensory cortex lies posterior to the central sulcus in theparietal lobe. It is noteworthy that the precentral motorgyrus is thicker than the postcentral sensory gyrus witha mean cortical thickness ratio of 1.54. Also, in axial im-ages, the posterior aspects (pars marginalis) of the rightand left cingulate sulci form a horizontal bracket calledpars bracket. In 97% of cases, the medial end of the cen-tral sulcus lies just anterior to this pars bracket and so it

6 SECTION 1 • CENTRAL NERVOUS SYSTEM

helps in central sulcus identification. However in 3% ofcases, the postcentral sulcus may lie immediately ante-rior to this horizontal bracket, negating the value of thispars bracket sign.

The sylvian fissure in axial images helps to differen-tiate the frontal lobe anteriorly from temporal lobe pos-teriorly. On coronal images, the posterior ramus of syl-vian fissure (lateral sulcus) separates the anterior part ofparietal lobe superiorly from the temporal lobe inferi-orly. Behind the point, where the posterior ramus of syl-vian fissure ends (by turning superiorly into parietallobe), there is no anatomic demarcation between theparietal and temporal lobes. A horizontal imaginary lineis drawn posteriorly along the horizontal course of theposterior ramus of sylvian fissure to join another imagi-nary vertical line drawn between the end of the pari-etooccipital sulcus on the superomedial margin of thecerebral hemisphere and a notch on its inferolateral mar-gin. This imaginary horizontal line separates the poste-rior aspect of the parietal lobe superiorly from thetemporal lobe inferiorly. The imaginary vertical lineseparates the occipital lobe posteriorly from the parietaland temporal lobes anteriorly on the lateral parasagittalimages. In medial sagittal images, the parietooccipitalsulcus demarcates the occipital lobe posteriorly from theparietal lobe anteriorly. The occipital and temporal lobeson the inferomedial surface run into one another with noanatomic structures separating them.

On coronal images, the superior temporal gyrus liesbetween the sylvian fissure and superior temporal sul-cus. The transverse temporal gyrus of Heschl, which isthe primary auditory cortex, projects medially from thesuperior temporal gyrus. The Heschl gyrus can be easilyidentified in coronal images at the coronal level showingthe tent formed by the convergence of fornices and pres-ence of eighth cranial nerves and in axial images at thelevel of massa intermedia connecting the two thalami.The sensory speech area or Wernicke area is located inthe superior temporal gyrus.

On coronal images, the middle temporal gyrus liesbetween the superior and middle temporal sulci. The in-ferior temporal gyrus lies between the middle and infe-rior temporal sulci. Further inferomedially, the fusiformgyrus, which continues posteriorly to join the occipitallobe, lies between the inferior temporal sulcus and col-lateral sulcus.

The mesial temporal structures of the limbic systemlie medial to the collateral sulcus on coronal imageswith the parahippocampal gyrus inferiorly and hip-pocampus superiorly. If we follow the hippocampus an-teriorly on serial coronal sections, we will reach the hip-pocampal head at the level of temporal horn of lateralventricle. The amygdalla lies anterosuperomedial to thehippocampal head. As we follow the hippocampus pos-

teriorly, we can see the head and body of hippocampusfollowed by its tail. The hippocampal white matter(alveus), which outlines the hippocampal gray matter,continues as fimbria and crus of the fornix on both sidesalongside the lateral ventricles. The crura of fornicescan in turn be traced anteriorly merging into the columnof fornix.

On lateral sagittal images, the frontal lobe anterior tothe precentral sulcus is divided by a series of sulci into su-perior, middle, and inferior frontal gyri. The posterior partof the inferior frontal gyrus is separated from the temporallobe by the sylvian fissure that has an anterior horizontaland anterior ascending rami. This divides this portion ofinferior frontal gyrus into an “M” shaped area, the anteriorvertical line of M representing the pars orbitalis, the mid-dle V of M representing the pars triangularis, and posteriorvertical line of M representing the pars opercularis. Themotor speech area or Broca’s area is located in the oper-cula and triangular sections of the inferior frontal gyrus.

The lateral sagittal images are also helpful in demar-cating the two component gyri of the inferior parietallobule, namely the supramarginal gyrus and angulargyrus. The posterosuperior end of the posterior ramus ofsylvian fissure is surrounded by a horseshoe-shapedgyrus, the supramarginal gyrus. Similarly, the posteriorend of the superior temporal sulcus is surrounded by thehorseshoe-shaped angular gyrus. The sulcus forming thesuperior border of these gyri is the intraparietal sulcusand the remainder of the parietal lobe superiorly is thesuperior parietal lobule.

