Acoustic Neuroma
What is an Acoustic Neuroma?
Acoustic neuroma, which is actually a vestibular schwannoma, is a benign, non-cancerous growth on the vestibular (balance) nerve that affects approximately 1 in 100,000 people. Although VS is a tumor of the sheath of the vestibular nerve (schwannoma and not neuroma; vestibular and not acoustic), it has been incorrectly called AN for over 100 years and both names are now considered acceptable.
It arises in the middle of the internal auditory canal (IAC) – the bony canal of approximately 1 centimeter in length that transmits the facial nerve, the acoustic (hearing) nerve, and both the inferior and superior vestibular (balance) nerves between the brainstem and the inner ear. The VS can grow outwards and deep, filling the IAC, and displacing the brainstem by gentle encroachment as it grows slowly.
VS (AN) is a slow-growing tumor. It can present with hearing loss, especially difficulty understanding words, but patients can also have normal hearing. Even though it is a growth on the balance nerve, patients rarely complain of dizziness or imbalance until the tumor becomes very large. It is often discovered on routine head MRI scan.
What testing is done for AN (VS)?
Audiograms (hearing tests) can demonstrate the trouble detecting words or an asymmetry between the ears; more comprehensive testing such as an auditory brainstem response test (ABR) will show delays in hearing nerve conductivity caused by pressure from the tumor in 80% of tumors larger than 1 centimeter in size. An MRI scan with gadolinium injection will diagnose all tumors as small as 3 millimeters in size. Vestibular testing such as an electronystagmogram (ENG) will be weak on the side of some VS’s that are on the superior (upper) vestibular nerve.
What is the treatment for VS (AN)?
VS tumors are classified as small, medium and large. Treatment is personalized based on tumor size, hearing status, and patient age and health status. Treatment options include observation with serial MRI scans and hearing tests, radiation (stereotactic, gamma knife or Linac radiosurgery), and skull base microsurgery.
Because these tumors are very slow-growing overall but have unpredictable growth rates in the particular instance, it is prudent that, if the patient and physician opt for radiation, the tumor is observed initially with serial MRI scans. Radiation can be instituted if the tumor demonstrates growth. This is because radiation halts tumor growth and does not remove the tumor, and radiation has significant potential side effects, including hearing loss, facial weakness, dizziness, etc.
Surgical options for VS (AN) include suboccipital craniectomy, middle fossa craniectomy, and translabyrinthine craniectomy for tumor removal. Dr. Chandrasekhar performs these surgeries in conjunction with renowned neurosurgeon Dr. Kalmon Post at Mount Sinai Hospital. Surgical removal is geared toward total tumor removal with preservation of facial nerve function and hearing preservation where possible. Surgery is performed with complete real-time cranial nerve monitoring including hearing nerve and facial nerve monitoring. Our team’s excellent results have been published.
You can read more in Dr. Chandrasekhar and her colleagues’ published literature:
- Chandrasekhar SS, Brackmann, DE, and Devgan, KK: Utility of auditory brainstem response audiometry (ABR) in diagnosis of acoustic neuromas. Am J Otol 1995 Jan;16(1):63-67.
- Leeman DJ, Chandrasekhar SS, Brackmann DE, Poletti BJ: Collision tumors at the cerebellopontine angle: case report with literature review. Otolaryngol-Head Neck Surg 1997 Dec;117(6):S76-80.
- De La Cruz A, Chandrasekhar SS: Transcochlear approach for cerebellopontine angle lesions. In Otologic Surgery, Chap 54, DE Brackmann, C Shelton and M Arriaga, eds. WB Saunders, Publishers. Revised in 1999.
- Chandrasekhar SS: Pathology of Acoustic Neuroma. In: Acoustic Tumors: 3rd edition, Luetje, House, Doyle, editors.
- Betchen SA, Walsh J, Post KD: Long-term hearing preservation after surgery for vestibular schwannoma. J Neurosurg 2005 Jan;102(1):6-9.