Vestibular Schwannoma
A vestibular schwannoma is a benign, slow-growing tumor arising from the Schwann cells that form the myelin sheath of the vestibular branch of the eighth cranial nerve (the vestibulocochlear nerve). Despite the common name acoustic neuroma, which is widely recognized in patient communication, the tumor does not originate on the cochlear (acoustic) branch. Vestibular schwannoma is the preferred clinical and surgical term.
As the tumor develops, it grows within the internal auditory canal or the cerebellopontine angle, the space between the brainstem and cerebellum. Growth can compress the cochlear nerve (causing progressive unilateral hearing loss and tinnitus), the facial nerve (potentially causing facial numbness or weakness in larger tumors), and the brainstem in cases of significant enlargement. Most tumors are slow-growing and unilateral. Bilateral vestibular schwannomas are rare and associated with neurofibromatosis type 2, a genetic condition.
Diagnosis typically involves audiological testing showing asymmetric sensorineural hearing loss with poor speech discrimination, followed by MRI of the internal auditory canals. Management options include active surveillance with regular monitoring, stereotactic radiation (Gamma Knife radiosurgery), and surgical removal. The decision depends on tumor size, growth rate, the patient's hearing level, and clinical factors. In Canada, management is coordinated through neurotology or neurosurgery programs at tertiary centres.
