Ruptured parasellar dermoid cyst
Sudden onset headache.
MRI of the brain
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Left sided extra-axial space occupying lesion in a left parasellar location. It occupies the medial aspect of the left middle cranial fossa and extends along the lateral aspect of the left cavernous sinus to indent the left frontal lobe and the left gyrus rectus that is mildly displaced towards the right side. The mass shows markedly high T1 and intermediate T2 signals with heterogeneous texture.
The lesion is pushing the M1 segment of left middle cerebral artery posteriorly as well as the A1 segment of the left anterior cerebral artery medially. No intra-sellar extension could be noted.
It has near complete suppression on FAT SAT FLAIR as well as the multiple subarachnoid droplets on the same side as the lesion. No definite enhancement could be noted, although FAT SAT T1 C+ are not available.
Multiple droplets of fat signal material are scattered in the left subarachnoid space consistent with rupture.
The described features are in favor of left para-sellar sizable space-occupying lesion of high-fat content. Left para-sellar dermoid cyst is by far the most probable diagnosis. Rupture with the subarachnoid spread of sebum results in brisk arachnoiditis and sudden onset of headache.