Acoustic Neuroma

Overview

Acoustic neuroma is a benign tumor that develops on the nerve running from the ear to the brain. This tumor consists of Schwann cells attached to the balance and hearing nerve. While its medical name is vestibular schwannoma, it is commonly known as acoustic neuroma or acoustic neurinoma.

Acoustic neuroma usually grows very slowly. In some cases, it does not grow at all or develops so slowly that it does not cause symptoms. However, in some situations, as the tumor grows, it presses on the hearing and balance nerves. This pressure causes symptoms such as hearing loss, tinnitus, balance problems, and facial numbness. Very large tumors can press on vital structures in the brain and lead to serious complications.

The tumor is benign and does not turn into cancer. It does not spread to other parts of the body. However, if left untreated, it can grow over time and damage surrounding structures. The tumor's size, location, and growth rate affect the treatment decision. Small tumors can be monitored, medium-sized tumors can be treated with surgery or radiosurgery.

Acoustic neuroma is a relatively rare condition. Approximately 1 new case is seen per 100,000 people each year. The disease is generally diagnosed between ages 30-60 but can occur at any age. Unilateral acoustic neuroma is slightly more common in women. Bilateral acoustic neuroma is a sign of a genetic disease called neurofibromatosis type 2 (NF2).

Symptoms

Acoustic neuroma symptoms usually develop slowly and are mild initially. If the tumor is very small, it may not cause any symptoms. Symptoms vary depending on which nerves the tumor is pressing on and how large it is.

Acoustic neuroma symptoms include the following:

• Unilateral hearing loss. This is the most common and usually first-seen symptom. Gradual hearing loss occurs in one ear. Hearing loss progresses so slowly that most people do not notice initially. Starting to prefer one ear on the phone or difficulty hearing sounds from one side may be the first signs. Rarely, sudden hearing loss can also occur.
• Tinnitus (ringing in the ear). Continuous or intermittent ringing, buzzing, humming, or whistling sounds are heard in the affected ear. This sound does not actually exist but the person constantly hears it. The ringing becomes more pronounced in quiet environments and is disturbing.
• Balance disorders and dizziness. When the tumor affects the balance nerve, imbalance, swaying sensation, or dizziness (vertigo) develops. The person may stumble while walking and have difficulty maintaining balance in the dark or with eyes closed. Dizziness can be sudden and severe or mild and continuous.
• Facial numbness or tingling. As the tumor grows, it can affect the facial nerve (trigeminal nerve). Numbness, tingling, or loss of sensation occurs on one side of the face. Usually the same side where the tumor is located.
• Facial paralysis or weakness. In advanced cases, the tumor can affect the facial nerve (facial nerve), causing weakness or paralysis on one side of the face. One side of the face may droop, closing the eye may become difficult, and smiling may become asymmetric.
• Headache. As the tumor grows and presses on brain structures, headache can develop. Headache is usually felt on the side where the tumor is located and at the back of the head.
• Coordination problems. When the balance nerve is affected, there may be deterioration in hand-eye coordination and clumsiness in movements.
• Difficulty swallowing. Very large tumors can cause difficulty swallowing by pressing on the brainstem.

Symptoms usually begin in one ear and progress slowly. Acute symptoms such as sudden hearing loss or severe dizziness can occur, although rarely.

When to See a Doctor

Because acoustic neuroma is a slowly progressive condition, symptoms may initially be ignored. However, early diagnosis increases treatment options and prevents complications.

See a doctor in the following situations:

• If you have noticed gradual or sudden hearing loss in one ear
• If there is persistent tinnitus
• If you are experiencing balance problems or unexplained dizziness
• If you feel numbness or tingling on one side of your face
• If facial weakness or asymmetry has developed
• If you have persistent unilateral headache

Especially unilateral hearing loss should always be taken seriously. It may result from simple causes such as ear infection or earwax but must definitely be evaluated to rule out serious conditions like acoustic neuroma.

Causes

The exact cause of acoustic neuroma is not known in most cases. The tumor develops from Schwann cells that surround the hearing and balance nerve. Genetic changes occurring in these cells lead to uncontrolled cell multiplication and tumor formation.

