A young male patient with right sided trigeminal neuralgia clinically.
MRI study of Brain (Axial FLAIR, T2w, T1w, T2*GRE and STIR)
A lobulated well circumscribed T1 hyper intense tissue at right CP angle extending in middle cranial fossa in right para sellar region through Meckel’s cave, along the course of Trigeminal nerve giving it a so called dumbbell shape.
Signals are isointense to subcutaneous fat on T1w and T2w images with complete signal suppression on STIR corresponds to 'fat', it’s a lipoma. Low signals on T2w *GRE is due to an associated calcification which is known.
Right side trigeminal nerve seen separately lateral to the lipoma stretched and displaced. Basillar is close and medial to the Lipoma.
No brain stem compression. No parenchymal invasion.
Imaging diagnosis : Meckel's Cave Lipoma causing Trigeminal nerve compression, presenting as Trigeminal Neuralgia.
Intracranial-lipoma lateral to Pons
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.