An acoustic neuroma is a tumor that is noncancerous or benign that affects the nerves running from the inner ear to the brain.
This prevents the nerves that are responsible for hearing and balance from properly functioning, resulting in hearing loss and tinnitus or ringing in the ears.
In later stages, an acoustic neuroma may affect the cerebellum and brainstem nerves, and may increase brain pressure. These can have life-threatening effects. However, the tumor does not spread to other areas of the body.
Certain acoustic neuroma names include acoustic neurinoma, vestibular schwannoma, and auditory nerve tumor.
A layer of cells called Schwann cells by doctors covers nearly all healthy nerves in the body. Schwann cells provide nerve impulses with an insulation and protection. If they start multiplying over the eighth cranial nerve too quickly, acoustic neuroma occurs.
Over a number of years, the tumor normally develops gradually but finally the symptoms may appear unexpectedly.
Acoustic neuroma is rare. It affects about 1 in every 100,000 people according to the National Association of Rare Diseases (NORD). There are around 2,500 new diagnoses each year in the United States, and it usually appears between the ages of 30 and 60 years.
Treatment depends on several factors, including:
- age of the affected individual
- general health of the person
- location and tumor size
A doctor will in some cases prescribe watchful waiting. If the tumor is small or growing slowly, then no further action may be required.
If care is required, as we explain here there are many choices.
This is a kind of radiation therapy which precisely targets the tumor with radiation. Doctors also call it the “gamma knife,” and consider it a non-invasive treatment.
A doctor uses local anesthesia to numb the scalp and then a lightweight head frame is attached.
Imaging scans identify the tumor location and show the doctor where the radiation beams should be applied to.
Over multiple sessions the individual may need treatment. It may also take weeks , months, or years to feel the treatment ‘s effects and often the tumor returns.
Radiosurgery is typically only an option if the tumor is 3 centimeters (cm) or less across.
This procedure helps a surgeon to extract all or part of the tumor using special instruments, through an incision in the skull under general anesthesia.
Occasionally, surgeons can remove only part of the tumor because removing all of it could damage facial nerves. Damage to the facial nerves could lead to facial paralysis.
A doctor can use radiosurgery to reduce the size or restrict tumor growth, or to remove any remaining tumor traces after microsurgery. Careful radiation targeting allows the doctor to minimize damage to healthy tissue around the tumour.
A doctor can monitor the person’s recovery after surgery and test for symptom recurrence.
Sometimes, after surgery, there is a high risk of hearing loss, especially if the person has a tumor on every acoustic nerve. In this case the doctor may suggest that surgery be delayed for as long as possible.
Other side effects of treatment may include:
- facial weakness or numbness
- reduction in mental alertness if blood clots or a blockage of cerebrospinal fluid occur
- possible eye problems, including double vision or a drooping eyelid if treatment interferes with nerves
Researchers are currently looking into the following as possible future treatments aids:
- a role for aspirin in limiting tumor growth
- the use of new drugs to inhibit the cell mechanisms that cause the tumor to develop
Symptoms of an acoustic neuroma include:
- hearing loss in one ear in 90 percent of people with acoustic neuroma
- tinnitus, or ringing in the ears
- dizziness, loss of balance, and vertigo if the tumor affects the inner ear
- loss of sensation, sometimes affecting one side of the face and mouth
- loss of the sense of taste on the back half of the tongue
Headaches, vomiting, and altered consciousness may occur when the brain is under pressure from a large tumor. Problems with vision can sometimes arise.
Acoustic neuroma is a slow-growing tumor but if not treated, it can move against essential brain structures and become life-threatening.
Acoustic neuroma size grading
An acoustic neuroma is:
- Small — when under 2 cm in size
- Medium — when 2 to 4 cm
- Large — when 4 cm or more
It is unknown exactly what makes Schwann cells replicate and contributes to an acoustic neuroma. There is in most cases no clear cause. There can be several risk factors, however, including:
Age: Acoustic neuroma tend to appear between the ages of 30 to 60 years
Family history: Neurofibromatosis type 2 can run in families. However, this accounts for only 5 percent of cases.
Radiation exposure: Significant exposure to radiation to the head and neck during childhood may increase the risk later in life.
Studies have suggested that certain cases may have to do with long-term exposure to loud noise. People have also hypothesized that the use of mobile phones could help grow an acoustic neuroma, but research does not support this.
Neurofibromatosis type 2
Sometimes a person develops type 2 (NF2) neurofibromatosis which causes the development of acoustic neuromas on both sides of the head. This is usually an hereditary or genetic disorder.
Patients with NF2 usually have many tumors that affect the spinal cord and brain and can interact with numerous nerves and functions of the body
A doctor will conduct an evaluation and ask the person what their symptoms are.
If they suspect an acoustic neuroma, then they are likely to order a head MRI scan. This mri procedure will reveal that there is a tumor, where it is and how large it is.
The individual may undergo a hearing test, a balance test, and a brainstem function test to rule out other causes of dizziness, hearing loss or vertigo.
Certain disorders with similar signs include:
Other conditions with similar symptoms include:
- meningioma, a tumor that develops on the brain lining
- Meniere’s disease
- neuritis, an inflammation of the nerves
- atherosclerosis, when the blood vessels narrow
Several complications can arise, including:
- Hearing loss: This may persist even after treatment.
- Dizziness and loss of balance: If this occurs, it can make daily activities difficult to do.
- Facial palsy: If surgery, or rarely, the tumor itself, affects the facial nerve, which is close to the acoustic nerve, the face may droop on one side, and swallowing and speaking clearly may be difficult. This is facial palsy, also known as Bell’s palsy.
- Hydrocephalus: If a large tumor presses against the brainstem, this can affect the flow of fluid between the spinal cord and the brain. If fluid accumulates in the head, it can lead to hydrocephalus.
There’s no way to avoid acoustic neuroma, but scientists are looking at ways to use gene therapy to regulate Schwann cell overproduction.
Anyone interested in acoustic neuroma clinical trials can click here to find out more.