Acoustic Neuroma Statistics

[Irati Klute]

Observationmight be a valid treatment strategy for small, slow-growing acoustic neuromas; however, patients can experience significant anxiety after a tumor diagnosis. When immediate treatment is indicated, physicians and patients must choose between highly specialized options.

Mayo Clinic in Rochester, Minnesota, has strong experience treating acoustic neuroma with a range of treatment options. Treatment is tailored to the needs, both immediate and long term, of the individual patient.

"Acoustic neuroma is a rare disorder that requires very specialized treatment. We have decades of experience and also have done a great deal of research looking at what patients experience after treatment," says Michael J. Link, M.D., a consultant in Neurosurgery at Mayo Clinic's campus in Minnesota.

Acoustic neuromas, which develop in only two to four people per 100,000, are typically discovered on MRI after patients present with unilateral hearing loss, tinnitus, and sometimes dizziness or headache. Surgical removal was once standard treatment; however, reduced tolerance of post-treatment morbidity has resulted in a greater proportion of patients undergoing observation or stereotactic radiosurgery.

"Only about 30 percent of acoustic neuromas show growth four years after diagnosis. In the remaining 70 percent of cases, we can just watch for a while," Dr. Link says. "But in those cases, patient anxiety must be managed. A major finding of our research is that having a diagnosis of acoustic neuroma significantly impacts a person's quality of life, even though the tumor is benign and possibly small."

Treatment is generally recommended for patients whose tumors are growing or who have symptoms amenable to treatment, particularly if those patients are young. Outcomes are generally good, whether treatment involves stereotactic radiosurgery or surgical removal of the acoustic neuroma.

"When treated by an experienced team, most patients with small to medium tumors experience high rates of tumor control and excellent facial nerve outcomes, regardless of treatment modality," Dr. Link says. Indeed, in the largest quality-of-life study conducted among patients with acoustic neuromas, published in the April 2015 issue of the Journal of Neurosurgery, Mayo Clinic researchers and colleagues in Bergen, Norway, found that patient-related factors such as overall physical and emotional health have a stronger impact on quality of life than treatment strategy does.

Although tumors can be successfully controlled, many patients continue to experience symptoms after treatment. Regardless of treatment strategy, the long-term prospects for hearing in the affected ear are poor. More than 75 percent of patients studied had nonserviceable hearing in the affected ear eight years after treatment for acoustic neuroma, according to a paper by the Mayo Clinic and Bergen researchers published in the August 2015 issue of Neurosurgery.

"We've learned that there's not a big advantage of one treatment over another for long-term quality of life," Dr. Link says. "But when we spend time talking with a patient, we can usually figure out the best treatment for that individual. If a patient says, 'I can't live like this; I have to get this tumor removed,' then we can tell the patient what we think life will be like eight years from now if the tumor is removed using surgery, or if the patient receives stereotactic radiosurgery and the tumor is controlled."

Mayo Clinic was among the first centers in the United States to offer Gamma Knife radiosurgery. Over the past 26 years, it has been used at Mayo Clinic's campus in Minnesota to treat approximately 1,000 acoustic neuromas. In addition, Mayo Clinic neurosurgeons have surgically removed thousands of acoustic neuromas.

Otolaryngologists work with neurosurgeons on each case. Intraoperative monitoring is used to avoid damaging auditory, facial and other cranial nerves. "We think it's important to take out all of the tumor. But sometimes we do a less than complete resection to keep the facial nerve intact," Dr. Link says. "We follow up on those patients and might treat them with Gamma Knife radiation down the road, if the tumor grows."

Patients who continue to experience severe headache after treatment can be referred to Mayo Clinic neurologists who specialize in headache. Vestibular rehabilitation is offered to patients with balance problems.

"All of the treatment strategies for acoustic neuroma have advantages and disadvantages," Dr. Link says. "We are starting to learn that if a tumor is fast-growing, it might not respond as well to radiation. In those cases we tend to lean toward surgery. But we look at each case individually to determine what is best for that patient."

Carlson ML, et al. Long-term quality of life in patients with vestibular schwannoma: An international multicenter cross-sectional study comparing microsurgery, stereotactic radiosurgery, observation, and nontumor controls. Journal of Neurosurgery. 2015;122:833.

NORD gratefully acknowledges Howard W. Francis, MD, Professor, Seth E. Pross, MD, Fellow and Yuri Agrawal, MD, Associate Professor, Division of Otology and Neurotology, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, for assistance in the preparation of this report.

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). Although there is no standard or typical pattern of symptom development, hearing loss in one ear (unilateral) is the initial symptom in approximately 90 percent of affected individuals. Additional common findings include ringing in the ears (tinnitus) and dizziness or imbalance. 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.

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 patients. 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. While rare, symptoms 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 patients, 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.

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.

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.

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 about 1 in 100,000 people in the general population. Racial differences have been reported in which Black, Hispanic, and Asian Americans have relatively lower rates of acoustic neuroma diagnoses than White Americans.

Approximately 2,500 new patients 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.

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