The medial sagittal images help to demarcate theparietal lobe from the occipital lobe. The parietooccipitalsulcus is bounded anteriorly by the precuneus (a parietallobe gyrus) and posteriorly by the cuneus (an occipitallobe gyrus). Inferior to cuneus in the occipital lobe is thecalcarine sulcus and the striate cortex in and aroundthe calcarine sulcus serves as the primary visual cortex.The lingual gyrus of the occipital lobe lies inferior tocalcarine sulcus. If we trace further anteriorly, the lin-gual gyrus becomes continuous with the mesial tempo-ral parahippocampal gyrus. On the inferior surface ofthe occipital lobe, lateral to the lingual gyrus, lies thefusiform gyrus, which connects the temporal lobe withthe occipital lobe. Thus as noted previously, the tempo-ral and occipital lobes on the inferior surface run intoone another with no anatomic structures separatingthem.

The anterior aspect of the medial sagittal imagesdemonstrates the corpus callosum and is well demar-cated superiorly by the callosal sulcus, which is contin-uous posteroinferiorly with the hippocampal sulcus. Thecingulate gyrus lies parallel to and above the callosalsulcus and is demarcated superiorly by the cingulate sul-cus. Near the region of splenium of corpus callosum, the

CHAPTER 2 • BRAIN AND SPINE ANATOMY 7

cingulate sulcus gives the paracentral branch and mar-ginal branch and then continues as the subparietal sulcusoutlining the isthmus of cingulate gyrus (which be-comes continuous with parahippocampal gyrus).

In the medial sagittal images, the paracentral lobuleis divided by the medial end of the central sulcus into alarger anterior part belonging to the frontal lobe and asmaller posterior part that belongs to the parietal lobe.Anterior to the paracentral lobule lies the superiorfrontal gyrus and posterior to it lies the precuneus ofparietal lobe.

BRAINSTEM

MIDBRAIN

Two large bundles of fibers called crura lie on either sideof midline anteriorly divided by the interpeduncular orcrural CSF cistern anteriorly and diverge to enter thecorresponding cerebral hemispheres superiorly (cere-bral peduncles). The third (oculomotor) cranial nervesemerge from the medial aspect of the crus on the sameside and exit the midbrain via the interpeduncular cis-tern on their way to the cavernous sinus and superior or-bital fissure to supply the four extraocular muscles, me-dial rectus, inferior rectus, superior rectus, and inferioroblique. The cerebral aqueduct of Sylvius divides themidbrain into tegmentum anteriorly and tectum or roofposteriorly.

The mesencephalic tegmentum contains the whitematter tracts-medial longitudinal fasciculus (oculomo-tor/vestibular), medial (somatosensory) and lateral (audi-tory) leminisci, spinothalamic (somatosensory), andcentral tegmental motor tract including the reticular for-mation. The gray matter includes the substantia nigra,red nucleus, periaqueductal gray matter, and third/fourthcranial nerve nuclei. On thin section T2-weighted MRI,the pars compacta of substantia nigra can be seen as a hy-perintense band between the hypointense band of parsreticularis of substantia nigra anterolaterally and hy-pointense nodular red nucleus posteromedially inparamidline location. The pars compacta atrophies inparkinsonian disorders. The third nerve nucleus lies atthe superior colliculus level in a paramedian location an-terior to cerebral aqueduct and posterior to the red nu-cleus. The parasympathetic nuclei of the third nerve,Edinger-Westphal nuclei, lie in the periaqueductal graymatter posterior to the third nerve nucleus. The fourthnerve nucleus lies at the inferior colliculus level in aparamedian location anterior to cerebral aqueduct andposterior to medial longitudinal fasciculus.

The tectal plate or quadrigeminal plate is composedof the paired superior colliculi for extraocular muscle

coordination and inferior colliculi for hearing relay.Each colliculus is related laterally to a ridge called thebrachium. The superior brachium connects the superiorcolliculus to the lateral geniculate body and the inferiorbrachium connects the inferior colliculus to the medialgeniculate body on either side. The cistern posterior tothe midbrain is called the quadrigeminal plate cistern asit is closely related the quadrigeminal plate. It is impor-tant to note that the persistent cavum veli interpositi(CVI) communicates with quadrigeminal cistern.The perimesencephalic or ambient cistern extends fromthe posterior margin of the interpeduncular cistern to thelateral edge of the midbrain colliculi, around the lateralsurface of the upper portion of the brainstem. The ambi-ent cistern mainly contain P2 segment of the posteriorcerebral artery, superior cerebellar artery, anteriorchoroidal artery, basal vein of Rosenthal, and fourth cra-nial nerve.

