Acoustic neuroma is an uncommon condition that is caused by a noncancerous type of tumor. Also known as vestibular schwannoma, an acoustic neuroma generally grows slowly, if at all. This type of tumor can put pressure on the main nerve that connects the brain to the inner ear, called the vestibulocochlear nerve. This may result in difficulty with hearing and balance. A specialist who treats neurological disorders that affect the ears, a neurotologist, can often diagnose this condition with the use of an MRI.
Causes of Acoustic Neuromas
Each year, approximately 1 in 100,000 patients are diagnosed with this condition. It is not entirely clear what causes the development of acoustic neuroma, however, it is believed to be genetic in nature. Those with another genetic condition called neurofibromatosis, which results in tumor formation around the brain and nerves, seem to be at an increased risk for developing acoustic neuroma.
Symptoms of Acoustic Neuroma
If the tumor is not pressing on any nerves, there may not be any symptoms. The most common symptom of this condition is hearing loss, often only present on one side. This can be referred to as asymmetric hearing loss. Symptoms may develop rapidly or may occur over time. Pressure on the vestibulocochlear nerve may also result in dizziness or difficulty with balance. Patients may also experience numbness in the face. Some individuals with acoustic neuroma may also notice a ringing in the affected ear, called tinnitus.
Diagnosis of Acoustic Neuroma
Patients who experience hearing loss or other symptoms may be referred by their primary care physician to an ear, nose and throat specialist. The specialist will take into account the medical history of the patient, symptoms, and the results of any tests, such as an MRI, into account when making a diagnosis. Early detection and diagnosis can prevent further hearing loss often associated with this condition.
Monitoring the Progression of Acoustic Neuroma
If the tumor is small, generally less than 2 cm, or if the patient is elderly or has other risk factors for treatment, it may be advisable to delay certain treatments to see if the tumor will grow and cause a progression of symptoms. An MRI can be completed once or twice a year and patient symptoms recorded on a regular basis in order to check for tumor growth.
The least invasive treatment available for acoustic neuroma is radiation. Stereotactic radiation has been shown to halt the growth of these tumors or even to shrink them in many cases. Radiation treatment is typically recommended for small- to medium-sized tumors. It can also be a first-case option for those who would experience too much risk from surgery.
Tumors that are larger than 3 cm usually require the need for surgical intervention. Additionally, those tumors that do not respond to radiation treatments may need to be surgically removed. The neurotologist will determine the specific type of surgery to use based on the size and the exact location of the tumor. This procedure is performed under general anesthesia. Surgery for acoustic neuroma has become much safer for patients due to technological advances such as ultrasonic removal of bone and assisted navigation. The neurotologist will often enlist the help of a neurosurgeon for this type of surgery.