Presentation
The patient presents with progressive left hemifacial spasm over a 2-year duration.
Patient Data
Features consistent with an intracranial, insinuating, left cerebellopontine angle, extra-axial epidermoid cyst with typical signal intensities on pre-contrast imaging, and heterogeneous signal on T2 Flair imaging.
There is a heterogeneous signal on diffusion imaging due to a combination of true diffusion and shine-through artifact as evidenced by the associated ADC mapping.
There is a mass effect on the left pons and medulla with a displaced vertebral artery towards the right.
There is no abnormal enhancement.
MRI brain is otherwise normal.
Case Discussion
Features consistent with a typical, left extra-axial, cerebellopontine angle, epidermoid cyst.
Patients often present due to the gradual mass effect on the brainstem as the cyst enlarges and insinuates and encases regional intracranial nerves.
Typical symptoms include chronic headaches, cranial deficits, brainstem, and cerebellar symptoms, seizures, and features of raised intracranial pressure.
This patient presents with a rare symptom of progressive left hemifacial spasm.
This is likely due to compression of the left facial nerve at the nerve root entry zone due to the epidermoid cyst rather than the more typical cause of a vascular loop compression.
The incidence of hemifacial spasms due to an epidermoid cyst has been reported at 1.2%.