Acute Stroke Imaging Goals: Determine stroke subtype Understand mechanism Institute treatment Radoslav Raychev, MD
Acute Stroke Facts Leading cause of disability 4 rd leading cause of death in USA 2 nd leading cause of death worldwide >5 million stroke survivors $40 to $50 billion per year in the US 1 in 6 Americans will be affected 90% of those who survive will have deficits 30% of strokes can be reversed 80 % of strokes can be prevented
Stroke: Definition Permanent injury to the brain or spinal cord of vascular origin (reduced blood flow or bleeding into or around the brain or spinal cord)
Stroke imaging objectives Brain tissue Brain vessels
Brain Tissue Imaging - Non Contrast Head CT Stroke Suspected ISCHEMIC HEMORRHAGIC
Hemorrhagic stroke imaging Non-traumatic Intracerebral hemorrhage (ICH) = Intraparenchymal hemorrhage» 70% of intracranial hemorrhage Subarachnoid hemorrhage» 30% of intracranial hemorrhage
Head CT Advantages:» Quick» Best for bony anatomy» Excellent for blood» Widely available Disadvantages:» Radiation» Limited detail
MRI for ICH Blood dark on GRE weighted sequence AVM nidus Large draining vein
Gradient Echo Imaging best for blood FLAIR GRE: Multiple microbleeds, not visible on other sequences
Traumatic ICH» Epidural» Subdural» Intraprenchymal» Subarachnoid Mostly in the convexities
All Traumatic hemorrhages at once
Intraparenchymal Hemorrhage Cortical (lobar) Deep (basal ganglia)
Basal ganglia hemorrhage
Basal ganglia = small vessel rupture usually due to chronic HTN
Lobar hemorrhage - multiple etiologies
Lobar hemorrhage = r/o vascular lesion VASCULAR LESIONS CAUSING ICH AVM DURAL AV FISTULA CAVERNOUS MALFORMATION VENOUS SINUS THROMBOSIS ANEURYSM Mycotic Blister Dissecting VASCULITIS
VASCULAR IMAGING CTA Advantages» Great spacial resolution Aneurysms Dissections Stenosis» Quick» Readily available Disadvantages» Radiation» Contrast MRA Advantages» No contrast» No radiation» Special sequencing for arterial wall Dissection Intraluminal clot Disadvantages» Less optimal spacial resolution» Prolonged acquisition» Motion artifact» Contraindicated in some implants
Good for LARGE lesions CTA MRA
Patient with posterior fossa ICH
CTA - negative
Angiogram The gold standard vascular imaging Most detailed Dynamic Invasive (0.5% risk of stroke) Therapeutic» The most advanced way to treat stroke
AVM Tiny residual post embolization Complete treatment with surgical resection
Vascular lesions requiring catheter angiogram AVM Dural AV Fistula Small (mycotic and blister ) aneurysms Vasculitis
Dural AV Fistula 15 % of all cerebral vascular malformation» Direct high-flow communication between dural veins and arteries» No intervening nidus (as opposed to AVM) Often missed on CTA or MRA Leading to hemorrhage due to high venous pressure Completely curable endovascularly Artery Vein
Patient with ICH and SAH CTA negative
Cervical Dural AV fistula No residual fistula after embolization with Onyx Microcatheter in the fistula
Aneurysmal subarachnoid hemorrhage - facts 10-15% of patients die before reaching the hospital 30-60% in-hospital mortality Lower at facilities with Interventional Neuroradiology Johnston S et al. Stroke. Jan 2000 80 % of survivors will have deficits Better outcome with dedicated Neuro ICU team Samuels et al, Neurocritcal Care 2001
Common location of cerebral aneurysms surrounding the circle of Willis. A, Middle cerebral (proximal to bifurcation, bifurcation, distal to bifurcation); (B) carotid terminus; (C) anterior choroidal; (D) superior hypophyseal; (E) anterior communicating (proximal to communicating artery, at communicating artery); (F) posterior communicating; (G) ophthalmic; (H) basilar artery (terminus, trunk); (I) superior cerebellar; (J) V4 segment, vertebral; (K) posterior inferior cerebellar; (L) pericallosal artery. Meyers P M et al. Stroke 2009;40:e366-e379 Copyright American Heart Association
Aneurysmal subarachnoid hemorrhage - imaging Blood is mostly in the cisterns and fissures, often accompanied by Intraventricular Hemorrhage (IVH) Hydrocephalus Cerebral edema Intraparechymal hemorrhage (IPH) Frontal lobe (A-comm) Temporal lobe (MCA)
SAH FIISHER GRADING SCALE 1 - No hemorrhage evident. 2 - SAH < 1mm thick 3 - SAH > 1mm thick 4 - SAH of any thickness with intra-ventricular hemorrhage (IVH) or parenchymal extension
