KEY FACTS Imaging General features Empty-delta sign on CECT, T1WI C+ MR CT Hyperdense sinus on NECT (usually > 70 Hounsfield units) ± hyperdense cortical veins (cord sign) CTV: Filling defect (thrombus) in dural sinus MR Hypointense thrombus “blooms” on T2* GRE Absence of flow in occluded sinus on 2D TOF MRV Protocol recommendations NECT, CECT scans ± CTV as initial screening If CTs negative, MR…

KEY FACTS Terminology Rare (1-3%) disorder most commonly occurring as complication of cerebral revascularization Other etiologies less common – Status epilepticus – MELAS Major increase in ipsilateral cerebral blood flow (CBF) well above normal metabolic demands Imaging Ipsilateral gyral swelling, sulcal effacement in post-carotid endarterectomy (CEA) patient ↑ CBF, CBV on perfusion MR, perfusion CT Top Differential Diagnoses Acute cerebral ischemia-infarction Status epilepticus MELAS Acute hypertensive…

KEY FACTS Terminology Small, deep cerebral infarcts located in basal ganglia and thalamus, pons, or cerebral white matter (WM), ≤ 15 mm Imaging Commonly deep gray nuclei, especially putamen, thalamus, caudate nuclei; internal capsule, pons Other locations include deep and periventricular WM Range in size from microscopic to 15 mm Because of small size, most acute lacunar infarcts are not seen on CTs Acute: T2/FLAIR increased…

KEY FACTS Terminology Acute stroke related to fat emboli Imaging Acute ischemia with appropriate clinical history Long bone or pelvic fractures, cardiac surgery, joint replacement surgery Often mimics thromboembolic stroke Commonly affects both gray and white matter May affect deep and periventricular white matter May affect deep gray nuclei May involve typical vascular territory May mimic “watershed” infarct NECT: Typically negative acutely Hypodense MCA sign related…

KEY FACTS Terminology Infarcts in multiple arterial distributions from embolic source, often cardiac origin Imaging Best imaging clue: DWI restriction in multiple vascular distributions NECT: Multiple regions of low attenuation, loss of gray-white differentiation T2/FLAIR: Multiple supratentorial and infratentorial regions of hyperintensity, often in vascular distribution May be of different ages Embolic infarcts tend to involve terminal cortical branches, producing wedge-shaped infarcts Cardiac echocardiography may show…

KEY FACTS Imaging Volume loss with gliosis along affected margins Classic: Wedge-shaped area of encephalomalacia Territorial infarction Involves brain supplied by major cerebral artery Watershed infarction Involves brain between main vascular territories Lacunar infarction(s) Most common in basal ganglia/thalami, deep white matter Top Differential Diagnoses Porencephalic cyst Arachnoid cyst Postsurgical/posttraumatic encephalomalacia Low-attenuating tumors Pathology Volume loss, gliosis are pathological hallmarks Clinical Issues Elderly patient with typical…

KEY FACTS Terminology Subacute infarction ~ 2-14 days following initial ischemic event Imaging Best diagnostic clue: Gyral edema and enhancement within basal ganglia and cortex Typically wedge-shaped abnormality involving gray and white matter within vascular distribution Hemorrhagic transformation of initially ischemic infarction occurs in 20-25% of middle cerebral artery occlusions, usually by 48-72 h “2-2-2” rule = enhancement begins at 2 days, peaks at 2 weeks,…

KEY FACTS Terminology Interrupted blood flow to brain resulting in cerebral ischemia/infarction with variable neurologic deficit Imaging Major artery (territorial) infarct Generally wedge-shaped; both GM and WM involved Embolic infarcts Often focal/small, at GM-WM interface NECT Hyperdense vessel = clot (dense middle cerebral artery sign) Loss of GM-WM distinction in first 3 hours (50-70%) – Insular-ribbon sign: GM-WM interface lost – Disappearing basal ganglia sign Calcified…

KEY FACTS Terminology Acute alteration of neurologic function due to loss of vascular integrity Imaging Best imaging MR with diffusion, perfusion, MRA MRV if MRA negative and DWI positive Can do emergent “limited” MR (FLAIR, DWI, SWI) Imaging findings CT – Insular-ribbon sign = loss of distinction of insular cortex – Hyperdense MCA sign = increased density of thrombosed MCA – Look for calcified emboli (suggests…

KEY FACTS Terminology Hypotensive cerebral infarction (HCI) Infarction resulting from insufficient cerebral blood flow (CBF) to meet metabolic demands (low-flow state) 2 types of border zone or watershed infarcts – Border zone between major arterial territories □ Typically at cortex, gray matter (GM)-white matter (WM) junctions – Border zone between perforating arteries □ Typically in deep WM Imaging Best imaging tool MR with DWI/ADC ± MR…

