Pauci-symptomatic large epidermoid cyst of cerebellopontine angle: case report

It is estimated that 10% of intra-cranial tumours are localized in the cerebellopontine angle and internal auditory canal and early symptoms of the different histological forms are almost identical. Acoustic neuroma account for 90% and meningioma for 5-10% of these tumours, while a small percentage of rare tumours exist, the most frequent being epidermoid cyst, also known as congenital cholesteatoma or keratoma. The case is reported here of a large epidermoid cyst of the right cerebellopontine angle, and the clinical-radiological course is reviewed. The patient, a 35-year-old, male, initially presented an episode of objective rotatory vertigo, and a history of right ear fullness, of a few months' duration, with normal otoscopy. Audiometric test was normal in left ear, while slight pantonal sensori-neural hypoacusia was observed in the right ear. The impedenzometric findings were normal as was the vestibular test. Auditory brainstem evoked response showed an increased latency of fifth wave. Gadolinium-enhanced magnetic resonance imaging of brain revealed the presence of a voluminous epidermoid cyst occupying the extra-axial side of the right cerebellopontine cistern with superior extension into the cistern. Due to the low-grade of symptoms, we had chosen to wait and not perform surgery immediately, with otologic and vestibular test-controls every 6 months, with cerebral magnetic resonance imaging to control extension of the mass, without radiation exposure for the patient. One year after diagnosis, at the last control, otofunctional findings were not modified and repeat magnetic resonance imaging did not demonstrate important variations compared to the first. Thus, the choice not to proceed with surgery was justified since surgery is burdened by the risk of important complications. At magnetic resonance imaging, the epidermoid cyst, unlike the majority of intra-cranial tumours, such as acoustic neuroma and meningioma, does not show gadolinium-enhancement; this again supporting the important role of magnetic resonance imaging in the differential diagnosis of intra-cranial neoformations. It is, therefore, worthwhile stressing the validity of the approach, step by step, in the diagnosis of patients with otologic symptoms, together with the importance of magnetic resonance imaging that, in comparison with computed tomography, allowed us to exactly assess the growth rate of the mass and to "wait and see" without risks and without radiations for the patient.