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

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Presentation on theme: "Brian A. Stettler, MD, FACEP Head CT Interpretation in the ED: The Complete Primer Brian A. Stettler, MD Assistant Professor Department of Emergency Medicine."— Presentation transcript:

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

2 Brian A. Stettler, MD, FACEP Objectives 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

3 Brian A. Stettler, MD, FACEP Clinical History CC: 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

4 Brian A. Stettler, MD, FACEP ED 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

5 Brian A. Stettler, MD, FACEP ED Presentation PE: 176/94, 65, 16, 98.8, 93% RA Gen: 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

6 Brian A. Stettler, MD, FACEP Points 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?

7 Brian A. Stettler, MD, FACEP Non-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

8 Brian A. Stettler, MD, FACEP Non-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

9 Brian A. Stettler, MD, FACEP Non-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

10 Brian A. Stettler, MD, FACEP Head 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

11 Brian A. Stettler, MD, FACEP Head CT Interpretation Look at the scout Adequate study? –Minimize motion –Subject to artifact from metal

12 Brian A. Stettler, MD, FACEP Head CT Interpretation Quick look –Get the gestalt –Assess for gross abnormalities

13 Brian A. Stettler, MD, FACEP Head CT Interpretation Extra-axial hemorrhage –Epidural hematoma –Subdural hematoma –Subarachnoid hemorrhage Intracerebral hemorrhage Intraventricular hemorrhage

14 Brian A. Stettler, MD, FACEP Epidural Hematoma “Lens” shaped Does not cross suture lines Typically acute or hyperacute Frequently associated with mass effect

15 Brian A. Stettler, MD, FACEP Subdural Hematoma Located along calvarium, falx, tentorium Crosses suture lines, usually spreads more extensively than epidural Acute

16 Brian A. Stettler, MD, FACEP Subdural 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

17 Brian A. Stettler, MD, FACEP Subdural 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

18 Brian A. Stettler, MD, FACEP Subarachnoid 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

19 Brian A. Stettler, MD, FACEP Subarachnoid Hemorrhage Source: –Post-traumatic –Aneurysmal –AVM –Other Hounsfield units –Blood is (80)

20 Brian A. Stettler, MD, FACEP Intracerebral 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

21 Brian A. Stettler, MD, FACEP Intracerebral 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

22 Brian A. Stettler, MD, FACEP Volume 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

23 Brian A. Stettler, MD, FACEP Mass 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

24 Brian A. Stettler, MD, FACEP Herniation Herniation is an ominous sign on CT Types –Uncal (3 rd nerve palsy – the “blown pupil”) –Transtentorial –Sub-falcine –Tonsillar Look for structures where they should not be

25 Brian A. Stettler, MD, FACEP Tying it Together Spontaneous ICH Supratentorial (L basal ganglia) Approx 45cc 8mm of midline shift Evidence of uncal herniation

26 Brian A. Stettler, MD, FACEP Trauma - 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

27 Brian A. Stettler, MD, FACEP Trauma - 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

28 Brian A. Stettler, MD, FACEP Ischemia 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

29 Brian A. Stettler, MD, FACEP Ischemia 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

30 Brian A. Stettler, MD, FACEP Being 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

31 Brian A. Stettler, MD, FACEP Case 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

32 Brian A. Stettler, MD, FACEP Head 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

33 Brian A. Stettler, MD, FACEP Head 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

34 Brian A. Stettler, MD, FACEP Questions?


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