What is acoustic neuroma? (Vestibular schwannoma)
Acoustic neuroma (or vestibular schwannoma) is a rare, benign tumor in the auditory and vestibular nerves. Treatment depends on the size of the tumors. However, the chances of cure are usually good.
Typical anatomic location of acoustic neuroma. Source: wikipedia.org
In general, the tumor originates from the Schwann cells of the vestibular nerve. In that case, it is also called vestibular schwannoma. The Schwann cells represent an insulation of the nerve pathways. Information can thus be transported more quickly. In rare cases, this benign tumor is located in the tissue of the auditory nerve.
Causes and incidence of acoustic neuroma
The incidence for the disease increases with increasing age. However, this grows slowly. This tumor also does not tend to metastasize. It usually encapsulates itself in connective tissue. According to the German Cancer Society, this form of tumor accounts for 8% of tumors inside the skull. As technical diagnostic procedures are constantly improving, acoustic neuroma can be detected at an early stage. In many patients, it remains undetected. Yet it usually does not cause pain.
Where is an acoustic neuroma located?
Right acoustic neuroma, approximately 20 x 22 x 25 mm extra- and intrameatal. Source: wikipedia.org
A distinction is made between two forms of the tumor depending on their location. The tumor may arise in the cerebellopontine angle lying toward the center or toward the side in a canal of the rocky bone.
The medial tumor is lying toward the middle and is located in the cerebellopontine angle. This can be thought of as a particularly narrow space that lies between the cerebellum and the petrous bone. Central portions of many cranial nerves are located here. Depending on which nerves the tumor affects, the patient will experience different symptoms.
This form is located to the side. It is located in the meatus acusticus internus, a canal in the rocky bone. Nerves of balance and the auditory nerve pass through here. The facial nerve and the gustatory nerve also run here. Growth can cause pressure damage to the nerves.
What are the symptoms of aucous neuroma?
Symptoms often appear only after larger growth. Because this benign tumor takes quite a long time to grow, symptoms are not noticed until years later. At first, impairments in hearing can be noticed. Usually only one ear is affected. The first sign of the tumor is the onset of unilateral hearing loss.
This comes suddenly as a sudden hearing loss or manifests itself as a slowly increasing hearing loss. In addition, there is often dizziness and eye twitching. Rarely, there may be facial pain or numbness in the jaw. Affected individuals often notice restrictions only by accident. Typically, there is a change in the sense of hearing, especially in the range of high-pitched sounds. Affected persons notice changes in the way birds chirp or find it difficult to follow a telephone conversation in the affected ear. Often there is also ringing in the ears. These can sometimes also be the only symptom.
Neck pain in aucous neuroma
In severe cases, cerebrospinal fluid drainage can no longer occur and intracranial pressure increases. Typical symptoms of this include visual disturbances, headache, neck pain, nausea, and vomiting.
How does acoustic neuroma develop?
Why this tumor occurs is not yet well understood. It is neither a hereditary nor a contagious cause. In rare cases, the hereditary disease is neurofibromatosis type 2. The genetic defect causes tumors throughout the body. In about 5% of the patients an acoustic neuroma develops. However, the tumor proliferates in the nerve cells and can lead to permanent damage if there are signs of pressure. Most often, these are extreme courses of the disease.
How is acoustic neuroma diagnosed?
The examination is usually performed by the otolaryngologist. First, it is important to rule out other diseases that cause dizziness or hearing problems. To do this, patients perform a hearing test. The patient indicates what they hear when they hear different sounds.
Brainstem audiometry can test the auditory nerve without the patient having to cooperate. Clicking sounds are played through a speaker. An electrode behind the ear then measures whether the information is transmitted to the brain without interference. The EEG then provides information about changes in the skull.
The doctor will also take a temperature reading of the vestibular organ. To do this, he or she will flush the external auditory canal with warm water. A reflex of the eye muscles causes the eyes to twitch back and forth in a horizontal position. The reflex can be disturbed in the case of an aucous neuroma. In addition, the vestibular organ is hyperexcited and the patient suffers from dizziness. This helps determine how far the tumor has already damaged the auditory nerve.
What happens during an MRI exam for aucous neuroma?
Acoustic neuroma on MRI image (arrow). Source: wikipedia.org
If tumor disease is suspected, the doctor will have an MRI done. This can be used to definitively determine if it is a tumor. The patient is then pushed into the diagnostic tube on a couch, where cross-sectional images of the inside of the body are made using magnetic fields and electromagnetic waves. A contrast agent is sometimes also injected into the vein for better visibility. The MRI examination itself does not cause radiation exposure. Because of the narrow tube and the loud noise the machine produces, some patients often find the procedure uncomfortable.
What is the treatment/therapy for aucous neuroma?
The disease can be treated in several ways. Either one waits to see if the tumor changes. This involves regular MRI scans, or radiation and surgery.
For smaller growths, doctors often choose to simply wait in a controlled manner and monitor the growth via MRI scans. In older patients, the tumor usually does not change in size or even regresses. As long as the patient has no symptoms, they try to avoid radiation or interventions through surgery.
When does surgery occur for acoustic neuroma?
If the tumor begins to grow and reaches a size of two to three centimeters or more, surgery is always required. Specialists try to spare tissue or healthy nerves that have not been damaged. There is a risk that bleeding or nerve damage may occur in the process. The sense of hearing and balance can therefore remain impaired in the long term in the case of an acoustic neuroma. In principle, however, surgery is the most effective way to treat the tumor and bring about a cure.
When does radiation have to take place?
The gentler treatment is irradiation with gamma rays. Here, the tumor is destroyed by targeted radiation. However, damage to the surrounding tissue cannot be avoided. Larger tumors can usually also not be completely covered. Radiation is used when surgery is not possible for medical reasons.
Aucous neuroma dangers and late effects?
Because the tumor grows very slowly and does not metastasize, the prognosis is usually good. However, the course also depends on the position and size of the tumor. Small growths do not always require therapy. Larger growths heal after surgery and there are no recurrences. Only if the tumor in the skull could not be removed completely, the tumor may recur. However, the tumor often remains undetected for years because it does not cause any symptoms.