A benign (noncancerous) tumor that appears on the nerve that goes from the inner ear to the brain is called an acoustic neuroma. The nerve is called the vestibular nerve, and it affects balance and hearing. When a person develops an acoustic neuroma, he/she may experience deafness (loss of hearing), ringing in the ear (also called tinnitus), and problems with balance. In some cases, this tumor is called a vestibular schwannoma.
Another name for this condition comes from the cells (Schwann cells) that cover the vestibular nerve. While this is a slow-growing tumor, sometimes, it may grow quite fast and become large enough to put pressure on the brain. As a result, it may negatively affect certain vital functions.
In most cases, acoustic neuromas are treated with radiation therapy and surgery to remove the tumor.
Symptoms
The symptoms of this tumor are easy to miss, and people usually do not experience symptoms in the early stages of the condition. Sometimes, those who experience hearing and balance problems may have an acoustic neuroma. However, some people may experience problems with facial muscles or sensations because this tumor may put pressure on other nerves, such as the facial nerve, trigeminal nerve, and others. Acoustic neuroma symptoms often appear when the tumor grows enough to put pressure on nearby structures. Check below the most common symptoms of an acoustic neuroma:
- Deafness (also known as hearing loss) that happens gradually over months to years. In rare cases, hearing loss may occur suddenly.
- Tinnitus (ringing in the ear)
- Dizziness
- Loss of balance
- Facial numbness
- Weakness
- Loss of muscle movement (rarely)
In severe cases, the tumor grows large enough to put pressure on the brainstem, which may cause life-threatening symptoms.
If you experience hearing problems even in one ear, do not hesitate to see a doctor. Early diagnosis and treatment can prevent severe symptoms and serious complications.
Causes
While the exact cause of acoustic neuromas cannot be identified, experts think there is a link between this tumor and a gene on chromosome 22. Normally, this gene makes a tumor suppressor protein that helps control Schwann cell growth. Commonly, people with a rare disorder known as neurofibromatosis type 2 have this abnormal gene. Moreover, they usually develop acoustic neuromas on both sides of the head (bilateral vestibular schwannomas).
Risk Factors
Neurofibromatosis Type 2
This rare disorder is the only confirmed risk factor for acoustic neuromas. People usually get this abnormal gene when they have a family history of neurofibromatosis type 2. However, only about 5% of all acoustic neuromas occur due to this rare disorder.
Noncancerous tumors that develop on balance nerves, usually on both sides of the head, are a primary characteristic of neurofibromatosis type 2. Furthermore, these benign tumors may also develop on other nerves.
In general, this disorder is an autosomal dominant disorder, which means the abnormal gene can be passed to children even from one parent. If you have neurofibromatosis type 2, there is a 50% chance your child will get this abnormal gene.
What Are The Possible Complications of Acoustic Neuroma?
People with acoustic neuromas may also experience some complications that cannot be treated. These include:
- Facial numbness
- Weakness
- Balance problems
- Ringing in the affected ear
- Deafness
If the tumor grows large enough as it can put pressure on the brainstem, and you may also experience fluid buildup in the head (also called hydrocephalus). It happens because the tumor prevents the cerebrospinal fluid from flowing between the spinal cord and the brain.
Diagnosis
Commonly, it is difficult to diagnose this tumor, especially in the early stages of the disease, because it does not cause symptoms, or they are easy to miss. The main symptom of acoustic neuromas is hearing loss. However, there are a lot of middle and inner ear conditions that may also cause loss of hearing. Check below some tests often used by doctors to diagnose the tumor:
- Hearing test (audiometry) – During this procedure, sounds are directed to the ear, and you should indicate each time you hear the sound.
- Imaging tests – These include an MRI (magnetic resonance imaging) scan or CT (computerized tomography) scan to get detailed pictures of the head. Sometimes, imaging tests may show the exact size and location of the tumor. However, if the tumor is smaller than 1-2 millimeters in diameter, these tests cannot identify it.
Treatment
Treatments are often different among people with acoustic neuromas because they depend on several factors. For example, the size, location, and growth rate of the tumor, existing health problems, and your symptoms. In any case, physicians usually recommend monitoring and surgery or radiation therapy.
Monitoring
When the tumor is small and does not cause symptoms, your healthcare team may recommend monitoring it and may not give you treatment. Monitoring is usually recommended for older adults who should not receive more aggressive treatments.
Furthermore, regular checkups that involve imaging and hearing tests are required during monitoring. It helps determine how fast the tumor grows.
Surgery
Healthcare providers usually recommend surgery if the tumor continues to grow, becomes very large, or causes symptoms. However, there are several options to remove the tumor.
The goal of this treatment is to remove the tumor, preserve facial nerves, and prevent serious complications. In some cases, surgeons cannot remove the tumor completely. Therefore, doctors may prescribe additional radiation therapy to destroy the part of the tumor that remains after surgery.
Usually, the surgery to remove an acoustic neuroma is performed under general anesthesia. Unfortunately, this surgery carries certain risks, which may worsen existing symptoms due to damage to the nerves that control balance, hearing, or facial muscles. Check below for other surgery complications:
- Cerebrospinal fluid leakage
- Hearing loss (also called deafness)
- Facial numbness or weakness
- Tinnitus
- Chronic headaches
- Problems with balance
- Infections (such as meningitis)
- Stroke or brain bleeding (these complications happen quite rarely)
Radiation Therapy
There are several types of radiation surgery that can be used to destroy an acoustic neuroma. For example:
- Fractionated stereotactic radiotherapy (SRT) – During this procedure, the patient gets a small dose of radiation to the tumor. It is often recommended for people with a slow-growing tumor.
- Proton beam therapy – In such cases, it uses powerful energy beams that come from protons to destroy the tumor. This type of radiation therapy also reduces the radiation exposure to the nearby tissues.
Stereotactic Radiosurgery
This is another type of radiation therapy that can be used to treat acoustic neuromas. Healthcare professionals also recommend this therapy when the tumor is less than 2.5 centimeters in diameter, and for older adults who cannot tolerate more aggressive treatments.
Therapies such as Gamma Knife and CyberKnife use multiple small gamma rays to destroy the tumor. Moreover, it does not cause damage to the nearby tissues and does not require an incision (cut).
However, it may take months or even years until you notice the effects of this therapy. During this time, doctors will perform regular checkups to monitor the progress. However, like other surgeries, stereotactic radiosurgery carries some risks. For example:
- Hearing loss
- Ringing in the ears
- Facial weakness
- Balance problems
- Recurrent tumor
Frequently Asked Questions
What is the survival rate for acoustic neuroma?
In general, with treatment, the mortality rate is below 0.5%. Unfortunately, there are some permanent complications (such as loss of hearing) if the tumor grows very large.
What happens if an acoustic neuroma goes untreated?
If you ignore the symptoms and do not get treatment, it may lead to certain complications. For example:
- Hydrocephalus
- Permanent deafness
- Infections (such as meningitis)
This article does not contain a full list of acoustic neuroma complications. Do not hesitate to see a doctor if you experience problems with hearing or balance without obvious reasons.
What can be mistaken for an acoustic neuroma?
There are certain conditions that can be mistaken for acoustic neuromas. These include:
- Meniere’s disease
- Benign paroxysmal positional vertigo (BPPV)
- Neurological disorders
- Temporomandibular disorders (TMD)
Ask your healthcare provider if you have additional questions.
