*21-year-old male.
What is the most likely diagnosis?
Answer
Answer: Pericallosal lipoma
Case Discussion:
MR images showed posterior pericallosal curvilinear lipoma.
Intracranial lipomas are rare lesions, which are congenital malformations originating from abnormal permanent differentiations of the meninx primitiva during development of the subarachnoid cistern (1, 2). Most lipoma occurs on the midline or close to it. There may sometimes be a relationship with other brain anomalies (2). Intracranial lipomas are rarely symptomatic due to the location. Moreover, they are generally benign and asymptomatic (3).Diagnosis of intracranial lipoma is achieved easily with CT or MR images. Nodules or tubular nodules in homogenous fat density are determined on sharply demarcated cranial CT. Densitometric measurements of between -50 and -100 HU taken from the lesions determine the fat attenuation. Dense calcification is sometimes observed (4). While intracranial lipomas are seen as hyperintense on standard SE T1-weighted images, in fat suppression sequences, they appear hypointense. On standard T2-weighted images chemical shift artifacts are seen as hypointense. Round or linear filled defects associated with vessels or cranial nerve passing through the lipoma can be observed. Sometimes, calcified foci can be seen with low signal intensity. On FSE T2-weighted images, the j-coupling effect is seen as iso-hyperintense. On standard SE PD images, TE is seen as chemical shift artifact, particularly iso-hyperintense associated with TR and TE. Lipomas are determined as hypointense in the STIR sequences and hyperintense in the FLAIR sequences. In diffusion tensor images, altered fiber connections related to corpus callosum disgenesis are observed. There is no contrast enhancement of intracranial lipomas. Aberrant anterior cerebral artery (ACA) in callosal agenesis can be observed by MR angiography (4).
References:
1. Verga P. Lipoma ed osteolipomi della pia madre. Tumori 1929;15:321–357
2. Truwit CL, Barkovich AJ. Pathogenesis of intracranial lipoma: an MR study in 42 patients. AJR Am J Roentgenol 1990;155:855–865
3. Maiuri F, Cirillo S, Simonetti L, De Simone MR, Gangemi M. Intracranial lipomas: diagnostic and therapeutics considerations. J. Neurosurg Sci 1988;32:161–167.
4. Osborn Anne G, Salzman Karen L and Barkovich A James. Lipoma. In: Amirsys (ed) Diagnostic Imaging Brain, 1st Edition, Salt Lake City, USA 2004; I:1:22–5