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Overview

ANAUSA’s most recent “Patient Survey” (2014) reported that 87% of the 846 respondents said they were able to continue regular employment following treatment. This was very encouraging news for VS patients and the medical community. One needs only to compare this achievement to the almost unbelievable statistic from 100 years ago that the mortality rate from surgery for VS had declined to 80%. Outcomes today continue to improve, enabled greatly by the development of computed tomography (CT) and magnetic resonance imaging (MRI). In the Introduction to “Guidelines on the Treatment of Adults with VS” (2018), the Congress of Neurological Surgeons observed: “The evolution in treatment over the last century has ultimately led to an environment where functional outcome has taken precedence over disease eradication. With multiple noninvasive management options available, the tolerance of cranial neuropathy in patients with small to medium-sized tumors is low. Today, hearing preservation, facial nerve function, and tumor control remain the primary benchmarks used to evaluate treatment effectiveness and compare outcomes.”

     Hearing preservation, facial nerve function and tumor control are worthy benchmarks to select, and surely much less worrisome than ‘life preservation’ for patients to have to think about. Beyond such basic measures of clinical success, however, present-day patients and doctors are also giving attention to a wide range of ‘Quality of Life’ (QOL) concerns. The  “Patient Survey” (2014) tabulated the great variety of problems reported on by VS patients over the years 1983-2014, to include: single-sided deafness, tinnitus, balance, vertigo, dizziness, headache, fatigue, depression, eye problems, memory difficulties, concentration difficulties, smell, taste, swallowing. It’s intriguing that in 2018 the Mayo Clinic’s ongoing study (“Prospective Quality of life in Patients with Acoustic Neuroma”) found that “the main symptoms that drive a reduced QOL in VS patients are primarily ongoing dizziness, followed by headache, followed by tinnitus, with facial weakness and hearing loss actually coming in fourth and fifth place, respectively.” Type of treatment for VS did not predict which patients would have these bothersome symptoms. “For example, the only predictor for long-term dizziness was the presence of severe dizziness at the time of diagnosis – treatment did not really positively or negatively impact it.”    

Notice: For postoperative conditions, ANAUSA provides “Patient Info Booklets” for: Basic Overview (May 2018); Hearing Loss (Sept 2017); Balance (July 2017); Facial Nerve (Dec 2017); Headache (2018); and Eye Care (June 2018). ANAUSA also maintains an online “Patient Registry” to establish a database of information about the AN experience directly from patients. Periodic reports are published in ANA’s newsletter, NOTES

Hearing Preservation

Age and sex are not strong predictors of hearing preservation following treatment for VS. On the other hand, the quality of hearing at the time of diagnosis seems very important, and best outcomes are for small tumors. Hearing rarely improves after treatment. Gradual deterioration in hearing in the affected ear occurs over time regardless of the type of treatment employed, whether surgery, radiation or observation.

     For small to medium tumors, “hearing preservation surgery” is being offered via the Middle Fossa (MF) and Retrosigmoid (RS) approaches. Probability rates of 60-80% for ‘long-term’ preservation of useful hearing have been cited. But patients are cautioned that “long-term” means 10 years at most. Follow-up data is lacking for maintenance and quality of hearing beyond 10 years. Patients need to ask for definition of words such as ‘useful’ or ‘serviceable’ when used to predict post-treatment hearing quality. (See M. Sanna, “Hearing Preservation Surgery in VS: The Hidden truth,” Annales Otol Rhinol Laryngol, vol 113 (Feb 2004).

     CNS Guidelines (2018) reported that patients with small to medium VSs (<2.0 cm) and serviceable hearing at diagnosis, when treated by MF or RS surgery, can anticipate a probability of 25 to 50% preservation of serviceable hearing at 10 years. The same probability at 10 years was assigned for VS treated with single-fraction radiosurgery, provided the radiation dosage to the tumor margin is 13 Gy or less and the cochlear dose  is no more that 4 Gy. Whether or not hyperfractionation protocols do better has yet to be determined.

