Monday 21 November 2011

Intracranial lipoma

MRI Brain Axial T1, T2 and FLAIR. 
This MRI study of brain shows:
A focal extra axial fat in the groove between Pons and right cerebellar hemisphere, follow same signal as that of sub cutaneous fat on MRI, hyper intense on T1 as well as T2w and FLAIR images.
T1 bright tissue or lesions are very few for example fat and Meth Hb ' a sub acute stage blood degradation product'.
In such situation low 'fat' density on CT is very definitive of Lipoma.

Intracranial lipoma 

Syn : Lipomatous hamartomas, as normally fat not present in CNS.
A congenital malformation , not true neoplasm.
Contributes < 0.5% of all intracranial tumors.
A focal fat density (dark 'z' black) on CT or fat signal intensity (white on T1w image) and is often out standing in the background of adjacent normal grayish brain parenchyma.
Noted as an isolated incidental finding or as part of an associated anomalies. Most common anomaly associated is Corpus callosal agenesis or dysgenesis.

Most common location is supra tentorium ~80%. In that most common location is mid line along corpus callosum ~ 50%, Suprasellar cistern attached to infundibulum, hypothalamus ~ 20%,  Pineal region ~15%. Meckel's cave and lateral fissures are rare locations.
Infra tentorium contributes remaining 20%, in that common locations are Cp angles, jugular foramen and foramen magnum.

Two types of intracranial lipoma:
1. Curvilinear type is a thin stripe along CC.
2. Tubulonodular type is a bulky nodular mass, frequently show dense nodular calcifications, and often associated with Corpus callosal or adjacent parenchymal anomalies.

Related posts:
Lipoma along Trigeminal nerve
Lipoma at incisura
Lipoma along normal Corpus callosum
Lipoma with Corpus callosal malformation

Reference : Anne G Osborn 

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