Acoustic Neuroma Symptoms

Acoustic neuroma symptoms typically arise from a slow-growing, noncancerous tumor on the main nerve connecting the inner ear to the brain. These symptoms often include gradual hearing loss in one ear, ringing in the ear (tinnitus), and problems with balance or dizziness. Symptoms usually worsen over time as the tumor grows and presses on the nerve.

What is Acoustic Neuroma Symptoms?

Acoustic neuroma symptoms are signs caused by a noncancerous (benign) tumor that grows on the main nerve leading from your inner ear to your brain. This nerve, called the vestibulocochlear nerve, is responsible for both hearing and balance. The symptoms appear as the tumor slowly grows and presses on this vital nerve.

An acoustic neuroma, also known as a vestibular schwannoma, is a slow-growing tumor. It develops on the eighth cranial nerve, which has two parts: one for hearing (cochlear nerve) and one for balance (vestibular nerve). Because the tumor is benign, it does not spread to other parts of the body. However, even though it is not cancerous, an acoustic neuroma can cause serious problems. As it grows, it can press on the vestibulocochlear nerve, leading to hearing and balance issues. If the tumor becomes very large, it can also press on other nearby nerves or even the brainstem, which can cause more severe and life-threatening symptoms.

Symptoms

The most common symptoms of an acoustic neuroma include gradual hearing loss in one ear, a ringing or buzzing sound in the affected ear (tinnitus), and problems with balance or dizziness. These symptoms usually develop slowly over months or years, often becoming more noticeable as the tumor enlarges.

Hearing loss is typically the first symptom noticed, affecting one ear. It often starts subtly and worsens over time, particularly for high-frequency sounds. Some people may experience sudden hearing loss, though this is less common. Difficulty understanding speech, especially in noisy environments, can also occur. Tinnitus, a persistent ringing, buzzing, or hissing sound, is also common and usually occurs in the ear with hearing loss. Many people also experience problems with balance, such as unsteadiness when walking, or dizziness (vertigo), which is a sensation of spinning. Less common symptoms, which tend to appear with larger tumors, include facial numbness or tingling, facial weakness, or even paralysis on one side of the face. In very rare cases, extremely large tumors can cause headaches, double vision, or changes in voice or swallowing difficulties by pressing on other brain structures.

Causes & risk factors

The exact cause of most acoustic neuromas is unknown. However, about 5% of cases are linked to a genetic disorder called neurofibromatosis type 2 (NF2), which causes noncancerous tumors to grow on nerves. Most acoustic neuromas occur spontaneously without a clear genetic link.

For the majority of people, an acoustic neuroma develops without any identifiable cause. These are called sporadic cases. Researchers believe these tumors may result from a random genetic mutation that occurs during a person's lifetime, rather than being inherited. In cases linked to neurofibromatosis type 2 (NF2), the condition is inherited. People with NF2 typically develop acoustic neuromas on both sides (bilateral), along with other types of tumors. This genetic disorder involves a defect on chromosome 22, which normally produces a protein that helps control cell growth. When this protein is missing or faulty, cells can grow uncontrollably, leading to tumor formation. While some studies have explored other potential risk factors, such as exposure to loud noise or radiation, there is no strong evidence to definitively link these to the development of sporadic acoustic neuromas. The primary known risk factor remains the genetic condition NF2.

How it's diagnosed

Diagnosing an acoustic neuroma typically begins with a physical and neurological exam, followed by hearing tests. The most definitive diagnostic tool is a magnetic resonance imaging (MRI) scan of the head with contrast, which can clearly show the tumor's size and location.

If you report symptoms like one-sided hearing loss or tinnitus, your doctor will likely perform a physical exam and a basic neurological assessment to check your balance, reflexes, and facial sensation. They will then refer you for specialized tests. One of the first tests is an audiometry exam, which measures your hearing ability across different pitches and volumes. This test can identify the characteristic patterns of hearing loss associated with an acoustic neuroma. Balance tests, such as electronystagmography (ENG) or videonystagmography (VNG), may also be performed to assess the function of your balance system. The most accurate way to diagnose an acoustic neuroma is with an MRI scan using a special dye (gadolinium contrast). This imaging technique provides detailed pictures of the brain and the nerves, allowing doctors to see even very small tumors on the vestibulocochlear nerve. An MRI can confirm the presence of an acoustic neuroma and help determine its size and exact position.

Treatment options

Treatment for an acoustic neuroma depends on the tumor's size, growth rate, your symptoms, and overall health. Options include watchful waiting (observation), surgery to remove the tumor, or radiation therapy to stop its growth. Your doctor will discuss the best approach for your specific situation.

