Cerebellopontine angle epidermoid cyst
see also Cerebellopontine angle dermoid cyst.
Epidemiology
Epidermoid cysts are the third most of the cerebellopontine angle tumors.
The cerebellopontine angle epidermoid cyst account for 3-6% of cerebellopontine angle tumors. Comparatively, vestibular schwannomas, the most common CPA angle tumor, account for 85%.
Men and women are equally affected and the symptoms usually arise between the mid-20’s and early 50’s 1) with a mean age of 38.8 years at presentation 2).
Pathophysiology
Although several mechanisms for cranial nerve dysfunction due to these tumors have been proposed.
Hasegawa et al. report the first direct evidence of etiology of cranial nerve dysfunction caused by cerebellopontine angle epidermoid tumors. Young age and rapidly progressive neurological deficit might be the characteristics for strangulation of the affected nerves by the cyst capsule 3).
Clinical features
CPA epidermoid cysts can compress the surrounding cranial nerves, brainstem, and cerebellum. Ataxia and cranial nerve palsies often result 4).
Thirty cases of cerebellopontine angle epidermoid cysts treated over a period of 20 years were reviewed with regard to their clinical features, the pathophysiology of their symptoms and their management. The predominating symptoms were related to the 7th and 8th cranial nerves and headaches. The signs and symptoms were present for an average period of 4 months. It was not always possible to determine if the signs and symptoms were due to local involvement by the epidermoid, increased intracranial pressure, or both 5).
Diagnosis
Differential diagnosis
Cerebellopontine angle epidermoid cyst may mimic an cerebellopontine angle arachnoid cyst, but are high signal on DWI MRI.
Treatment
Outcome
The extent of tumor removal had no effect on the risk of recurrence, and thus it may be acceptable to leave tumor capsule fragments adhering closely to nerves, vessels, or brainstem. During long-term follow-up, resolution or improvement of present preoperatively and new postoperative neurological deficits may be expected in most patients 6).