Brief overview
- Symptoms: Hearing loss, tinnitus and dizziness
- Prognosis: Prognosis usually good, sometimes complications such as loss of balance, complete hearing loss, facial paresis (facial paralysis with involvement of the seventh cranial nerve), hemorrhage, damage to the brain stem, cerebrospinal fluid (CSF) leakage
- Cause: Probably due to hereditary disease neurofibromatosis type 1 and type 2; possibly strong noise favors the formation of the tumor
- Diagnosis: Physical and neurological examinations, hearing test, magnetic resonance imaging (MRI)
- Treatment: surgery or radiation directly on the tumor tissue
What is acoustic neuroma?
Acoustic neuroma, now called vestibular schwannoma, is a benign neoplasm inside the skull. It originates from the auditory and vestibular nerve (vestibulocochlear nerve) and is thus not a true brain tumor in the strict sense, but a neoplasm of the peripheral nervous system.
The acoustic neuroma usually grows between the two brain sections cerebellum (cerebellum) and bridge (pons). Physicians also refer to it as a cerebellopontine angle tumor. It often encapsulates itself from surrounding structures with connective tissue and does not metastasize.
Since technical diagnostic procedures have improved significantly in recent years, acoustic neuroma is usually detected earlier today than in the past. Nevertheless, it is assumed that many patients remain undetected because the tumor is often small and does not cause any symptoms.
What are the symptoms of acoustic neuroma?
An acoustic neuroma does not cause symptoms until it enlarges significantly and displaces other structures in its vicinity. However, because the tumor grows very slowly, years usually pass before an acoustic neuroma causes symptoms.
The first to be affected are usually hearing and the organ of balance. Hearing loss is often the first sign of the tumor. It occurs on one side of the tumor. Affected individuals often notice this hearing loss only by chance, for example, when listening to a telephone conversation with the affected ear. Even a routine hearing test then indicates the disease. Typically, the high-frequency range in particular deteriorates, so that birdsong is often altered or no longer perceptible.
If the tumor affects the vestibular nerve, acoustic neuroma often causes symptoms such as dizziness (spinning or staggering vertigo) and nausea. This usually also changes the gait pattern. In addition, in some patients, the eyes tremble back and forth horizontally (nystagmus). These symptoms occur especially during rapid head movements and in the dark, when balance is less well coordinated through the eyes.
In some cases, a very large acoustic neuroma compresses various facial nerves and restricts their function. In this case, for example, the mimic muscles in the face are then impaired (disturbance of the facial nerve) or the feeling of the facial skin disappears (disturbance of the trigeminal nerve).
In extreme cases, acoustic neuroma shifts the drainage of cerebrospinal fluid (CSF), causing it to back up in the head and increase intracranial pressure. Typical signs include headaches, neck stiffness, nausea, vomiting and visual disturbances.
What is the course of an acoustic neuroma?
Since acoustic neuroma grows very slowly and does not metastasize, the prognosis is good. The course of the disease basically depends on the site of growth and the size of the tumor. In the case of small, asymptomatic tumors, it is not necessarily necessary to treat.
What late effects are possible?
If, for example, the tumor cannot be carefully removed during surgery, bleeding or nerve damage are sometimes the result. In the case of an acoustic neuroma, there is therefore also long-term impairment of the sense of hearing and balance. This may lead to complete hearing loss. Facial paresis (facial paralysis involving the seventh cranial nerve) or cerebrospinal fluid (CSF) leakage is also possible.
What leads to acoustic neuroma?
Acoustic neuroma forms from the so-called Schwann cells. These coat nerve structures in the brain and thus accelerate the flow of information. In acoustic neuroma, however, these cells proliferate uncontrollably and form an encapsulated focus. Since it is usually the vestibular nerve that is affected, physicians also speak of a vestibular schwannoma.
Why this disease develops has not yet been sufficiently clarified. However, it is neither hereditary nor contagious. Rarely, an acoustic neuroma occurs in the context of the hereditary disease neurofibromatosis type 1 and type 2. Due to a genetic defect, tumors form all over the body in this disease. Although acoustic neuroma does not necessarily occur, about five percent of those affected even develop bilateral ulcers.
How do you recognize an acoustic neuroma?
The first contact person for an acoustic neuroma is usually the ear, nose and throat specialist or the neurologist. In the anamnesis (taking of the medical history) he asks the affected person about his complaints and the temporal course.
Using a small ear funnel and a lamp, he examines the external auditory canal and the eardrum. Since various other diseases also cause symptoms such as dizziness or hearing problems, the doctor clarifies these to rule them out. The following examinations are useful for this purpose:
Hearing test
In a hearing test, the doctor plays sounds of different pitches (sound audiometry) or words (speech audiometry) to the patient through headphones. The patient indicates what he or she hears. This is therefore a subjective test.
Brainstem evoked response audiometry (BERA) tests the auditory nerve without the affected person actively participating. Clicking noises are played over the loudspeaker. An electrode behind the ear measures whether the auditory nerve transmits the information undisturbed to the brain.
Temperature measurement of the vestibular organ
Magnetic resonance imaging (MRI)
An acoustic neuroma can only be definitively diagnosed by means of magnetic resonance imaging (MRI, also known as magnetic resonance imaging). To do this, the patient lies on a couch while the doctor slides him or her into a diagnostic tube that uses magnetic fields and electromagnetic waves to take detailed cross-sectional images of the inside of the body. Sometimes the patient is injected with a contrast medium into a vein before the image is taken.
The MRI does not cause any radiation exposure. However, some people find the examination unpleasant because of the narrow tube and loud noises.
What are the treatment options?
There are three treatment options for acoustic neuroma: controlled waiting, surgery and radiation.
For small tumors, physicians often opt for controlled waiting (“wait and scan”). In this case, the physician uses MRI to monitor at regular intervals whether the acoustic neuroma is growing. Especially in older individuals, the size of the tumor usually no longer changes or even decreases. If there are no symptoms, those affected are spared surgery or radiation in this way.
A newer method, which is particularly suitable for older patients with a higher surgical risk, is stereotactic radiosurgery (SRS for short). This is a highly precise radiation therapy guided by imaging techniques and computer-assisted. The treatment is performed with a gamma or cyber knife, which destroys the tumor cells.
However, it is impossible to avoid that this also damages surrounding healthy tissue. However, it is often difficult to completely cover larger tumors.