     For Observation (Wait-and-Watch) management of small to medium VS with serviceable hearing, the CNS Guidelines give the hearing preservation probabilities of 75-100% (2 years), 50-75% (5 years) and 25-50% (10 years).

Facial Nerve Preservation

The need for postoperative rehab therapy for facial movement problems was reported by 12.9% of surgery patients who participated in ANA’s 2014 “Patient Survey.” The figure was 6.0% for radiosurgery patients (SRS) and 3.3% for radiotherapy (FSR). Currently in practice but under review (“Acoustic Neuroma Subtotal Resection Study”) is a procedure called ‘facial nerve-sparing surgery’ whereby a large acoustic neuroma is partially removed and the ‘residual’ is treated subsequently (as needed) by stereotactic radiosurgery or fractionated  radiotherapy. The basic goal of this less aggressive surgery approach is to maximize both facial nerve function and quality of life (QOL). Preliminary reports on the procedure are promising. CNS Guidelines (2018) recommended the need for more evidence to show that subtotal resection provides comparable facial nerve preservation to patients who undergo complete surgical resection. There have been concerns that less experienced surgeons may oversell the benefits of partial resection surgery, and that the radiation treatment may impair hearing preservation. A recent evaluation is M. Harris & N. Zwagerman, “Near-Total Resection of Large VS for Facial Nerve Preservation,” ANA Notes (March 2019).                

Balance

The need for postoperative balance therapy was reported by 27% of patients responding to ANA’s 2014 “Patient Survey.” Essentially everyone diagnosed with a vestibular schwannoma (VS) can expect to experience difficulty with balance to some degree. After all, the tumor is growing on the balance part of the vestibulocochlear (8th cranial) nerve. If the tumor is removed by microsurgery, the damaged balance nerve fibers are cut away. They have been compromised by the tumor and are for the most part either non-functioning or close to it. Patients with disabling vertigo have reported significant improvement in quality of life following surgery for their VS. Of course, cutting the nerve results in an abrupt loss of balance input to the brain on the affected side, but the plasticity of our amazing brain will compensate on the good side for the loss. With radiation treatment there is no “cutting” of the nerve and adjustment does not occur as quickly as with microsurgery. Change “occurs more slowly, often with some troublesome persistence of balance function on the treated side.” There is a potential for unsteadiness over a longer period of time. Some visual-vestibular balance therapy will help to speed the adjustment. A recent ANA ‘Medical Report’ is Jeffrey Sharon, “Dizziness and Vestibular Schwannoma,” ANA Notes (March 2020).

 

Brain

Tinnitus

A large number (66.2%) of respondents to ANA’s 2014 “Patient Survey” listed tinnitus as a main symptom. It’s a major issue for many ANers at the time of diagnosis as well as post-operatively. Treatment of the VS by either microsurgery or radiation cannot be expected to make the tinnitus go away. A basic House Ear Clinic survey of 500 patients in 1998, for example, showed that tinnitus after surgery may improve a bit (40%), or stay the same (50%), or get worse (10%). For radiation treatment there is similar unpredictability. Although there is no definitive cure for tinnitus, there are ways to manage it and make it less of a problem. The American Tinnitus Association recommends that patients with persistent tinnitus consult the American Academy of Otolaryngology’s Clinical Practice Guideline: Tinnitus (2014), available as a free full-text copy at www.entnet.org. This important Guideline evaluates and recommends “habituation” via sound therapy as one of the primary methods for helping to manage tinnitus, as in Tinnitus Retraining Therapy (TRT). For the more serious cases, adding Cognitive Behavioral Therapy is recommended. The Guideline does not recommend the use of medications such as antidepressants; dietary supplements such as Ginkgo Biloba or zinc; or transcranial magnetic stimulation. Evidence is found insufficient to either recommend or discourage using acupuncture for treating tinnitus. A recent evaluation recommending TRT is D.Pineault, Aud.D. (Canadian Hearing Society), “How Can Tinnitus Retraining Therapy Facilitate Habituation to a Problematic Tinnitus,” The Connection (Spring 2019), Acoustic Neuroma Association of Canada, online at www.anac.ca/newsletters.

