ACOUSTIC NEUROMA
Understanding Your Options: Surgeons’ Advice to the Newly Diagnosed

This article is contributed by the physicians at the House Ear Clinic in Los Angeles, CA.  It presents a surgeon's point of view on Acoustic Neuroma Treatments.


You’ve been diagnosed with an "acoustic neuroma"… a brain tumor. The physician you’ve seen for what you thought might be an ear infection sends you to a neurotologist who recommends removal of the tumor, and the prospect of major surgery seems overwhelming. At this point I’d like to share with you from my perspective – as a surgeon - the various treatment options available, the potential benefits and risks I associate with each, and address some misconceptions about this disease and its treatment.

What is an acoustic neuroma?

Actually, acoustic neuromas are more accurately termed vestibular schwannomas. These are benign (non-cancerous) tumors of the insulating cell layer of the balance (vestibular) nerve. They arise in approximately one-in-one-hundred-thousand people. Why they occur in any given person is not known; but, a small fraction (less than 5%) of them arise from an inherited disorder called neurofibromatosis type 2 (NF2). Patients with NF2 have tumors on both sides of the brain. Prior to the 1960’s, patients having vestibular schwannomas suffered greatly from both the disease and its therapy. About this time, William House introduced revolutionary concepts in microsurgery that changed the face of this disease. Like many areas in medicine, the management of this problem is continuing to undergo change with advances in technology. The frontiers of medicine in general, and vestibular schwannomas in particular, lie in understanding the basic mechanisms of disease development so that therapies, one day, will be directed at prevention.

How do these tumors behave?

By and large these are slow growing benign tumors that cause problems by compressing nervous tissue. For example, hearing loss, the earliest symptom in most cases, arises from pressure on the hearing nerve and the blood supply to the inner ear. Likewise, ringing in the ear (tinnitus) and dizziness arise from compression of the hearing and balance nerves, respectively. As tumors enlarge, the brain itself can be compressed leading to symptoms such as unsteadiness, headache (often from hydrocephalus), and facial numbness. Left untreated, these tumors can ultimately lead to brainstem compression and death. These latter symptoms were much more common in the earlier part of the last century and rarely if ever occur in the modern era.

The average growth rate of a vestibular schwannoma is about 2 to 4 millimeters (1/12 to 1/6 of an inch) per year. Their growth rate is also not constant and can speed up or slow down at unpredictable times. We analyzed the growth rate of tumors in patients who elected to undergo observation of their tumors and discovered, in many cases, that the tumors remained stable for years. Despite not changing size, however, symptoms such as hearing loss and ringing in the ear can worsen.

What do I do if I am diagnosed with a vestibular schwannoma?

Again, except in extremely rare conditions, remember that these tumors are benign. The most important thing to do is remain objective and educate yourself by reading, speaking with other patients and identifying a treating physician that you are certain is experienced and willing to spend the time necessary to provide you with the information you need to make, what may be, the most difficult decision of your life. No matter what path you take for treatment, it is imperative that you are cared for by a competent team with a great deal of experience, what is termed "a center of excellence". The ultimate treatment decision should be one reached together with an experienced professional.

Observation

In some patients, especially those with small tumors and few side effects, careful observation is a very viable option. This option, often referred to as "wait and watch," should only be entertained under the guidance of an experienced treating physician. One must keep in mind that just because a tumor does not grow does not mean it won’t continue to increase your hearing loss, or increase the tinnitus or other related symptoms. We strongly recommend MRIs at intervals of 6 months to a year in order to monitor the tumor.

Radiation Therapy

The treatment of tumors with radiation is appealing to many because it will allow them to avoid surgery. Radiation treatment exists in many forms and, like microsurgery, is undergoing continued innovation. It involves delivering doses of radiation to the tumor with avoidance of surrounding vital structures. It is generally not recommended for tumors exceeding 3 centimeters in diameter. Although in existence for decades, the newer modalities will require longer-term follow-up before concrete conclusions can be made about cure. Like microsurgery, there are many different treatment protocols and skill levels making comparisons of results difficult. Dosage levels, targeting methods and accuracy are just a few factors that may vary. Just as for micro-surgery, it is essential to consult experts with direct experience in the protocol you are considering.

Patients sometimes get the impression that after radiation, the tumor will "disappear" or be "gone". This is not usually the case. If radiation therapy is successful, one may expect growth arrest or some amount of shrinkage; however, the tumor will remain. The percentage of tumors that regrow after radiation at the lower doses currently being used is not known and will require long-term data. A recently reported study from the University of Virginia concluded that in the hands of competent microsurgeons, surgical removal was still the preferred modality for patients able to undergo this form of therapy. Despite this, it is a treatment option for some patients and, like any medical treatment, should be undertaken with an experienced and supportive physician.

