acoustic neuroma

Acoustic neuroma: description

The acoustic neuroma is a benign neoplasm within the skull. It is based on the auditory and equilibrium nerve (vestibulochochlear nerves) and is thus in the narrower sense not a true brain tumor, but a new formation of the peripheral nervous system.

The acoustic neuroma usually grows between the two cerebellar cerebellum and the cerebrum and is therefore also called the cerebellar angle tumor. Among professionals, the acoustic neuroma is also referred to as vestibular schwannoma. It usually encapsulates with connective tissue from the surrounding structures and does not form metastases.

Neurinomas (such as the acoustic neuroma) are benign tumors and usually grow slowly. They are rare – according to the German Cancer Society they account for about eight percent of the tumors inside the skull. Most patients fall ill between the 30th and 50th year of age on a neurinoma.

Since the technical diagnostic procedures have improved significantly in recent years, an acoustic neuroma can be detected earlier today than in the past. Nevertheless, it is believed that many patients go undetected, as the tumor is often small and does not cause discomfort.

Acoustic neuroma: symptoms

An acoustic neuroma only causes discomfort when it gets bigger and displaces other structures in its vicinity. However, as the tumor grows very slowly, it usually takes years before an acoustic neuroma causes symptoms.

As a rule, the hearing and the organ of balance are impaired as a rule. A hearing loss is often the first sign of the tumor. It occurs unilaterally on the side of the tumor. Affected, this hearing loss is often coincidental, for example, when they follow a telephone conversation with the affected ear. Even a routine hearing test can indicate the disease. Typically, the high-pitch range deteriorates, so that birdsong often changes or is no longer perceived.

An acoustic neuroma can also be manifested by a hearing loss. This results in a sudden and almost complete hearing loss in the affected ear. Often additional ear noises (tinnitus) occur. They are usually in the high frequency range and are perceived as very stressful. Tinnitus can be the only symptom that causes an acoustic neuroma. The hearing loss is often added later.

If the tumor affects the balance nerve, the acoustic neuroma may cause symptoms such as dizziness (vertigo or swaying vertigo) and nausea. This can also change the gait pattern. In addition, the eyes tremble horizontally in some patients (nystagmus). These symptoms are especially noticeable in rapid head movements and in the dark, when the balance is less well coordinated through the eyes.

A very large acoustic neuroma can also compress and restrict the function of various facial nerves. In this case, for example, the mimic muscles in the face may be impaired (disorder of the facial nerve) or the feeling of the facial skin disappear (disturbance of the trigeminal nerve).

In extreme cases, the acoustic neuroma may drain the outflow of cerebrospinal fluid (cerebrospinal fluid), causing it to build up in the head and increase intracranial pressure. Typical symptoms include headache, neck stiffness, nausea, vomiting and blurred vision.

Acoustic neuroma: causes and risk factors

The acoustic neuroma is formed by the so-called Schwann cells. These envelop nerve structures in the brain and thereby accelerate the flow of information. In an acoustic neuroma, however, these cells proliferate uncontrollably and form an encapsulated stove. Since most of the balance nerve (vestibular nerve) is affected, doctors also speak of a Vestibularisschwannom.

Why this disease arises, has not been sufficiently clarified. However, it is neither hereditary nor infectious. Rarely does an acoustic neuroma occur as part of the hereditary disease neurofibromatosis type 2. Due to a genetic defect, tumors develop on the whole body in this disease. Although it does not necessarily come to an acoustic neuroma, develop in about five percent of those affected even bilateral ulcers.

Acoustic neuroma: examinations and diagnosis

The first point of contact with an acoustic neuroma is usually the ear, nose and throat doctor or the neurologist (neurologist). In the anamnesis (survey of medical history), he asks the patient about his symptoms and their time course. With a small ear funnel and a lamp, he examines the external auditory canal and the eardrum. Since various other illnesses can also cause symptoms such as dizziness or hearing problems, they must be excluded. The following investigations offer themselves for this purpose.

hearing test

In a hearing test, the patient is auditioned via headphones with different levels of sound (tone audiometry) or words (speech audiometry). The patient indicates what he hears. It is therefore a subjective test.

A brainstem evoked response audiometry (BERA) tests the auditory nerve without the patient having to actively participate. Clicks are played over the loudspeaker. An electrode behind the ear measures whether the information about the auditory nerve is transmitted undisturbed into the brain.

Temperature measurement of the equilibrium organ

If patients with suspected acute acoustic neuroma under dizziness, the organ of equilibrium is usually checked with a temperature measurement (calorimetry). For this, the outer ear canal is rinsed with warm water. Through a reflex of the eye muscles, the eyes twitch in the horizontal back and forth. An acoustic neuroma can interfere with this reflex.

Magnetic Resonance Imaging (MRI)

An acoustic neuroma can only be definitively diagnosed by MRI (also called magnetic resonance imaging). For this purpose, the patient is pushed onto a couch in a diagnostic tube, where magnetic fields and electromagnetic waves can be used to create detailed sectional images of the inside of the body. Sometimes a contrast agent is injected into a vein before shooting. The MRI does not cause radiation exposure. The examination is perceived as unpleasant only because of the narrow tube and the loud noises of some patients.

Acoustic neuroma: treatment

The acoustic neuroma can be treated in three different ways: controlled waiting, surgery and radiation.

For small tumors, physicians often opt for a controlled wait. It is monitored at regular intervals by MRI, if the acoustic neuroma grows. Especially in older patients, the size of the tumor usually no longer changes or even goes back. If there are no symptoms, the patient may be spared surgery or radiation.

On the other hand, if the acoustic neuroma assumes a size of three or more centimeters, it must be operated on. ENT specialists and neurosurgeons try to protect healthy tissue, blood vessels and nerves. Failure to do so may result in bleeding or nerve damage. In the case of an acoustic neuroma, the sense of hearing and balance can therefore remain impaired in the long term.

Something gentler is the treatment with a gamma or cyber knife. The acoustic neuroma is destroyed by radiation. However, it can not be avoided that even surrounding healthy tissue is damaged. In addition, larger tumors usually can not be completely detected. This therapy is therefore used only in patients who can not be operated on medical grounds.

Acoustic neuroma: disease course and prognosis

Since an acoustic neuroma grows very slowly and does not form metastases, the prognosis is good. The course of the disease is determined by the growth site and the size of the tumor. Small, asymptomatic tumors do not necessarily have to be treated. Larger tumors can be cured by surgery and usually do not recur. Only if a residual tumor remains in the skull can again acoustic neuroma arise.