Just below the colliculi lies the uppermost part of amembrane called the superior medullary velum, whichstretches between the two superior cerebellar peduncles,forming the roof of the fourth ventricle. The fourth(trochlear) cranial nerve, which is the only cranial nervethat exits the brainstem dorsally, courses posteriorlyaround the cerebral aqueduct and decussates in the su-perior medullary velum, crosses over in the quadrigem-inal cistern, and winds round the opposite side of themidbrain in the ambient cistern to reach its ventral as-pect on the way to enter the contralateral cavernous si-nus and orbit to supply the superior oblique muscle.During their course, both the third and fourth cranialnerves pass between the posterior cerebral artery andsuperior cerebellar artery and may be compressed byaneurysms. The superior cerebellar peduncles (brachiumconjunctivum) decussate in the midbrain posterior to rednuclei, flank the upper fourth ventricle, and connect themidbrain to cerebellum.

PONS

The ventral surface of the pons is grooved by the sulcusbasilaris along which the basilar artery passes. The fifth(trigeminal) cranial nerve emerges from the anterolat-eral surface of pons and passes through prepontine cis-tern to be connected to the Gasserian Ganglion inMeckel cave. The bulky middle cerebellar peduncles(brachium pontis) connect the pons with the cerebellumon each side. The sixth (abducens) cranial nerveemerges from the junction of pons and medulla antero-medially, just off the midline above the medullary pyra-mids, and passes through the prepontine cistern, pene-trates dura of basisphenoid to enter the Dorello canal,arches over petrous apex below petrosphenoidal ligament

8 SECTION 1 • CENTRAL NERVOUS SYSTEM

into posterosuperior cavernous sinus, and then enters su-perior orbital fissure and orbit to innervate the lateralrectus muscle. The seventh (facial) and eighth (vestibu-locochlear) cranial nerves emerge from the pon-tomedullary junction, laterally above the medullaryolives, and enter the cerebellopontine angle cistern ontheir way to the internal auditory canal. The pons is sep-arated from the cerebellum posteriorly by the fourthventricle, which is continuous superiorly with the cere-bral aqueduct.

The ventral pons, which forms the bellylike anteriorprojection on sagittal images, contain the longitudinalcorticospinal, corticobulbar and corticopontine whitematter tracts, and the multiple transverse pontine fibers,which make up the bulk.

The dorsal pontine tegmentum is composed of whitematter tracts-medial longitudinal fasciculus (oculomo-tor/vestibular), medial (somatosensory) and lateral (au-ditory) leminisci, trapezoid body (auditory), spinothala-mic tract (somatosensory), and central tegmental motortract including the reticular formation. The gray matterincludes the bulk of the motor, main sensory, and mes-encephalic nuclei of fifth nerve located in the upper lat-eral dorsal pontine tegmentum in a location far antero-lateral to fourth ventricle. The sixth nerve nucleus islocated in lower dorsal pontine tegmentum near midlinejust anterior to fourth ventricle. The axons of facialnerve loop around the sixth nerve nucleus creating abulge in the floor (anterior aspect) of the fourth ventri-cle, called the facial colliculus. The seventh nerve mo-tor, superior salivatory, and tractus solitarius nuclei lie inthe lower lateral dorsal pontine tegmentum in a locationfar anterolateral to fourth ventricle. The medial, lateral,inferior, and superior vestibular nuclei of eighth cranialnerve lie along the lateral aspect of the floor of the fourthventricle at the pontomedullary junction. The dorsal andventral cochlear nuclei of the eighth nerve lie dorsallyand ventrally on the lateral aspect of the inferior cere-bellar peduncle (restiform body) at the pontomedullaryjunction.

MEDULLA OBLONGATA

The ventral medulla is composed of the medullary pyra-mids and olives. The pyramids are two paramedian lon-gitudinal projections anteriorly, composed of the corti-cospinal (pyramidal) tracts, and separated in the midlineby ventral median fissure. Posterolateral to the pyramids,separated by the preolivary sulcus from which therootlets of the twelfth (hypoglossal) cranial nerve exit oneach side, lie the medullary olives that consist of inferiorolivary nucleus (largest and forms the bulge on the surfaceof medulla), dorsal and medial accessory olivary nuclei,

and superior olivary nucleus. The postolivary sulcus fromwhich the rootlets of the ninth (glossopharyngeal), tenth(vagus), and eleventh (spinal accessory) cranial nervesexit the medulla lies posterolateral to olive.

