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Brian A. Stettler, MD, FACEP
Head CT Interpretation in the Head CT Interpretation in the ED: The Complete PrimerED: The Complete Primer
Brian A. Stettler, MDAssistant Professor
Department of Emergency MedicineUniversity of Cincinnati
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Brian A. Stettler, MD, FACEP
ObjectivesObjectives
• Discuss the utility of Head CT
• Discuss what Head CT will miss
• Review basic interpretation of the Head CT
• Discuss a few specific disease processes
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Brian A. Stettler, MD, FACEP
Clinical HistoryClinical HistoryCC: Headache and weakness
HPI: 67 year old female with several months of dull headaches relieved by Tylenol and subjective “dizziness” without falls. Symptoms worsened today about 2 hours ago and she now complains she cannot walk secondary to dizziness
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Brian A. Stettler, MD, FACEP
ED PresentationED Presentation
PMHx: DM, HTN, CAD
Meds: Atenolol, HCTZ, ASA, Insulin
All: NKDA
SocHx: 1PPD, Occasional Etoh, denies drugs
ROS: mild anorexia, weight loss approx 5 lbs over past month, o/w neg
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Brian A. Stettler, MD, FACEP
ED PresentationED Presentation
PE: 176/94, 65, 16, 98.8, 93% RAGen: alert and conversive, sl uncomfortable
appearing
HEENT: WNL
Pulm: sl wheezes, otherwise WNL
CV: WNL
Neuro: strength 4/5 throughout, gait unsteady without overt ataxia, no deficits to cranial nerves
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Brian A. Stettler, MD, FACEP
Points of DiscussionPoints of Discussion
• In addition to other labs, a non-contrast head CT is ordered– How is this study interpreted?
– What findings affect the treatment of the patient?
– What findings portend a bad outcome for the patient?
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Brian A. Stettler, MD, FACEP
Non-contrast Head CTNon-contrast Head CT• The most common
neuroimaging tool employed in the ED– Performed in seconds, usually
read in minutes– No IV access required – Available 24 hours/day in most
EDs– No real contraindications– Good sensitivity and specificity
for many disease processes
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Brian A. Stettler, MD, FACEP
Non-contrast Head CTNon-contrast Head CT
• Benefits:– Gold standard in assessment for acute
hemorrhage
– Very good at documenting mass effect and herniation
– Will visualize acute ischemia, neoplasm, localized intracranial infection
– Good at visualizing skull fracture
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Brian A. Stettler, MD, FACEP
Non-contrast Head CTNon-contrast Head CT
• Drawbacks– Poor at visualizing disease in the posterior
cranial fossa, especially ischemia– Poor at diagnosing intracranial mass that does
not have significant mass effect– Sensitivity is not high enough to completely
eliminate SAH– Will miss delayed disease, such as delayed SDH
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Brian A. Stettler, MD, FACEP
Head CT InterpretationHead CT Interpretation
• Scout, assessment for adequacy
• Quick look
• Detailed look (force yourself)– Extra-axial blood
– Mass effect
– Ischemia
– Ventricles
– Vessel density
– Bone windows
– Extras (sinuses, mastoids)
– Compare to old
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Brian A. Stettler, MD, FACEP
Head CT InterpretationHead CT Interpretation• Look at the scout
• Adequate study?– Minimize motion – Subject to artifact from metal
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Brian A. Stettler, MD, FACEP
Head CT InterpretationHead CT Interpretation
• Quick look– Get the gestalt
– Assess for gross abnormalities
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Brian A. Stettler, MD, FACEP
Head CT InterpretationHead CT Interpretation
• Extra-axial hemorrhage– Epidural hematoma
– Subdural hematoma
– Subarachnoid hemorrhage
• Intracerebral hemorrhage
• Intraventricular hemorrhage
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Brian A. Stettler, MD, FACEP
Epidural HematomaEpidural Hematoma
• “Lens” shaped
• Does not cross suture lines
• Typically acute or hyperacute
• Frequently associated with mass effect
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Brian A. Stettler, MD, FACEP
Subdural HematomaSubdural Hematoma
• Located along calvarium, falx, tentorium
• Crosses suture lines, usually spreads more extensively than epidural
Acute
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Brian A. Stettler, MD, FACEP
Subdural HematomaSubdural Hematoma
• Can be acute, subacute, or chronic– Density on CT helps to
age hematoma– Can frequently be a
mix of ages
• Can have mass effect that ranges from none to severe
Subacute
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Brian A. Stettler, MD, FACEP
Subdural HematomaSubdural Hematoma
• Not all SDH are bright white
• MUST follow gyri/sulci to edge of calvarium on every cut
• Falx may be calcified but should be thin
Chronic
Osborn, Diagnostic Imaging Brain 2004
