Acoustic neuroma

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at April 26, 2016
StartDiseasesAcoustic neuroma

An acoustic neuroma is a benign tumor located on the main nerve that runs from the inner ear to the brain. The size of the noncancerous tumor influences the symptoms and the treatment of the disease. Prognosis of patients is positive, given early diagnosis and treatment.

Contents

Definition & Facts

Acoustic neuromas are tumors that develop on the vestibulocochlear nerve. This nerve has two main jobs: to transmit sound from the ear to the brain and promote good balance. These tumors are normally slow growing and will not metastasize to other parts of the body. There are two types of acoustic neuromas: sporadic and a rare type associated with neurofibromatosis type II, an inherited disorder. The rare form only accounts for 5% of cases of acoustic neuroma.

Symptoms & Complaints

The symptoms of this noncancerous tumor vary depending on its size and exact location. Many of the early symptoms are very similar to those of normal aging such as a reduction in hearing in one ear as well as tinnitus in which one experiences a ringing in the ears. The hearing loss is usually gradual, so it can go unnoticed for some time. It can be as mild as simply losing the ability to hear certain pitches or sounds.

Sudden hearing loss can also be evidence of an acoustic neuroma though this rapid change is rare. Feeling as though the ear is full of fluid or clogged is another common complaint by patients. Over time, as the tumor grows the following symptoms may appear:

Periodic vertigo is more often associated with the presence of small acoustic tumors, whereas large tumors are more likely to cause the feeling of being off balance. Facial numbness, tingling and weakness tends to appear as the tumor grows so large it presses against surrounding nerves. In even more severe cases, this can lead to facial paralysis.

Untreated acoustic neuromas can have devastating symptoms. The tumor can press against the brainstem and negatively affect its functions. Difficulty breathing, muscle tremors, and the reduction in reasoning ability are only a few of the serious symptoms associated with these large acoustic tumors. In extremely rare cases, the untreated tumor can cause coma and death. It is important to seek out a medical professional when symptoms arise.

Causes

Doctors and scientists are unsure of the exact cause of sporadic acoustic neuromas. Possible risk factors include the exposure to high levels of radiation around the head and neck during childhood and prolonged exposure to intensely loud noises. Nevertheless, no direct cause of this type of acoustic neuroma is confirmed.

On the other hand, the rarer form is developed from inheriting neurofibromatosis type II. This disorder is blamed for the development of multiple benign tumors grown throughout the central nervous system. Acoustic neuromas are the most common tumor seen with the disorder and often occur in both ears, causing bilateral symptoms. By contrast, sporadic acoustic neuromas are the most common type of acoustic neuroma at approximately 95% and are only seen in one ear.

Diagnosis & Tests

Detection and proper diagnosis of an acoustic neuroma can be a difficult task due to the fact its symptoms are commonly seen in other middle ear infection and inner ear infections and problems. Hearing tests are most often ordered first to determine the extent of hearing loss in each ear. A series of tones or words are played in various volumes and pitches. This helps the practitioner determine the presence of an acoustic tumor, especially when there is asymmetrical hearing loss.

When a tumor is suspected after the preliminary hearing test, a CT scan with intravenous dye can be performed. Unfortunately, this type of test is unable to uncover small tumors, so if the patient is able, an MRI will be ordered and executed. The MRI scan is able to detect nearly 100% of acoustic tumors in a range of sizes. After positive diagnosis, DNA testing by a genetic specialist may be recommended to determine the inheritance of the neurofibromatosis type II gene.

Treatment & Therapy

The prescribed treatment for an acoustic neuroma will vary depending on the tumor's size, location, and severity of symptoms. Small, slow-growing tumors are often treated with simple observation. MRI scans would be periodically performed to watch for bigger growth and establish if other courses of treatment are needed.

Surgery could also be completed on the tumor and this is the most common treatment. Sometimes this is to remove only a piece of the tumor as opposed to a complete removal depending on various factors including age of the patient as well as the size and location of the acoustic tumor.

Various surgical methods and procedures are performed on acoustic neuromas. Unfortunately, permanent hearing loss is a possibility, and due to the delicate location of the surgery, a multiple day hospital stay is required to evaluate for surgical side effects.

Radiation therapy is the third option to treat the noncancerous tumors of a small to medium size. It is an outpatient procedure and works by aiming small beams of radiation directly at the tumor with the goal of killing the tumor cells. With this technique, the tumor will not be completely removed. Instead it is hoped the radiation may slow or stop the growth of the tumor, and in some cases even shrink it.

Prevention & Prophylaxis

Unfortunately, there is no true prevention of the acoustic neuroma since there is no definitive cause. Genetic testing can be performed to determine the presence of neurofibromatosis type II, but this also will not guarantee the future presence of the tumor or its location.