Acoustic Neuroma

Acoustic Neuroma

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Acoustic Neuroma is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • acoustic neurilemoma
  • acoustic neurinoma
  • fibroblastoma, perineural
  • neurinoma of the acoustic nerve
  • schwannoma of the acoustic nerve
  • vestibular schwannoma
  • neurofibroma of the acoustic nerve

Disorder Subdivisions

  • None

General Discussion

An acoustic neuroma, also known as a vestibular schwannoma, is a rare benign (non-cancerous) growth that develops on the eighth cranial nerve. This nerve runs from the inner ear to the brain and is responsible for hearing and balance (equilibrium). There is no standard or typical pattern of symptom development, although hearing loss in one ear (unilateral) is the initial symptom in approximately 90 percent of cases. Additional findings include ringing in the ears (tinnitus) and dizziness. The symptoms of an acoustic neuroma occur from the tumor pressing against the eighth cranial nerve and disrupting its ability to transmit nerve signals to the brain. An acoustic neuroma is not cancerous (malignant); it does not spread to other parts of the body. The reason an acoustic neuroma forms is unknown.

Symptoms

Some individuals, especially those with small tumors, may not have any associated symptoms (asymptomatic). However, even small tumors, depending upon their location, can cause significant symptoms or physical findings.



Acoustic neuromas are slow-growing tumors that can eventually cause a variety of symptoms by pressing against the eighth cranial nerve. Hearing loss in one ear (the ear affected by the tumor) is the initial symptom in approximately 90 percent of cases. Hearing loss is usually gradual, although in some rare cases it can be sudden. In some cases, hearing loss can also fluctuate (worsen and then improve). Hearing loss may be accompanied by ringing in the ears, a condition known as tinnitus, or by a feeling of fullness in the affected ear. In some cases, affected individuals may have difficulty understanding speech that is disproportional to the amount of hearing loss.



Acoustic neuromas can also cause dizziness and problems with balance such as unsteadiness. In rare cases, dizziness or balance problems may occur before noticeable hearing loss. Because these tumors usually grow very slowly, the body can often compensate for these balance problems.



Although slow-growing, acoustic neuromas can eventually become large enough to press against neighboring cranial nerves. Although rare, complications resulting from the involvement of other cranial nerves include facial weakness or paralysis, facial numbness or tingling, and swallowing difficulties. Facial numbness or tingling can be constant or it may come and go (intermittent).



In some cases, acoustic neuromas may grow large enough to press against the brainstem, preventing the normal flow of cerebrospinal fluid between the brain and spinal cord. This fluid can accumulate in the skull, leading to a phenomenon called hydrocephalus, which causes pressure on the tissues of brain and results in a variety of symptoms including headaches, an impaired ability to coordinate voluntary movements (ataxia), and mental confusion. Headaches may also occur in the absence of hydrocephalus and in some rare cases may be the first sign of an acoustic neuroma. In very rare cases, an untreated acoustic neuroma that presses on the brain can cause life-threatening complications.

Causes

The exact cause of an acoustic neuroma is unknown. Most cases seem to arise for no apparent reason (spontaneously). No specific risk factors for the development of these tumors have been identified.



A variety of potential risk factors for acoustic neuroma have been studied including prior exposure to radiation to the head and neck area (as is done to treat certain cancers) or prolonged or sustained exposure to loud noises (as in an occupational setting). Research is under way to determine the specific cause and risk factors associated with an acoustic neuroma.



In a small subset of cases, acoustic neuromas occur as part of a rare disorder known as neurofibromatosis type II. This rare genetic disorder is usually associated with acoustic neuromas affecting both ears at once (bilateral). (For more information on this disorder, choose "neurofibromatosis" as your search term in NORD's Rare Disease Database.)



An acoustic neuroma arises from a type of cell known as the Schwann cell. These cells form an insulating layer over all nerves of the peripheral nervous system (i.e., nerves outside of the central nervous system) including the eighth cranial nerve. The eighth cranial nerve is separated into two branches the cochlear branch, which transmits sound to the brain and the vestibular branch, which transmits balance information to the brain. Most acoustic neuromas occur on the vestibular portion of the eighth cranial nerve. Because these tumors are made up of Schwann cells and usually occur on the vestibular portion of the eighth cranial nerve, many physicians prefer the use of the term vestibular schwannoma. However, the term acoustic neuroma is still used more often in the medical literature.

