Hamartoma in the internal auditory canal.

An 11 year old girl presented with hearing loss in her left ear and left trigeminal and facial nerve palsy. Radiological examinations revealed an enlargement of the left internal acoustic canal and the existence of a mass protruding from the canal into the cerebellopontine angle. The partial resection of the mass by a suboccipital craniectomy resulted in ceasing the progression of her symptoms. Histological diagnosis was hamartoma with cerebellar heterotopia. The concurrence of heterotopic cerebellar tissue could help to understand the pathogenesis of hamartomas.