KEY FACTS Terminology Hypoxic ischemic injury (HII): Global hypoxic ischemic injury, global anoxic injury, cerebral hypoperfusion injury Etiologies: Cardiac arrest, cerebrovascular disease, drowning, asphyxiation Imaging Injury patterns highly variable depending on brain maturity, severity, and length of insult Mild to moderate: Watershed zone infarcts Severe: Gray matter structures (basal ganglia, thalami, cortex, cerebellum, hippocampi) MR best to assess overall extent of injury within hours after HII…

KEY FACTS Terminology Vertebral artery (VA) dissection Irregularity of VA contour from intimal tear or subadventitial hematoma Imaging Stenoocclusive dissection Dissection to subintimal plane with vessel luminal narrowing or occlusion Dissecting aneurysm Dissection into subadventitial plane with dilatation of outer wall Intramural hematoma is pathognomonic Best seen as bright crescent on T1 FS MR CTA source images show contour changes of lumen Conventional angiography is gold…

KEY FACTS Terminology Internal carotid artery (ICA) dissection (ICAD) ICAD: Tear in ICA wall allows blood to enter & delaminate wall layers Imaging Pathognomonic findings of dissection: Intimal flap or double lumen (seen in < 10%) Aneurysmal dilatation seen in 30% Commonly in distal subcranial segment of ICA Focal pseudoaneurysm unusual Flame-shaped ICA occlusion (acute phase) ICAD most commonly originates in ICA 2-3 cm distal to…

KEY FACTS Terminology Fibromuscular dysplasia (FMD) Arterial disease of unknown etiology Overgrowth of smooth muscle, fibrous tissue Affects medium/large arteries Imaging Renal artery is most common overall site (~ 75%) Cervicocranial FMD (~ 70%) Internal carotid artery (ICA) (30-50%) > external carotid artery > vertebral arteries (10-20%) Carotid bifurcation is typically spared > 50% of cases are bilateral Intracranial rare (supraclinoid ICA, middle carotid artery) CTA…

KEY FACTS Terminology Microangiopathy of brain, retina, and cochlea Imaging T2 hyperintense corpus callosum lesions in patient with clinical triad Encephalopathy, bilateral hearing loss, and branch retinal artery occlusions Multifocal T2 hyperintensities similar to MS More often round, midcallosal rather than callososeptal location May involve brainstem, basal ganglia, thalamus, subcortical white matter, centrum semiovale Lesions may show acute diffusion restriction Variable enhancement of lesions and leptomeninges…

KEY FACTS Terminology Chronic, idiopathic relapsing-remitting multisystem vascular-inflammatory disease characterized by recurrent orogenital ulcerations and uveitis CNS involved in up to 20-25% of patients Imaging Best diagnostic clue: T2 hyperintense brainstem lesion in patient with oral and genital ulcers Midbrain > pons > basal ganglia > thalami > white matter Focal or multifocal lesions May see expansion of involved structures acutely T2WI: Hyperintense lesions T1WI C+:…

KEY FACTS Terminology C erebral A utosomal D ominant A rteriopathy with S ubcortical I nfarcts and L eukoencephalopathy ( CADASIL ) Hereditary small-vessel disease due to mutations in NOTCH3 gene on chromosome 19, which causes stroke in young to middle-aged adults Imaging Diffuse white matter (WM) hyperintensities = leukoaraiosis, early finding Multiple lacunar infarcts Anterior temporal pole, external capsule, and paramedian superior frontal lobe highly…

KEY FACTS Terminology Cerebral amyloid deposition occurs in 3 morphologic varieties Common: Cerebral amyloid angiopathy (CAA) Uncommon: Mass-like lesion (amyloidoma) Rare: Inflammatory; diffuse (encephalopathic) white matter involvement Imaging General findings Normotensive demented patient Lobar hemorrhage(s) of different ages Multifocal “black dots” on T2* or SWI MR Protocol advice Best initial screening (for acute hemorrhage) = CT MR with T2* &/or SWI Top Differential Diagnoses Multifocal “black…

KEY FACTS Terminology Systemic lupus erythematosus (SLE), neuropsychiatric (NPSLE), CNS lupus Multisystem autoimmune disorder that affects respiratory, cardiovascular, GI, GU, musculoskeletal systems, and CNS CNS involved in up to 75% Imaging 4 general patterns New infarcts (associated with ↑ anticardiolipin, ↑ lupus anticoagulant antibodies) Focal areas of hyperintensity, primarily in gray matter Multiple T2WI hyperintensities (microinfarctions) Extensive, reversible white matter (WM) changes (cerebral edema) Multifocal WM…

KEY FACTS Terminology Reversible stenosis of intracranial arteries Common with aneurysmal subarachnoid hemorrhage (SAH) Caused by exposure to blood breakdown products Contraction of vascular smooth muscle Histological changes in vessel wall Imaging General features (CTA/MRA/DSA) Typically occurs 4-14 days after SAH Smooth, relatively long segmental stenoses Seen as arterial luminal irregularity/undulations Multiple arteries, usually > 1 vascular territory CT perfusion ↑ time to peak, ↑ mean…