Headaches

ANAUSA’s “Patient Info Booklet” entitled Headache Associated with Acoustic Neuroma Treatment  (January 2018) examines how preventive measures during surgery introduced in recent years have greatly ameliorated post-craniotomy headaches. Some headache immediately following surgery should be anticipated due to the craniotomy and head positioning involved, but typically responds well to medication. Maintaining hydration is important. Getting up and moving around is important. For relief from headaches that persist, possible causes to examine with professionals and to investigate in the literature are (1) over-medication with painkillers; (2) headache ‘triggers’ such as caffeine, red wine, nuts, stress, tiredness, diet pills; (3) occipital nerve damage or entrapment. Some corrective measures to consider are: (1) preventive medication; (2) muscle relaxants and neck muscle therapy; (3) cranioplasty; (4) alternative treatments such as massage, acupuncture, stress reduction. Keeping a headache diary to review with your physician is a good idea. Achieving chronic headache control can be difficult and is best done under the supervision of a neurologist experienced in headache management. For the most treatment-resistant cases, working with a multidisciplinary pain center may be advisable.

Fatigue

Basic fatigue is the condition of being tired briefly because of physical or mental exertion. Stress or depression can also cause this kind of fatigue. Chronic fatigue is a persistent tiredness and lack of energy that just won’t go away. The majority of patients who undergo surgical treatment for acoustic neuroma experience fatigue for only a brief period of time. That is, there is a noticeable decrease in energy immediately following the trauma of anesthesia and a long surgery, but usually within about 3-4 months the patient ‘bounces back’ and resumes normal activity. For any more prolonged period of fatigue, patients are advised to seek professional help. Acoustic neuroma patients need to keep in mind that as time moves on fatigue-causing conditions not related to AN may occur to complicate perceptions. For example, prolonged fatigue may be caused by diabetes, hypothyroidism, sleep apnea, iron deficiency anemia, various prescription drugs (“medication fog”), and even a special condition defined as chronic fatigue syndrome (CFS/Myalgic Encephalomylitis). What causes CFS remains maddeningly elusive, but common symptoms are profound fatigue lasting more than 6 months and cognitive trouble often described as “brain fog.” NIH’s Institute for Neurological Disorders and Stroke is currently researching the biology of CFS.

Depression & Memory

Depression can be set off by a traumatic situation or stressful time; undergoing testing and a long surgery under general anesthesia for a brain tumor is no picnic. There are other life-changing side effects of acoustic neuroma surgery, such as facial problems, hearing loss, tinnitus, imbalance, head pain, fatigue. All of which helps to explain why the post-surgery depression rate has been reported as higher for AN patients than for other surgeries. Depression disorders can be helped by participation in a support group, individual counseling and appropriate anti-depressant medications. Guidance by a doctor specializing in depression disorders is advisable.

Problems especially with short-term/working memory can result after a major surgery. “The true art of memory is the art of attention,” and clearly, the acoustic neuroma experience coes loaded with potential ‘attention-busters.’ There can be problems, at least temporarily, with listening, concentration, remembering, learning new things. A possible anatomic cause of memory difficulty is retraction of the temporal lobe of the brain during surgery, which can put stress on the temporal lobe’s memory circuitry. Then too, it has been theorized that a memory-important area of the brainstem, the locus ceruleus, may be disturbed by the size and/or treatment of an acoustic neuroma.

  • See also “Cognitive Changes and Depression with Acoustic Neuroma,” by Dr.Elisabeth Kunkel (Thomas Jefferson University), ANA Notes, Issue 107 (September 2008).
  • See also “Acoustic Neuroma & Memory Problems,” ANA/NJ Newsletter (September 2007 - click here and April 2008 - click here).

