Brian A. Stettler, MD, FACEP Head CT Interpretation in the ED: The Complete Primer Brian A. Stettler, MD Assistant Professor Department of Emergency Medicine.

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


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


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


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


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


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?


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


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


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


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


Head CT InterpretationHead CT Interpretation• Look at the scout

• Adequate study?– Minimize motion – Subject to artifact from metal



• Quick look– Get the gestalt

– Assess for gross abnormalities



• Extra-axial hemorrhage– Epidural hematoma

– Subdural hematoma

– Subarachnoid hemorrhage

• Intracerebral hemorrhage

• Intraventricular hemorrhage


Epidural HematomaEpidural Hematoma

• “Lens” shaped

• Does not cross suture lines

• Typically acute or hyperacute

• Frequently associated with mass effect


Subdural HematomaSubdural Hematoma

• Located along calvarium, falx, tentorium

• Crosses suture lines, usually spreads more extensively than epidural

Acute



• 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



• 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


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


Subarachnoid HemorrhageSubarachnoid Hemorrhage

• Source:– Post-traumatic– Aneurysmal– AVM– Other

• Hounsfield units– Blood is 50-100 (80)


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


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


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


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


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


Tying it TogetherTying it Together

• Spontaneous ICH• Supratentorial (L

basal ganglia)• Approx 45cc• 8mm of midline

shift• Evidence of uncal

herniation


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


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


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


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


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


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


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


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


Questions?

Brian A. Stettler, MD, FACEP Head CT Interpretation in the ED: The Complete Primer Brian A. Stettler, MD Assistant Professor Department of Emergency Medicine.

Documents

utility of head ct

old slide

dizziness slide

facep objectives

metal slide

neg slide

complete primer brian

delayed sdh slide