Conditions that lead to or increase the risk of acoustic neuroma are as follows:

• Sporadic (random) cases. The vast majority of acoustic neuromas are sporadic. There is no known cause or genetic connection. The tumor develops spontaneously. In these cases, usually only one ear is affected.
• Neurofibromatosis type 2 (NF2). This is the only known genetic cause of acoustic neuroma. NF2 is a rare hereditary disease and results from a gene mutation on chromosome 22. People with this disease usually develop acoustic neuroma in both ears. Additionally, other tumors can form in the brain and spinal cord. NF2 is usually seen in families but sometimes can emerge as a new mutation.
• Radiation exposure. High-dose radiation exposure to the head or neck region during childhood may increase the risk of acoustic neuroma. However, this is a very rare situation.

Why mutations occur in Schwann cells is unclear in most cases. Age, environmental factors, or other unknown causes may play a role.

Risk Factors

Risk factors for acoustic neuroma are as follows:

• Neurofibromatosis type 2 (NF2). This is the most important and known risk factor. In people with NF2, the risk of developing acoustic neuroma in both ears is very high. The disease usually appears at a younger age (in the 20s).
• Family history. If there is NF2 or acoustic neuroma in first-degree relatives, risk increases. However, in sporadic cases there is no familial connection.
• Age. Acoustic neuroma is usually diagnosed between ages 30-60. Risk increases with age but can occur at any age.
• Sex. Unilateral acoustic neuroma is slightly more common in women compared to men. However, the difference is not very pronounced.
• High-dose radiation exposure. Having received radiotherapy to the head or neck region especially during childhood may increase risk.

There are no known modifiable risk factors for acoustic neuroma. The contribution of lifestyle, diet, or other environmental factors to disease development has not been demonstrated.

Diagnosis

Acoustic neuroma is diagnosed with clinical examination, hearing tests, and imaging methods. Early diagnosis increases treatment options and prevents complications.

The methods used in acoustic neuroma diagnosis are as follows:

• Ear, nose, throat (ENT) examination. The doctor examines the ear canal and eardrum. Evaluates whether hearing loss results from simple causes such as ear infection or earwax. Facial and balance examination is performed.
• Hearing tests (audiometry). This is the most basic diagnostic test. The patient's ability to hear different sound frequencies and intensities in both ears is measured. In acoustic neuroma, hearing loss is usually more pronounced in high-frequency sounds. Speech comprehension testing is also done.
• Auditory brainstem response (ABR) test. Evaluates nerve pathways from the ear to the brain. Sound is given to the ear and brain activity is recorded with electrodes. If acoustic neuroma disrupts nerve conduction, abnormalities are seen in this test.
• Magnetic resonance imaging (MRI). This is the gold standard test in acoustic neuroma diagnosis. Brain and inner ear structures are imaged in detail. Using contrast material, the tumor's presence, size, location, and relationship with surrounding structures are clearly seen. Even very small tumors (a few millimeters) can be detected.
• Computed tomography (CT). Can be used as an alternative in patients who cannot have MRI (pacemaker, metal implant, etc.). However, soft tissue detail is not as good as MRI.
• Balance tests. Balance functions are evaluated with electronystagmography (ENG) or videonystagmography (VNG). These tests measure the function of the inner ear and balance system by recording eye movements.

When diagnosis is made, the tumor's size and characteristics are recorded. Small tumors (smaller than 1 cm) are usually monitored. Medium and large tumors (larger than 1 cm) may require treatment.

Treatment

Acoustic neuroma treatment is personalized according to the tumor's size, growth rate, patient's age, general health status, and severity of symptoms. There are three main treatment approaches.

