Acute stroke imaging

Acute stroke imaging

Aims Imaging modalities and differences Why image acute stroke Clinical correlation to imaging appearance

What is stroke Classic definition: acute focal injury to the central nervous system (CNS) by a vascular cause Diagnosis-documentation Pathological, imaging or other objective evidence of CNS ischemic injury Clinical evidence of CNS injury lasting > 24 hr or until death Stroke types CNS infarction, ischemic stroke, silent CNS infarction Intracerabral hemorrhage, silent intracerebral hemorrhage Subarachnoid hemorrhage Central venous thrombosis Sacco RL et. al. Stroke 2013;44:2064-2089

Stroke statistics Frequency US 5th cause of death Approximately 795,000 strokes per year 610,000 new 185,000 recurrent Leading cause of long-term disability in US Subtypes management different Ischemic 87% ICH 10% SAH 3% Circulation 2015;132:000-000

Age adjusted incidence Stroke/ TIA Circulation 2015;132:000-000

Imaging modalities stroke Anatomic Cross-sectional Vascular Functional Perfusion

Cross-sectional - CT Strengths Identification of acute hemorrhage Rapid No contraindications Physiologic monitoring easy Limitations Limited identification acute ischemic infarct Ionizing radiation

Cross-sectional - MRI Strengths Early identification acute ischemic infarct Anatomic detail Tissue specificity No ionizing radiation Limitations Slow (relatively) Patient motion problematic Physiologic monitoring difficult Blood signal is complex Patient contraindications

Contraindications to MR Pacemakers Metal in eyes Aneurysm clips Stents, other devices* Neuro-stimulators** Indwelling pumps** Renal failure*** Claustrophobia * Time limitations, device limitations ** Control issues

Patient motion No drugs Drugs

Acute stroke imaging #1 84 y Korean speaking woman, headache, dizziness, weakness, agitation Exam L hemiparesis, awake, talking Diagnostic issues Localization? Kind of stroke?

If the initial imaging is MRI Imaging diagnosis T1 Diffusion Location Subinsular (R lateral lenticulostriate a.) Type Hemorrhagic Age Acute vs. subacute FLAIR T2

If the initial imaging is CT and CTA Imaging diagnosis CT CTA Location Subinsular (R lateral lenticulostriate a.) Type Hemorrhagic Age Acute FLAIR DIFFUSION

Intracranial hemorrhage within brain Appearance over time CT Density reflects protein in Hgb molecule Acute blood: dense Subacute blood: decreasing density Chronic blood: encephalomalacia MR Signal reflects biochemical state of Hgb molecule T1 and T2 change with metabolic changes in Hgb

Imaging appearance of blood MR Form of Hemoglobin T1 signal T2 signal Oxyhemoglobin Isointense to brain Higher signal than brain Deoxyhemoglobin Lower signal than brain Lower signal than brain Intracellular methemoglobin Lower signal than brain Iso to-higher signal than brain Extracellular methemoglobin Higher signal than brain Hemosiderin Lower signal than brain Lower signal than brain Higher signal than brain

Acute intra-parenchymal hemorrhage: CT vs. MR Day 1-2 48 hours T1 T2 FLAIR Gradient/ SWI

Subacute hemorrhage 4 days T1 Deoxyhemoglobin Intracellular methemoglobin T2 FLAIR

Late subacute hemorrhage 19 days Deoxyhemoglobin Intracellular methemoglobin Extracellular methemoglobin Hemosiderin

In practice, both CT and MR are used for ischemic infarct imaging CT Acute presentation Hemorrhage Follow-up: ventricular size, shift, etc MR Infarct extent Acute vs. chronic ischemia Chronic micro hemorrhage

Acute ischemic infarct CT appearance Sulcal effacement Loss gray / white differentiation Hyperdense vessel No contrast enhancement Visibility 4-12 hours Scan may be normal

Acute infarct - CT appearance Admission 24 hours

Acute infarct - CT appearance Hyperdense M1, insular ribbon sign

Acute ischemic infarct MR appearance Sulcal effacement Abnormal signal Diffusion, T2-weighted, FLAIR Visibility Diffusion 1 hour - 10 days FLAIR 4 hours T2 4-8 hours

Diffusion weighted imaging Motion of water (protons) Translational movement of water molecules Distance - 10 microns (cell dimensions) Restricted diffusion Decreased movement of water Decreased extra-cellular space Membrane disruption May reflect cell death Mukherjee P. et al, AJNR 29;2008: 632-641

Acute infarct Restricted diffusion Imaging Increased signal diffusion images Decreased diffusivity (ADC, e-adc maps) Causes Cell death Acute infarct (immediate - 10 days) Abscess Acute MS plaque (rare) Contusion (rare) Epidermoid

DWI images & ADC maps DWI FLAIR ADC Map e-adc map

Acute stroke imaging #2 72 yo with RA, using a walker. Hx of spondyloarthropathy Exam Acute on chronic weakness, L> R Diagnostic question New infarct vs. worsening of spondyloarthropathy and chronic weakness

MR showed chronic white matter changes DWI showed new acute lacunar infarct FLAIR T2 DWI

Acute ischemic infarct MR more sensitive than CT Smaller infarcts visible Earlier infarct visible CT FLAIR DWI Timing of infarct visibility sequence dependent Diffusion > FLAIR > T2

Vascular imaging ischemic infarct CTA / MRA Reasonable vascular detail Large vessel occlusion clear Contrast required CTA MRA neck (not required for MRA head) Catheter angiography Required for intra-arterial treatment Good vascular detail Invasive Inherent stroke risk Expensive

Acute stroke imaging #3 61 yo male, H/o DM, Hep C, PVD, IVDU Normal in front of hotel at 0700. Exam R hemiplegia, R hemianesthesia, R facial droop, L gaze deviation and worsening aphasia NIHSS 27 Diagnostic issues Location? Intervention?