The inferior cerebellar peduncle (restiform body)arises from the superior aspect of the dorsal medulla andconnects the medulla with the cerebellum. As alreadystated, the cochlear nuclei lies on the lateral aspect ofthe inferior cerebellar peduncle at the pontomedullaryjunction. In the lower aspect of the dorsal medulla liesthe paired gracile tubercles formed by the nucleus gra-cilis, separated in the midline by dorsal median sulcus.Immediately lateral to these lie the cuneate tubercles oneach side, formed by the nucleus cuneatus and boundedanterolaterally by the postolivary sulcus. These are con-nected to the fasciculus gracilis and fasciculus cuneatus,respectively, and white matter tracts that enter themedulla from the posterior funiculus of the spinal cord.The lower part of the medulla, immediately lateral tofasciculus cuneatus, is another longitudinal elevationcalled the tuberculum cinereum formed by the spinalnucleus of the fifth (trigeminal) nerve. The spinal tractof the trigeminal nerve covers this and they actually ex-tend into the upper cervical canal. The dorsal medullarytegmentum also contains the white matter tracts-mediallongitudinal fasciculus (oculomotor/vestibular), me-dial (somatosensory) and lateral (auditory) leminisci,spinothalamic tract, spinocerebellar tract (somatosen-sory), and central tegmental motor tract including thereticular formation. The ninth and tenth cranial nervenuclei, namely nucleus ambiguous and solitary tract nu-cleus, lie in upper and middorsal medullary tegmentumlaterally. They have sensory fibers that terminate inspinal nucleus of trigeminal nerve. The ninth nerve alsohas the inferior salivatory nucleus and the tenth nerve hasthe dorsal vagal nucleus in addition. The eleventh nervehas bulbar nuclei in lower nucleus ambiguous in upperand midmedulla. The twelfth nerve nuclei in the mid-dorsal medullary tegmentum paramedially produces thehypoglossal eminence, which is a bulge in the floor offourth ventricle. The medulla is separated from the cere-bellum posteriorly by the inferior portion of the fourthventricle (obex), the outlet foramina of which is contin-uous with the cisterna magna through the Foramen ofMagendie posteriorly in the midline, and with the cere-bellopontine angles through the paired foramina ofLuschka laterally. The obex communicates with the cen-tral canal of the spinal cord.

CEREBELLUM

Cerebellum consists of the median vermis and two lat-eral cerebellar hemispheres. The deepest fissures in the

CHAPTER 2 • BRAIN AND SPINE ANATOMY 9

cerebellum are the primary fissure superiorly, horizontalfissure in the middle, and posterolateral fissure inferi-orly. The cerebellar cortex lies superficial to white mat-ter as in the cerebrum. Also, there are deep cerebellarnuclei embedded within the white matter, namely den-tate nucleus, emboliform nucleus, globose nucleus, andfastigial nucleus. The white matter of the two sides isconnected by a thin lamina of fibers that are closely re-lated to the fourth ventricle. The upper part of this lam-ina forms the superior medullary velum and its inferiorpart forms the inferior medullary velum. Both these takepart in forming the roof (posterior boundary) of thefourth ventricle. The cerebellar peduncles connectingthe cerebellum with midbrain, pons, and medulla are al-ready described in those sections.

DIENCEPHALON

The diencephalon consists of thalamus, hypothalamus,subthalamus, and epithalamus. The thalami lie on eitherside of the third ventricle. Massa intermedia or interthal-amic adhesion connects the two thalami.

The hypothalamus lies around inferior aspect of thethird ventricle and consists of the preoptic region ad-joining the lamina terminalis, supraoptic region abovethe optic chiasm, infundibulotuberal region consistingof the pituitary infundibulum, tuber cinereum and the re-gion above it, and mamillary or posterior region consist-ing of the mamillary bodies and the region above it. Ofthese, the preoptic region is actually a derivative of thetelencephalon.

The subthalamus or ventral thalamus lies behind andlateral to the hypothalamus. Inferiorly it is continuouswith the upper ends of substantia nigra and red nucleusof the midbrain and laterally it is related to the lowestpart of the internal capsule.

The epithalamus consists of the pineal gland andhabenular nuclei. The pineal gland lies anteroinferior tothe splenium of corpus callosum and vein of Galen/-Internal cerebral vein and posterosuperior to the tectalplate/quadrigeminal cistern. Pineal masses elevate thevein of Galen/Internal cerebral veins and depress thetectal plate. The suprapineal recess of the third ventricleextends posteriorly immediately above the pineal gland.The quadrigeminal plate cistern lies posterior to thepineal gland and its anterior extension called the veluminterpositum lies above the pineal gland/internal cere-bral vein and extends anteriorly below the corpus callo-sum/fornix. The tentorial apex arches above and behindthe pineal gland and the course of fourth cranial nerveslies in close relationship. The attachment of the pinealbody to the posterior wall of the third ventricle isthrough a stalk that has two laminae, superior and

inferior. The superior lamina is traversed by fibers of thehabenular commissure and the inferior lamina by fibersof the posterior commissure.

