The three basic options are: Wait-and-Watch, Microsurgery, Radiosurgery/Radiotherapy. The Acoustic Neuroma Association’s 2007-2008 Patient Survey showed the treatment choices made by 1,934 participants in the survey: Wait-and-Watch (20%), Microsurgery (61%), Single-session Radiosurgery (12%), Multiple-session Radiotherapy (8%). Compared to ANA’s earlier 1998 survey, this was a significant increase for Radiosurgery-Radiotherapy (20% vs. 5%) and Wait-and-Watch (20% vs. 4%).
If an acoustic neuroma is small and acute symptoms are not present, a first option is to wait-and-watch by monitoring the growth characteristics of the tumor with periodic MRIs. Any perceived growth needs to be watched closely to avoid complications that are more likely to occur when a large tumor has to be treated. A second caution is the troublesome fact that worsening of hearing can occur regardless of whether or not tumor growth is demonstrated. The critical point for deciding upon intervention appears to be when tumor size approaches about 18 to 20 mm. A study of 72 wait-and-watch patients at Toronto University Hospital was reported on in February 2000. The patients chose this “conservative management” of their tumors because of either poor general health, advanced age, small tumor size, patient preference, minimal symptoms, or because the tumor was in the only or better hearing ear. The patients’ tumors were monitored by periodic MRIs for an average of 37.8 months; the range was 12 to 194 months. The mean tumor growth rate for these patients was found to be 1.16 mm/yr. Approximately 83% of tumors grew at less than 2.0 mm/yr. No growth or insignificant growth was seen in 50% of tumors; significant growth in 36.4%; and negative growth in 13.6%. Patients were deemed to have failed conservative management if there was evidence of continuous or rapid growth and/or increased symptoms. Such failure, in which active treatment was required, occurred in 15.3% of cases. In those patients who failed, the mean tumor growth rate was greater (4.2mm/yr) than in those who did not fail (0.5mm/yr). The final outcome for the failed patients appeared to be as favorable as for those who underwent primary treatment without a period of wait-and-watch.
A study (2003) at the Gentofte University Hospital of Copenhagen, Denmark, has compared the long-term socio-economic and quality of life changes experienced by acoustic neuroma patients who either underwent surgery (716) or chose to wait-and-watch (226). The tumors in the wait-and-watch group were mostly below 20mm and were evaluated as of the less aggressive type. Surgical intervention at the hospital was standard for tumors larger than 20mm with documented growth verified by MRI. The abstract of this study states, in part: “Regardless of tumor size, employment was unchanged for the majority of observed and operated patients. . . The majority of both observed and operated patients experienced no change in their ability to handle daily chores. . . Among various changes in their psycho-social well-being, decrease in social ability was the most frequent complaint in both groups, followed by increased fatigue, decreased concentration, increased irritability, depression and headache, decreased intellect and libido. Regardless of tumor size, the change in social ability, concentration and fatigue was worse for operated patients.” The study concluded: “It has to be realized that surgery of even small tumors has consequences worse than those of observation, concerning psycho-social well-being, ability to handle daily chores and vocational status. This clearly justifies a policy of observation and repetitive MRI of the increasing number of intra-meatal and small tumors, at least until growth is documented.”
- See also “Update from the 5th International Conference on Vestibular Schwannoma,” by Dr. Richard Wiet (Northwestern University), ANA Notes, Issue 103 (September 2007).
- See also “Making a Decision About Treatment,” by Dr. Rick Friedman (House Ear Clinic), ANA Notes, Issue 105 (March 2008).
Surgical removal of the tumor under general anesthesia is a second option. Advances in microsurgical techniques and the development of the medical team approach have greatly reduced the risks of damaging vital nerves during tumor removal. Brainstem response monitoring can be used to assist in the preservation of useful hearing. Facial nerve monitoring may also be employed. In cases of especially large tumors, partial removal followed by radiosurgery treatment may be indicated to avoid complications. The best surgical outcomes are from medical centers with experienced acoustic neuroma teams.
There are three main surgical approaches used for removal of an acoustic neuroma. First, the translabyrinthine approach is used for large tumors and where preservation of hearing is not an issue. The incision is made in the hairline behind the ear and the tumor is exposed by removal of the mastoid bone, which results in total hearing loss in the affected ear. Facial nerve preservation, on the other hand, is facilitated by this approach. Minimal retraction of the brain is needed. Total removal of the tumor has been achieved in a high percentage of cases.
Secondly, the retrosigmoid (suboccipital) approach affords the likelihood of hearing preservation in cases of tumor size up to about 2.5cm. The incision is behind the ear and an opening is made behind the mastoid part of the ear. There is retraction of the cerebellar portion of the brain. The risk of facial nerve damage is limited. The incidence of persistent postoperative headache has been reported as high, especially for small tumors (<1.0cm), although recent modifications in microsurgical procedures (e.g., greater attention to bone dust removal, cranioplasty rather than craniectomy) have helped avoid this complication.
Thirdly, for small tumors of 2.0cm or less, the middle fossa approach may be used where hearing preservation is a major consideration. The incision is made above the ear with care taken to shave only a small area of the scalp. There is retraction of the temporal lobe of the brain, which may put some stress on the temporal lobe’s memory circuitry. Possible damage to the facial nerve has been a major concern with this approach, although in recent years neural monitoring has improved functional outcomes. Total tumor removal rates have been high.