Initial imaging CT CTA

MRA (different patient) 66 year old male posterior circulation infarct, worsening visual changes

Acute stroke imaging #4 71 yo woman awake, alert, talking and eating Possible sz at 8 pm, found down at 9:30 pm Exam L hemiparesis NIHSS 22 Diagnostic issue Location of infarct Acute treatment?

ED management, Imaging Standard window Stroke window Treatment IV tpa at 11:34 pm IA treatment 1 am CTA

Criteria for intra-arterial thrombolysis Time from onset Imaging appearance ASPECTS score Anterior circulation Large vessel occlusion NIHSS and clinical exam No contraindications

ASPECTS score (Alberta Stroke Program Early Computed Tomography Scale) A=anterior circulation; P=posterior circulation; C=caudate; L=lentiform; IC=internal capsule; l=insular ribbon; MCA=middle cerebral artery; Ml=anterior MCA cortex; M2=MCA cortex lateral to insular ribbon; M3=posterior MCA cortex; M4, M5, M6 = anterior, lateral and posterior MCA territories superior to M1, M2, and M3 Lancet 355 (9216); 2000:1670 1674

Imaging evaluation for stroke treatment IV thrombolysis ASPECTS score >7 correlated to functional outcome (better) and less hemorrhage (<1%) IA thrombolysis ASPECTS score used for MR CLEAN Only completed evidence Collaterals, perfusion (RAPID) Insufficient evidence- studies stopped early NEJM 2015;372:11-20 NEJM 2015;372:1019-30 NEJM 2015;372: 1009-1018

Intra-arterial treatment Pre-treatment Post-treatment Discharge Improved hemiparesis, dysarthria

Acute stroke imaging #5 65 yo male, h/o hypertension, DM, coronary disease Went to bed at 9 pm, heard to fall out of bed at 2 am Exam (4:30 am) Aphasic, R hemiparelgia, NIHSS = 23 Diagnostic issue Acute intervention?

Admission CT, CTA M1 occlusion

Treatment decision no intervention No collaterals Outside treatment time window RICA occlusion M1 occlusion No collaterals

Acute stroke imaging #6 57 yo male, hypertensive. Severe HA, took ASA, then had sz. Exam Somnolent, arousable, followed some commands bilaterally, moving all extremities Diagnostic issue Location, type of stroke

Intraparenchymal hemorrhage CT Spot sign CTA 1st pass Delayed

IPH and outcome Hemorrhage volume / GCS predictive of 30 day mortality Volume <30cc 30-60cc >60cc <30cc 30-60cc >60cc GCS >9 >9 >9 <8 <8 <8 Predicted mortality 19% 46% 75% 44% 74% 91% Broderick JP et al, Stroke 1993:24: 987-993

Spot sign Predictor of hematoma expansion Expansion and mortality are different Ave rate of expansion and hematoma size independent predictors of mortality Accuracy(single study example) Pos predictive value 61% Neg predictive value 78% Sensitivity 51% Specificity 85% Demchuk AM et al. Lancet Neurol 2012;11,307-

Causes intra-parenchymal hemorrhage Underlying cause and common locations Hypertension Basal ganglia Cerebellum, pons Amyloid Lobar Aneurysm Subarachoid > IPH Tumor, subacute infarct Intra-lesion/abnormality AVM Near AVM Vasculitis, drugs No clear distribution HTN HTN Amyloid HTN SAH

Intraparenchymal hemorrhage - 63 y male Hypertension

Intraparenchymal hemorrhage - 28 y male Vascular malformation

Intra-parenchymal + subarachnoid hemorrhage

Subarachnoid hemorrhage Acute imaging CTA Catheter angiography Non-acute imaging MRA CTA Catheter angiography Treatment Surgical Endovascular

Acute stroke imaging #7 59 yo woman, worst HA of life Exam LOC, GCS 3 Diagnostic issue Cause

Subarachnoid hemorrhage : CT, CTA Posterior communicating artery aneurysm

Aneurysm detection by size CTA Goddard AJP et al. Clinical Radiology (2005) 60, 1221 1236

Aneurysm detection by location CTA vs MRA Sailer AMH et al. Stroke 2014;45:1190=126

Subarachnoid hemorrhage CTA Posterior communicating artery aneurysm Catheter angio

SAH grading- vasospasm occurence Fisher scale-modified Fisher scale Thickness of cisternal blood Presence of IVH Rosen, Mcdonald Neurocrit Care2005;2:110-118

Subarachnoi d hemorrhage Pericallosal aneurysm Mod. Fisher 1 CT CTA Catheter angio

Subarachnoid hemorrhage MCA aneurysm Mod. Fisher 4 Post-clip catheter angio

Summary Causes of acute stroke Infarct Intraparenchymal hemorrhage Subarachnoid hemorrhage Similar presentation possible Seizure Masses

Summary Imaging acute stroke Imaging modalities and differences CT / CTA initial imaging modality MRI / MRA usually second Angio for treatment Why image stroke Distinguish ischemic vs. IPH vs. SAH Acute mangement Later management / etiology