Microsurgical Removal

As mentioned earlier, microsurgery has undergone, and continues to undergo, change and innovation. A variety of surgical approaches are available, and the specific approach taken depends upon a number of variables. For example, for small tumors (generally under 2 centimeters) in patients with useful hearing, we have had tremendous success with the middle cranial fossa approach (above the ear). The retrosigmoid (behind the mastoid bone) approach is used by many surgeons for similar indications. For larger tumors, we prefer the translabyrinthine approach (through the mastoid) as it requires little, if any, movement of the cerebellum for tumor access and removal. It also provides us with an excellent view of the facial nerve. Many centers also use the retrosigmoid approach in these instances. We have chosen not to use the retrosigmoid (suboccipital) approach in patients with larger tumors for a number of reasons: 1) a better view of the facial nerve is provided by both the middle fossa (hearing preservation) and the translabyrinthine (non-hearing preservation) approaches, and; 2) we avoid brain retraction and the chronic headaches that are often associated with the retrosigmoid approach.

Whatever treatment is chosen, microsurgical or radio-surgical, it is imperative to seek out centers of excellence with a team of experienced physicians. Questions to be asked include the number of cases done annually, fellowship training, published results and complications. It is not within the scope of this publication to describe all centers of excellence, but information can be obtained through the Acoustic Neuroma Association (www.ANAusa.com) and your local physician. Since tumors are never the same in size or location, each case is very individual, and inexperience is the leading cause of unfavorable outcomes.

Several reports appear in the literature about surgical and non-surgical (radiation) treatment of these tumors. It is our feeling that, in the hands of experienced surgeons, complete microsurgical removal is still the treatment of choice for those patients who are surgical candidates. Again, in experienced hands, this approach affords minimal risk in the vast majority of cases and cure, with recurrences in less than 0.1%.

What are the risks of treatment?

No management strategy, even observation, is without risks. For this reason it is essential that you, as a patient, seek out expert advice no matter what path you choose. Whether non-surgical or surgical therapy is chosen, the side effects may include hearing loss, various degrees of facial weakness, facial numbness and dizziness. Other symptoms reported include headache, fatigue, memory loss and cognitive dysfunction. These symptoms have also been described in patients receiving radiation therapy, indicating that most treatments of disorders involving the brain have potential short and long-term effects. In our hands, we have only very rarely (much less than 1-in-one-thousand) seen these latter side effects in our postoperative patients. Those rare instances have been in patients with very large life-threatening tumors.

Again, the best results come from centers of excellence where hundreds, if not thousands, of these procedures have been performed. As a microsurgeon at the House Ear Clinic I can speak to our experience. When a hearing preservation attempt is chosen (middle fossa approach), we are successful at maintaining hearing at the preoperative level in approximately 70% of cases. When considering facial nerve results, the size of the tumor at the time of treatment is a major issue. For tumors under 2 centimeters, our facial nerve results are excellent (normal or complete) in over 90% of cases. For large tumors, similar outcomes can be expected in over 70%.

Spinal fluid leaks occur infrequently (less than 5%) and rarely require surgical repair. Our experience has shown that more serious complications, death and permanent brain damage, are extremely rare and compare favorably to the statistics for radiation therapy. The recurrence rate at our institution is less than one-in-one-thousand. Presently, our institution is doing a study comparing patients’ pre- and postoperative quality of life. We are doing this rigorous assessment of our outcomes in order to improve our methods to assure quality patient care.

Some commonly asked questions…

I am frequently asked about the following and would like to mention these common questions about acoustic neuromas and their treatment:

Opinions vary on whether a tumor is more difficult to surgically remove after radiation therapy should it be aggressive and continue to grow. I can only comment based on my experience and that within our institution. To date we have seen approximately 16 tumors that required removal after prior radiation. These cases were more challenging due to the scarring effects of radiation. Microsurgery to remove a tumor that has regrown after prior surgery can also be more challenging due to scarring. It is for this reason that we advocate total tumor removal and achieve it in over 99% of cases. Each case is highly individual, but the risks do increase with multiple treatments of any kind.

Patients often ask if the nerves are going through the tumor or wrapping around it. I can state from experience that there is presently no imaging technique that will show us this. We can only determine the exact location of the nerve upon surgical investigation.

 So now what?

As a patient, you must explore all of your options and never feel forced into a premature decision. Your relationship with your physician is of utmost importance, and your ultimate care should be in the hands of a highly experienced team that is dedicated to the careful treatment of these delicate tumors. I often feel that the decision-making process is the most difficult for my patients, and that their recovery is more taxing emotionally than physically, regardless of their treatment choice. In summary, try to remember the following:


House Ear Clinic
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Last Edited: Wednesday, October 30, 2002