Ruptured intracranial dermoid cyst with aseptic chemical meningitis
Acute onset of severe headaches.
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The MRI sequences demonstrate a large lobulated midline extra-axial complex mass of suprasellar location, measuring 50 x 45 x 40 mm, ruptured within the subarachnoid spaces. It displays a low signal on T1 and FLAIR and a high signal on T2 with restricted diffusion. The fatty material appears of high signal on all sequences with a chemical shift artifact on the T2 sequence. No enhancement seen on postcontrast sequences.
Innumerable small droplets of high signal on T1, T2, and FLAIR attenuated on T2*, disseminated within the subarachnoid spaces (subarachnoid seeding), indicating aseptic chemical meningitis. No fatty material seen within the ventricular system.
Moderate mass effect is noted on the frontal horn with moderate dilatation of the lateral ventricles.
MRI features of an intracranial dermoid cyst ruptured within the subarachnoid spaces with aseptic chemical meningitis.
Cyst rupture within the subarachnoid spaces of the ventricular system is the most common complication. The best diagnostic is fat-like droplets in cortical sulci, subarachnoid cisterns and ventricles. The rupture within the ventricles gives a fat-fluid level.