Acoustic Neuroma Research

[Tamar Navratil]

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.

Researchers at University of California San Diego School of Medicine found that using an innovative surgical approach to remove an acoustic neuroma, a slow-growing, benign brain tumor, improved hearing preservation and quality of life for patients while also presenting excellent facial nerve outcomes.

The results, published in the May 21, 2024 online edition of Otology & Neurotology, showed that surgically removing an acoustic neuroma by exposing the area above the inner ear and the internal auditory canal significantly improved hearing preservation and quality of life, along with balance, anxiety, energy, pain and general health in patients at the one-year post-surgery mark.

The middle fossa craniotomy approach is used to treat smaller tumors, up to about 1.7 centimeters in length, generally confined to the internal auditory canal. It involves a skilled specialist looking down at the floor of their cranial cavity and making an incision above the ear. They then carefully expose and dissect the tumor, without compromising the surrounding structures of the brain or inner ear to preserve hearing.

An acoustic neuroma, also referred to as a vestibular schwannoma, is a tumor that can grow on the nerve that connects the ear to the brain. Schwann cells wrap around nerve fibers to help support and insulate them, including hearing and balance nerves inside the ear. Overproduction of these cells, however, can cause tinnitus (ringing in the ear), hearing loss, dizziness, and loss of balance. If left untreated, the tumor can grow and place pressure on the nerve and nearby brain structures and become life threatening.

Patients like Julie Sifford, a Las Vegas resident, deeply understand the desire for greater relief from symptoms caused by a small tumor. In early 2023, she experienced the effects of an acoustic neuroma firsthand.

Following her extensive research to ensure she was in the hands of qualified surgeons, Sifford was referred to the acoustic neuroma program at UC San Diego Health where world-renowned specialists Friedman and Marc Schwartz, MD, co-director of the program and neurosurgeon at UC San Diego Health, evaluated her and made recommendations on how best to proceed with treatment.

Recognized as an Acoustic Neuroma Association Center of Excellence, the international, multidisciplinary program at UC San Diego Health is skilled in newer techniques, including the middle fossa craniotomy. They are the highest-volume acoustic neuroma center in the nation by a significant margin, averaging 160 surgeries annually.

Sifford added she did not want to subject herself to possible future complications for the rest of her life. Leaning toward the middle fossa craniotomy and considering the collective information she received from both doctors, Sifford, who was not part of the study cohort, made the informed decision to have surgery.

Unilateral/asymmetric hearing loss and/or tinnitus and loss of balance/dizziness are early signs of a vestibular schwannoma. Unfortunately, early detection of the tumor is sometimes difficult because the symptoms may be subtle and may not appear in the beginning stages of growth. Also, hearing loss, dizziness, and tinnitus are common symptoms of many middle and inner ear problems (the important point here is that unilateral or asymmetric symptoms are the worrisome ones). Once the symptoms appear, a thorough ear examination and hearing and balance testing (audiogram, electronystagmography, auditory brainstem responses) are essential for proper diagnosis. Magnetic resonance imaging (MRI) scans are critical in the early detection of a vestibular schwannoma and are helpful in determining the location and size of a tumor and in planning its microsurgical removal.

Early diagnosis of a vestibular schwannoma is key to preventing its serious consequences. There are three options for managing a vestibular schwannoma: (1) surgical removal, (2) radiation, and (3) observation. Sometimes, the tumor is surgically removed (excised). The exact type of operation done depends on the size of the tumor and the level of hearing in the affected ear. If the tumor is small, hearing may be saved and accompanying symptoms may improve by removing it to prevent its eventual effect on the hearing nerve. As the tumor grows larger, surgical removal is more complicated because the tumor may have damaged the nerves that control facial movement, hearing, and balance and may also have affected other nerves and structures of the brain.

Unilateral vestibular schwannomas affect only one ear. They account for approximately 8 percent of all tumors inside the skull; approximately one out of every 100,000 individuals per year develops a vestibular schwannoma. Symptoms may develop at any age but usually occur between the ages of 30 and 60 years. Most unilateral vestibular schwannomas are not hereditary and occur sporadically.

Bilateral vestibular schwannomas affect both hearing nerves and are usually associated with a genetic disorder called neurofibromatosis type 2 (NF2). Half of affected individuals have inherited the disorder from an affected parent and half seem to have a mutation for the first time in their family. Each child of an affected parent has a 50 percent chance of inheriting the disorder. Unlike those with a unilateral vestibular schwannoma, individuals with NF2 usually develop symptoms in their teens or early adulthood. In addition, patients with NF2 usually develop multiple brain and spinal cord related tumors. They also can develop tumors of the nerves important for swallowing, speech, eye and facial movement, and facial sensation. Determining the best management of the vestibular schwannomas as well as the additional nerve, brain, and spinal cord tumors is more complicated than deciding how to treat a unilateral vestibular schwannoma. Further research is needed to determine the best treatment for individuals with NF2.

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