Primary Solitary Intralabyrinthine Schwannoma: A Report of 7 Cases and a Review of the Literature

Intralabyrinthine schwannomas (ILSs) are uncommon benign tumors that originate in the Schwann cell sheath of the intralabyrinthine distal branches of the vestibulocochlear nerve. They have no initial involvement in the internal auditory canal although that might develop later. These lesions can arise inside the cochlea, originate in the vestibule or, in rare cases, develop in the semicircular canals. From these sites, spread might take place via the anatomic connections between the perilymphatic spaces in the scala vestibuli and the anterior vestibule. Thus, ILSs centered in the cochlea might involve the vestibule, and those originating in the vestibular end organs would reach the cochlea. Presenting signs and symptoms include a progressive or sudden sensorineural hearing loss (which occurs in more than 95% of patients), as well as tinnitus and vertigo. Magnetic resonance imaging characteristics include sharp circumscription and hypointensity on thin, heavily T2-weighted 3D images and strong enhancement after gadolinium administration on TI-weighted images. We describe a series of 7 cases of primary ILS that were managed at two of our institutions. We also discuss the need for a comprehensive otoneurologic evaluation that encompasses the functional derangement and the tumor location as delineated by MRI, and we describe the treatment options.