Learn more about acoustic neuroma and its options for treatment.
Difficulty with hearing and balance is sometimes caused by a non-cancerous tumor known as an acoustic neuroma (vestibular schwannoma). It’s the type of tumor that typically grows very slowly or not at all. Yet it may still place pressure on the eighth cranial nerve (vestibulocochlear nerve) connecting the brain to the inner ear. Treatment for acoustic neuromas may involve:
Some growths can be sporadic in nature. Others are related to neurofibromatosis type II (NF2), a disorder where noncancerous tumors develop within the nervous system. NF2 is rare and only accounts for about five percent of all acoustic neuromas. Most growths are the sporadic form. The cause of sporadic abnormal vestibulocochlear nerve formations isn’t known. The only identified risk factor is exposure to large amounts of radiation in the head and neck area.
Signs and Symptoms
Early symptoms may be subtle and are sometimes assumed to be age-related hearing loss, since this is the most common symptom associated with the condition. If nerves are not being compressed, there may be no symptoms experienced. When hearing loss is experienced because of an acoustic neuroma, it’s usually gradual and asymmetric (present in one ear only). Hearing loss may be accompanied by tinnitus (persistent sound/ringing in the ear). In some people, symptoms will progress rapidly, although gradual progression is more common. Additional symptoms associated with acoustic neuromas may include:
Severe symptoms that include mental confusion should be treated right away. This is usually a sign that nerve compression is affecting certain parts of the brain.
Diagnosing Acoustic Neuromas
Diagnosing an acoustic neuroma often involves ruling out other possible causes. Image tests such as an MRI scan can determine whether or not there is a growth affecting the vestibulocochlear nerve. A patient’s medical history and the specific symptoms experienced will be taken into account when diagnosing an acoustic neuroma. If hearing loss is the only symptom, patients may be referred to an ear, nose, and throat specialist.
Sometimes referred to as “watchful waiting," observation is a common treatment recommendation for patients with acoustic neuromas. For tumors that are less than 2 centimeters, not causing significant symptoms, or the patient is elderly and has other health issues that may make surgery or other treatments risky, observation is usually preferred. During follow-up examinations, progression of symptoms will be monitored to determine if further treatment is necessary.
Advances in how radiation therapy is done have made it safer to deliver high doses of radiation to the tumor without significant risk to surrounding tissues. Stereotactic radiation, in particular, may stop the growth of a vestibulocochlear nerve tumor or reduce the size of the tumor. Radiation treatment is typically recommended for small or medium-size acoustic neuromas. Radiation may also be used when surgery is deemed too risk for a patient since it’s far less invasive.
Radiation may be delivered single fraction stereotactic radiosurgery. With SRS, several beams of radiation are directed at the tumor during a single session. Radiation is applied to a tumor gradually during several sessions with multi-session fractionated stereotactic radiotherapy (FRS), which may preserve hearing more effectively than SRS.
Surgery for Acoustic Neuromas
Surgery may become an option of tumors larger thaxn 3 centimeters. All or part of an acoustic neuroma may be removed during surgery. Performed under general anesthesia, surgery for vestibulocochlear nerve tumors may involve a translabyrinthine procedure where an incision is made behind the ear and bone and part of the middle ear are removed to reach the tumor.
The skull near the back of the head is opened with a retrosigmoid/sub-occipital procedure. Bone of the ear canal is removed to access smaller tumors relegated to the internal auditory canal with a middle fossa procedure. Advancements such as assisted navigation, endoscopic resection, and ultrasonic removal have made surgery safer for patients.
Due to the nature of a condition like this, preventing an acoustic neuroma from developing isn’t possible. There’s some evidence suggesting environmental factors may play a role in the genetic abnormality that results in acoustic neuromas. One in 100,000 patients are diagnosed with this type of tumor each year. Individuals with a condition called neurofibromatosis that causes tumors to form on nerve tissue appear to have a greater risk of developing growths on the vestibulocochlear nerve.