Acoustic neuromas are benign nerve tumors that occur in the vestibulocochlear nerve. These nerves help us to hear and maintain our balance. These tumors occur at the bottom of the brain before the nerve exits the skull. 

Small tumors do not cause any symptoms. You will have problems only when the tumors grow and start putting pressure on the brain. Hearing problems and problems with body balance are the most common ones. It will also put pressure on the facial nerve to cause symptoms. 

The exact cause of acoustic neuroma is not clear. It occurs when some cells that make the nerve divide and live longer than usual to form tumors.

It occurs more commonly in those in their thirties and forties. Hearing tests in those with symptoms can help to know the progress of the disease. MRI scans will help to detect even the smallest of tumors.

Treatment for acoustic neuroma will depend on the size of the tumor and the severity of the symptoms. Usually, the doctors will adopt a 'wait and watch' policy if there are no symptoms. Surgery can help to remove the tumor if it is large. Radiosurgery, where the doctors use high energy particles or x-rays to destroy the tumor, is another option.

What causes acoustic neuroma? 

Acoustic neuromas occur when some cells that cover the branches of the acoustic nerve divide rapidly to form tumors. A change in the mechanism that controls the division of these cells may be a reason. Also, these cells live for a longer time than normal cells. Most of those who have the condition will have a defect in chromosome 22.

Risk factors of acoustic neuroma

The major risk factor is having a disease called Type -2 Neurofibromatosis. In this condition, you have numerous benign nerve cell tumors in different nerves. If you have it, you will have acoustic neuromas that affect both ears. You also have a higher risk if you have a parent with the disease.

There are a few things that may slightly increase your risk. These include exposure to loud noises as part of a job or for leisure. If you have had radiation treatment in the past for head and neck cancers, you have a small risk.

Symptoms of acoustic neuroma

The common symptoms are

• Hearing loss- It affects only the ear where the tumor is present. You will not know it most of the time, as the other ear is normal. But as the condition worsens, the hearing loss will be more prominent. In some persons, the hearing loss happens all of a sudden.
• Tinnitus- It is a ringing or hissing sensation in the ears when no other external sounds are present. You may have it always or only in intervals.
• Loss of body balance- It occurs as the tumor affects the nerve responsible for maintaining your balance. Large tumors that press against the cerebellum may cause difficulty in walking.
• Headaches- You will have headaches due to the pressure of the tumor in the brain. The pain may radiate to the front or top of the head or your neck.
• Numbness or weakness of the face- You will have this if the tumor is large and presses against the facial nerve.
• Loss of taste- It happens when the tumor presses against a branch of the facial nerve that contributes to taste.
• Dry eyes- It occurs due to the pressure on the nerves that supply the tear glands. In some, there will be excessive tears, as well.

Diagnosis of acoustic neuroma

You will have symptoms only when the tumor becomes large and press against the brain. If your doctor suspects an acoustic neuroma from the symptoms, you will have a few tests to confirm it.

Audiometry test- It helps to check your hearing levels. If you have an acoustic neuroma in an ear, you will have hearing problems.

MRI scans- It helps the doctor to know the exact size and site of the tumor. You will have a contrast dye injection before the test. The tumor will absorb more of this dye, which will show as bright spots in the scan. 

Treatment of acoustic neuroma

Different treatments are available for acoustic neuroma, depending on your symptoms and the size and site of the tumor.

Watchful waiting

If your tumor is small, you will not need treatment. The doctor will take scans of the tumor once in six months or a year. It will help the doctor to watch whether it is growing. Your doctor will wait until symptoms appear to start any treatment.

Surgery for acoustic neuromas

Surgery will help to remove the tumor from the nerve. Before the surgery, you will have general anesthesia to help you sleep so that you will not feel any pain. 

The surgeon will then make a small cut behind your ear to expose the skull bone in the region. After this, the surgeon will make a small hole in the skull bone to reach the tumor. The surgeon will then remove the tumor from the nerve with care to prevent any damage to other nerves or structures around it. 

Once this is over, the surgeon will close the hole in the skull by placing the piece of skull bone back. 

In endoscopic surgery, the surgeon will make two small holes in the skull than a single large hole.

The surgery is usually safe but also has a few risks too. The risks include the leakage of CSF, damage to nerves and other structures, etc. 

Radiosurgery for acoustic neuroma

It is not a surgery but a type of radiation treatment that kills the cells that form the tumor.

During the procedure, the doctor will fix your head in a stereotactic head-frame. The next step is to direct low dose radiations towards the tumor with a machine. The head-frame helps the doctor to control the amount and time of radiation. The low dose radiations join together in the tumor to destroy it. The advantage of this treatment is that it causes very little damage to other tissues. 

Gamma knife, Cyberknife, etc. are some of the common types of radiosurgery