The most common presenting symptoms are one-sided hearing loss and/or tinnitus. Vertigo and disequilibrium are relatively uncommon presentations. As the tumor expands, it may compress the facial or trigeminal nerves, resulting in decreased facial sensation or facial muscle weakness. Late complications include cerebellar and brainstem dysfunction as a result of compression. Obstructive hydrocephalus is also possible due to effacement of the fourth ventricle.
On physical examination, the Weber and Rinne tests and formal audiogram may be used to uncover unilateral sensorineural hearing impairment. Neurologic examination may reveal defects of the fifth and seventh cranial nerves, such as a decreased or absent corneal reflex or hypoesthesia. Romberg and Hall-Pike tests are typically normal.
Patients with neurofibromatosis type 2 classically develop bilateral vestibular schwannomas at a young age. Other risk factors associated with the development of vestibular schwannomas include childhood exposure to low dose radiation and a history of parathyroid adenoma.
Vestibular schwannomas are typically slow-growing tumors. They usually grow at a rate of 2-4 mm/year but can occasionally grow as rapidly as 2 cm/year. If treated with current techniques, patients have a very good prognosis with minimal complications. However, if left untreated, these tumors eventually lead to lethal brain stem compression or intracranial hypertension.
D33.3 – Benign neoplasm of cranial nerves
126949007 – Acoustic neuroma
Differential Diagnosis & Pitfalls
- Cerebrovascular accident
- Vertebrobasilar insufficiency
- Meniere disease – Constellation of clinical symptoms including episodic vertigo, sensorineural hearing loss, and tinnitus; requires all other causes ruled out.
- Benign positional vertigo – Vertigo experienced in specific positions, no hearing loss.
- Multiple sclerosis – Demonstration of plaques on MRI.
- Perilymphatic fistula – History of head injury, barotrauma, or heavy lifting; imaging may show fluid collection in region of round window recess.
- Viral cochleitis (see sensorineural deafness) – History of viral disease.
- Ototoxic drugs – Review medication history (aminoglycosides, some diuretics).
- Thyrotoxicosis – Order TSH/T4 levels.
- Sudden sensorineural hearing loss – Evaluation will reveal no underlying condition by history, examination, or imaging.
- Meningioma – Hearing loss is a less prominent symptom; often has a dural tail on MRI.
- Primary cholesteatoma – Presence of chronic drainage and granulation tissue in the ear canal and middle ear; CT is diagnostic modality of choice to evaluate bony defects.
- Epidermoid – Hearing loss is less prominent symptom; no enhancing component on MRI.
- Facial nerve schwannoma – Clinically associated with more prominent and earlier facial weakness; enhancement on MRI extends into the geniculate ganglion of the facial nerve and facial canal.
- Trigeminal schwannoma – Clinically associated with more prominent facial numbness; enhancement on MRI does not extend into the internal acoustic meatus.