Acoustic Neuroma

Acoustic neuroma, also known as vestibular schwannoma, is a kind of rare, noncancerous and a slow-growing tumour that occurs on the main nerve – vestibular leading from the inner ear to the brain. The vestibular nerves are the eighth cranial nerves, which functions by transmits sound and equilibrium (balance) information from the inner ear to the brain.

This type of tumours usually grows slowly and do not spread through the body, instead, it affects hearing, balance and facial nerves of a patient. Though acoustic neuroma is a non-cancerous tumour, it can be dangerous if they grow large and press against the brainstem or brain. According to the medical records, it is estimated that only one person in every 100,000 births is diagnosed with acoustic neuroma every year and this tumour can develop at any age and sex but most commonly found between the age of 40 to 50.

What is Acoustic Neuroma?

Acoustic neuroma is kind of a brain disease or a brain tumour. It is also called a benign tumour since it is non-cancerous. It is a slow-growing tumour, but it can push against vital brain structures and become life-threatening if not treated.

The nerve along which the tumour develops inside the brain is known as acoustic nerve and it controls hearing sense. Acoustic neuromas grow as a kind of cell known as Schwann cell and surround nerve cells. It tends to grow slowly and sometimes it is too small and does not cause any signs and symptoms, but at the higher stage of acoustic neuromas, they are capable of interfering with the vestibulocochlear nerves. The size of an acoustic neuroma can vary from 2cm to 4cm or more.

Causes of Acoustic neuromas

The main cause of acoustic neuromas appears to be an abnormal or non-functioning of a gene on a chromosome- NO -22. This gene produces a tumour suppressor protein that helps in controlling the growth of Schwann cells by covering the nerves. The exact cause of this tumour is still unidentified, and as per the studies and evaluations, about 8 out of 100 cases are caused by neurofibromatosis type 2 (NF2). NF2 is a rare genetic disorder and causes benign tumours in the nervous system. In most cases, there is no identifiable cause, but there may be some risk factors, including:

• Age
• Long-term exposure to loud noise
• A family history of acoustic neuroma
• Exposure to radiations during childhood.

Symptoms of  Acoustic neuroma

The sign and symptoms of acoustic neuroma usually vary with the type, size of a tumour. The common symptoms of an acoustic neuroma are as follows:

• Earache
• Vomiting
• Dizziness
• Headaches
• Vision problems
• Facial numbness
• Unsteadiness or loss of balance
• Weakness or loss of muscle movement
• Loss of sensation to one side of the face and mouth
• Loss of the sense of taste on the back half of the tongue
• Tinnitus – a perception of noise or ringing in the affected ear
• Loss of hearing, usually gradual and occur on only one side or affected ear.

Diagnosis of Acoustic neuroma

Acoustic neuroma is often difficult to diagnose in the early stages because signs and symptoms develop gradually over time. If any of the symptoms are analyzed, then certain physical tests are carried out to test the presence of tumour on the main nerve – vestibular. The most commonly used diagnostic tests are:

• Physical examination of an ear
• MRI and CT scans of the head
• Audiometry – A test to check the functioning of the ear
• BAER – Brainstem auditory evoked response

Treatment for Acoustic neuroma

The treatment usually depends on several factors, including:

• Patient’s age
• The general health of the person
• The size and location of the tumour.

There are several different treatments available to cure or stop the growth of the tumour.  The major treatments include:

• Surgery
• Microsurgery
• Radiation therapy
• Stereotactic radiosurgery

Questions for You

• Is Acoustic Neuroma a cancerous tumour?

No, Acoustic Neuroma is a benign or non-cancerous tumour and a slow-growing tumour.

• What is a tumour?

A tumour is generally defined as a swelling or abnormal growth and enlargement of a cell. There are two types of tumour:

1. Benign tumour – A non-cancerous tumour
2. Cancerous tumour – A cancerous tumour

• What are the causes of tumour?

The main cause for the tumour is still unknown. There are a few factors which may be responsible for the growth of the tumour cells. The factors include:

1. Diet
2. Stress
3. Genetics
4. Local trauma or injury
5. Inflammation or infection
6. Exposure to toxins and radiation

Stay tuned with BYJU’S to learn more about Acoustic Neuroma and other related topics @ BYJU’S Biology.