- See also “Surgery for Acoustic Neuromas: A Modern Day Paradigm,” Dr. Philip Theodosopoulos (University of Cincinnati College of Medicine) review of surgical approaches in ANA Notes, Issue 99 (September 2006).
Radiosurgery & Radiotherapy
Radiosurgery and Radiotherapy have become increasingly attractive treatment options for acoustic neuroma patients because they are non-invasive procedures with fewer possible complications. There is no surgery involved, no incision or risk of infection, no long period of anesthesia or lengthy hospital stay. Treatment is virtually painless and costs are less than for microsurgery. The return to normal activities is usually immediate. The radiation technology and computer guidance involved in the procedures is impressive and is being constantly improved. Patients do need to understand that the tumor is not removed by radiation treatments; rather, the goal of radiosurgery or radiotherapy is to kill the tumor by destroying the blood vessels supporting its growth. This basic objective of “tumor growth control,” meaning shrinkage or unchanged size of the tumor, has been achieved in 95-100% of cases. Patients may experience some initial radiation-induced swelling of the tumor. For this reason, patients with large tumors or with tumors located on or near the brain stem may not be candidates for radiation treatment. Microsurgery remains the appropriate first choice of treatment if tumor symptoms are acute or life-threatening. Surgical excision of the tumor may also be preferred by patients for personal reasons.
Radiosurgery is the delivery of a single, relatively high dose of radiation in a one-day session, whereas radiotherapy involves multiple treatment sessions in which the total dose is spread over several days or weeks. Dividing the dose over time in this manner is called fractionation. Thus we can speak of fractionated stereotactic radiotherapy, or FSR, where the term stereotactic refers to three-dimensional computerized target planning. Both stereotactic radiosurgery, or SRS, and fractionated stereotactic radiotherapy, FSR, use computerized planning for precise delivery of the radiation dose to the tumor while sparing surrounding normal tissue. Radiosurgery provides a more precise, concentrated effect, but may not be the appropriate treatment if the tumor is very large or in a critical location. Radiotherapy, by splitting the total dose into fractions, may help in hearing preservation, but whether or not radiation delivered in several small doses will provide tumor growth control equivalent to radiosurgery’s single high dose remains to be determined.
The two main instruments used for stereotactic radiosurgery (SRS) are the Gamma Knife and the Linac (linear accelerator). The Gamma Knife is a dedicated instrument developed in Sweden specifically for the radiation of brain abnormalities. It was first introduced in the US at the University of Pittsburgh in 1987. The newest model Gamma Knife is called “Perfection.” Linac machines (e.g., the Novalis, CyberKnife) are currently being used mainly for multiple-session stereotactic radiotherapy. The CyberKnife protocol for acoustic neuromas developed at Stanford University is unique in that radiation treatments are limited to three fractions; the treatment is called hypofractionated stereotactic radiosurgery, to distinguish it from the hyperfractionation of traditional radiotherapy. Proton Beam treatment is a third external beam radiation device sometimes used for acoustic neuroma, but has not been widely available because the technology is very expensive. A proton beam facility has only just recently been established (2012) in Somerset, NJ. The various radiation instruments have been described and compared at the website of the International RadioSurgery Association.
Sometimes it is said that radiation treatment for acoustic neuroma is inadvisable because the long-term effects of such radiation are not known, or because radiation may cause the tumor to become malignant, or because an irradiated tumor that regrows will be difficult to remove surgically. More than three decades of experience with radiosurgery have shown these concerns to be exaggerated. The chance of a malignant tumor being induced by stereotactic radiosurgery is extremely small, and microsurgical removal of previously irradiated tumors has not been shown to be more difficult in all cases.
- See also: “Different Techniques of Acoustic Neuroma Radiosurgery,” by Dr. Douglas Kondziolka, ANA Notes (December 2006); “Introducing New Ideas in Medicine: Stereotactic Radiosurgery,” ANA/NJ Newsletter (October,2011); “Hypofractionated Stereotactic Radiosurgery for Acoustic Neuroma: The CyberKnife,” by Dr. John Lipani, ANA/NJ Newsletter (June 2013); “Proton Beam Update,” ANA/NJ Newsletter (September 2009).
ANA/NJ believes that individual treatment is best decided by the informed patient in consultation with medical professionals who specialize in acoustic neuroma. In this regard, ANA/NJ recommends that new patients consider the following:
- Become familiar as soon as possible with all treatment options.
- Consult with physicians who are Board certified and have extensive training and experience treating acoustic neuroma.
- Get at least two or three opinions from different physicians about the best treatment for your particular acoustic neuroma.
- Consider treatment with physicians who present and willingly discuss all treatment options.
- Consider treatment with physicians who use a team approach when treating acoustic neuroma.
- Speak with other patients who have been treated for acoustic neuroma. Ask physicians for names of patients they have treated. (New Jerseyans may wish to consult ANA/NJ’s Directory of Members & Friends for names of patients willing to speak about their experiences.)
- When researching on the Internet:
- Be careful using websites that do not offer information about all treatment options
- Evaluate whether or not the website is trying to make a sincere effort to present up-to-date information about treatment outcomes based on the peer-reviewed literature
- Be careful using websites that appear to promote individual physicians or particular hospitals or foundations
- Avoid websites that obviously promote one type of treatment while disparaging others.