Affected Populations

Acoustic neuromas affect women more often than men. Most cases of acoustic neuroma develop in individuals between the ages of 30 and 60. Although quite rare, they can develop in children. Acoustic neuromas are estimated to affect 1 in 100,000 people in the general population. Approximately 2,500 new cases are diagnosed each year. The incidence has risen in the last several years, which some researchers attribute to the greater frequency in which small tumors are recognized. However, many individuals with small acoustic neuromas may remain undiagnosed, making it difficult to determine its true frequency in the general population.

Standard Therapies

Diagnosis

A diagnosis of an acoustic neuroma is made based upon a thorough clinical evaluation, a detailed patient history, identification of characteristic findings and a variety of specialized tests. Such tests include hearing exams, x-ray scans such as magnetic resonance imaging (MRI) or computed tomography (CT), a specialized test that evaluates balance (electronystagmography), and a brainstem auditory evoked response (BAER).



An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. MRIs are the most sensitive study to confirm the presence of an acoustic neuroma.



An electronystagmography test evaluates balance by detecting abnormal, involuntary eye movements, a condition known as nystagmus. Nystagmus may occur as a result of inner ear complications such as an acoustic neuroma.



A BAER exam checks hearing and neurological function and interaction by recording the brain's response to certain sounds. Since an acoustic neuroma can disrupt the nerve pathway that relays sound from the ear to the brain, a positive result of a BAER exam could be caused by these tumors.



Treatment

The treatment of an acoustic neuroma may involve observation (if the tumor does not cause symptoms), surgical removal (microsurgery or excision) of the tumor, or the use of radiation to stop the tumor from growing (radiation therapy or radiosurgery).



Observation

This option may be preferred in cases where no associated symptoms are present or where a small tumor is not growing or growing at a slow rate. This period of observation may be called "watch and wait". In elderly individuals who do not have symptoms, watch and wait may be appropriate because an acoustic neuroma may not require treatment during an individual's normal life expectancy and the inherent risks and complications of removal can be avoided.



Watchful waiting is also appropriate if an individual with hearing in only one ear is found with an acoustic neuroma in that ear. The patient may choose to live with the acoustic neuroma as long as it is not a life-threatening condition rather than risk further hearing loss that can potentially occur from therapy.



If an acoustic neuroma eventually causes symptoms, then radiation therapy or microsurgery may be necessary. There is not a single, "best" therapy for all affected individuals. The specific location and size of an acoustic neuroma as well as an affected individual's overall level of hearing and general health are all considered when determining which treatment method is used.



Microsurgery

Surgery performed with specialized instruments under a microscope (microsurgery) may be necessary in some individuals with an acoustic neuroma. Microsurgery allows physicians to perform surgery on very small body parts.



During microsurgery, a physician may remove all or part of an acoustic neuroma. Partial tumor removal is undertaken to reduce the risk of unwanted surgical complications. In other words, it may be easier and safer to take out part of the growth rather than the whole tumor. If the tumor is very large or if the person is older, partial removal may be more appropriate. Further surgery may be necessary in the future if partial tumor removal is performed.



When total tumor removal is indicated, the objective of the procedure is to protect the facial nerve and avoid facial paralysis. In addition the surgeon tries to preserve hearing as much as possible in the affected ear.



Three different surgical approaches are commonly used for individuals with an acoustic neuroma: retrosigmoid, middle fossa, and translabyrinthine. The size and location of the tumor as well as additional factors are all weighed when determining which approach is used.



Radiation Therapy (Radiosurgery or Radiotherapy)

Three dimensional focusing of radiation has become more accurate in recent years so that affected individuals may be treated at one session on an outpatient basis or, alternatively, smaller doses may be delivered over several sessions. The objective is to aim so accurately that the tumor cells are affected and damage to surrounding cells is minimized. Radiation therapy stops the growth of a tumor. Radiation therapy provides a noninvasive treatment option for individuals with an acoustic neuroma, but in some cases it may take weeks, months or even a couple years to see significant effects from this treatment. Tumors treated with radiation therapy can start to grow again at some point later on.