Cerebrospinal Fluid (CSF) Leakage

ANAUSA’s 2008 “Patient Survey” reported an overall incidence rate of 18% for cerebrospinal (CSF) leak after acoustic neuroma surgery (211 of 1,188 patients). However, because of advances in surgery and closure repair techniques, reports in the medical literature were already showing lower rates for postoperative leaks. In 2004, New York University, for example, reported a drop in the overall rate from 17% for surgeries performed during 1979-1995 to 6.6% for surgeries during 1995-2000. In 2010, the VU University in Amsterdam reported a less than 1% CSF leakage for Translabyrinthine surgery cases (1993-2009). Jumping ahead to 2019, the University of Cincinnati has reported a leak rate of only 3% for patients during 2007-2017 having the Middle Fossa surgical approach. The trend has continued downwards for the three main surgical approaches. The majority of CSF leaks occur in the first days after surgery. They almost always require treatment with a lumbar drain (a catheter placed through a spinal tap needle for 3-5 days). They don’t tend to resolve spontaneously. It’s uncommon for leaks to develop after the patient leaves the hospital. One caution for post-hospital patients is that drainage of mucus from the nose because of a common head cold or sinus viral infection can be mistaken for CSF leakage. Patients who feel they may be having CSF leak (CSF rhinorrhea) should consult with their treating physician. 

(See A.Fishman et al, “Prevention and Management of CSF Leak Following VS Surgery,” Laryngoscope, vol 114(3) (March 2004); P.Merkus et al, “Less Than 1% CSF Leakage in 1,803 Translabyrinthine VS Surgery Cases,” Otology Neurotol, vol 31(2) Feb 2010); N. Lipschitz et al, “CSF Leak Rate after VS Surgery via Middle Fossa Approach,” Jour Neurol Surgery B Skull Base, vol 80(4) (Aug 2019).

 

The three basic options for treating an acoustic neuroma (VS) are Wait-and-Watch, Microsurgery, and Radiosurgery/Radiotherapy. The Acoustic Neuroma Association’s 2014 ‘Patient Survey’ showed  percentages for these treatment choices for the 846 patients who participated: Wait-and-Watch (20%), Microsurgery (51%), Single-session Radiosurgery (17%), Multiple-session Radiotherapy (12%).  When compared to ANA’s 1998 patient survey, these data revealed a significant increase for Radio-surgery/Radiotherapy (29% vs. 5%) and Wait-and-Watch (20% vs. 4%). There was a  decrease in microsurgery: the patient survey in 1998 showed 85% for Microsurgery, compared to only 51% for 2014. ANA’s first survey in 1983 showed 100% for Microsurgery.

     A Mayo Clinic report in 2015 observed that “one of the most significant recent advances in VS management has been the understanding that many cases of VS do not require treatment.” The report predicted that “by 2026, half of all cases of VS will be managed initially with observation” (Wait-and-Watch). The report recalled an optimistic prediction made in 1998 that more than two-thirds of newly diagnosed VS would eventually be treated with primary radiosurgery. But this prediction has not been realized. “While there has been a stable, slow decline in the use of microsurgery in favor of less invasive treatment, in recent years this volume has been increasingly allocated to observation rather than radiation therapy.” For the use of radiation for VS in the United States, “the current study demonstrates an apparent plateau.”

 (See B.E.Pollack, L.D.Lunsford & G.Noren, “Vestibular Schwannoma Management in the Next Century: a Radiosurgical Perspective,” Neurosurgery, vol 43 (1998); J.Patel et al, “The Changing Face of Acoustic Neuroma Management in the USA: Analysis of the 1998 and 2008 Patient Surveys from the Acoustic Neuroma Association,” British Journal of Neurosurgery, vol 28 (Jan 2014) Free full text copy at PubMed.gov; M. Carlson, M. Link et al (Mayo Clinic), “The Changing Landscape of Vestibular Schwannoma Management in the United States – A Shift Toward Conservatism,” Otolaryngology-Head and Neck Surgery, vol 153(3) (2015).

