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Acoustic Neuroma

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Acoustic neuroma is also called as vestibular schwannoma. It is a rare benign tumor of the 8th cranial nerve that helps one balance and hear. It grows slowly and expands at its site of origin. As it continues to grow, it leads to many problems related to the neurological functions.

What is an Acoustic Neuroma?

An acoustic neuroma is a benign growth of the 8th cranial nerve that comes from the brain and connects the inner ear. This nerve has two important parts. One is involved with the sense of hearing and the other sense of balance. The 8th cranial nerve lies adjacent to the 7th cranial nerve (facial nerve) as it passes through the internal auditory canal. The acoustic neuroma generally originates from the sheath around the 8th cranial nerve.

What Happens in Acoustic Neuroma?

Acoustic neruroma is a slow growing tumor. It expands in size over the years at the site of origin. As it starts becoming larger, it begins to displace the brain tissue. The tumor starts pushing the brain as it grows. Gradually, the tumor protrudes from the internal auditory canal into the cerebellopontine angle. This is the region that lies behind the temporal bone. The tumor may press the 7th cranial nerve leading to problems with facial sensation. As it presses the brainstem and cerebellum, it could lead to life threathening problems.

Size of Acoustic Neuroma

Acoustic neuroma is generally described as:

  • Small – less than 1.5 cm in size
  • Medium – between 1.5 cm to 2.5 cm
  • Large – more than 2.5 cm

Symptoms of Acoustic Neuroma

Signs and symptoms of acoustic neuroma appear when the tumor starts pressing the adjacent nerves, blood vessels and brain tissue. Symptoms may include:

  • Gradual or sudden loss of hearing
  • Tinnitus (ringing in the ear)
  • Unsteady gait or loss of balance
  • Vertigo
  • Facial numbness and weakness

Causes of Acoustic Neuroma

Acoustic neuroma may be idiopathic in nature, that is, the cause is unknown. In some cases, it may occur due to an abnormal gene on chromosome 22. This gene controls the production of a protein that helps control the growth of Schwann cells. These Schwann cells cover and support the nerves. There are two types of neuromas in this case:

  • Neurofibromatosis type 1: The Schwann cell overproduction that leads to the tumor generally in adults between the age group of 30 to 60.
  • eurofibromatosis type 2: A rare disorder, where the tumors grow on both sides of the head, that is bilateral vestibular schwannomas. Generally, it presents itself in people before the age of 21.

Diagnosis of Acoustic Neuroma

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A hearing tests vestibular and contrast-enhanced CT scan will help in the detection of neuromas that are 2.0 cm in diameter. Smaller ones can be detected using an MRI with gadolinium enhancement.

Treatment for Acoustic Neuroma

After diagnosis, the doctor will choose conservative treatment initially. This is called as an observation period, where the doctor will monitor the growth of the tumor with an MRI. This is usually carried out in patients above the age of 70 years. It is observed the tumor may shrink spontaneously in some cases or it may not grow detectably for over 3 to 5 years. In many cases, the patients who develop acoustic neuroma die of something else, before the tumor itself grows fatal.

Surgery is an option for treatment of acoustic neuroma. Other than surgery, radiation therapy is also an important line of treatment for acoustic neuroma.

Acoustic neuroma is a benign tumor. It takes years to grow large and in some cases, it may develop rather quickly. Speak to your healthcare provider for more details and learn about support groups for people with acoustic neuroma.

Written by: Saptakee sengupta
Date last updated: April 01, 2015

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