Acoustic neuromas, also known as vestibular schwannomas, arise from the hearing and balance nerve. While some patients have no noticeable symptoms or problems, others complain of dizzy spells, vertigo, trouble hearing, facial numbness, and sometimes weakness and swallowing difficulties. Though most acoustic neuromas are benign and confined to the inner ear canal, some grow larger and push on the brainstem, which can be life-threatening.
Doctors have refined how they handle acoustic neuromas over the years, to a point where “treatment is very successful in the right hands, using a fairly standardized approach for when to observe, operate, or radiate a tumor,” says Jennifer Moliterno, MD, an assistant professor of neurosurgery at Yale School of Medicine. “When surgery is necessary, our goal is to remove as much of the acoustic neuroma as safely possible without causing permanent weakness to the face. Because our surgeons perform both surgery and radiosurgery, we are able to combine the use of both, leading to better outcomes.”
What is an acoustic neuroma?
An acoustic neuroma is a growth on the vestibular nerve, anywhere along the area where the nerve exits the brainstem at the base of the skull and enters the ear canal.
“Neuroma” is actually a misnomer as this tumor is actually a "schwannoma." (Doctors may use the terms “acoustic neuroma” and “vestibular schwannoma” interchangeably.) By definition, a schwannoma is any slow-growing, benign tumor that originates in a certain type of cell, called a Schwann cell. They most commonly develop on the hearing and balance nerve, also known as Cranial Nerve (CN) 8, but they can also arise from some of the other nerves in the head and spine. The 12 CNs—which originate in the brain and lead to the head, neck, and body—control various important senses and responses.
What are symptoms of acoustic neuromas?
Because CN 8, the nerve that gives rise to acoustic neuromas, controls hearing and balance, symptoms most often include hearing loss, dizziness, vertigo, or problems with balance.
Some patients, especially those with larger tumors, experience facial weakness or numbness because CN 8 is very closely related to CN 7 (the facial nerve), which controls facial strength and function on the same side of the face—and CN5, the trigeminal nerve. Some patients may also experience facial pain (trigeminal neuralgia). Another occasional symptom is loss of taste.
Acoustic neuromas typically grow slowly, so symptoms may develop over time, be subtle, and go largely unnoticed as a result. Only when they reach a very large size can they cause other problems, including difficulty with swallowing and obstruction of the flow of cerebrospinal fluid.
How is acoustic neuroma diagnosed?
The first step is to see a doctor (either a primary care physician or an otolaryngologist) if a spell of dizziness, vertigo, or hearing loss does not improve quickly.
Because there are many potential causes of dizziness or hearing loss, the doctor will do a full examination in order to identify the underlying problem. This includes a hearing test and possibly magnetic resonance imaging (MRI). The MRI can reveal a tumor in the region of the cerebellopontine angle (CPA), which is the part of the brain where CN 8 exits the brainstem and enters the inner ear canal.
Acoustic neuromas can also be found incidentally, or by chance, during a work-up after head trauma.
How are acoustic neuromas treated?
With many factors considered in determining treatment, acoustic neuromas are managed with close follow-up, radiation, or surgery. At Yale Medicine, the patient's symptoms, tumor size, age and overall health, and medical condition are considered in making treatment decisions.
In relatively young and healthy patients with symptomatic and relatively large neuromas, surgery is usually the best option. Unlike other types of primary brain tumors, these acoustic neuromas always occur in the same location. To reach the tumor, neurosurgeons will often operate in collaboration with a highly skilled and specialized ear, nose, and throat surgeon. Surgery is performed with specialized neuromonitoring, whereby neurophysiologists in the operating room monitor the function of the CNs during surgery while the patient is asleep. This allows the surgeon to remove as much tumor as safely as possible, ensuring the best facial function long-term.
For smaller neuromas, treatment may involve open surgery, close monitoring with serial MRIs, or Gamma Knife radiosurgery, which uses very focused radiation to target and kill the tumor’s cells to impede its growth.
What are the risk factors for acoustic neuromas?
Acoustic neuromas, as well as other types of tumors involving the nervous system, are common in a syndrome called neurofibromatosis, in which genetic mutations cause tumor growth.
It's important to note that having an acoustic neuroma does not always mean a person has neurofibromatosis. Some acoustic neuromas arise spontaneously, in people who don't have neurofibromatosis.
What makes Yale Medicine’s approach to treating acoustic neuromas unique?
Acoustic neuromas can be challenging to treat, so surgical removal should only be done by physicians with substantial clinical experience and expertise. At Yale Medicine, we bring together a highly experienced, multidisciplinary team of doctors who treat the whole patient—not just the acoustic neuroma.
If the patient is a good candidate for surgery, we are able to access the location of the neuromas via a few different pathways—through the inner ear or the skull—and explain the pros and cons of each approach to the patient. We perform every surgery with state-of-the-art monitoring capabilities, allowing us to ensure the function of the CNs are preserved in the long-term.
Often, our surgeons will opt to leave a small amount of tumor on the facial nerve to ensure facial function is maintained. This very small area can be followed or receive very focused radiation, if necessary. In some cases, surgery can be avoided entirely and Gamma Knife radiosurgery can be the first line for treatment of these tumors.
“Our team and its unparalleled expertise and access to state-of-the-art facilities, both in and out of the operating room, allow us to provide the best, most comprehensive care for each patient," says Dr. Moliterno. "Management of acoustic neuromas should be done only by experts who do so on a daily basis, and we are pleased to take care of many patients with acoustic neuromas.”