Advisory

ANA/NJ believes that individual treatment is best decided by the informed patient in consultation with medical professionals who specialize in acoustic neuroma. New patients should 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.
  • 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 especially may wish to consult ANA/NJ’s Directory (2020) for the names of patients willing to speak about their experiences with acoustic neuroma.

  • When researching on the internet:
  • 1) Be careful using websites that do not offer information about all treatment options.
  • 2) Avoid websites that obviously promote one type of treatment while disparaging others.
  • 3) 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.
  • 4) Be careful using websites that appear to promote individual physicians or particular hospitals or foundations.

 Wait-and-Watch (Observation)

If an acoustic neuroma (VS) is small (< 1.5 cm) and symptoms for the patient are tolerable, a first option is to Wait-and-Watch by carefully monitoring the growth characteristics of the tumor with periodic MRIs.

      Mutations causing sporadic VSs are known to vary from mild to severe, resulting in considerable variability in tumor growth behavior. Many small tumors do not grow at all. Some may grow at first and then shrink. Spontaneous shrinkage was observed in 3.8% of sporadic VSs during one reported period of Wait-and-Watch management. Although active treatment is generally recommended for tumors larger than 1.5 cm, it has been suggested that observation might be applied for VS patients with tumors up to 2 cm. (X.Huang, S.Stangerup et al, “Spontaneous Tumor Shrinkage in 1261 Observed Patients with Sporadic VS,” Jour Laryngol Otol, vol 127 (2013).

      Wait-and-Watch (also called Wait-and-Scan) does not mean you are going to simply wait to see if the tumor will go away. Rather, it involves a personal commitment to “active surveillance” requiring interval MRI scans. Having an MRI about 6 months after diagnosis will help to determine whether a tumor is likely to continue to grow or is suitable for observation. In general, VSs grow very slowly with the average annual growth rate varying from 0.4 to 2.9 mm.

      For the majority of small intrameatal (in the canal) tumors, the recommendation has been observation with yearly MRIs for five years, followed by decreasing frequency of observation if no growth has occurred. Any perceived growth needs to be watched closely to determine if or when active intervention should be considered. Danish studies have shown that hearing may decline during observation even though periodic MRIs indicate little or no tumor growth. Much depends on the quality of hearing at the time of tumor diagnosis.

     ANA’s patient survey in 2014, reported that 63% of patients who chose to Wait-and-Watch said that they did so because their tumors were less than 1.5 cm. Besides small tumor size, acoustic neuroma patients may opt for “conservative management” because of advanced age, poor general health, minimal symptoms, or because the tumor is in the only or better hearing ear. The current “Treatment Options” section for ANA’s website calls attention to another important consideration: “All medical treatments, surgical or radiation, carry some risks. In time, safer treatments for acoustic neuroma, other than surgery or radiation, may be found.” A recent review of the medical literature by Drs. Zou (Changhai Hospital, China) and Hirvonen (Helsinki University, Finland) concluded that   “the wait- and-scan management of VS is a safe method with the least problems and provides a better QOL for the patient than active treatments.”         

(See Jing Zou & Timo Hirvonen, “Wait and Scan Management of Patients with Vestibular Schwannoma and the Relevance of Non-contrast MRI in the Follow-up,” Journal of Otology, vol 12(4) (December 2017). Free full text copy at PubMed.gov. See also the letter by Dr. John Rutka (Univ of Toronto) to his patient Judy Haust (President of the ANAC Board of Directors) regarding his advice to ‘Wait and Scan’ for her small IAC tumor: “To Judy: A Letter with a Purpose. Further Insights in the Conservative Management of a Vestibular Schwannoma,” The Connection (Summer, 2019), online at www.anac.ca/newsletters.)

