04 July 2011

Hypothalamic Lipoma

Not enhanced and contrast enhanced T1 sequences showing high signal well defined lesion dorsally to pituitary infundibulum and anterior to corpora mammillaria, caudally to hypothalamus. Lesion shows no contrast enhancement and its signal characteristics are of fat tissue. This is an incidental finding of Hypothalamic Lipoma.

Note the lesion location on non enhanced T1, contrast enhanced T1, T2 and FLAIR (with fat saturation - see subcutaneous tissue).

Also CT confirms fat tissue. The learning point is that in the hypothalamus region one can encounter various types of lesions. In this case the first next differential diagnosis would be Craniopharyngioma, or Germinoma. However lack of enhancement proves against the malign tumor. Always check for possible ectopic neurohypophysis, that in this case is in normal position (see first image). Tuber Cinereum Hamartoma - that can be found in this location has different signal characteristics.
For further reading about this region check Radiology of the Pituitary.