BASAL GANGLIA

The caudate nucleus is a C-shaped mass of gray matterwith a head abutting the lateral wall of the frontal horn oflateral ventricle and lies anteromedial to the lentiform nu-cleus separated by the anterior limb of internal capsule, abody that abuts the body of lateral ventricle, and a tail thatcontinues anteroinferiorly with the lentiform nucleus.

The lentiform nucleus lies lateral to the internal cap-sule, the anterior limb of which separates it from thecaudate nucleus, and the posterior limb from the thala-mus. It consists of the globus pallidus medially and theputamen laterally. Laterally, the lentiform nucleus isseparated from the claustrum by the external capsule.

Note that the so-called corpus striatum consists ofcaudate nucleus and putamen and has the main arterialsupply from the medial and lateral striate branches of themiddle cerebral artery (MCA). Also, their anteriormostparts including the head of caudate nucleus receive sup-ply from the Heubner recurrent artery, a branch of ante-rior cerebral artery (ACA). Their posterior parts includ-ing tail of caudate nucleus also receive blood supplythrough anterior choroidal artery. The main blood supplyof globus pallidus is from anterior choroidal artery. Themedialmost part of globus pallidus receives branchesfrom the posterior communicating artery (PCOM).

The claustrum is a thin lamina of gray matter lateralto the external capsule. Laterally, it is separated from theinsula by the extreme capsule.

INTERNAL CAPSULE

The condensed projection fibers white matter structure,internal capsule, has an anterior limb, a genu that con-nects it to the posterior limb, a retrolentiform part, and asublentiform part. The upper parts of the anterior limb,genu, and posterior limb are supplied by the lateral lentic-ulostriate branches of the middle cerebral artery. Thelower parts have a different supply—the anterior limb byHuebner recurrent artery branch of anterior cerebral ar-tery, genu by direct internal carotid artery branches/posterior communicating artery branches, and posteriorlimb by anterior choroidal artery branches. The retrolen-tiform and sublentiform parts of the internal capsule arealso supplied by the anterior choroidal artery.

The internal capsule is continuous inferiorly with thewhite matter fibers of crus cerebri of the midbrain andsuperiorly with that of the corona radiata of the cerebral

10 SECTION 1 • CENTRAL NERVOUS SYSTEM

hemispheres. The corona radiata is continuous superi-orly with the centrum semiovale.

CORPUS CALLOSUM

The corpus callosum is a large mass of commissuralnerve fibers that connects the two cerebral hemispheres.It has a central body, anterior end bend on itself calledthe genu, and an enlarged posterior end called splenium.A thin lamina of nerve fibers called rostrum connects thegenu to the upper end of lamina terminalis. The under-surface of corpus callosum gives attachment to septumpellucidum and this callososeptal interface is an area tobe specifically looked for the dot–dash appearing T2 hy-perintense demyelinating plaques in conditions likemultiple sclerosis. The corpus callosum forms from an-terior to posterior except for the rostrum, which isformed last. In partial callosal agenesis, splenium androstrum are always missing.

The fibers of the genu run forward into frontal lobesforming the forceps minor and fibers of splenium runbackward into occipital lobes forming the forceps ma-jor. The forceps major bulges into the upper aspect ofoccipital horn of lateral ventricles on each side, formingthe bulb of the posterior horn. The fibers of the body andsome from splenium run laterally and intersect the whitematter fibers of corona radiata. As they pass laterally,some fibers of the body and splenium form a flattenedband called the tapetum, which is closely related to theoccipital and temporal horns of lateral ventricles.

VENTRICLES OF THE BRAIN

LATERAL VENTRICLES

The paired lateral ventricles have a frontal horn, body,atrium or trigone, temporal horn, and occipital horn. Thebody of lateral ventricle has a roof formed by body ofcorpus callosum, medial wall formed by septum pellu-cidum, and body of fornix and floor formed by thalamusmedially and caudate nucleus laterally with thalamostri-ate vein and stria terminalis in between.

The atrium or trigone of the lateral ventricle connectsthe temporal horn inferiorly, the occipital horn posteri-orly, and the body of the lateral ventricle anteriorly.

The frontal horn is bounded anteriorly by genu and ros-trum of corpus callosum, roof is formed by anterior aspectof body of corpus callosum, floor is formed mainly byhead of caudate nucleus and partially by rostrum of corpuscallosum and medial wall by septum pellucidum.

The occipital horn has a roof and lateral wall formedby tapetum (fibers from splenium of corpus callosum)

and a medial wall formed by an upper elevation calledbulb of posterior horn (fibers of forceps major), and alower elevation called calcar avis (white matter pushedin by formation of calcarine sulcus of occipital lobe).

