Fact-sheet: Lipome encéphalique

Updated on 10/03/2018 at 9:34 AM

Note : 0/10

Definition

Benign tumor composed of fat cells.

No mass effect.

Vascular and neural structures course through the lesion.

Classic location: midline

Location: subarachnoid spaces:

Interhemispheric (50% of cases): anterior: rounded, >2 cm, associated in 90% of cases with agenesis or hypoplasia of the corpus callosum and absence of the septum pellucidum.
posterior: curvilinear, < 1 cm. Hypoplastic corpus callosum in 30% of cases.
Quadrigeminal: associated with a developmental defect of the inferior colliculus or superior vermis.
Suprasellar: associated with hypoplasia of the mammillary bodies.
Sylvian fissure

Epilepsy if located in the Sylvian fissure

Lesion of very low density, with values always negative (mean -60 HU).

Fatty lesions are better delineated on bone window.

Homogeneous MRI signal.

Characteristic intense T1 hyperintensity.
Intense T2 hyperintensity.
Fat sat sequence: signal isointense to gray matter (confirms its fatty nature)

Note the chemical shift artifact:

Suggests the fatty nature of the lesion
Artifact related to differences in resonance frequency between water and fat protons
Manifests as a shift along the frequency-encoding gradient axis.
Increases with field strength and lesion size
Spin echo: hyperintense band at the water-fat junction and hypointense at the fat-water junction
T1 gradient echo: hypointense rim surrounding the lesion; India ink artifact

Watchful waiting or surgery (to be avoided if possible)