Suprasellar cistern lipomas are uncommon, usually incidental findings, with characteristic imaging features and a very limited differential diagnosis.
For a general discussion of intracranial lipomas please refer to the general article: intracranial lipoma.
Suprasellar cistern lipomas have an incidence of approximately 0.4% 3, and account for ~15% of all intracranial lipomas, third in frequency after pericallosal lipomas and quadrigeminal cistern lipomas 1.
Unlike the more common pericallosal lipomas, which are usually associated with dysgenesis or hypogenesis of the corpus callosum and other congenital malformations (and associated symptoms), suprasellar lipomas are usually asymptomatic and are only found incidentally either at autopsy or when the brain is imaged for other reasons.
Suprasellar lipomas appear as small fat density regions in the suprasellar cistern, with matching negative density measurements (-30 to -100 HU). No calcification is present.
MRI is the modality of choice for assessing these lesions as not only does it have exquisite sensitivity and specificity for the detection and characterisation of fatty lesions (provided fat saturated sequences are performed), but it is also able to demonstrate local anatomy.
The sine qua non of intracranial lipomas is a nodule tissue which follows fat on all sequences including fat suppressed sequences, and does not demonstrate solid enhancing components 1-2.
The tissue is usually applied to the floor of the third ventricle immediately behind the infundibulum of the pituitary gland, in close proximity to the hypothalamus, tuber cinereum and mammillary bodies.
The differential diagnosis for a suprasellar cistern lipoma is very limited, and is essentially that of pituitary region masses with intrinsic high T1. As CT and fat saturated sequences (or presence of chemical shift artifact) are usually able to confirm that the mass is fatty the differential is narrowed further:
dermoid: mature teratoma
- less common
- often more heterogeneous in signal (due to presence of hair desquamated cells, etc)
- often there is evidence of previous rupture with fat droplets scattered in the subarachnoid space
teratoma: immature teratoma
- similar to dermoid, but usually have a solid enhancing or cystic component
- 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. Atlas SW. Magnetic resonance imaging of the brain and spine. Philadelphia : Wolters Kluwer Health/Lippincott Williams & Wilkins, c2009. (2008) ISBN:078176985X. Read it at Google Books - Find it at Amazon
- 3. Miller NR, Walsh FB, Hoyt WF. Walsh and Hoyt's Clinical Neuro-Ophthalmology. Philadelphia : Lippincott Williams & Wilkins, c2005. (2005) ISBN:0781748127. Read it at Google Books - Find it at Amazon