The methods used in acoustic neuroma treatment are as follows:

• Watch and wait (active surveillance). Preferred for small tumors (usually smaller than 1.5 cm) and mild symptoms. The tumor is not operated on but instead monitored with regular MRI imaging (usually every 6-12 months). Hearing tests are repeated. If the tumor does not grow or grows very slowly, monitoring continues. If growth accelerates or symptoms worsen, treatment is initiated. This approach is usually most appropriate for elderly patients or people with serious health problems.
• Surgical treatment (microsurgery). This is complete removal of the tumor by surgery. Preferred for medium and large tumors, rapidly growing tumors, or cases causing serious symptoms. There are three main surgical approaches. The translabyrinthine approach is done from behind the ear and hearing preservation is not possible but removing the tumor completely is easier. The retrosigmoid approach is done from the back of the skull and there is a chance of preserving hearing. The middle fossa approach is done from the side of the skull and is used to preserve hearing in small tumors. Surgery usually takes 4-6 hours. Hospital stay is between a few days and one week. Surgery risks include hearing loss, facial paralysis, cerebrospinal fluid leak, and infection.
• Stereotactic radiosurgery. This is a non-surgical treatment method. Tumor cells are killed or their growth is stopped with high-dose focused radiation. Gamma Knife, CyberKnife, or linear accelerator (LINAC) can be used. Treatment is applied in a single session or several sessions. Each session lasts 30-60 minutes. The tumor usually does not shrink but its growth stops. Effective in small and medium-sized tumors (usually smaller than 3 cm). Preferred in patients with high surgical risk or who do not want surgery. Side effects are less than surgery but hearing loss or facial numbness can develop years later.
• Combined approach. In some cases, radiosurgery is applied first and if growth continues, surgery is performed. Or in very large tumors, first most of the tumor is removed surgically and the remainder is treated with radiosurgery.

Treatment selection is made considering the patient's preference as well. The advantages and disadvantages of each method are explained to the patient in detail.

Complications

Acoustic neuroma can lead to complications both from the tumor itself and from treatment. Early diagnosis and appropriate treatment reduce these risks.

Complications that may be seen in acoustic neuroma are as follows:

• Permanent hearing loss. This is the most commonly seen complication. The tumor damages the hearing nerve over time. Even if not treated, hearing loss progresses as the tumor grows. The chance of preserving hearing after surgery depends on tumor size and surgical technique. In small tumors, the chance of preserving hearing is around 50 percent. In large tumors, hearing is usually completely lost. Hearing loss after radiosurgery can develop slowly.
• Facial paralysis (facial palsy). The facial nerve is very close to the tumor and can be damaged during surgery. Temporary facial weakness is common after surgery and usually improves within a few weeks or months. The risk of permanent facial paralysis is below 5 percent in small tumors and between 10-20 percent in large tumors. If facial paralysis develops, the eye cannot close and the cornea can be damaged. Smiling is asymmetric. Physiotherapy and sometimes surgical interventions can help.
• Balance problems. Temporary balance disorder after surgery or radiosurgery is common. The brain compensates by using the other side over time and balance improves. However, permanent imbalance may remain in some patients. Vestibular rehabilitation (balance exercises) accelerates recovery.
• Tinnitus. After treatment, existing ringing may continue or new ringing may develop. It may lessen over time but is sometimes permanent.
• Headache. Temporary headache after surgery is normal. Chronic headache can develop in some patients.
• Cerebrospinal fluid (CSF) leak. If the brain membrane is opened during surgery, CSF can leak. It usually closes spontaneously but sometimes repeat surgery may be needed.
• Hydrocephalus. Very large tumors can block the circulation of cerebrospinal fluid, causing fluid accumulation in the brain (hydrocephalus). This condition leads to headache, nausea, and impaired consciousness. Shunt (drainage tube) placement may be needed.
• Meningitis. This is a rare but serious complication after surgery. It is an infection of the brain membranes. It manifests with fever, severe headache, and neck stiffness. Antibiotic treatment is required.
• Stroke. Very rarely, brain vessels can be damaged during surgery and stroke can develop.

Living with Acoustic Neuroma

Receiving an acoustic neuroma diagnosis can be worrying but most patients can continue their normal lives with appropriate treatment or monitoring. The basic principles of living with the disease are regular follow-up, adapting to hearing and balance problems, and getting support when needed.

