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Fat Containing Lesions of the Brain PowerPoint Presentation

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On : Mar 14, 2014

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  • Slide 1 - Fat and Cholesterol Containing Intracranial Lesions Pat Farley, MD Neuroradiology Division, UNC
  • Slide 2 - Objectives To name fat containing lesions of the brain. Give differentiators of these lesions. Recognize associations and complications of these lesions. Recognize that dermoid and epidermoid do not look alike, just sound alike.
  • Slide 3 - Dermoid Cyst Unilocular cyst with thick walls of connective tissue Rare <0.5 % of intracranial tumors Clinical Issues Uncomplicated Dermoids: Headache (30%) Seizure (30%)
  • Slide 4 - Dermoids, Complications Rupture This can cause a chemical meningitis as the fat droplets spread within the subarachnoid space with resultant inflammatory changes. Larger lesions are associated with higher risk of rupture. Transformation Rarely can transform in to a malignant squamous cell cancer. Dermal sinus Can lead to infection.
  • Slide 5 - Dermoids, Imaging Appearance Well-circumscribed lipid containing masses Location Most often in sellar/parasellar/frontonasal region Posterior fossa; midline vermis & 4th ventricle May be intraventricular in lateral, 3rd, or 4th ventricles May also be located in spine and orbits Ruptured Dermoid Subarachnoid/intraventricular spread of fat contents Size Variable
  • Slide 6 - Dermoids, CT Appearance Non Contrast CT Classic Round/lobulated, well-delineated, cystic mass Fat hypodensity 20% contain capsular calcifications Rupture, droplets of fat disseminate in cisterns, may cause fat-fluid level within ventricles Atypical "dense" dermoid: Hyper attenuating on CT Skull/scalp dermoid expands diploic space Frontonasal - Bifid crista galli, large foramen cecum with possible sinus tract Post Contrast - No enhancement
  • Slide 7 - Dermoids, MRI T1 and T2: Hyperintense mass on T1WI. Heterogeneous signal on T2. Chemical shift artifact in frequency encoding direction Ruptured Dermoid Droplets very hyperintense on T1WI Fat suppression sequence confirms Fat-fluid level in cyst, ventricles common "dense" dermoid also hyperintense on T1WI
  • Slide 8 - Dermoid (large arrow, left) and fat droplets in SAS (arrows, right) are clearly seen.
  • Slide 9 - Dermoids, MRI with Contrast Unruptured No enhancement Ruptured Can have intense meningeal enhancement secondary to chemical meningitis. MR Spectroscopy Strong and broad resonances from mobile lipids at 0.9 and 1.3 ppm
  • Slide 10 - Dermoids, Angiography/MRA Vasospasm may be present with rupture Vessels encased by dermoid have an increased risk of rupture.
  • Slide 11 - Dermoids, Prognosis/Therapy Complete microsurgical excision Residual capsule may lead to recurrence Rarely surgical remnants may degenerate in to squamous cell cancer Subarachnoid dissemination of contents may occur during operative/postoperative course Cause aseptic meningitis or other complications (hydrocephalus, seizures, CN deficits) Disseminated fat particles can remain silent without neurologic changes
  • Slide 12 - Dermoid vs. Epidermoid Epidermoid = congenital inclusion cyst Usual appearance is similar to CSF Appearance is not identical to CSF however FLAIR usually does not completely suppress T1/T2 may be slightly off, CISS/FIESTA show internal structures Diffusion restriction is key Can see internal structures on CISS imaging Mass interdigitates in cisterns, and encases nerves and vessels. Most common differential for epidermoid is arachnoid cyst.
  • Slide 13 - Epidermoid in left CPA cistern is similar to CSF but not exactly like it. Note internal structures.
  • Slide 14 - DWI shows high signal from this epidermoid in the left CPA cistern.
  • Slide 15 - Epidermoid that could be confused with Dermoid Rare variant Uncommonly hyperintense to brain ("white epidermoid") due to high triglycerides & unsaturated fatty acids
  • Slide 16 - Epidermoid vs. Arachnoid Cyst Diffusion is key Epidermoid is restricted Arachnoid cyst is not Also epidermoids insinuate into adjacent tissues, arachnoid cysts tend to displace them.
  • Slide 17 - Left middle cranial fossa arachnoid cyst shows no enhancement and no restricted diffusion on ADC map (right).
  • Slide 18 - Craniopharyngioma Benign epithelial tumor derived from Rathke’s pouch epithelium Two Types: Adamantinomatous type (classic) hyperintense cyst and heterogeneous nodule More common in children (first age peak) Papillary type (more rare) isointense solid component More common in adults (second age peak)
