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Neuroimaging of Stroke Andrew Perron, MD A ssistant Professor Department of Emergency Medicine University of Virginia Charlottesville, VA. Case Presentation. Community ED No Neurologist Radiologist…65 minutes away No teleradiology CT scanner. Case Presentation. 58 year old female
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Neuroimaging of Stroke Andrew Perron, MDAssistant ProfessorDepartment of Emergency MedicineUniversity of VirginiaCharlottesville, VA
Case Presentation • Community ED • No Neurologist • Radiologist…65 minutes away • No teleradiology • CT scanner
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)
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)
Dense MCA Insular Ribbon Sign ECASS Criteria Visible vessel Stroke Mimic Diffusion/Perfusion NINDS Criteria
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
3 Possible CT Findings • Stroke Mimic • Non-stroke mass lesion (Abscess, Tumor) • Intracerebral Hemorrhage • Subarachnoid Hemorrhage • Normal CT • Cerebral Infarction
Stroke Mimics • Tumor • Blood clot • EDH • SDH • SAH • IPH • Abscess
Stroke Mimics • Blood clot EDH SDH
Stroke Mimics • Subarachnoid Hemorrhage
Stroke Mimics • Subarachnoid Hemorrhage
Stroke Mimics • Intraparenchymal Hemorrhage/IVH
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
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
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
Cerebral Infarction • Hyperdense Artery Sign • Insular Ribbon Sign • Loss of Cortical Gray-White Differentiation • Mass Effect
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
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
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
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
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
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
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
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
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
Summary for t-PA: Inclusion • No evidence of : • Hemorrhage • EDH/SDH • IPH • SAH • Non-stroke etiology • Tumor • Abscess • Trauma
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
Future Trends • MRI/MRA • MR diffusion/perfusion/spectroscopy • Transcranial doppler • PET (Positron Emission) /SPECT (Single Photon Emission)
Our Case • Acute L MCA stroke (Loss of insular ribbon, gray-white differentiation) No Blood…done? Gray/white Insular ribbon Gray/White
Our Case • Right frontal tumor with edema Tumor Edema
Our Case • Thrombolysis witheld due to tumor • Patient transferred to neurosurgical center • Craniotomy yields diagnosis of astrocytoma