Post-treatment problems (from either surgery or radiation therapy) may include: cranial nerve deficits such facial weakness or numbness, hearing loss and dizziness. Headache, obstruction of fluid that surrounds the brain and spinal cord (cerebrospinal fluid), and/or decreased mental alertness due to blood clots or obstruction of flow of cerebrospinal fluid can also occur. Cerebrospinal fluid leakage or an infection that produces meningitis are rare complications of surgical therapy.



Damage to the facial nerve and eye problems are two potential complications of treatment for an acoustic neuroma. The facial nerve may be damaged by the acoustic neuroma or as a result of surgery. In some cases, it may be necessary for the surgeon to remove portions of the facial nerve, resulting in temporary or permanent facial paralysis. The regrowth of the nerve (regeneration) and restoration of function to the muscles of the face may take up to a year. If the facial paralysis persists, a second surgery may be performed to connect the healthy portion of the facial nerve to the hypoglossal nerve (nerve that controls the tongue) in the neck. This may bring some improvement in function to the muscles of the face. There are also other surgical procedures to aid in reanimating the sagging face.



Eye problems may develop in some individuals following surgical removal of an acoustic neuroma. Facial weakness in particular leaves the affected eye vulnerable to damage of the cornea potentially leading to blindness. The eye must be kept moist with frequent use of artificial tears, and a barrier applied especially during sleep, such as a moisture chamber, or taped closed. The use of an eye patch is discouraged as it may contribute to corneal damage.



Double vision (diplopia) may occur if there is pressure on the 6th cranial nerve, and there may be impairment of the muscles of the eyelids. Artificial tears or eye lubricants may be needed. Additionally, if prolonged facial paralysis is not treated, then it is possible that food may "get lost" in the mouth on the affected side, which could contribute to dental problems.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com



For information about clinical trials conducted in Europe, contact:

https://www.clinicaltrialsregister.eu/

References

TEXTBOOKS

Berkow R., ed. The Merck Manual-Home Edition.2nd ed. Whitehouse Station, NJ: Merck Research Laboratories; 2003:1260-1261.



Larson DE, ed. Mayo Clinic Family Health Book. New York, NY: William Morrow and Company, Inc; 1996:584.



JOURNAL ARTICLES

Agrawal Y, Clark HJ, Limb CJ, Niparko JK, Francis HW. Predictors of vestibular schwannoma growth and clinical implications. Otol Neurotol. 31(5):807-812, 2010.



Tan M, Myrie OA, Lin FR, et al. Trends in the management of vestibular schwannomas at Johns Hopkins 1997-2007. Laryngoscope. 2010;120:144-149.



Newton JR, Shakeel M, Flatman S, Beattie C, Ram B. Magnetic resonance imaging screening in acoustic neuroma. Am J Otolaryngol. 2009. [Epub ahed of print].



Roehm PC, Gantz BJ. Management of acoustic neuromas in patients 65 years or older. Otol Neurotol. 2007;28:708-14.



Regis J, Roche PH, Delsanti C, et al., Modern management of vestibular schwannomas. Prog Neurol Surg. 2007;20:129-41.



Edwards CG, Schwartzbaum JA, Lonn S, Ahlbom A, Feychting M. Exposure to loud noise and risk of acoustic neuroma. Am J Epidemiol. 2006;163:327-333.



Lin D, Hegarty JL, Fischbein NJ, Jackler RK. The prevalence of "incidental" acoustic neuromas. Arch Otolaryngol Head Neck Surg. 2005;131:241-44.



Maeta M, Saito R, Nameki H. False-positive magnetic resonance image in the diagnosis of small acoustic neuroma. J Laryngol Otol. 2001;115:842-44.



Brackman DE, Owens RM, Friedman RA, et al. Prognostic factors for hearing preservation in vestibular schwannoma surgery. Am J Otol. 2000;21:417-24.



Magnan J, Barbieri M, Mora R, et al. Retrosigmoid approach for small and medium-sized acoustic neuromas. Otol Neurotol. 2002;23:141-45.



Petit JH, Hudes RS, Chen TT, et al. Reduced-dose radiosurgery for vestibular schwannomas. Neurosurgery. 2001;49:1299-306, discussion 1306-07.



