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What is an Acoustic Neuroma (Vestibular Schwannoma)?
An Acoustic Neuroma is a tumor found in the area of the brain where the auditory (hearing) nerve enters the bony opening of the skull between the brain and the inner ear. The tumor arises in the vestibular nerve, which is involved in balance, and therefore the proper name is a vestibular schwannoma. These tumors are typically benign. People with Neurofibromatosis Type 2 (NF-2) commonly have acoustic neuromas. Because the treatment of acoustic neuromas is rarely urgent, patients should strongly consider obtaining second opinions prior to undergoing treatment. The chances of a good outcome are increased at larger centers treating a high volume of acoustic neuroma patients.
Acoustic Neuroma Symptoms
- Primary symptoms are one-sided hearing loss, ringing in the ears and problems with balance.
- Hearing loss progresses slowly in most patients and often is first recognized as difficulty in hearing conversation while on the telephone.
- The ringing in the ears is high pitched. By the time of diagnosis most patients have these two symptoms.
- Facial numbness, facial weakness, and taste changes occur as the tumor causes pressure on the fifth and seventh cranial nerves.
- Large tumors also place pressure on the lower cranial nerves, causing difficulty swallowing and hoarseness.
Acoustic Neuroma Diagnosis
- Audiometric and audiologic studies (hearing tests)
- Pure tone audiograms can detect loss of high tones.
- A speech discrimination test can determine hearing function.
- Radiographic evaluation
- Magnetic resonance imaging (MRI) is the preferred test. MRI best shows the size and shape of the tumor and its relationship to important brain structures.
- Special temporal bone computed tomography (CT) scans are necessary to reveal information about the bony areas surrounding the tumor.
Acoustic Neuroma Treatment
- Factors to consider
- Tumor size: Large tumors typically require surgical removal.
- Pressure on the brainstem: Tumors that significantly compress and distort the brainstem may not be good radiation candidates.
- Tumor growth: In many cases, acoustic neuromas are followed on serial MRI scans to see how quickly they grow. If small and stable, no treatment may be necessary.
- Patient’s age and medical condition: Radiation therapy may be recommended more highly for older and/or medically ill patients.
- Symptoms: Degree will impact urgency and type of treatment.
- The surgical difficulty associated with acoustic neuroma removal varies greatly. Some smaller tumors can be removed in less than four hours, whereas others may require more than 20 hours of surgery.
- At UCLA, the surgery is typically performed by a neurosurgeon and a head and neck surgeon (neuro-otologist) working closely as a team. The head and neck surgeon exposes the tumor by carefully and precisely drilling down the portion of the skull (petrous portion of the temporal bone) overlying the tumor. The neurosurgeon then meticulously removes the tumor using microdissection techniques.
- Neurosurgeons in the UCLA Skullbase Tumor Program have special expertise in the surgical management of acoustic neuromas.
- Radiation therapy
In some cases, radiation is the preferred treatment for newly diagnosed, growing or residual tumor. UCLA offers state-of-the-art radiation delivery techniques that enable high radiation doses to be delivered to the tumor while minimizing radiation exposure to the surrounding brain, skull and skin. Depending on the circumstances, the radiation can be delivered as a single treatment (stereotactic radiosurgery) or spread out over multiple doses (stereotactic radiotherapy).
- Stereotactic radiosurgery (SRS)
- SRS precisely delivers a high dose of radiation to the tumor in a single setting.
- If there is no useful hearing (for example, if patient cannot use the telephone with the affected ear), SRS may be a good choice. In patients who have useful hearing, too much radiation to the auditory nerve, given all at once, can cause hearing loss.
- UCLA uses the Novalis shaped-beam stereotactic radiosurgery unit, which is equally or more effective than Gamma Knife and CyberKnife.
- Stereotactic radiotherapy (SRT)
- If trying to preserve hearing (and/or not injure the brainstem), SRT may be a better choice than SRS for acoustic neuromas. SRT delivers precise stereotactic radiation divided into multiple smaller doses (fractionation, or also called radiotherapy). Fractionation reduces the risk of radiation damage to the brainstem and cranial nerves.
- The UCLA Novalis shaped-beam system is capable stereotactic radiotherapy. Most Gamma Knife units do not have this capability.
- Stereotactic radiosurgery (SRS)
- Advantage: Treatment holds greatest chance for a cure if complete removal is possible. Surgery is often the best choice for patients for whom radiation therapy is higher risk or not possible, such as large tumors or very young patients.
- Disadvantages: Higher risk of hearing loss and facial paralysis compared to SRS and SRT. Other possible complications include cerebrospinal fluid leak and meningitis.
- Advantages: Treatment does not involve surgery, holds lower risk of complications, takes a single day and is nearly painless.
- Disadvantages: Compared to SRT, higher risk of hearing loss and facial paralysis exists. Not appropriate for large tumors that are compressing the brainstem. Remote chance of developing radiation-induced cancer decades after treatment exists.
- Advantages: Treatment does not involve surgery and is painless. Compared to SRS, holds lower risk of hearing loss, facial paralysis and radiation necrosis (cell death) of the brainstem.
- Disadvantages: Treatment may require up to 30 treatments (five days a week for six weeks), and therefore is more practical for patients who live reasonably close to the treatment center. Patients who are claustrophobic may not be candidates. Like SRS, the tumor remains (slightly shrinks in about half the cases). Also, treatment does not remove the mass effect on the brainstem if present, and therefore some symptoms may persist. A remote chance of developing radiation-induced cancer decades after treatment exists.
The best treatment option(s) for any individual patient is based on multiple factors. Consultation with a neurosurgeon with expertise in, and with access to, all state-of-the-art treatment options is recommended.
The Neuro-ICU cares for patients with all types of neurosurgical and neurological injuries, including stroke, brain hemorrhage, trauma and tumors. We work in close cooperation with your surgeon or medical doctor with whom you have had initial contact. Together with the surgeon or medical doctor, the Neuro-ICU attending physician and team members direct your family member's care while in the ICU. The Neuro-ICU team consists of the bedside nurses, nurse practitioners, physicians in specialty training (Fellows) and attending physicians. UCLA Neuro ICU Family Guide