The temporal horn has a roof or lateral wall formedby the tail of caudate nucleus laterally and stria termi-nalis medially (which extends from the floor of the bodyof lateral ventricle); the most anterosuperomedial part ofroof is formed by amygdalla. The floor or medial wall isformed mainly by the hippocampus along with thealveus and fimbria medially and collateral eminence lat-erally (produced by inward bulging of collateral whitematter lying deep to collateral sulcus).

THIRD VENTRICLE

The third ventricle is the cavity of the diencephalons situ-ated in between the two thalami. It communicates with thetwo lateral ventricles through the interventricular foraminaof Monroe anterosuperiorly just behind the columns offornix. Posteroinferiorly, it is continuous with the cerebralaqueduct of Sylvius within the midbrain, which connects itto the fourth ventricle. The lateral walls are formed by thethalamus superiorly and hypothalamus inferiorly. The ante-rior wall is formed mainly by the lamina terminalis; andupper parts by the anterior commissure/columns of fornix.The posterior wall is formed by pineal gland and posteriorcommissure. The floor is formed from anterior to posteriorby the optic chiasm, the hypothalamus including pituitaryinfundibulum, tuber cinereum and mamillary bodies, theposterior perforated substance, and the midbrain tegmen-tum. The roof is formed by ependyma stretching across thetwo thalami, tela choridea and choroid plexuses. The in-terthalamic adhesion or massa intermedia pass through thecavity of the third ventricle. The cavity has many recessesincluding the optic recess that lies just above the optic chi-asm, the infundibular recess that extends into the pituitaryinfundibulum, the pineal recess that lies between superiorand inferior laminae of pineal stalk, and the suprapineal re-cess that lies above the pineal gland.

FOURTH VENTRICLE

The important features of fourth ventricle are alreadydescribed in the section on brainstem.

TELA CHOROIDEA AND CHOROID PLEXUSES

The tela choroidea is a double-layered fold of pia materthat lies in the roof of the third ventricle. The posteriorend of tela choroidea lies in the gap between (transverse

CHAPTER 2 • BRAIN AND SPINE ANATOMY 11

fissure) the splenium of corpus callosum and the poste-rior part of roof of third ventricle. When traced furtherposteriorly, the two layers of pia mater separate with theupper layer curving upward over the posterior aspect ofthe splenium and the lower layer turning downward overthe pineal body and tectum. The anterior end of the telachoroidea of third ventricle lies near the interventricularforamina of Monroe and passes through the gap (choroidfissure) between the fornix superiorly and thalamus in-feriorly into the body of lateral ventricle on either side.The highly vascular choroid plexuses secrete CSF andare lined by a membrane formed by the fusion of ven-tricular ependyma with the pia mater of tela choroidea.The choroid plexus of the lateral ventricle extends intothe temporal horn. It is noteworthy that the telachoroidea and the choroid plexus do not extend into thefrontal horn. The fourth ventricle also possesses its owntela choroidea and choroids plexus, which also extendsinto the foramina of Magendie and Luschka.

PERSISTENT MIDLINE CSF CAVITIES

During intrauterine life, there are three potential midlinecavities related to the cerebral ventricles that regress be-tween the seventh month of intrauterine life and the sec-ond year of postnatal life. In adults, if they persist, cavumseptum pellucidum (CSP), cavum vergae (CV), andcavum veli interpositi (CVI) occur from anterior to poste-rior. CSP lies within the two leaflets of septum pellu-cidum; CV extends further posteriorly and these usuallydo not communicate with the ventricles or cisterns. CVIis an anterior continuation of quadrigeminal plate cistern.

SELLA AND PITUITARY

The sella is a depression in the basisphenoid bone andcontains the pituitary gland and inferior part of its stalk.Its anterior bony wall is called tuberculum sellae and iscontinuous anterosuperiorly with the anterior clinoidprocess. Its posterior bony wall is called dorsum sellaeand is continuous posterosuperiorly with the posterior cli-noid process. The sphenoid sinus lies directly below thesellar floor. The floor has thin bone called lamina dura.

The sella is bounded superiorly by a dural reflectioncalled the diaphragma sellae. Suprasellar cistern abovethe diaphragma sellae is CSF filled and contains opticnerves/chiasm and upper part of infundibular stalk. Theoptic chiasm lies in the bony groove that leads to opticcanal on each side, called sulcus chiasmaticus, anteriorto tuberculum sellae. The hypothalamus and anteriorthird ventricular recesses lie just above the infundibularstalk. The suprasellar cistern is surrounded by the circle

of Willis. The cavernous sinus lies lateral to the sella oneither side and contains the cavernous internal carotid ar-tery and sixth cranial nerve within it. The third, fourth,and ophthalmic and maxillary divisions of the fifth cra-nial nerve lie in the lateral wall of cavernous sinus.

