Tumors of the Intracranial Cranial Nerves:
The most common tumor of the intracranial cranial nerves is the vestibular schwannoma (widely known by its historical misnomer, acoustic neuroma or acoustic neurinoma)—a benign neoplasm arising from the Schwann cell sheath of the vestibulocochlear nerve (cranial nerve VIII). Typical clinical manifestations include vertigo, balance disorders and gait instability, tinnitus (ringing in the ear), and progressive sensorineural hearing impairment (or sudden hearing loss). In the vast majority of cases, it presents unilaterally. When vestibular schwannomas occur as part of a hereditary syndrome, specifically Neurofibromatosis Type 2 (NF2), they may present bilaterally and involve multiple cranial nerves. The optimal treatment strategy depends on tumor dimensions, anatomical extension, and symptoms. Lesions exceeding 15 mm in maximum diameter are generally best treated with microneurosurgical resection. Smaller, non-compressing tumors may alternatively be managed with focused stereotactic radiosurgery (Gamma Knife or CyberKnife) or active MRI surveillance.
Example 5: A 58-year-old patient noticed that for about a year he could no longer use his left ear when speaking on the phone. Over the preceding three months, he additionally developed troublesome dizziness, unsteady balance, and annoying tinnitus. An evaluation by an ENT specialist confirmed profound hearing loss on the left side, with no external or middle ear cause. A cranial MRI demonstrated an approximately 4 cm mass in the posterior cranial fossa (cerebellopontine angle) exerting critical compression on the brainstem. The tumor originated within the internal acoustic canal, expanded toward the cerebellum, and showed homogeneous contrast enhancement. Given the large tumor size and life-threatening brainstem compression, surgical resection was indicated. Because the auditory and balance nerve travels alongside the facial nerve within the exact same bony canal, the microsurgical resection was conducted under continuous intraoperative neurophysiological monitoring (IONM) of the facial nerve. This electrophysiological surveillance was vital to preserving facial nerve motor function. Following complete tumor resection, the patient remained deaf on the affected ear as expected, but brainstem compression was entirely relieved and facial nerve function was completely preserved intact. Nota bene: The clinical course in your specific case may differ from the example described here.