Acoustic Neuroma Neurosurgery

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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.

Acoustic neuroma, also known as vestibular schwannoma, can happen to anyone, and some of the causes appear sporadic. Often experts can't pinpoint what causes acoustic neuroma. Still, there are two known main acoustic neuroma risk factors:

If a patient has received high dose cranial radiation therapy for the treatment of cancer, they may be at risk of developing an acoustic neuroma. Procedures such as dental X-rays do not predispose a person to this disease.

Acoustic neuroma symptoms are often ear-related, causing problems with hearing and balance. These symptoms may be difficult to detect early on and can develop as the tumor grows. The canal in the skull is only large enough for the seventh and eighth cranial nerves. The eighth crania nerve travels from inside the brain stem out through a small piece of bone into the hearing apparatus, or the vestibular apparatus. As the mass grows, it can compress on both nerves, leading to the following symptoms of acoustic neuroma:

An acoustic neuroma diagnosis is often difficult to make early because symptoms may be minor and appear similar to other inner ear problems. Diagnosing acoustic neuroma begins with a physician examining the patient. An acoustic neuroma hearing test, usually an audiogram, assesses the hearing in each ear. If diminished hearing is found, a patient may undergo an MRI for acoustic neuroma, CT scan or other diagnostic imaging procedure to determine if a mass is present.

Acoustic neuroma treatment depends on the size and growth speed of the acoustic neuroma, severity of the patient's symptoms, and overall age and health of the patient. Doctors may choose to monitor the acoustic neuroma if the patient isn't a good candidate for surgery because of other conditions. Surgeries and radiation therapy are key treatment options.

If a patient has a relatively minor tumor with no symptoms or is of an age or has a health condition that makes surgery less appropriate, doctors may choose to monitor the benign tumor. During observation, the patient will undergo scans or MRIs to track the potential growth of the tumor and take regular hearing tests to log symptom changes.

The advantages of the surgical removal of acoustic neuromas are twofold. The first benefit to surgery is pathologic diagnosis. By removing the tumor, neuropathologists can examine and conduct genetic tests on the tumor tissue to determine the variant of the tumor and learn more about its origin. The other advantage of surgery is that the acoustic neuroma is completely removed. Once taken out, the chances of an acoustic neuroma recurring are greatly diminished.

The function of the seventh cranial nerve, which controls facial movement on the same side that is being operated on, is observed during surgery via a process called neuromonitoring. The nerve is stimulated electrically to monitor how the facial nerve and the cochlear apparatus are doing. Using a device that sits in the ear, the neurosurgeon can register whether a signal is being sent down the nerve and into the brain stem.

This surgical procedure is completed by a neuro-otologist, who approaches the surgery by entering through the hearing apparatus. With this method, there is no attempt to save hearing. Translabyrinthine is ideal if the patient has no serviceable hearing when they are diagnosed with an acoustic neuroma.

Depending on your age and health, the recovery period for surgical removal of the acoustic neuroma is four to eight weeks. Your dedicated skull base physician assistant will guide you through each step of the surgical process and will be available to answer any questions and concerns you may have throughout and during the follow-up process of your surgery.

It is important to note that none of the areas operated on during acoustic neuroma surgery has anything to do with personality, memory, language or movement, and you will be the same person you were prior to surgery. You will be up and walking around the day after surgery with assistance from our dedicated neuro-trained nurses during your hospitalization. Most people recover very well from cranial surgery. While you may experience pain from the incision and potentially some neck stiffness, you will get stronger each day.

Vestibular schwannoma is a common name for acoustic neuroma. The name arises because acoustic neuroma is an overgrowth of the Schwann cells that insulate the nerve of the brain and the cranial nerves. It is vestibular because it grows off the eighth cranial nerve, the vestibulocochlear nerve.

Acoustic neuroma treatment depends on the size and growth speed of the acoustic neuroma, severity of the patient's symptoms and overall age and health of the patient. Doctors may choose to monitor the acoustic neuroma if the patient isn't a good candidate for surgery because of other conditions. Surgeries and radiation therapy are other key treatment options.

Like all cranial surgeries, there is a risk of bleeding, infection, injury to the brain and risk of injury to one of the blood vessels in the brain that may result in a stroke, coma or even death, which is why having a well-trained and experienced care team is vital. The goal of the surgical procedure is about removing the acoustic neuroma while simultaneously preserving the facial nerve and hearing.

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