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					Neuroimaging of Stroke


      Andrew Perron, MD


       Assistant Professor
Department of Emergency Medicine
      University of Virginia
       Charlottesville, VA
          Case Presentation
•   Community ED
•   No Neurologist
•   Radiologist…65 minutes away
•   No teleradiology
•   CT scanner


                       Andrew Perron, MD
        Case Presentation
• 58 year old female
• 2 hours 15 minutes of dysarthria,
  right sided weakness
• “Mildly obtunded” per EMS
• Code Stroke called (gets you and CT
  scan tech ready)

                      Andrew Perron, MD
            Case Presentation

• Dysarthric, weak RUE/RLE, NIHSS = 18
• Toes up-going bilaterally
• Family relates a few weeks of left arm tingling and
  clumsiness
• Off to CT…returns with the films on the bed
• Nurse asks if you are going to read the CT, since
  only 15 minutes left before the 3 hour mark
  (Radiologist still 45 minutes away)

                                 Andrew Perron, MD
Head CT




          Andrew Perron, MD
Andrew Perron, MD
         Cranial CT Scanning

• First line imaging study in suspected
  stroke patients
  – Exquisite sensitivity for the detection of
    blood
  – Ubiquitous in hospitals

• Fundamental branch point in the
  work up of a suspected stroke
  patient
                                 Andrew Perron, MD
       3 Possible CT Findings
• Stroke Mimic
  – Non-stroke mass lesion (Abscess, Tumor)
  – Intracerebral Hemorrhage
  – Subarachnoid Hemorrhage

• Normal CT

• Cerebral Infarction
                             Andrew Perron, MD
            Stroke Mimics
• Tumor
• Blood clot
  – EDH
  – SDH
• SAH
• IPH
• Abscess
                      Andrew Perron, MD
               Stroke Mimics
• Blood clot




       EDH                          SDH
                          Andrew Perron, MD
          Stroke Mimics
• Subarachnoid Hemorrhage




                      Andrew Perron, MD
          Stroke Mimics
• Subarachnoid Hemorrhage




                      Andrew Perron, MD
          Stroke Mimics
• Intraparenchymal Hemorrhage/IVH




                      Andrew Perron, MD
      CT scan fundamentals
• Even 3rd and 4th generation
  scanners will not demonstrate acute
  ischemic stroke in the first few
  hours
  – “Normal CT Scan” is the most
    common CT finding in the patient with
    acute stroke

                         Andrew Perron, MD
        CT scan fundamentals

• Gray matter is more susceptible to
  ischemia than white matter
  – More metabolically active

• Loss of gray-white differentiation is
  the earliest CT change
  – Due to edema in the gray matter
                            Andrew Perron, MD
Grey-White Differentiation




                 Andrew Perron, MD
       CT scan fundamentals
• Subtle edema can be seen in < 1 hour
• By 6 hours, 3/4 of patients with MCA
  strokes will show edema in the insular
  cortex
  – “Insular Ribbon Sign”
• After12-24 hours, additional edema is
  recruited into the area
  – Lesion will become conspicuous on CT

                            Andrew Perron, MD
           Cerebral Infarction

• Hyperdense Artery Sign

• Insular Ribbon Sign

• Loss of Cortical Gray-White Differentiation

• Mass Effect
                            Andrew Perron, MD
           Hyperdense Artery Sign

• Typically MCA, PCA, or ACA

• Indicates a major vessel occlusion with thrombus
  formation

• False positives can occur
   – Unilateral calcification

• ICA or MCA proximal trunk occlusions more serious
  than occlusions of MCA branches, PCA, or ACA


                                    Andrew Perron, MD
Hyperdense Artery Sign




               Andrew Perron, MD
      Hyperdense Artery Sign
• Whether the at risk territory will undergo
  ischemic necrosis is a matter of
  collateral blood supply

• Therefore, this is NOT an infarct sign
  – Indicates the volume of at risk tissue
    • If collateral supply fails
    • Recanalization not achieved

                                Andrew Perron, MD
            Insular Ribbon Sign
• Area of extreme gray-white
  differentiation in the MCA
  artery territory

• Located between the
  sylvian fissure and the
  basal ganglia

• Supplied by perforators off
  of the MCA                    Andrew Perron, MD
         Insular Ribbon Sign
• Loss of the insular stripe is one of the
  earliest indications of MCA stroke

• Normal stripe = Thin white line (gray
  matter) adjacent to darker gray line
  (subcortical white matter)

• Ischemia effects metabolically active gray-
  matter
  – Causes intracellular edema
                                 Andrew Perron, MD
Insular Ribbon Sign




              Andrew Perron, MD
        Insular Ribbon Sign
• With ischemia
  – Insular stripe is lost
  – Homogeneous appearance is noted

• NOT an exclusion criterion for
  thrombolytic therapy

• Should prompt re-confirmation of stroke
  ictus reported by patient/family
                          Andrew Perron, MD
         Loss of Cortical
     Gray-White Differentiation
• Similar process as loss of insular stripe

• Loss of cortical gray-white indicates edema in
  metabolically active gray-matter

• ECASS studies have suggested withholding t-
  PA from patients with > 1/3 of the MCA territory
  effected by de-differentiation
  – Increased risk for hemorrhagic conversion

                                 Andrew Perron, MD
    Loss of Cortical
Gray-White Differentiation




                  Andrew Perron, MD
             Loss of Cortical
         Gray-White Differentiation

• No similar rules for anterior/posterior
  circulation

• Interobserver consistency for defining 1/3 of
  MCA territory de-differentiation is low

• Use as an exclusion criterion is controversial
                                Andrew Perron, MD
                 Mass Effect

• Brain swelling is extremely subtle in the
  first hours after arterial occlusion
  – Sulcal effacement
  – CSF space compression
  – Ventricular shift

• Swelling often not visible for the first 6
  hours
                              Andrew Perron, MD
Mass Effect




         Andrew Perron, MD
                 Mass Effect

• In ECASS, 21% of initial CT scans
  demonstrated focal brain swelling
  – Associated with a poorer outcome

• Use as an Exclusion Criterion is
  controversial

                             Andrew Perron, MD
    Summary for t-PA: Inclusion
• No evidence of :
  – Hemorrhage
    • EDH/SDH
    • IPH
    • SAH
  – Non-stroke etiology
    • Tumor
    • Abscess
    • Trauma


                          Andrew Perron, MD
    Summary for t-PA: Relative
       Contraindications
• Controversial
  – Evidence of a large MCA territory
    infarction
    • Gray-white de-differentiation > 1/3 of
      territory
    • Sulcal effacement/mass effect > 1/3 of
      territory


                             Andrew Perron, MD
              Future Trends
•   MRI/MRA
•   MR diffusion/perfusion/spectroscopy
•   Transcranial doppler
•   PET (Positron Emission) /SPECT (Single
    Photon Emission)




                            Andrew Perron, MD
Returning to our case…Diagnosis?




                    Andrew Perron, MD
                      Our Case
• Acute L MCA stroke (Loss of insular ribbon,
  gray-white differentiation) No Blood…done?


                                                       Gray/white


                                                         Insular
                                                         ribbon

                                                       Gray/White
                                   Andrew Perron, MD
                Our Case
  • Right frontal tumor with edema




Tumor




 Edema

                           Andrew Perron, MD
               Our Case
• Thrombolysis witheld due to tumor
• Patient transferred to neurosurgical
  center
• Craniotomy yields diagnosis of
  astrocytoma


                         Andrew Perron, MD
Questions?




         Andrew Perron, MD

				
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posted:1/25/2013
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