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Brian A. Stettler, MD, FACEP
Subarachnoid HemorrhageSubarachnoid Hemorrhage
• Can be present in cisterns, around gyri and sulci
• Almost always acute
• Sensitivity of NCHT– Not well known or agreed upon
– Probably in the high 90’s early
– Decreases as time progresses from onset of symptoms
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Brian A. Stettler, MD, FACEP
Subarachnoid HemorrhageSubarachnoid Hemorrhage
• Source:– Post-traumatic– Aneurysmal– AVM– Other
• Hounsfield units– Blood is 50-100 (80)
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Brian A. Stettler, MD, FACEP
Intracerebral HemorrhageIntracerebral Hemorrhage• Location can be
anywhere in the parenchyma
• Can be caused by hypertension, AVM, amyloid
• Typically present with headache, focal neurologic findings, AMS, N/V
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Brian A. Stettler, MD, FACEP
Intracerebral hemorrhageIntracerebral hemorrhage
• CT findings that affect outcome– Volume of hemorrhage– Location of hemorrhage
(supra vs infratentorial)– Presence of intraventricular
hemorrhage
• Also describe:– Presence of midline shift– Presence of herniation– Presence of hydrocephalus
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Brian A. Stettler, MD, FACEP
Volume of HemorrhageVolume of Hemorrhage
• (A x B x C)/2• A and B are perpendicular
dimensions in the slice that shows the maximal amount of hemorrhage
• C is the total number of slices that show hemorrhage x the slice thickness
• Ex: 4cm x 5.5 cm by (8 x 5mm slices)/2– 4 x 5.5 x 4/2 = 45cc
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Brian A. Stettler, MD, FACEP
Mass Effect and Midline ShiftMass Effect and Midline Shift
• Mass effect can be local or generalized
• When generalized, typically seen as shift of the midline structures away from the area of mass effect
• Midline shift– Use drawing tools to draw line down
center of skull– Measure from midline structure (pineal
gland, falx, septum pellucidum) to line drawn
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Brian A. Stettler, MD, FACEP
HerniationHerniation
• Herniation is an ominous sign on CT• Types
– Uncal (3rd nerve palsy – the “blown pupil”)– Transtentorial– Sub-falcine– Tonsillar
• Look for structures where they should not be
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Brian A. Stettler, MD, FACEP
Tying it TogetherTying it Together
• Spontaneous ICH• Supratentorial (L
basal ganglia)• Approx 45cc• 8mm of midline
shift• Evidence of uncal
herniation
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Brian A. Stettler, MD, FACEP
Trauma - ContusionsTrauma - Contusions
• Patchy hemorrhage contained to the superficial grey matter
• Frequently associated with local edema
• Caused by brain impact to bone
• Locations most commonly temporal lobes and frontal, but can occur anywhere
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Brian A. Stettler, MD, FACEP
Trauma - ContusionsTrauma - Contusions
• Contusions frequently evolve from small petechiae to large areas of edema and hemorrhage over the course of 1-2 days
Osborn, Diagnostic Imaging Brain 2004
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Brian A. Stettler, MD, FACEP
IschemiaIschemia
• Very early CT typically negative
• Early findings– Loss of grey-white
differentiation• Insular “ribbon”• Basal ganglia/internal capsule
– Effacement of ventricles and local mass effect
– Hyperdense artery
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Brian A. Stettler, MD, FACEP
IschemiaIschemia
• ASPECTS– Larger areas of grey-white
changes on initial CT have worse outcomes
– Score < 7 had OR 82 for worse functional outcome
Barber, Lancet 2000
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Brian A. Stettler, MD, FACEP
Being ThoroughBeing Thorough
• Use bone windows on every trauma
• Don’t forget the extras– Sinuses, mastoid air cells– Air where it shouldn’t be– Orbits– Old infarcts
• If abnormal, look for an old CT
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Brian A. Stettler, MD, FACEP
Case Follow-upCase Follow-up
• Pt’s CT showed a small, ill-defined parenchymal hemorrhage
• Follow-up MRI showed multiple enhancing lesions suspicious for mets
• Pt undergoing treatment for metastatic lung CA
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Brian A. Stettler, MD, FACEP
Head CT - ConclusionsHead CT - Conclusions
• Scan early and often• Beware the lurking slit subdural• Contusions can be tiny – at first• Ischemia can be subtle• You still can’t completely trust the negative
SAH CT• Negative early doesn’t always mean negative
late – and vice versa
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Brian A. Stettler, MD, FACEP
Head CT - ConclusionsHead CT - Conclusions
• Useful imaging screening tool for many life-threatening neurologic processes
• May miss early findings in hemorrhage or ischemia
• Interpretation must be done thoroughly– The same way every time
– Assess not only primary pathology, but factors contributing to outcome
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Brian A. Stettler, MD, FACEP
Questions?