  • Slide 19 - Imaging of Adamantinomatous Craniopharyngioma CT: Partially calcified, partially solid, cystic suprasellar mass MR : T1 without Gd High signal intensity suprasellar mass on pre-contrast T1WI (protein, cholesterol, blood products in fluid) T1 with Gd: Solid portions enhance heterogeneously, cyst walls enhance strongly.
  • Slide 20 - Nearly cystic craniopharyngioma in the suprasellar space.
  • Slide 21 - Craniopharyngioma, Locations Relation to Sella Suprasellar (75%) Suprasellar and intrasellar components (21%) Entirely intrasellar (4%) Often extend into multiple cranial fossae: Anterior (30%), middle (23%), posterior and/or retroclival (20%) Rare locations : Optic chiasm, 3rd ventricle Nasopharynx, pineal gland, sphenoid (sinus, clivus)
  • Slide 22 - Craniopharyngioma, Other Imaging Appearances Variable size often large at presentation (> 5 cm) Effect on surrounding brain Hyperintense signal in brain parenchyma adjacent to tumor Gliosis, tumor invasion, irritation from leaking cyst fluid Edema from compression of optic chiasm/tracts
  • Slide 23 - Teratoma Midline mass calcium, soft tissue, cysts, and fat Locations: Midline from optic chiasm to pineal gland Supratentorial most commonly
  • Slide 24 - Teratoma, CT CT without contrast Hyper, iso- and hypo-dense components of fat, fluid, soft tissue, and calcification Post Contrast Soft tissue components enhance
  • Slide 25 - Teratoma, MRI T1WI Hyperintense signal from fat Variable signal from calcium MR helps characterizes relationship of teratoma to midline structures
  • Slide 26 - Two examples of mature 3rd ventricular and suprasellar teratomas show cysts, solid components, and fat on non contrast studies.
  • Slide 27 - Teratoma, Prognosis Depends on size and location Benign vs. Malignant 5 year survival for malignant teratomas is 18%
  • Slide 28 - Teratoma, Variant Holocranial Teratoma in newborns Be suspicious of it in a newborn with an intracranial mass replacing nearly all normal brain tissue.
  • Slide 29 - Lipomas Mass made up of mature non-neoplastic adipose tissue Congenital malformations, not true neoplasm Arise from malformation of cells in primitive subarachnoid space (meninx primitiva)
  • Slide 30 - Lipomas, Location Midline location common Supratentorial 80% 40-50% interhemispheric fissure (over corpus callosum) may extend into lateral ventricles, choroid plexus 15-20% suprasellar attached to infundibulum, hypothalamus 10-15% pineal region usually attached to tectum Uncommon Meckel cave, lateral cerebral fissures, middle cranial fossa 20% infratentorial Cerebellopontine angle may extend into IAC, vestibule Uncommonly in jugular foramen, foramen magnum
  • Slide 31 - Lipomas, Imaging CT -50 to -100 H (fat density) Calcification varies from none to extensive MRI Hyperintense on T1WI Hypointense with fat suppression Striking chemical shift artifact on T2WI Enhancement None
  • Slide 32 - Two examples of pericallosal lipomas. Left: nodular type with callosal agenesis. Right: tubular with normal corpus callosum.
  • Slide 33 - Lipomas, Vascular Imaging Angiographic Findings Conventional ACA courses directly superiorly if CC agenesis present Arteries & veins often embedded within lipoma Similar findings may also be seen with MRA
  • Slide 34 - Lipomas, Morphology Interhemispheric lipomas Curvilinear type Thin, curves around CC body, splenium Tubulonodular type Bulky mass frequent calcification, usually associated with corpus callosal dysgenesis
  • Slide 35 - Neoplasms with Fat Lipomatous differentiation/transformation of neoplasm Neuroectodermal tumors PNETs, ependymoma, gliomas is rare Cerebellar liponeurocytoma Mixed mesenchymal/neuroectodermal posterior fossa neoplasm Primarily hypointense on T1WI, mixed with hyperintense foci with patchy, irregular enhancement Meningioma lipomatous transformation is uncommon
  • Slide 36 - Lipomatous Transformation of Meningioma Mature adipocytes from metaplasia and meningioma or from production of triglycerides by cells Rare variant of meningioma CT Heterogeneous with heterogeneous enhancement Can mimic necrotic malignant tumors Demonstration of fat attenuation suggests a benign process but differential diagnosis of an extra-axial fat-containing tumor should include lipomatous meningioma.
  • Slide 37 - Summary Dermoid Hyperintense on T1 can be heterogeneous on T2. No enhancement. Lipoma Hyperintense on T1, no enhancement, can have calcifications, look for CC dysgenesis Craniopharyngioma Contains hyperintense T1 cholesterol/blood products, soft tissue, cystic structures and calcification, enhances Teratoma Contains hyperintense T1 fat, soft tissue, cystic structures and calcification, enhances

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