Does the MRI fit with a lipoma?
Yes, absolutely. This is a typical appearance and location for a small incidental lipoma. Suprasellar lipomas account for ~15% of all intracranial lipomas.
What are other characteristic locations for intracranial lipomas?
Pericallosal is most common (~45%), followed by quadrigeminal plate cistern (25%), cerebellopontine angle (10%).
Which location is most commonly associated with other malformations?
Pericallosal lipomas are associated with agenesis of the corpus callosum in ~50% of cases.
What treatment is required in this case.
Nothing other than reassurance; this is very unlikely to be related to the patient's vague symptoms.
Establishing that a lesion is composed of fatty material is easy on CT, merely requiring a density measurement. How do you do this on MRI?
Fat saturated images are the easiest to interpret. The region of high T1 signal becomes very low signal intensity once fat saturation is applied. Chemical shift artefact is also often visible.
Explain chemical shift artefact and why it is helpful when fat suppressed sequences are not available.
Chemical shift is due to the differences between resonance frequencies between fat and water. It occurs in the frequency encode direction where a shift in the detected anatomy occurs because fat resonates at a slightly lower frequency than water. On spin echo sequences the mismapping will occur in the frequency encoding direction, and show up as a bright band on one side and a dark band on the other side of a fat-soft tissue interface.
Suprasellar mass present which lies posterior to the infundibulum, likely centred in the tuber cinereum measures 4.5 x 7 x 5 cm (AP X CC x ML) demonstrates homogeneous T1 and T2/FLAIR hyperintensity, demonstrates chemical shift artifact and saturates out on fat saturation consistent with fatty lesion. Small nodule of non-fatty component is present within it measuring less than 1 mm, possibly demonstrating enhancement.
The optic nerves and chiasm do not contact the lesion. No evidence of mass effect on the infundibulum. The midline structures are otherwise normal.