The pituitary gland lies within the sella and has theanterior adenohypophysis and posterior neurohypophysis.The adenohypophysis, which comprises 75% of the pitu-itary volume appears isointense to gray matter on T1- andT2-weighted images and is composed of three parts—parstuberalis (part of the infundibular stalk and median emi-nence of hypothalamus), pars intermedia, which is verysmall in humans, and pars distalis. which forms most ofthe intrasellar adenohypophysis. The posterior neurohy-pophysis appear-hyperintense on T1-weighted imagesand hypointense on T2-weighted images.

The height of the pituitary gland varies with age andsex. It measures up to 6 mm in children, 8 mm in malesand postmenopausal females, 10 mm with upward bulgein young menstruating females, and 12 mm in pregnantor lactating females. The pituitary stalk measures up to2 mm in maximum thickness near insertion on pituitaryinferiorly and 3 to 3.5 mm near median eminence of hy-pothalamus superiorly. A rough guide to pituitary stalkthickness is that it should not be thicker than the adja-cent basilar artery diameter.

SPINE ANATOMY

GENERAL CHARACTERISTICS

There are 33 spinal vertebrae: 7 cervical, 12 thoracic,5 lumbar, 5 fused sacral, and 4 to 5 coccygeal. A typicalvertebra has a body and posterior elements, namely twopedicles, two transverse processes, two laminae (one oneach side), and a spinous process from anterior to pos-terior. Also the posterior elements have, on each side,articular processes consisting of a superior and inferiorarticular facet and pars interarticularis. The ligamentsinclude the anterior longitudinal ligament, posteriorlongitudinal ligament, interspinous and supraspinousligaments, ligamentum flavum, and the craniocervicalligaments namely alar ligament, transverse/cruciate lig-aments, and membrane tectoria. The intervertebral discis composed of inner nucleus pulposus and outer annu-lus fibrosus and adheres to the fenestrated hyaline carti-lage of vertebral endplates. They are avascular except inchildren and the peripheral annular fibers in adults. Thespine may also be divided into three columns for stabil-ity assessment—the anterior column consisting of ante-rior longitudinal ligament and anterior half of vertebralbody, disc, and annulus; the middle column consistingof the posterior half of vertebral body, disc, and annulus

12 SECTION 1 • CENTRAL NERVOUS SYSTEM

and posterior longitudinal ligament; and the posteriorcolumn consisting of the posterior elements, ligamen-tum flavum, and inter-/supraspinous interconnectingligaments.

MR SIGNAL INTENSITIES

In young children, the vertebral body has red marrow,which is isointense to paraspinous muscle on T1-weighted images. The marrow show marked enhance-ment postgadolinium in those younger than 2 years of ageand gradually disappears by around 7 years of age. From7 years to adolescence, the replacement of hematopoeticred marrow by fatty yellow marrow causes progressivechange to hyperintensity on T1-weighted images andrelative hypointensity on conventional spin echo T2-weighted images with mixed inhomogeneous signal inbetween. The intervertebral discs of infants are hyper-intense on T2-weighted images except for small centralhypointensity of notochord remnants. From the seconddecade onward, a hypointense band of compact fibroustissue develops in the centre. In adults, the outer annu-lus is hypointense on both T1- and T2-weighted imagesand the inner nucleus pulposus appear hyperintense onT2-weighted images with a low-signal intranuclearcleft. As the disc degenerates, the nucleus pulposusloses its high signal.

VERTEBRAL BODIES

Lumbar: Large, more or less square-shaped vertebralbodies.

Thoracic: Vertebral bodies are slightly wedge-shapedfrom front to back and gradually increase in sizefrom upper to lower thoracic spine.

Cervical: The typical cervical vertebrae are from C3 to C7and their bodies gradually increase in size from C3 toC7. They have bilateral posterosuperolateral projectionscalled uncinate processes that form the uncovertebralsynovial joints of Luschka with the posterolateral mar-gin of disc/vertebra above. The C2 or axis vertebra hasan odontoid process that extends superiorly from itsbody and articulates anterosuperiorly with the anteriorarch of atlas. The C1 or atlas vertebra has no body orspinous process. It has anterior and posterior arches,two lateral masses, and transverse processes. It is a bonyring with oblong or round inferior articular facets thatarticulate with superior facets of C2 and ellipsoid supe-rior articular facets that articulate with the occipitalcondyles to form the atlantooccipital joints. Theanatomy of the craniocervical junction is described inChapter 13.

INTERVERTEBRAL DISCS

Lumbar: A normal lumbar disc is slightly concave pos-teriorly, but appears flat or slightly rounded atL5–S1.

