Brain Tumor: Neuroma And Acoustic Neuroma

A neuroma (Neuron = nerve cell) is a benign, slow-growing brain tumor that occurs mostly in the posterior fossa. The most commonly occur in the Schwann cells of the eighth cranial nerve. This nerve is a twin Cochleovestibular nerve, therefore has two components – the auditory nerve (cochlear nerve) and the balance nerve (vestibular nerve).

The acoustic neuroma almost always grows from the vestibular portion of the 8th cranial nerve, resulting in the name often used vestibular schwannoma.

Cranial nerves are made of very, very thin fibers that are encased by a sheath of connective tissue. This case is made from the so-called Schwann cells and is therefore called Schwann sheath. The comparison with a copper wire made up of many thin wires and an insulating sheath is not the worst.

Unlike malignant tumors , the acoustic penetrates neither into the surrounding tissue, yet it does not forms secondary tumors (metastases).

The functions of the cranial nerves are:

Smell
See
Eye movements
To roll one’s eyes
Innervation of facial skin, eye socket, teeth, muscles of upper and lower jaws
Eye movements
Facial movements (facial expressions), lacrimation, submandibular gland and sublingual gland, small palate and nasal glands, taste in anterior two thirds of tongue
Hearing and Balance
Pharyngeal muscles (swallowing), mucous membrane of the throat and ear tympanic cavity, taste in the back third of the tongue
Larynx movements (also vocal cords), throat muscles, sensitivity in the outer ear canal, care of the heart, lungs, stomach and intestines!
Head turns
Tongue movements

Neuroma And Acoustic Neuroma: Frequency

The acoustic neuroma is the most common tumor of the posterior fossa. Overall, however, it is only rarely before. Particularly people are affected in middle age, especially at the age of 50. In women, the acoustic neuroma occurs about twice as often as men. Specifically, a hereditary disease (neurofibromatosis type 2) is behind it when the acoustic neuroma occurs on both sides.

Neuroma And Acoustic Neuroma: Causes

A neuroma or acoustic neuroma occurs in the so called Schwann cells . These cells surround the cranial and peripheral nerves and are important elements of fast conducting nerve fibers. If the Schwann cells are degenerated they form a tumor (neuroma) around the concerned nerve.

Both the risk factors and the causes of an acoustic neuroma are usually unknown . If there are neuroma on both sides of the balance and acoustic nerve, however than the cause is usually a genetic disease : the so-called neurofibromatosis type 2. However this genetic defect is rare (approximately 1 of 35,000 births).

Neuroma And Acoustic Neuroma: Symptoms

Initially a neuroma have only uncharacteristic symptoms that can occur with other diseases. There is often an incidental finding for example through a study carried out for other reasons by computed tomography (CT) or magnetic resonance imaging (MRI) of the head.

As acoustic neuroma grows, it can damage the nerve fibers of the eighth cranial nerve (vestibulocochlear nerve). This nerve fibers is important for the sense of equilibrium and the sense of hearing. Therefore, many sufferers complain a unilateral hearing loss , which may continue to deafness. Also (unilateral) ear noise or buzzing in the ears ( tinnitus ) are typical signs of an acoustic neuroma. Incoordination or dizziness may draw as additional symptoms of acoustic neuroma.

A very extensive neuroma affects the facial nerve . A facial paralysis may occur but it is rare. As acoustic neuromas are close to the brainstem, there is sometimes a risk that the tumors may constrict the brain tissue. This increases the intracranial pressure and leads to characteristic brain pressure symptoms such as:

Nausea
Vomiting
Visual disturbances
Headache

Neuroma And Acoustic Neuroma: Diagnosis

On suspicion of a neuroma, or acoustic neuroma, the doctor perform different equilibrium and hearing tests to confirm it . It can measure, for example, how the auditory cells respond to acoustic stimuli. For accurate neuroma diagnosis and planning of subsequent treatment, the doctor uses imaging techniques, such as magnetic resonance imaging ( MRI ). Unlike computed tomography ( CT ), MRI has the advantage that it can also represent a very small acoustic neuromas well.

Neuroma And Acoustic Neuroma: Treatments

If a neuroma or an acoustic neuroma causes no symptoms, there is a therapy usually from regular inspections , in which the doctor observes the development of the tumor (among doctors as ” watch and wait ” hereinafter).

In case of complaints for large acoustic neuromas the doctor surgically removes the tumor. If neuroma grows near the inner ear and the auditory canal leading to a ear, nose and throat than it is removed surgically by specialist. In other cases where the acoustic neuroma has been further extended, than a neurosurgeon operates through the skull. A common side effect of the operational acoustic therapy, is deterioration of hearing which may lead up to the hearing loss. The risk depends on the location and size of the tumor and is high in very large acoustic neuromas. For tumors which has three centimeters size also increases the risk of the facial nerve compromising.

For smaller acoustic neuromas, the doctor can also perform radiotherapy (called Gamma Knife irradiation) for therapy. Sometimes a single irradiation is enough for neurinoma therapy. Often, however, a multiple application of irradiation for weeks are necessary.