Imaging in Neurology

Perimesencephalic Nonaneurysmal Subarachnoid Hemorrhage (pnSAH)

KEY FACTS Terminology Subarachnoid hemorrhage (SAH) centered immediately anterior to midbrain ± pons No source demonstrated at CTA/DSA/MRA Imaging NECT: Hyperdense prepontine, perimesencephalic cerebrospinal fluid (CSF) Often involves interpeduncular, ambient, quadrigeminal cisterns ± thin extension into posterior suprasellar, proximal sylvian/interhemispheric…

Aneurysmal Subarachnoid Hemorrhage

KEY FACTS Terminology Subarachnoid hemorrhage (SAH) caused by ruptured aneurysm (aSAH) Saccular aneurysm (SA) > > dissecting aneurysm (DA) Imaging CT/CTA Hyperdense sulci on NECT Distribution varies with aneurysm location Suprasellar cistern (IC-PCoA, ACoA aneurysms) Sylvian fissure (middle cerebral artery…

Deep Cerebral Venous Thrombosis

KEY FACTS Terminology Thrombotic occlusion of deep cerebral veins Usually affects both internal cerebral veins (ICVs) ± vein of Galen (VOG), straight sinus (SS) May occur with more widespread dural sinus thrombosis Imaging NECT Hyperdense ICV ± VOG, SS Hypodense…

Cortical Venous Thrombosis

KEY FACTS Terminology Cortical/cerebral venous thrombosis (CVT) Dural sinus thrombosis (DST) CVT with DST > isolated CVT without DST Imaging NECT Cord sign (hyperdense vein) Involved veins usually enlarged (distended with clot), irregular ± petechial parenchymal hemorrhage, edema CECT If…

Cavernous Sinus Thrombosis/Thrombophlebitis

KEY FACTS Terminology Cavernous sinus (CS) Blood clot in CS Imaging CT Bone CT – Look for sinus infection, erosive changes CECT – Nonenhancing filling defects (clot) inside enhancing dural walls of cavernous sinus (CS) – CS margins convex (not…

Dural Sinus Thrombosis

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…

Cerebral Hyperperfusion Syndrome (CHS)

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,…

Lacunar Infarction

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…

Fat Emboli Cerebral Infarction

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…