Neuroimaging of Stroke Andrew Perron, MD Assistant Professor Department of Emergency Medicine University of Virginia Charlottesville, VA 54 1 54

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)

Head CT

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 Normal CT Cerebral Infarction 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

Grey-White Differentiation

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

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

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

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

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)

Returning to our case…Diagnosis?

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

Questions?