embryology and developmental pathology

Spinal Embryology and Developmental Pathology

Richard C Rooney, MD, [email protected]

Stages of Neural-Spinal Development- First Week

Moore, K. The Developing Human

Stages of Neural-Spinal Development- Second Week


Stages of Neural-Spinal Development- Third Week

• Primitive Streak


Stages of Neural-Spinal Development- Third Week• Notochord


Stages of Neural-Spinal Development- Third Week• Mesoderm- Day 16

Stages of Neural-Spinal Development- Third Week• Somites


Stages of Neural-Spinal Development- Third Week• Mesoderm

Stages of Neural-Spinal Development- Third Week• Neural Plate


Stages of Neural-Spinal Development- Fourth Week

• Neural Plate– Neuralization- closure of the neural groove to

form the neural tube



• Somites- 42 pairs• Neural Plate and cranial-most 4 somites form

the brain



• Somites- divide into dense and sparse areas



• Centrum- dense portion of cephalad with sparse portion of caudal somite


Primodial Vertebral Segment

Bullough, Atlas of Spinal Diseases

Vertebral Development

Bullough, Atlas of Spinal Diseases

Stages of Neural-Spinal Development- Fifth Week

• Neural Plate- Thinning of 4th ventricle for Foramen of Magendie

• Notochord- Degeneration in Vertebral Body area


Stages of Neural-Spinal Development- Fifth Week

• Vertebrae- Mesenchymal model finished


Stages of Neural-Spinal Development- Sixth Week

• Vertebrae- – Chondrification- 6th week– Ossification Centers- 7th week


Further Vertebral Development• Neural Central Joint- fuses 3rd to 6th year• Vertebral Arch- fuses 3rd to 5th year


Further Vertebral Development

• Rib, Body and Vertebral Arch equivalents

Grey’s Anatomy

A Clarification of Terms• Physeal Plate- Cartilage plate where growth occurs.• Epiphysis- Area of bone on the end of the physeal plate that contributes to longitudinal growth of a long bone• Apophysis- An area of bone adjacent to a physeal plate that does not contribute to longitudinal growth (Secondary Centers of Ossification)

A Clarification of Terms• Apophysis- An area of bone adjacent to a

physeal plate that does not contribute to longitudinal growth (Secondary Centers of Ossification)


Recap Spinal Cord Development


Recap Spinal Cord Development• Neural tube-- CNS• Neural Crests-- PNS and ANS• Neural Canal– Ventricles and central canal


Vertebral Column Development


Where Things Go Wrong

• Failure of Canal to Close


Where Things Go Wrong• Failure of Canal to Close


Where Things Go WrongCSF Flow/ Drainage Problems

Chiari malformations- (aka Arnold-Chiari) definition- downward compression (not traction) of the lower cerebellar contents into the cervical region

Typed by amount of displacement--correlates with age of onset-correlates with severity of symptoms

Shrek, H. The Cervical Spine


Chiari malformations-Type I

- mildest- originally called adult onset- caudal displacement of cerebellar tonsils (with dentate ligaments, 4th ventricle, cervical roots and brain stem in normal position.)



Chiari malformations-Type II

- more severe- originally called congenital- caudal displacement of cerebellar vermis, 4th ventricle, medulla and lower pons



Chiari malformations-Type III

- most severe- caudal displacement of cerebellum and brain stem into high cervical meningiocele


Chiari Malformations con’t.• Symptoms- due to neural compression at foramen magnum

– Lower cranial nerve dysfunction– Long tract signs

• Associated with:– Scarring– Compressive atrophy– Fibrous band


Chiari Malformations con’t.• Bony deformity = Basilar Impression

– May be secondary to other conditions– MCC- congenital anomaly in cerv-occ. Area– Def.- upward movement of base of skull in the foramen magnum area– Measured by intracranial extension of the tip of odontoid


Basilar Impression- measurement• Chamberlain’s Line (Red)

– Hard palate to foramen magnum– Odontoid below line +/- 4 mm.


Basilar Impression- measurement• McRae’s Line (Green)

– AP of foramen magnum- odontoid below this line– Symptoms when AP diameter <20 mm.


Basilar Impression- measurement• Wackenheimer’s Line (Blue)

– Drawn along clivus– Odontoid is ventral


Fixation +/- Position Changes• Tethered Cord

– Cause unknown, probably multiple– Assoc. with cutaneous lesion 54%– Assoc. with lipoma 15%– Female 2:1– Slowly progressive motor dysfunction– Recovery after surgery- poor- operate early!

Weinstein, S. The Pediatric Spine

Fixation +/- Position Changes• Diastematomyelia

– Cord divided by fibrous, cartilagenous or bony septum– Cutaneous lesion +/-– Dural tube- one or two– Diagnose before spinal instrumentation!


Multisystem Problems• VATER/VACTERL

– V- vertebral anomalies/ dysgenesis, vascular– A- anal atresia– C- cardiac anomalies– T- tracheo-eophageal (T-E) fistulas– E- esophageal atresia– R- renal anomalies– L- limb anomalies, radial (forearm) dysplasia– S- single umbilical artery


Segmentation Problems• Hemivertebra- Segmented vs. non-segmented

(scoliosis lecture)


Segmentation Problems• Failure of Segmentation (aka congenital fusions)

– Klippel-Feil Syndrome• Short neck• Low posterior hair line• Limited cervical ROM• Beware of compensatory hyper-mobility• Familial component• Assoc. with Fetal Alcohol Syndrome


Questions?

• Fellowship Trained• Board Certified• Experienced• Diligent about the literature• Second opinion• [email protected]

Confidential

embryology and developmental pathology

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