Vestibular Schwannoma (Acoustic Neuroma)

Vestibular schwannoma, also called an acoustic neuroma, is a benign (non-cancerous) tumor that typically grows on the balance portion of the eighth cranial nerve.

The eighth cranial nerve is responsible for hearing and balance and carries that information from the inner ear to the brainstem. The nerve has three distinct parts that connect to the inner ear: the superior and inferior vestibular (balance) nerves and the cochlear (hearing) nerve, which come together at the brainstem.

The tumors are relatively uncommon, accounting for five to seven percent of all brain tumors. However, for the part of the brain where they are located, called the cerebellopontine angle, it is the most common tumor type.

Being diagnosed with a vestibular schwannoma is one per 20,000 people annually and may get as high as one per 5,000 people over the age of 70. This number is higher than previously thought because our ability to detect tumors with magnetic resonance imaging (MRI) has improved.

In most patients, hearing loss is the first symptom. In the 1800s, it was thought that the tumor grew on the cochlear (hearing) portion of the eighth cranial nerve, which is why it was referred to as an “acoustic neuroma.” We now know that the tumor most often appears on the vestibular (balance) portion of the eighth cranial nerve, therefore the more accurate name is vestibular schwannoma. Both names are still commonly used and refer to the same tumor.

Vestibular schwannomas come in different sizes and can cause different symptoms. This tumor does not spread (metastasize) nor does it invade the brain, but if large enough, it can put pressure on the brain and cranial nerves.

What Are the Symptoms of a Vestibular Schwannoma?

The symptoms of a vestibular schwannoma may include:

Sudden or gradual hearing loss (sensorineural hearing loss)
Ringing, roaring, buzzing, or hissing in the ears or head, known as tinnitus
Ear fullness
Vertigo, or feeling like you are spinning when you are still
Imbalance, or unsteadiness
Headache
Facial weakness
Facial numbness

css id:

What Causes a Vestibular Schwannoma?

The exact cause of most vestibular schwannomas is unknown. Ninety-five percent of tumors occur spontaneously and are found on one side (unilateral) only. A small subset of vestibular schwannomas is associated with a genetic condition called Neurofibromatosis Type 2 (NF2). NF2 is rare and results in bilateral vestibular schwannomas. Regardless of the cause, the tumor originates from Schwann cells, which insulate nerves allowing them to transmit their neural signal quickly. When a tumor develops, the Schwann cells grow too quickly and can damage the nerve. In general, vestibular schwannomas grow slowly with an average growth rate of one to two millimeters per year. However, some tumors do not grow for several years and others grow rapidly.

Researchers continue to look for potential causes of vestibular schwannomas. High-dose therapeutic radiation to the head may increase the risk. Overall, there is no clear evidence that environmental factors, such as cell phones, cause these tumors. The rising incidence of vestibular schwannomas likely relates to improvements in magnetic resonance imaging (MRI) and increased screening for concerning symptoms.

css id:

What Are the Treatment Options?

Management of vestibular schwannomas centers around three different options: observation with repeated imaging, radiation, and surgery. The decision is complex and must account for tumor size, hearing status, symptoms, patient health, patient preference, and physician preference. Weighing these factors requires a thorough discussion with your ENT (ear, nose, and throat) specialist, or otolaryngologist, and often referral to additional specialists in neurotology, neurosurgery, and/or radiation-oncology.

Tumors can be classified as small, medium, or large. In general, small tumors are less than 1.5 cm, medium tumors are between 1.5 – 2.5 cm, and large tumors are greater than 2.5 cm. As tumors grow, they tend to cause more problems including hearing loss and compression on the brainstem.

Observation—The “wait and scan” approach may be an option for small tumors or patients for whom treatment carries increased risk. Repeat imaging can help determine the tumor’s growth rate and whether symptoms are changing over time, both of which may influence eventual treatment decisions. In some patients, the tumor may grow at such a slow rate that treatment within their life expectancy is unlikely. With this option, continuing to monitor the tumor with MRIs is critical.

Radiation—Stereotactic radiosurgery (SRS) can be delivered in a single dose or the radiation may be divided into three to five treatment sessions. Radiation is often reserved for growing small- to medium-sized tumors, but other factors should be discussed with your treating physician(s). Different technologies can deliver SRS, such as Gamma Knife®, CyberKnife®, and Triology®. Research has not shown that one radiation technology is better than another. So far, proton beam technology has not been recommended for vestibular schwannoma treatment. In general, the goal of radiation is to stop tumor growth. For some patients, after radiation the tumor may enlarge or swell before it stabilizes or shrinks. Also, long-term hearing often gets worse after radiation. With this option, continuing to monitor the tumor with MRIs is critical.

Surgery—The goal of microsurgery is to remove the tumor while preserving the function of nearby nerves and the brainstem. This option may be selected for a variety of reasons, including large, symptomatic tumors or small tumors with a chance of hearing preservation. There are three primary approaches—behind (retrosigmoid/suboccipital), above (middle cranial fossa), or through (translabyrinthine) the ear—all of which require opening the skull to reach the tumor. The specific approach depends on tumor size, hearing function, and surgeon preference. After surgery, patients can expect a three- to five-day hospital stay. Further details about hospitalization and the risks of surgery should be discussed with the surgeon.

If removing the tumor jeopardizes facial function or brainstem health, a portion of the tumor may be left behind. If the portion of tumor left behind is very small, it can be monitored and sometimes does not grow. If it does grow, radiation or revision surgery may be recommended. If a larger portion of the tumor is left behind, there is an increased likelihood of needing additional treatment.

css id:

What Questions Should I Ask My Doctor?

General Questions

How big is my tumor? Is it growing?
How is my tumor affecting my hearing?
What options do I have for treating my hearing loss?
Are my family members at risk for also having a vestibular schwannoma?
What kind of specialists might be needed to help manage my tumor and symptoms?

Observation Questions

What are the risks and benefits of observation (“wait and scan”)?
How frequently do I need repeat MRIs?
How frequently do I need hearing tests?
What will our plan be if the tumor grows?
What should I do if I experience new symptoms?

Radiation Questions

What are the risks and benefits of radiation?
What type of radiation would you use?
How frequently do I need repeat MRIs?
How frequently do I need hearing tests?
In my tumor, do you think radiation will stop its growth?
What is the plan if the tumor grows despite radiation?

Surgery Questions

What are the risks and benefits of surgery?
What type of surgical approach would you recommend?
How frequently do I need repeat MRIs?
How frequently do I need hearing tests?
Can you describe the process for surgical treatment including hospitalization and recovery?
What is the plan if some tumor is left behind after surgery?

Last reviewed May 2020.

Other Ear Conditions

Hearing and balance are critical to how we conduct our daily lives. ENT specialists treat conditions such as ear infection, hearing loss, dizziness, ringing in the ears (called tinnitus), ear, face, or neck pain, and more.