Acoustic Neuroma

 An acoustic neuroma (more accurately called a vestibular schwannoma, also known as an acoustic tumour) is a benign growth that arises from the hearing and balance nerve. This nerve, known as the eighth cranial nerve, runs next to the facial nerve from the brainstem to the inner ear through a small bony canal, the internal auditory canal. The acoustic neuroma begins in the internal auditory canal and slowly expands towards the brainstem causing compression of this vital area of the brain.

Symptoms

The early symptoms of an acoustic neuroma are often subtle. Many people attribute the symptoms to normal changes of aging, so it may be a while before the condition is diagnosed.

The first symptom is usually a gradual loss of hearing in one ear, often accompanied by ringing in the ear (tinnitus) or a feeling of fullness in the ear. Less commonly, acoustic neuromas may cause sudden hearing loss.

Meeting a medical practitioner

It's important to see your doctor if you experience these symptoms. Symptoms like clumsiness and mental confusion can signal a serious problem that requires urgent treatment.

Acoustic Neuroma Causes

There are two types of acoustic neuroma: a sporadic form and a form associated with a syndrome called neurofibromatosis type II (NF2). NF2 is an inherited disorder characterized by the growth of noncancerous tumors in the nervous system. Acoustic neuromas are the most common of these tumors and often occur in both ears by age 30.

NF2 is a rare disorder. It accounts for only 5% of acoustic neuromas. This means the vast majority are the sporadic form. Doctors aren't certain what causes the sporadic form. One known risk factor for acoustic neuroma is exposure to high doses of radiation, especially to the head and neck.

 Treatment

Surgery for acoustic neuromas may involve removing all or part of the tumor.

There are three main surgical approaches for removing an acoustic neuroma:

·         Translabyrinthine, which involves making an incision behind the ear and removing the bone behind the ear and some of the middle ear. This procedure is used for tumors larger than 3 centimeters. The upside of this approach is that it allows the surgeon to see an important cranial nerve (the facial nerve) clearly before removing the tumor. The downside of this technique is that it results in permanent hearing loss.

·         Retrosigmoid/sub-occipital, which involves exposing the back of the tumor by opening the skull near the back of the head. This approach can be used for removing tumors of any size and offers the possibility of preserving hearing.

·         Middle fossa, which involves removing a small piece of bone above the ear canal to access and remove small tumors confined to the internal auditory canal, the narrow passageway from the brain to the middle and inner ear. Using this approach may enable surgeons to preserve a patient's hearing.

A newer, less invasive technique called total endoscopic resection enables surgeons to remove acoustic neuromas using a small camera inserted through a hole in the skull. This technique is offered only at major medical centers with specially trained surgeons. Initial studies show success rates similar to those with conventional surgery.

Radiation therapy is recommended in some cases for acoustic neuromas. State-of-the-art delivery techniques make it possible to send high doses of radiation to the tumour while limiting expose and damage to surrounding tissue.

Radiation therapy for this condition is usually delivered in one of two ways:

·         Single fraction stereotactic radiosurgery (SRS), in which many hundreds of small beams of radiation are aimed at the tumor in a single session.

·         Multi-session fractionated stereotactic radiotherapy (FRS), which delivers smaller doses of radiation daily, generally over several weeks. Early studies suggest multi-session therapy may preserve hearing better than SRS.

 Epidemiology

·         each year, 1 in 5,12,709 people develops

·         acoustic neuromaacoustic neuromas are caused by a genetic malfunction involving chromosome 22

·         unilateral acoustic neuromas (affecting only one ear)

o    occurs in about 6% of all cases of tumors in the skull

o    symptoms usually appear between ages 30 and 60, but may develop at any age

o    is not hereditary

·         bilateral acoustic neuroma (affecting both ears)

o    is hereditary

o    may appear as early as the teenage years

o    each child of a parent with the condition has a 50% chance of developing the condition, too

·         brain or ear canal surgery can usually remove the tumor completely

·         half of patients with small tumors may retain hearing after surgery

·         most patients with small tumors experience no facial paralysis following surgery

·         about 2/3 of patients with large tumors have some degree of permanent facial paralysis