Acustic neuroma is a benign tumor of Schwann cells that is most commonly found on cranial nerve VIII (vestibulocochlear nerve).
Classification of nervous system tumors
|Neuroepithelial tumors in the CNS|
|Sellar region tumors|
|Primary CNS lymphoma||Primary CNS lymphoma|
|Metastasis to the brain (5x more common than primary brain tumors)||Most commonly arising from:|
- Median age of diagnosis: 53 years
- Most common tumor of cerebellopontine angle
- Most commonly unilateral
- Incidence: 11 per 1 million people in the United States
- No difference in incidence by gender
- Higher incidence in Asian Pacific Islanders
- Many cases have no known etiology.
- Sometimes associated with mutation in long arm of chromosome 22
- Associated with loud noises, head and neck radiation therapy, and neurofibromatosis type 2
Symptoms of acoustic neuroma are divided into early and late phases.
Tumor expansion in the internal auditory meatus exerting pressure on vestibulocochlear nerve (CN VIII):
- Vestibular nerve compression:
- Postural imbalance
- Cochelar nerve compression: unilateral sensorineural hearing loss (most common symptom)
Compression of adjacent structures in the cerebellopontine angle:
- Facial nerve compression: ipsilateral facial weakness or complete facial paralysis (Bell’s palsy)
- Trigeminal nerve compression:
- Decreased ipsilateral facial sensation
- Ipsilateral facial numbness
- Ipsilateral cerebellar compression:
- Dysdiadochokinesia (impaired rapid alternating movements)
Cranial nerve testing
- Vestibulocochlear nerve: audiometry
- Sensorineural hearing loss
- Difficulty perceiving high-frequency sounds
- Facial nerve:
- Ipsilateral facial weakness
- Ipsilateral facial twitching
- Trigeminal nerve:
- Ipsilateral decreased facial sensation
- Ipsilateral decreased corneal reflex
- MRI of the brain with contrast:
- Initial imaging test of choice
- Performed in patients with abnormal audiometry results and high suspicion for vestibular schwannoma
- Enhanced circular lesion in internal auditory meatus
- Expansion into the cerebellopontine angle
- Cystic and fat degeneration are often seen.
- CT of the brain with contrast:
- Performed in patients not eligible for MRI (e.g., patients with a pacemaker or metal implant)
- Findings similar to those of MRI scan
- Strongly reactive for S100
- Hypercellular areas with spindle cells alternating with hypocellular myxoid stroma
Large tumor with severe hearing loss
- Surgical excision:
- Surgery cannot restore hearing loss but can prevent further loss.
- Intraoperative monitoring of cranial nerves to reduce risk of nerve injury
- Hearing loss
- Facial paralysis
- Taste changes
- Radiation therapy:
- Stereotactic radiosurgery or fractionated stereotactic radiotherapy
- Goal of radiation is to control the tumor, prevent further growth, and sometimes cause a reduction in tumor size.
- Facial weakness
Small tumor with minor hearing loss
- MRI scan every 6–12 months to track tumor progression
- Hearing aids for hearing loss (about 50% of patients who are observed for a decade lose functional hearing)
- Meningioma: benign tumor arising from the meninges of the brain or the spinal cord. Risk factors include radiation exposure. Meningioma presents with headache, vision disturbances, and possible seizures. Brain imaging and biopsy are the main diagnostic tools. Meningioma is treated with surgical excision or radiation.
- Neurofibromatosis type II: autosomal dominant neurocutaneous syndrome caused by NF2 gene mutation on chromosome 22. NF2 gene codes for the merlin protein. Symptoms depend on the tumors and their locations. These tumors include bilateral cataracts, bilateral acoustic neuromas, meningiomas, ependymomas, and neurofibromas. Diagnosis is made with genetic patient history, physical examination, imaging, and genetic testing. Management includes surgical excision or radiation for the tumors and hearing aids for any functional hearing loss.
- Meniere’s disease: typically, a unilateral inner ear disorder causing a periodic sensation of spinning, tinnitus, and fullness in the ear. Symptoms seem to be caused by fluid accumulation in the inner ear’s labyrinth. The disease is considered progressive and may cause hearing loss. Diagnosis is based on clinical symptoms and hearing examination. Treatment is with antiemetics and anxiolytics (acute episodes) and includes physical therapy, dietary changes (low-salt diet), and counselling (chronic management). Unlike acoustic neuroma, there is no mass seen on imaging in Meniere’s disease.
- Park, J.K., Vernick, D.M. (2020). Vestibular schwannoma (acoustic neuroma). UpToDate. Retrieved May 23, 2021, from https://www.uptodate.com/contents/vestibular-schwannoma-acoustic-neuroma
- Martin, K.A. (n.d.). Patient education: Vestibular schwannoma (acoustic neuroma). UpToDate. Retrieved May 23, 2021, from https://www.uptodate.com/contents/vestibular-schwannoma-acoustic-neuroma-the-basics
- Kutz, J.W. (2020). Acoustic neuroma. Medscape. Retrieved May 23, 2021, from https://emedicine.medscape.com/article/882876-overview