Educational Objectives by CbDCunX0

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

               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


                       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
                    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



                       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


                            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?

                         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


                                  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
                         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


                         Brian A. Stettler, MD, FACEP
      Head CT Interpretation
• Scout, assessment for adequacy
• Quick look
• Detailed look (force yourself)
 – Extra-axial blood   – Vessel density
 – Mass effect         – Bone windows
 – Ischemia            – Extras (sinuses, mastoids)
 – Ventricles          – Compare to old
                           Brian A. Stettler, MD, FACEP
       Head CT Interpretation
• Look at the scout
• Adequate study?
  – Minimize motion
  – Subject to artifact from metal




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




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


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


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



                          Brian A. Stettler, MD, FACEP
        Subdural Hematoma
• Can be acute,                             Subacute
  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

                             Brian A. Stettler, MD, FACEP
         Subdural Hematoma
                                          Chronic
• 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
                               Osborn, Diagnostic Imaging Brain 2004



                           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
                        Brian A. Stettler, MD, FACEP
   Subarachnoid Hemorrhage
• Source:
  – Post-traumatic
  – Aneurysmal
  – AVM
  – Other
• Hounsfield units
  – Blood is 50-100 (80)



                           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


                           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

                                   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
                           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

                                  Brian A. Stettler, MD, FACEP
               Herniation
• 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


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


                      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

                             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



                         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



                                        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

                                       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


                                   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

                           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

                          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
                         Brian A. Stettler, MD, FACEP
Questions?




      Brian A. Stettler, MD, FACEP

								
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