Bush DA, McAllister CJ, Loredo LN, et al. Fractionated proton beam radiotherapy for acoustic neuroma. Neurosurgery. 2002:50:270-75.



Pothula VB, Lesser T, Mallucci C, et al. Vestibular schwannomas in children. Otol Neurotol. 2001;22:903-07.



INTERNET

Kutz JW, Jr., Roland PS. Skull Base, Acoustic Neuroma (Vestibular Schwannoma). Emedicine Journal. May 16, 2012. Available at: http://www.emedicine.com/ent/topic239.htm Accessed:February 6, 2013.



Mayo Clinic for Medical Education and Research. Acoustic Neuroma. Sept. 8, 2010. Available at: http://www.mayoclinic.com/health/acoustic-neuroma/DS00803 Accessed:February 6, 2013.

Resources

Vestibular Disorders Association

PO Box 13305

Portland, OR 97208-4467

USA

Tel: (503)229-7705

Fax: (503)229-8064

Tel: (800)837-8428

Email: veda@vestibular.org

Internet: http://www.vestibular.org



Children's Tumor Foundation

95 Pine Street

16th Floor

New York, NY 10005-4002

Tel: (212)344-6633

Fax: (212)747-0004

Tel: (800)323-7938

TDD: (212)344-6633

Email: info@ctf.org

Internet: http://www.ctf.org/



American Tinnitus Association

522 S.W. Fifth Avenue Suite 825

Portland, OR 97207

United States

Tel: (503)248-9985

Fax: (503)248-0024

Tel: (800)634-8978

Email: tinnitus@ata.org

Internet: http://www.ata.org



Hearing Health Foundation

363 Seventh Avenue, 10th Floor

New York, NY 10016-3904

United States

Tel: (212)257-6140

Fax: (212)257-6139

Tel: (866)454-3924

TDD: (888)435-6104

Email: info@hearinghealthfoundation.org

Internet: http://hearinghealthfoundation.org/home



Acoustic Neuroma Association

600 Peachtree Parkway

Suite 108

Cumming, GA 30014

USA

Tel: (770)205-8211

Fax: (770)205-0239

Tel: (877)200-8211

Email: info@anausa.org

Internet: http://www.anausa.org



Alexander Graham Bell Association for the Deaf and Hard of Hearing

3417 Volta Place NW

Washington, DC 20007-2778

United States

Tel: (202)337-5220

Fax: (202)337-8314

Tel: (866)337-5220

TDD: (202)337-5221

Email: info@agbell.org

Internet: http://www.agbell.org



Better Hearing Institute

1444 I Street NW

Suite 700

Washington, DC 20005

United States

Tel: (202)449-1100

Fax: (703)684-6048

Tel: (800)327-9355

Email: mail@betterhearing.org

Internet: http://www.betterhearing.org



NIH/National Institute on Deafness and Other Communication Disorders

31 Center Drive, MSC 2320

Communication Avenue

Bethesda, MD 20892-3456

Tel: (301)402-0900

Fax: (301)907-8830

Tel: (800)241-1044

TDD: (800)241-1105

Email: nidcdinfo@nidcd.nih.gov

Internet: http://www.nidcd.nih.gov



Acoustic Neuroma Association of Canada

PO Box 193

Buckthorn, Ontario, KOL 1JO

Canada

Tel: 8005612622

Email: info@anac.ca

Internet: http://www.anac.ca



British Acoustic Neuroma Association

Oak House B

Ransom Wood Business Park

Southwell Road West

Mansfield

Nottinghamshire, NG21 0HJ

United Kingdom

Tel: 01623632143

Fax: 01632635313

Tel: 08006523143

Email: admin@bana-uk.com

Internet: http://www.bana-uk.com



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



Madisons Foundation

PO Box 241956

Los Angeles, CA 90024

Tel: (310)264-0826

Fax: (310)264-4766

Email: getinfo@madisonsfoundation.org

Internet: http://www.madisonsfoundation.org



American Academy of Audiology

11730 Plaza America Drive, Suite 300

Reston, VA 20190

Tel: (703)790-8466

Fax: (703)790-8631

Tel: (800)222-2336

Email: infoaud@audiology.org

Internet: http://www.audiology.org



For a Complete Report

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