ACA SAH pattern Blood in the interhemispheric fissure Hematoma in the corpus callosum IVH with hydrocephalus
Pericallosal Artery Aneurysm CTA
ANGIO with coiling
Vasospasm after SAH Diagnostic» TCD great screening and diagnostic tool» CTA or MRA may be used for confirmation of suspected vasospasm Diagnostic and therapeutic» Angiogram
Vasospasm after SAH
Vasospasm after SAH
Ischemic Stroke Imaging
The Ischemic Penumbra Core Infarct Ischemic Penumbra: zone of salvageable tissue surrounding core infarct
In a typical acute ischemic stroke, every minute the brain loses 1.9 million neurons 14 billion synapses 7.5 miles myelinated fibers -- Saver, Stroke 2006
Strategies in Acute Ischemic Stroke Therapy Proven» Recanalization» Supportive Care» Early Implementation of Secondary Prevention Experimental» Neuroprotection» Reperfusion via Collateral Enhancement
NINDS tpa Stroke Trials 1 and 2 p <.001 Hemorrhage tpa Placebo tpa Placebo Excellent Recovery (mrs 0-1) Death
Absolute imaging contraindication for IV TPA:»Evidence of intracranial hemorrhage In the first 3 hours virtually every patient has potentially salvageable tissue
Impact of Acute Ischemic Stroke Treatments NNT Benefit per 100 pts TPA 1-3h 3 32 Thrombectomy (ICA/M1) 5 20 TPA 3-4.5h 6 16 IA Lytics 7 14 Stroke Unit 10 10 Aspirin 77 1
Ticking Clock Tissue Clock
Tissue Status Perfusion Status Vessel Status CBV CT PCT CTA Multimodal CT Multimodal MRI DWI PWI MRA Bioenergetic Compromise Hemodynamic Compromise Occlusions or Stenoses
Non contrast head CT Hyperdense vessel No Evidence of early ischemic changes in the territory
Early ischemic changes Effacement of the sulci Obscuration between the gray/white matter junction
Completed infarct frank hypodensity
CT Perfusion Imaging Cerebral blood volume - for core Time to peak - for tissue at risk Mismatch (penumbra) = Core / Tissue at risk
Vessel status CTA Collateral filling in the L MCA No visible contrast in the L ICA
MRI best for acute stroke Diffusion weighted imaging (DWI) Bright area = completed infarction Identifies infarcted tissue within minutes of onset The gold standard for visualization of core
Multimodal MRI DWI: Very tiny area of completed infarction GRE: No hemorrhage FLAIR: L ICA hyperintensity PERFUSION: Large area of tissue at risk MRA: No flow in the L ICA
FLAIR or T2 best for subacute and old strokes DWI FLAIR
MRI for acute stroke Advantages: Most accurate evaluation of stroke size and location Detailed brain tissue evaluation Potential pitfalls: Time consuming Cost Contraindicated for some patients
Case # 1 65 y/o male with acute global aphasia and right sided hemiplegia (NIHSS 20) Presented to ED within 1 hour of onset On full dose anticoagulation (contraindication for IV TPA)
Hyperdense L MCA No early ischemic changes
CTA Head L M1 occlusion
CTA Neck: - Severe R ICA stensosis - Complete L ICA occlusion
Tiny channel within the occluded L ICA Catheter passed through the channel in the L ICA terminus Injection through the catheter confirmed L MCA occlusion
Complete reperfusion after one pass with the Solitaire Device
L ICA remained occluded at the neck, but the L MCA was getting flow form the R ICA across the A-comm Final Angiogram MRA the following day
Patient was walking and talking in full sentences within 24h (NIHSS = 2) DWI sequence: Small area of infarcted tissue in the L frontal operculum
R ICA stenosis Ulcerated plaque causing 80% stenosis
Successful CEA 2 weeks later
Case 2 50 y/o male with acute aphasia and R hemiplegia (NIHSS 22) Witnessed onset at work 911 called EMS transported the patient to primary stroke center within 15 min (Riverside county)
Non contrast head CT
Patient received IV TPA No improvement noted Transferred to UCI Arrived at UCI 4.5 hours after onset Repeat exam showed persistent global aphasia and R sided hemiplegia NIHSS 22
Occluded L ICA Large Mismatch
INR suite» within 60 minutes of CT completion
Solitaire FR
Follow up Substantial improvement within 24 hours:» Patient is moving the right side against gravity, comprehends and utters simple words = NIHSS 10
CT CBV CTA Day 0 NIHSS 22 MRI FLAIR MRA Day 5 NIHSS 10
Acute Ischemic Stroke Care in the 21 st Century Symptoms Call EMS Primary Stroke Center Imaging Multimodal Imaging Comprehensive Stroke Center EMS IV Lytic Telemedicine INR Cath Lab Angiogram IA Mechanical or Lytic Stroke Unit