In Watch and Wait Approach

If you have a small tumor and a monitoring decision has been made, do not worry. Most small tumors do not grow for years or grow very slowly. However, regular follow-up is very important. Do not miss your MRI appointments. Have hearing tests done regularly.

If there is a change in symptoms (increased hearing loss, worsening balance problems, development of facial numbness), notify your doctor immediately. These changes may indicate the tumor is growing and may require treatment.

Recovery After Surgery

The first days after surgery are spent in the hospital. Headache, nausea, and fatigue are normal. A few weeks of rest are needed after surgery. Avoid heavy lifting and sudden head movements.

Balance problems are pronounced in the first weeks. Move slowly, use a cane or walker if necessary. Join a vestibular rehabilitation program. Balance exercises help the brain compensate and accelerate recovery.

If facial weakness has developed, use eye drops or ointment to prevent eye dryness. Wear an eye patch at night. Do facial exercises with a physiotherapist.

Coping with Hearing Loss

Unilateral hearing loss can affect daily life. Understanding conversations in noisy environments becomes difficult. Determining where sound is coming from becomes harder. Some adaptation strategies can help.

Turn your good hearing ear toward the speaker. Sit next to the wall in noisy places like restaurants. Ask the speaker to face you and speak slowly.

Hearing aids can help. CROS (Contralateral Routing of Signal) hearing aid transmits sound from the bad ear to the good ear. Bone conduction devices are also an option. Cochlear implants are usually not appropriate for unilateral losses.

Managing Tinnitus

Tinnitus can be disturbing but over time the brain gets used to it and notices it less. Use background sound (white noise, nature sounds) to mask the ringing. Avoid quiet environments.

Stress worsens ringing. Relaxation techniques, meditation, or yoga can help. Caffeine and alcohol can increase ringing, reduce consumption. Tinnitus retraining therapy can be beneficial in some patients.

Regular Follow-up

Regular follow-up is required after treatment. MRI is taken more frequently in the first year (every 6 months), then once a year thereafter. Whether there is tumor recurrence or tumor growth after radiosurgery is checked.

Hearing tests are repeated regularly. Preserving hearing in the remaining ear is very important. Protect from noise, keep volume low when using headphones.

Psychological Support

Hearing loss and balance problems can lead to social isolation. People may avoid social settings because they have difficulty understanding conversations or fear falling. This can cause depression and anxiety.

Share your feelings with loved ones. If necessary, seek support from a psychologist or psychiatrist. Joining acoustic neuroma support groups can be beneficial. Connecting with people who have had similar experiences makes you feel you are not alone.

Safe Living Arrangements

Unilateral hearing loss can lead to safety risks. You may have difficulty hearing sounds from cars. Place the fire alarm at home on the side where you can hear it from your good ear. Use a vibrating alarm clock in the bedroom.

If you have balance problems, reduce the risk of falling at home. Remove rugs, install grab bars for bathroom and stairs. Use night lights for nighttime.

Preparing for Your Appointment

What you can do:

• Note when you noticed hearing loss and how it progressed
• Record other symptoms such as tinnitus and dizziness
• Write how symptoms affect your daily life
• Mention if there is a family history of neurofibromatosis or acoustic neuroma
• Report if you have received radiotherapy to the head or neck region in the past
• List all medications you use
• Write your questions down in advance

Questions you can ask your doctor are as follows:

• How large is my tumor?
• Is the tumor growing?
• What are my treatment options?
• Is watch and wait appropriate or is treatment necessary?
• Is surgery or radiosurgery more appropriate?
• What is my chance of preserving hearing?
• What are the treatment risks?
• What will the recovery process be like after treatment?
• How often should I have checkups?
• How can I protect hearing in the other ear?

Questions your doctor may ask you are as follows:

• When did you notice hearing loss?
• Which ear has hearing loss?
• Did hearing loss develop gradually or suddenly?
• Is there tinnitus?
• Are you experiencing balance problems or dizziness?
• Is there numbness or weakness in the face?
• Is there a family history of acoustic neuroma or neurofibromatosis?
• Have you received head or neck radiation before?
• How do symptoms affect your daily life?