Cerebellopontine angle lipoma

Case contributed by Carolina Diaz

Presentation

Progressive hearing loss and tinnitus.

Patient Data

Age: 20 years
Gender: Female

Axial CT with contrast. Extra-axial lesion at the right cerebellopontine angle, lateral to the middle cerebellar peduncle, with smooth margins and rounded shape, homogeneously hypodense (HU of -92). The anterior inferior cerebellar artery (AICA) is encased by the lesion. A complimentary MRI must be acquired to evaluate nerve encasement.

MRI

Extra-axial mass at the right cerebellopontine angle, well-circumscribed, with a rounded shape and high intensity on T1, T2 images, with signal suppression on FLAIR images, no restricted diffusion, compatible with fat tissue. The lesion englobed the AICA, with the facial and the vestibulocochlear nerve coursing through it. 

Case Discussion

Intracranial lipomas are benign congenital malformations. 

CT Features: extra-axial lesion with smooth margin and pure fat density is consistent with the diagnosis of cerebellopontine (CPA) angle lipoma. 

MRI Features: Smooth margins extra-axial lesion with high signal on T1W and T2W images, with signal suppression on FLAIR and chemical shift artifact. The lesion shows a homogeneous signal, with artery and nerve encasement. The importance of the MRI is to determine the anatomical limits and the relationship with vascular structures and with the cranial nerves. A variation to the protocol could be made, adding T1 contrast fat sat sequences.  

Asymptomatic lipomas can be managed conservatively, but they may present slowly progressive focal signs, as they can infiltrate the cranial nerves, and partial resection may be needed.

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