For small, slow-growing tumors that cause minimal symptoms, especially in older individuals or those with other health concerns, doctors may recommend watchful waiting. This involves regular MRI scans to monitor the tumor's growth over time. If the tumor grows or symptoms worsen, other treatments may be considered. Surgery is an option to remove the tumor. The goal is to remove as much of the tumor as possible while preserving nerve function. Different surgical approaches exist, depending on the tumor's size and location. Potential risks include hearing loss, facial nerve damage, and balance problems. Complete tumor removal is often possible, but some small parts may be left to protect vital nerves. Radiation therapy, specifically stereotactic radiosurgery (like Gamma Knife or CyberKnife), is another treatment. This method uses highly focused radiation beams to target the tumor, aiming to stop its growth or shrink it over time. It is often used for smaller tumors, for patients who cannot undergo surgery, or as a follow-up to partial surgical removal. While it avoids surgery, it can still have side effects, including potential long-term hearing loss or facial nerve issues.

Recovery & outlook

The recovery and long-term outlook for people with acoustic neuroma are generally good, as these tumors are benign and usually slow-growing. Recovery depends on the chosen treatment, tumor size, and individual factors. Many people live full lives, though some may experience lasting effects like hearing loss or balance issues.

After treatment, recovery can vary significantly. For those undergoing watchful waiting, the outlook is generally stable, with ongoing monitoring. If surgery or radiation therapy is performed, recovery involves managing potential side effects and rehabilitation. Common long-term effects can include permanent hearing loss in the affected ear, persistent tinnitus, and ongoing balance problems. Physical therapy may be recommended to help improve balance and reduce dizziness. Facial weakness or numbness, if it occurs, may improve over time, but sometimes can be permanent. Regular follow-up appointments, including MRI scans and hearing tests, are crucial to monitor for any tumor regrowth or new symptoms. While an acoustic neuroma is not life-threatening in most cases, managing its effects requires ongoing care. Many individuals adapt well to any residual symptoms and maintain a good quality of life.

When to see a doctor

You should see a doctor if you experience new or worsening symptoms such as unexplained hearing loss in one ear, persistent ringing in one ear (tinnitus), or problems with balance and dizziness. Early diagnosis of an acoustic neuroma can lead to more effective treatment and better outcomes.

It is important to seek medical attention promptly if you notice any of the key symptoms, especially if they are affecting only one side of your head. Even if the symptoms seem mild or intermittent, they warrant evaluation by a healthcare professional. While these symptoms can be caused by many different conditions, it's crucial to rule out an acoustic neuroma. Early detection often allows for more treatment options and a better chance of preserving hearing and facial nerve function. Do not delay seeking advice, as waiting can allow the tumor to grow larger, potentially leading to more complex treatment and greater risk of permanent side effects. If you experience sudden, severe hearing loss in one ear, accompanied by dizziness or facial numbness, you should seek immediate medical attention. These could be signs of an acoustic neuroma or another serious condition that requires urgent evaluation.

Frequently asked questions

Is an acoustic neuroma a type of cancer?

No, an acoustic neuroma is not a type of cancer. It is a noncancerous (benign) tumor. This means it does not spread to other parts of the body. However, it can still cause serious health problems by growing and pressing on important nerves and brain structures.

How fast do acoustic neuromas grow?

Acoustic neuromas typically grow very slowly, often only a millimeter or two per year. Some tumors may not grow at all for long periods, while others can grow more quickly. The growth rate can vary significantly from person to person, which is why watchful waiting often involves regular MRI scans to monitor changes.

Can acoustic neuroma symptoms come and go?

While acoustic neuroma symptoms usually progress gradually and steadily, some people might experience fluctuations in symptoms like dizziness or tinnitus. However, the underlying hearing loss typically worsens over time rather than improving. Any new or worsening symptoms should be discussed with a doctor.

Does an acoustic neuroma always cause hearing loss?

Hearing loss in one ear is the most common initial symptom of an acoustic neuroma, affecting nearly all individuals at some point. However, the degree of hearing loss can vary, and in rare cases, other symptoms like balance issues or tinnitus might be more prominent initially. It's uncommon for hearing to be completely unaffected.

What are the risks of acoustic neuroma surgery?

Risks of acoustic neuroma surgery include permanent hearing loss in the affected ear, facial nerve damage leading to weakness or paralysis, balance problems, and cerebrospinal fluid leakage. Other general surgical risks like infection or bleeding also exist. The specific risks depend on tumor size and surgical approach.

Can acoustic neuromas recur after treatment?

While complete surgical removal aims to prevent recurrence, it is possible for an acoustic neuroma to recur, especially if a small portion of the tumor was left behind to protect vital nerves. After radiation therapy, the tumor cells are often inactivated, but the tumor itself may not disappear and can sometimes resume growth. Regular follow-up MRI scans are essential to monitor for any regrowth.

Sources

• MedlinePlus — Acoustic Neuroma Symptoms
• Mayo Clinic — Acoustic Neuroma Symptoms
• Cochrane Library — Acoustic Neuroma Symptoms