Acoustic Neuromas are the most common benign tumors of the cerebellopontine angle, and their treatment was pioneered at House Clinic
The temporal bones sit on each side of the skull and enclose the hearing and balance organs. Next to the temporal bone is an area called the cerebellopontine angle (CPA). If you have a diagnosis of a tumor in the CPA, most likely you have what is called an acoustic tumor (vestibular schwannomas; acoustic neuroma). These tumors are non-malignant fibrous growths originating from the balance (vestibular) nerve. They don’t spread (metastasize) to other parts of the body. Because acoustic tumors are located deep inside the skull and are adjacent to vital brain centers in the brainstem, as these tumors grow, they affect surrounding structures in the brain that control vital functions. The brain is not invaded by the acoustic tumors, but the tumor pushes on the brain as it enlarges. As the acoustic tumor grows, it typically first affects hearing because it protrudes from the internal auditory canal into an area behind the temporal bone. When large acoustic tumors cause severe pressure on the brainstem and cerebellum of the brain, vital functions that sustain life can be threatened.
Acoustic tumors constitute 6%-10% percent of all brain tumors and are found in roughly one of every 100,000 people per year in the United States. This translates to about 2500-3000 newly diagnosed acoustic tumors per year.
Their first signs or symptoms usually are related to ear function and include tinnitus (ear noise/ringing in the ear) and often disturbances in hearing on one side. You might also experience unsteadiness or loss of balance. As these tumors grow larger, they involve other surrounding nerves having to do with more vital functions. Headache may develop as a result of increased pressure on the brain. In most cases, these tumors grow slowly over a period of years. But sometimes the rate of growth is more rapid. Symptoms can be mild or severe, and multiple symptoms might develop rather rapidly. Although many people have hearing loss on one side, head noises, and balance difficulties, rarely are these symptoms due to an acoustic tumor. But a very careful evaluation of everyone with these symptoms should be performed. Today, the most common method of diagnosing an acoustic tumor is by a detailed MRI of the head. In some cases, the tumor becomes relatively large before a definite diagnosis is established.
The preservation of life is the most important objective of treatment. In the modern era, very few people die from treatment for an acoustic tumor. A secondary objective of treatment is to preserve as many vital structures as possible. For many, a completely normal life results following treatment. Some people experience minor physical handicap while a few may suffer physical handicap that persists. Below we discuss three treatment options: watchful waiting (observation), surgery, and radiation therapy. The choice of treatment may be based on tumor size, hearing in the ear at time of diagnosis,
patient age and health, and, of course, patient preference.
Risks and complications of acoustic tumor treatment vary with the size of the tumor: The larger the tumor, the more serious the complications, and the more likelihood there is of complications.
In most cases, it’s definitely best to actively treat a growing tumor by surgical removal or stopping its growth with radiation treatment. But in some people, monitoring the tumor at regular intervals to be sure it isn’t growing can be an appropriate alternative. This approach, also referred to as “watchful waiting” or “observation”, is usually used only in older patients who might be poor surgical candidates or those with other medical problems that make having surgery undesirable. You must have follow-up MRI scans of the head, using contrast material, as often as every six months for the first year after diagnosis. If the tumor hasn’t grown, repeated MRI’s are done at the discretion of your doctor, perhaps as often as yearly. Any change in symptoms also calls for an MRI to check for tumor growth. Because these tumors can grow rather suddenly, great care must be taken to treat the tumor before it’s so large that complications are more likely. Remember, the smaller the tumor at time of active treatment, the better the outcome of treatment is likely to be. On the other hand, some tumors do not grow or grow only very slowly.
The House Clinic is a high volume acoustic neuroma center, with specialized physicians trained to treat this condition, and hundreds of surgeries performed each year. Surgical procedures offered to treat acoustic tumors include translabyrinthine, middle fossa, and retrosigmoid approaches.
Surgery for these tumors, as well as the pre- and postoperative care, is performed and assisted by a team. This team includes an internist, an anesthesiologist, a specially trained surgical nurse, a neurosurgeon and a neurotologist.
The choice of surgical approach depends upon the size of the tumor and amount of remaining hearing. It’s possible to save hearing in only a minority of cases; if hearing preservation is successful, the preserved hearing will not be better than the preoperative level and can be worse. The larger the tumor is, the lower the chances for hearing preservation. In some cases with poor preoperative hearing or a larger tumor, it’s better to sacrifice the hearing in order to remove the tumor. All procedures are performed with the patient under general anesthesia. The surgeons look through an operating microscope, and special equipment is used to ‘monitor’ the facial and possibly hearing nerves to prevent injury.
In recent years, stereotactic radiation therapy has been used to treat acoustic tumors.
This type of radiation therapy is different than radiation used for cancer. It’s highly focused on the tumor, with only low levels of radiation affecting most of the brain. This type of treatment has proved effective for certain patients with acoustic tumors. Tumors up to 3.0 cm (small or medium) have been treated with radiation. While patients of all ages can be treated, stereotactic radiation therapy may be best for older patients, since the long-term effectiveness (20 years or more) has yet to be determined. As with surgery, there are risks to hearing and to the facial nerve.
In small tumors, it’s sometimes possible to save the hearing while still removing the tumor. When tumors are larger, however, the hearing is usually lost in the involved ear as a result of the surgical procedure. Following the surgery in these situations, the patient hears only with the remaining good ear. Many people function quite adequately with only one hearing ear.