A vestibular schwannoma, more commonly referred to as an acoustic neuroma, is a benign (noncancerous) tumor. Here’s what you should know.
A vestibular schwannoma (acoustic neuroma) is the second most common tumor found inside the head, affecting roughly one out of every 100,000 people per year, in the United States. The tumor forms from the Schwann cells that line the balance nerve fibers that connect the inner ear to the brain.
The tumor does not spread, but it does grow. As it enlarges, it infiltrates into the remaining balance and hearing nerves, causing disequilibrium and hearing loss. It can, ultimately, push on the brain or other nerves in the area, if it gets large. In most cases, these tumors grow slowly, over many years, but sometimes the rate of growth changes and becomes rapid.
Why did I get a vestibular schwannoma?
There are no known risk factors for most patients that have vestibular schwannoma. They are almost always only in one ear. Thus, for most patients, we don’t really know. However, there is a rare genetic disease (neurofibromatosis type 2), where patients get vestibular schwannoma in both ears (and sometimes other tumors inside the head, such as meningioma). This disease is usually only diagnosed in children or very young adults.
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- Tinnitus (ear noise/ringing in the ear)
- Hearing loss in one ear
- Vague disequilibrium, particularly with rapid head turns, such as when changing lanes on the highway
- Facial numbness
- Facial twitch
Evaluation and treatment
A careful examination of the ear is needed. An audiogram tells the amount of hearing loss. A magnetic resonance imaging (MRI) of the internal auditory canals, with and without gadolinium contrast, is necessary for the diagnosis.
Treatment options, risks and expected outcomes
These are very slow growing, benign tumors, and it is rare for urgent treatment to be needed. There are three main management strategies:
Serial MRI scans (typically every six-12 months) can be obtained to see if the tumor is growing. On average, they grow approximately 1 millimeter per year. If it is not growing and there is no change in the patient’s symptoms, observation can be continued indefinitely. One risk with observation is that, if the patient has serviceable hearing in the affected ear, the hearing loss can get worse. Unless the tumor is large and it would be risky to delay treatment, we typically recommend a period of observation for most patients to make the tumor “prove” that it needs treatment.
2. Stereotactic radiation
This is a highly conformal technique to delivering radiation to the tumor to stop it from growing. We typically use our Gamma Knife to deliver the radiation. While tumors can shrink, they never completely go away, and they will still need to be followed with serial MRI scans to make sure that the tumor does not start growing again later. This chance is very low (approximately 1%, although it depends upon the size of the tumor; long-term data are lacking). The tumor usually swells after the radiation therapy, about three-six months after the treatment. During this time, the tumor may compress the auditory nerve, within its bony canal, causing the hearing to drop. The chance of preserving hearing with radiation is roughly 50-60% at five years after treatment. The chance of preserving facial nerve function is approximately 98-99%. Stereotactic radiation should be considered for every patient, although it is often best used in smaller tumors and in older patients.
3. Microsurgical removal
Removing the tumor is the most definitive treatment. We perform this surgery in partnership with our neurosurgical colleagues, as part of the USC Skull Base Team. Small tumors can usually be completely removed, while a less-than-complete resection may be performed for large tumors, to offer the best chance at preserving facial nerve function. If a less-than-complete resection is performed, the tumor remnant will be followed with serial MRI scans and stereotactic radiation, given if it demonstrates growth (remnants usually do not grow). We use all three surgical approaches (translabyrinthine, middle fossa and retrosigmoid) and select the approach based on individual patient factors. The chance of preserving normal or near-normal facial nerve function is approximately 98-99% at one year after surgery, although temporary weakness is more common and may last for several months after surgery. Larger tumors (greater than 2.5 centimeters) have a lower rate of facial nerve preservation. Hearing preservation depends upon the tumor size and location but can be as high as 60-70% for small tumors. Other risks of surgery include cerebrospinal fluid leak, requiring additional hospitalization or further surgery; bleeding; stroke; seizure; and incoordination of the arms or legs. It is also possible (but unlikely) that the tumor is in fact not a vestibular schwannoma but a facial nerve schwannoma, meaning that facial weakness will occur.
Surgery to remove an acoustic neuroma will take up most of the day. Afterward, the patient will stay in the intensive care unit one night, so that they can be closely monitored. The next day, the patient will usually be transferred to a regular room. If needed for balance problems after surgery, physical therapy will be ordered to help the patient get up and walk around. Some people need to use a walker after surgery to help prevent falls.
Patients are considered safe to go home, when they are:
- Steady on their feet
- Eating and drinking fluids without vomiting
- Not experiencing extreme dizziness
- Controlling their pain
- Experiencing no complications
This can be anywhere from two to six days, but four days is our average.
Some people have weakness of half their face after surgery. This can occur immediately or have a delayed onset by a few days. If a patient has this, we will provide lubricating eye drops for the patient to use every one to two hours, during the day. We will provide lubricating eye ointment for the patient to apply at night, and we will teach the patient how to tape their eye shut, so it does not get dried out, red or scratched.
After surgery, it is normal to have some pain, discomfort, headaches, tiredness, dizziness, feelings of being off-balance and weak. The patient will have some difficulty focusing, while reading or on the computer, and will likely need frequent breaks. This may last several weeks to several months.
The patient should try to stay as active as possible. However, the patient should not bend over, exert themselves or lift anything heavy, for at least one month after surgery.
If you have hearing loss or ringing of the ears, make an appointment with a neurotologist. To learn more about USC Acoustic Neuroma Center, visit www.acousticneuroma.keckmedicine.org.
To schedule an appointment, call (800) USC-CARE (800-872-2273) or visit https://acousticneuroma.keckmedicine.org/request-an-appointment/.