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Lipoma

KEY FACTS Terminology Intracranial lipoma (ICL) Mass of mature adipose tissue (congenital malformation, not true neoplasm) Imaging Well-delineated lobulated extraaxial mass with fat attenuation/intensity CT: -50 to -100 Hounsfield units (HU) (fat density); Ca++ varies from none to extensive MR: Hyperintense on T1WI (becomes hypointense with fat suppression); may encase vessels and cranial nerves; often occurs with corpus callosum dysgenesis 80% supratentorial 40-50% interhemispheric fissure (over…

Callosal Dysgenesis

KEY FACTS Terminology Partial or complete absence of corpus callosum (CC), hippocampal commissure, or anterior commissure (AC); can be isolated or associated with additional cerebral malformations Spectrum of congenital CC structural abnormalities Total agenesis (absence from birth of all anatomically defined regions of CC) Partial agenesis (absence from birth of at least 1, but not all, regions of CC) Hypoplasia (thinner CC with normal anteroposterior extent)…

Chiari 2

KEY FACTS Terminology Complex hindbrain malformation Virtually 100% associated with neural tube closure defect, usually lumbar myelomeningocele (MMC) Imaging Crowded posterior fossa, widened tentorial incisura, tectal beaking, inferior vermian displacement Cascade or waterfall of cerebellum/brainstem downward Uvula/nodulus/pyramid of vermis → sclerotic peg Cervicomedullary kink (70%) Towering cerebellum → compresses midbrain, associated beaked tectum 4th ventricle elongated with no posterior point (fastigium) Lacunar skull: Focal calvarial thinning…

Chiari 1

KEY FACTS Terminology Chiari 1 malformation (CM1): Constellation of findings (not disease, not simply measurement) No clear consensus definition of what constitutes CM1 Traditional: Elongated, peg-shaped cerebellar tonsils extend below foramen magnum (FM) into upper cervical spinal canal 5-mm criterion for tonsillar position (TP) below FM is flawed criterion – TP is morphometric distribution, also changes with time – TP plus shape/configuration (elongated, pointed) – TP…

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Hepatic Adenoma

KEY FACTS Imaging Key features (not always present): Hypervascular, fat-containing, hemorrhagic, encapsulated MR shows some elements better than CT (lipid & hemorrhage) T1WI: Mass: Heterogeneous signal intensity – Increased signal intensity (due to fat or recent hemorrhage) – Decreased signal intensity (necrosis, calcification, old hemorrhage) T2WI: Mass: Heterogeneous signal intensity – Increased signal intensity (old hemorrhage, necrosis) – Decreased signal intensity (fat, recent hemorrhage) Gadoxetate-enhanced MR…

Hepatic Transplantation

KEY FACTS Terminology Orthotopic liver transplantation (OLT) Imaging Allograft rejection No reliable imaging findings to suggest or confirm diagnosis Biliary leak From entry of T tube: Easily treated From biliary anastomosis: Requires revision From intrahepatic ducts: Biliary necrosis; catastrophic Biliary obstruction Responds to balloon dilation & stenting Hepatic artery (HA) stenosis US: Damped waveform in HA distal to stenosis: Slow systolic upstroke; decreased resistive index (RI)…

Transjugular Intrahepatic Portosystemic Shunt (TIPS)

KEY FACTS Terminology Shunt between main portal vein and hepatic vein created with balloon-expandable metallic stent Imaging US is primary imaging tool following t ransjugular intrahepatic portocaval shunt (TIPS) Goal of US: Detect stenosis before shunt occludes or symptoms recur Echogenic stent easily seen on US but does not block sound transmission Color Doppler shows patency and flow direction within TIPS, portal vein, hepatic veins, and…

Budd-Chiari Syndrome

KEY FACTS Terminology Hepatic injury due to global or segmental hepatic venous outflow or inferior vena cava (IVC) obstruction Imaging Multiphasic CT, or MR [± gadoxetate (Eovist) enhancement] Characteristic findings: Nodular regenerative hyperplasia in dysmorphic liver with venous collateral and ascites Hypertrophied caudate lobe with atrophy and necrosis of peripheral liver ("pseudotumor") Intrahepatic and systemic venous collaterals bypass obstructed hepatic veins and IVC – Spider web…