Intracranial lipomas are not a tumours as such, but rather a result of abnormal differentiation of embryologic meninx primitiva. They are frequently associated with abnormal development of adjacent structures.
Intracranial lipomas are congenital lesions and as such are found at any age when the brain is imaged for other reasons.
They are usually asymptomatic, and either found incidentally or as a result of investigation of related malformations and their presentation (e.g. mental retardation, epilepsy, hydrocephalus etc...) 5-6.
Intracranial lipomas are widely distributed in the intracranial compartment and although they can be found essentially anywhere, certain regions are characteristic and are discussed separately.
pericallosal lipoma (45%)
- associated with agenesis of the corpus callosum is ~50% of cases
- divided morphologically into tubonodular and curvilinear types
quadrigeminal cistern lipoma (25%)
- associated with underdevelopment of the inferior colliculus
- suprasellar cistern lipoma (15%)
- cerebellopontine angle lipoma (10%)
- sylvian fissure (5%)
The characteristic finding on both CT and MRI is of a mass which has appearances consistent with fat.
Typically appears as a mass with uniform fat density (negative HU values). It has a lobulated 'soft' appearance, conforming to adjacent anatomy. No enhancement. Some peripheral calcification may be present.
MRI with and without fat saturation are able to make the diagnosis easily. In the absence of fat saturated images, then chemical shift artefact may be useful. Signal characteristics are not surprisingly that of fat:
- T1 - high signal intensity
- T2 - high signal intensity
- T1 C+ (Gd) - no enhancement
- fat saturated sequences - low signal
Often the lipomas are traversed by cranial nerves and adjacent vessels, best seen on high resolution sequences.
Treatment and prognosis
Intracranial lipomas are in most cases asymptomatic, and even when associated with symptomatic malformations (e.g. callosal dysgenesis) they usually require no treatment pe se. In fact attempts at resection have had relatively high morbidity with little benefit 5-6. Treatment of seizures or hydrocephalus is of course necessary if these are present 5-6.
The differential is essentialy that of masses which contain fat, and therefore includes:
- intracranial dermoid - if ruptured will often have multiple droplets scattered through the subarachnoid space. Usually midline.
- intracranial teratoma
- lipomatous transformation of neoplasm - PNET, ependymoma, glioma
On MRI, if no fat saturated sequences are available then a number of other possibilities should be entertained, which also have high T1 signal.
- 1. Truwit CL, Barkovich AJ. Pathogenesis of intracranial lipoma: an MR study in 42 patients. AJR Am J Roentgenol. 1990;155 (4): 855-64. AJR Am J Roentgenol (abstract) - Pubmed citation
- 2. Loevner LA. Case review, brain imaging. Mosby Inc. (1999) ISBN:032300430X. Read it at Google Books - Find it at Amazon
- 3. Wallace D. Lipoma of the corpus callosum. J. Neurol. Neurosurg. Psychiatr. 1976;39 (12): 1179-85. doi:10.1136/jnnp.39.12.1179 - Free text at pubmed - Pubmed citation
- 4. Ichikawa T, Kumazaki T, Mizumura S et-al. Intracranial lipomas: demonstration by computed tomography and magnetic resonance imaging. J Nippon Med Sch. 2000;67 (5): 388-91. J Nippon Med Sch (link) - Pubmed citation
- 5. Eghwrudjakpor PO, Kurisaka M, Fukuoka M et-al. Intracranial lipomas: current perspectives in their diagnosis and treatment. Br J Neurosurg. 1992;6 (2): 139-44. Pubmed citation
- 6. Maiuri F, Cirillo S, Simonetti L et-al. Intracranial lipomas. Diagnostic and therapeutic considerations. J Neurosurg Sci. 1989;32 (4): 161-7. Pubmed citation
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