Acoustic Neuroma: Definition, Causes, Symptoms, Diagnosis, and Treatment

Acoustic neuroma also called vestibular schwannoma, is a rare, slow-growing, noncancerous tumor that forms on the vestibular nerve, which links the inner ear to the brain. The vestibular nerves, also known as the eighth cranial nerves, transport sound and equilibrium (balance) information from the inner ear to the brain. This form of tumor grows slowly and does not spread across the body; rather, it impairs a patient's hearing, balance, and facial nerves. Even though acoustic neuromas are benign tumors, they can be hazardous if they grow large and press against the brainstem or brain. Hearing loss and unbalance may result from the tumor's pressure on the nerve. Here, we will learn more about acoustic neuroma, its causes, symptoms, treatment and will discuss some important questions.

Keyterms: Neuroma, Vestibular schwannoma, Equilibrium, Cranial nerve, Nerve, Brain, Ear, Tumor, Schwann cell

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What is Acoustic Neuroma?

Acoustic neuroma is a type of brain tumor or disease. It's also known as a benign tumor because it's not cancerous. It's a slow-growing tumor, but if it's not treated, it can push against important brain structures and become life-threatening.

Acoustic neuroma

The auditory nerve is the nerve that governs hearing and runs along which the tumor forms inside the brain. Acoustic neuromas develop into a type of cell known as a Schwann cell that surrounds nerve cells. Acoustic neuromas grow slowly and often are too small to cause any symptoms, but they are capable of interfering with the vestibulocochlear nerves in their advanced stages. An auditory neuroma can range in size from 2cm to 4cm or even more.

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Causes of Acoustic Neuroma

An issue with a gene on chromosome 22 may be the cause of auditory neuromas. This gene normally generates a tumor suppressor protein that aids in the control of the proliferation of Schwann cells that coat the nerves. Experts are baffled as to what is causing the gene abnormality. There is no known cause for an acoustic neuroma in the majority of cases. This defective gene is also inherited in neurofibromatosis type 2, an uncommon illness characterized by the formation of tumors on both sides of the hearing and balance nerves (bilateral vestibular schwannomas).

Although there is usually no obvious cause, there may be some risk factors, such as:

• Long-term loud noise exposure as an adult
• A history of acoustic neuroma in the family
• Radiation exposure throughout childhood.

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Symptoms of Acoustic Neuroma

Hearing and balance are controlled by the auditory nerve, which is where these tumors grow, hence common symptoms include:

• Hearing impairment

It's the first symptom in 90% of cases, and it's frequently accompanied by tinnitus or ringing in the ears.

This loss normally worsens over time, although some people may lose their hearing suddenly. Others notice a 'fullness' in the affected ear as a symptom.

• Problems with equilibrium

You may feel as though your surroundings are spinning, which is known as vertigo. This can make you feel uneasy and cause you to lose your equilibrium. It can happen at any time during the tumor's progression.

• Other signs and symptoms

Larger acoustic neuroma tumors may cause a rise in brain pressure, resulting in headaches and distorted or double vision.

Face numbness and tingling can occur if the tumor presses on the facial nerve (trigeminal nerve).

Symptoms of Acoustic Neuroma

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Diagnosis of Acoustic Neuroma

Acoustic neuromas can be difficult to diagnose because their symptoms are similar to those of other illnesses. Hearing loss, which can be attributed to age-related hearing loss or exposure to high levels of noise earlier in life, can also delay diagnosis.

Acoustic neuromas are frequently discovered after the following events:

• Regular audio testing to detect any hearing loss or speech deterioration
• An audiogram to determine the hearing level in both ears
• Tests that assess your sense of balance, reflexes, and arm and leg strength
• If you have a noticeable loss of hearing in one ear, you should get a diagnostic scan (typically an MRI).

Diagnosis of Acoustic Neuroma

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What are the Diagnostic Tests for Acoustic Neuroma?

Because acoustic neuroma symptoms develop gradually and symptoms like hearing loss can suggest abnormalities in the inner ear, doctors may have difficulty diagnosing the tumor. The inner ear will be examined once the doctor has discussed the symptoms with you.

The following tests may be used to diagnose acoustic neuroma:

• An audiologist will perform the audiometry or hearing test, and the patient will hear sounds directed to each ear. The audiologist will make a variety of sounds, and you will have to identify the ones you hear. The tones are repeated at different audible levels to assist determine the hearing capacity.
• To detect an acoustic neuroma, a computerized tomography (CT), contrasted magnetic resonance imaging (MRI), or head scans may be used.

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Treatment of Acoustic Neuroma

Treatment is frequently determined by a number of criteria, including:

• Age of the patient
• The individual's overall health
• The tumor's size and placement

There are a variety of treatments available to cure or stop the tumor from growing. The most common therapies are:

• Surgery
• Microsurgery
• Radiation therapy is a type of treatment that uses a
• Radiosurgery with stereotactic accuracy

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Risk Factors

Type 2 neurofibromatosis

Having a parent with the rare genetic illness neurofibromatosis type 2 is the only known risk factor for an auditory neuroma. However, type 2 neurofibromatosis accounts for only around 5% of all acoustic neuroma instances.

The development of noncancerous tumors on the hearing and balance nerves on both sides of the head, as well as other nerves, is a distinguishing feature of neurofibromatosis type 2.

Neurofibromatosis type 2 (NF2) is an autosomal dominant condition, which means that only one parent may pass on the mutation (dominant gene). Each child of a parent who is affected has a 50/50 chance of acquiring the condition.

Also read: Difference between Brain and Spinal Cord

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Things to Remember

• Acoustic neuromas, also known as vestibular schwannomas, are benign ear tumors that do not affect hearing or balance.
• Hearing loss on the side of the acoustic neuroma is the most prevalent symptom of acoustic neuromas, occurring in 90% of patients.
• A hearing test (audiogram) and imaging are used to identify acoustic neuroma (MRI).
• Observation (waiting and watching), surgery, or radiation are all options for treatment.
• Acoustic schwannoma, vestibular neuroma, auditory neuroma, and inner ear tumor are some of the other terms for acoustic neuroma or vestibular schwannoma.
• Important  nerves (such as the hearing, face, and balance nerves) may be compromised if the tumor is not treated, and the tumor may eventually encroach on the brain.