Epidermoid cyst (posterior fossa/skull vault)
Gradually increasing vertigo, gait disturbance and headaches.
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Ovoid mass measuring 77 x 75 x 50mm (FH x RL x AP) located at posterior cranial fossa with moderate mass effect on the brainstem, left temporal lobe. There is 6mm of contralateral midline shift and 10mm tonsillar herniation. The mass demonstrates heterogeneous T1 and T2 signal intensities, but more valuable is high DWI signal reflecting diffusion restriction, with corresponding low ADC values.
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These MRI findings are in keeping with an intracranial epidermoid cyst.
This patient has a large intracranial epidermoid cyst, which is a congenital lesion with an estimated prevalence about 1% of all intracranial tumors. This lesion was symptomatic and causes mass effect mainly on the cerebellum. It is difficult not to underestimate the value of DWIs - these are short but helpful sequences, especially in identifying epidermoids. So, the use of contrast-enhanced study in this case was doubtful.