There are various causes of hearing loss in one ear, including viral infections and blunt head trauma. In cases of sudden idiopathic hearing loss, the cause may never be determined. Once an audiologist has performed a complete audiometry test to determine the extent of your diminished hearing capabilities, diagnostic imaging tests may be recommended to detect the presence of an acoustic neuroma, one of the rare causes of unilateral hearing loss. An acoustic neuroma is a brain tumor that, although benign, must be diagnosed and addressed.
Benign But Bothersome Brain Tumor
Acoustic neuromas are also called vestibular schwannomas. An acoustic neuroma is a slow-growing, benign tumor that grows on the eighth cranial nerve, which is called the vestibulocochlear nerve and connects the inner ear to the brain. The vestibulocochlear nerve plays roles in maintaining balance and equilibrium and in conducting auditory function. One of the earliest symptoms signs of a potential acoustic neuroma is hearing loss in one ear. This hearing loss is usually gradual, but in rare instances, the hearing loss may be sudden. Tinnitus, or ringing in the affected ear, is another common complaint. As the tumor grows and compresses against the vestibucochlear nerve and other neighboring areas of the brain, you may experience any of the following additional symptoms:
- Diminished balance and coordination
- Facial weakness
These tumors are typically diagnosed in middle-aged individuals between the ages of 30 and 60, but acoustic neuromas are diagnosed in only one out of every 100,000 patients annually. Your doctor will recommend a magnetic resonance imaging (MRI) scan to rule out or confirm the presence of an acoustic neuroma. Although acoustic neuromas are benign in that they do not metastasize, or spread, to other parts of the body, an undiagnosed acoustic neuroma can eventually compress parts of the brain and cause life-threatening consequences.
Observe or Treat?
There are three options for addressing an acoustic neuroma. These options include:
- Observation without immediate treatment
- Surgical treatment
- Radiation treatment
Since acoustic neuromas grow slowly, observation without treatment is a viable option for some patients, especially for those who are diagnosed at an advanced age or those whose tumors are very small at the time of the initial diagnosis. Observation requires repeated MRI scans at periodic intervals to monitor the progress of the tumor's growth. If the tumor grows or begins to cause additional symptoms, then one of the treatment interventions may be pursued.
Going Under the Knife: Surgery or Radiation?
One treatment option for acoustic neuromas is surgical removal of all or part of the tumor. There are four methods for treating acoustic neuromas with surgery.
Translabyrinthine is employed when tumors are larger. Since part of the middle ear is removed in this procedure, complete and permanent hearing loss on the affected side will result.
Retrosigmoid/sub-occipital accesses the tumor by opening the skull at the back of the patient's head. Unlike the trandlabyrinthine method, this technique can preserve what remains of the patient's hearing on the affected side.
Middle fossa is performed on patients whose tumors are small and confined to within the auditory canal. This method enables patients to preserve their hearing on the affected side.
Total endoscopic resection is a fairly new option that offers the least invasive alternative of the four surgical methods. In this technique, the acoustic neuroma is removed laparoscopically through a small incision in the skull.
Postoperative patients can expect to require balance therapy and courses of action to cope with hearing loss and to enhance any remaining audial capacity.
For the least invasive treatment method, many patients are turning to radiation therapy to control their acoustic neuromas. Gamma Knife and CyberKnife are two types of stereotactic radiation therapy that may be employed. Both options require no general anesthesia, and the entire treatment protocol may be administered in one or more sessions that are administered on an outpatient basis. These methods apply precisely targeted beams of radiation to the tumor. The tumor is not removed during stereotactic radiation therapy. The goal of this treatment option is to control the growth of the tumor, which may present as slowing the rate of its growth or stopping its growth altogether, and some acoustic neuromas have been shown to shrink in size following treatment. Stereotactic radiation therapy must be followed up with repeated MRI scans and audiograms performed at periodic intervals to track the results.
Your Support Team
If you are diagnosed with one of these rare tumors, you will be referred to several specialists that possess the expertise necessary for treating acoustic neuromas. In addition to your primary care physician and your audiologist, this multidisciplinary team may include otologists, neurosurgeons and radiation oncologists. The members of this team will work together to review your medical history, MRI scans, your symptoms and audiograms to help you determine the best course of action for monitoring, treatment and post treatment care for your acoustic neuroma.