Thoracic: The height of the thoracic discs is less thanthat of cervical or lumbar discs, but the annulusfibrosus is thicker.

Cervical: The discs are slightly thicker anteriorly thanposteriorly.

PEDICLES, LAMINAE, AND SPINOUSPROCESSES

Thoracolumbar spine: The pedicles are thick bony pillarsthat are directed posterolaterally to join the broad andthick laminae in the thoracolumbar spine. In the lum-bar spine, the interpedicular distance widens as we godown the spine, which is reversed in conditions likeachondroplasia. The long spinous processes extendposteroinferiorly from the midline where the two lam-inae fuse.

Cervical spine: The laminae are thin in the cervicalspine. The spinous processes are often bifid. C7 hasthe longest spinous process.

TRANSVERSE PROCESSES

Lumbar spine: Transverse processes project laterally oneach side.

Thoracic spine: Transverse processes project superolat-erally on each side from the articular pillars betweenthe superior and inferior articular facets. The tip ofeach transverse process from T1 to T10 has an ovalcostal facet to form the costotransverse joint with therib tubercle. Also from T2 to T9, the vertebral demi-facets above and below the disc articulate with the ribhead to form the costovertebral joint.

Cervical spine: The transverse processes project anteroin-ferolaterally from the vertebral bodies. The thin bonybar called costotransverse bar connects the anteriorand posterior parts of the transverse process creatingthe transverse foramen for vertebral artery and vein.

ARTICULAR PILLARS AND FACET JOINTS

The articular pillars consist of the pars interarticularis,which is a bony plate that extends posteriorly from thepedicle and the superior and inferior articular facets thatit gives rise to. The synovial facet joints are formed bythe anteriorly positioned superior articular process of

CHAPTER 2 • BRAIN AND SPINE ANATOMY 13

the lower vertebra and the posteriorly positioned infe-rior articular facet of the lower vertebra. A tough fibrouscapsule covers the posterolateral aspect of the jointwhich is deficient ventrally, where the ligamentumflavum covers the joint.

LIGAMENTS

Anterior longitudinal ligament extends from basiocciputto S1, seen as a hypointense band in direct contact withthe anterior surface of vertebral bodies and discs.

Posterior longitudinal ligament is a thinner band thatextends from C1 to S1 vertebra and does not adhere tovertebral bodies. Epidural fat and veins are interposedbetween the posterior longitudinal ligament and verte-bral bodies. The posterior longitudinal ligament widenslaterally at the intervertebral discs attaching firmly tothe annulus fibrosus reinforcing the mid-/ paramedianzones of the disc.

Ligamentum flavum arises from the anterior aspectof the lower margin of the lamina of the upper vertebraand attaches to the posterior surface of the lamina below.On axial MRI, it is seen as a hypointense structure thatcovers the facet joint anteriorly and sometimes filledwith fat posteriorly. It thickens and buckles with degen-eration and can become fat infiltrated or calcified.

NEURAL FORAMEN AND LATERAL RECESS

The neural foramen lies between the pedicles of the upperand lower vertebrae with the anterior margin formed bythe vertebral body superiorly and the disc and posteriorlongitudinal ligament inferiorly. The posterior boundaryis formed by the articular facet and ligamentum flavum.The lumbar nerve root exits the fat-filled foramen throughthe widest superior part of the foramen and on sagittal T1-weighted MRI looks like a bird’s head and beak with thebird’s eye formed by the dorsal root ganglion directly be-low the superior pedicle. The lateral recess is the region ofthe lumbar canal that is bordered laterally by the pedicle,posteriorly by the superior articular facet and ligamentumflavum, and anteriorly by the vertebral body, endplatemargin, and disk margin. Measurements of the bone mar-gins of the lateral recess suggest narrowing with possibleroot compression when the anteroposterior dimension isbelow 4 mm. It is important to remember that at the lum-bar level, central disc protrusion produces compression ofthe descending lower nerve root and lateral recess/neuralforamen compression impinges the exiting upper nerveroot. For example, at L5–S1 level, central protrusioncompresses S1 nerve root and lateral recess/neural fora-men compression impinges on the L5 nerve root.

In the cervical spine, the nerve roots lie in the inferioraspect of the neural foramen just above the inferior pedi-cle and the dorsal root ganglia lies outside the neuralforamen. This is because the nerve roots exit above thepedicles at the cervical level. At the cervical level, centraldisc protrusion produces compression of a still lowernerve root than that intervertebral level and neural fora-men compression impinges the exiting lower nerve root.For example, at C5-6 level, central protrusion com-presses C7 nerve root and neural foramen compressionimpinges on the C6 nerve root. The C5 nerve root is not