Citation, DOI & article data
Intracranial lipomas are not tumors as such, but rather a result of abnormal differentiation of embryologic meninx primitiva. They are frequently associated with abnormal development of adjacent structures.
The term intracranial lipoma is used somewhat loosely. The broadest usage would include all causes of focal adipose tissue within the intracranial cavity (e.g. fatty falx cerebri). A narrower, and probably more useful, definition is to limit the use of the term to adipose tissue within the intradural space, specifically those located within the CSF-containing spaces (subarachnoid space and around the ventricles). The remainder of this article restricts itself to this narrower definition.
Intracranial lipomas are congenital lesions and as such are found at any age when the brain is imaged for other reasons.
A number of theories have been put forward to explain the development of intracranial lipomas. The favored theory is persistence and maldifferenitation of the meninx primitiva (subarachnoid space precursor), which accounts for the subarachnoid location, associated parenchymal anomalies, and traversing structures of intracranial lipomas 7,8.
Intracranial lipomas are widely distributed in the intracranial compartment. Although they can be found essentially anywhere, certain regions are characteristic:
pericallosal lipoma (45%)
- associated with agenesis of the corpus callosum in ~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%)
- choroid plexus lipoma (rare) 9
The characteristic finding on both CT and MRI is a mass which has appearances consistent with fat.
On CT, they typically appear as a non-enhancing mass with uniform fat density (hence negative CT attenuation values). It has a lobulated 'soft' appearance, conforming to adjacent anatomy. 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
- SWI: can produce blooming due to susceptibility artifact 10
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 per 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 essentially 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.
- thrombosed berry aneurysm: often will have a calcified rim and hemosiderin staining on gradient echo or SWI sequences
- white epidermoid: rare, and will restrict on DWI
- 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
- 7. McLendon RE, Rosenblum MK, Bigner DD. Russell & Rubinstein's Pathology of Tumors of the Nervous System. CRC Press. ISBN:0340810076. Read it at Google Books - Find it at Amazon
- 8. Tumors of the Central Nervous System, Volume 13: Types of Tumors, Diagnosis, Ultrasonography, Surgery, Brain Metastasis, and General CNS Diseases. Springer. ISBN:9400776012. Read it at Google Books - Find it at Amazon
- 9. Uchino A, Hasuo K, Matsumoto S, Masuda K. Solitary choroid plexus lipomas: CT and MR appearance. AJNR. American journal of neuroradiology. 14 (1): 116-8. Pubmed
- 10. Lingegowda D, Rajashekar C, Belaval VV, Thomas B, Keshavdas C. Susceptibility artifacts in lipomas. (2013) Neurology India. 61 (1): 56-9. doi:10.4103/0028-3886.108012 - Pubmed