Microsurgery

Surgical removal of an acoustic neuroma under general anesthesia is another option, especially appropriate for large or enlarging tumors causing serious problems in critical locations. Advances in microsurgical techniques and technologies, and the development of the medical surgical team approach, have greatly reduced the incidence of complications resulting from invasive intervention. Facial nerve preservation is being assisted by partial removals of large tumors followed by radiosurgery treatment of residual tumor. Long-term preservation of hearing remains an elusive goal. 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 translabrinthine approach is used for large tumors where preservation of hearing is not an issue. The incision is made in the hairline behind the affected ear and the tumor is exposed by removal of the mastoid bone. This results in total hearing loss in the affected ear. Facial nerve preservation, on the other hand, is facilitated by the approach. Minimal retraction of the brain is needed, which is good. Total removal of the tumor has been achieved in a high percentage of cases.
     
       Secondly, for small tumors, the retrosigmoid (subocciptal) approach may help with preservation of hearing. The incision is behind the ear and an opening is made behind the mastoid part. There is retraction of the cerebeller 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 (<1.0 cm), although recent modifications in microsurgical procedures have helped (e.g., greater attention to bone dust removal, craniopl asty rather than craniectomy). 
   
   Thirdly, for small tumors of 2.0 cm or less, the middle fossa approach may be used where hearing preservation is a major consideration. It is the least used of the three approaches. The incision is made above the ear with care to shave only a small area of the scalp. There is retraction of the temporal lobe of the brain, which may put 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. Long-term (ca. 10 years ) hearing preservation rates of 60-80% have been reported. Total tumor removal rates have been high.
 
(See Philip V.Theodosopoulos, “Surgery for Acoustic Neuromas: A Modern Day Paradigm,” ANA Notes, Issue 99 (Sept 2006); A.Monfared, “Treatment of Large Acoustic Neuromas and the ANSRS (Acoustic Neuroma Subtotal Resection Study),” ANA Notes (June 2016); S.Rahimpour et al (Duke Univ), “Microsurgical Resection of VS: Complication Avoidance,” Journal of Neurooncology, vol 130(2) (November 2016); R.Friedman & M.Schwartz (UC San Diego),“Post-Surgical Care Considerations for Acoustic Neuroma Patients,” ANA Webinar (August 5, 2019). 

Radiosurgery & Radiotherapy

 Radiosurgery and Radiotherapy are attractive treatment options for acoustic neuroma because they are non-invasive procedures that can usually be performed on an outpatient basis. Treatment is virtually painless and out-of-pocket costs for the uninsured are less than for microsurgery. The return to normal activities is usually immediate. The radiation technology and computer guidance involved today is very impressive and is being constantly improved. Patients do need to understand that tumors are not removed by radiation treatment; rather, the goal is to stop tumor growth, and possibly even reduce tumor size, by damaging cell DNA and destroying blood vessels in support of tumor cell growth. The main objective of “tumor growth control” has been achieved in 95-100% of cases.  Pretreatment counseling should include the information that tumors often swell following radiation treatment, but this increase in size does not signal a failed procedure. However, since transient radiation-induced swelling of the tumor may occur, patients with large tumors (>3.0 cm) located near the brain stem may not be good candidates for radiation treatment. Microsurgery would be 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 a few days or 3-4 weeks. Dividing the radiation dosage over time in this manner is called ‘fractionation.’ Thus we can speak of ‘fractionated stereotactic radiotherapy,’ or FSR, where the term stereotactic refers to the use of three-dimensional computerized target planning. Both FSR and stereotactic radiosurgery, SRS, 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 appropriate treatment if the tumor is very large or in a critical location. Radiotherapy, by splitting the total dose into fractions over time, may help with hearing preservation, although this advantage still remains to be determined.        

      The two main instruments used for Radiosurgery (SRS) are the Gamma Knife (gamma ray) and the Linac (X-ray). The Gamma Knife is a dedicated machine that was developed in Sweden specifically for brain abnormalities. It was first introduced in the U.S. at the University of Pitttsburgh in 1987. The newest, 6th generation model, called “Icon,” is also capable of providing fractionated radiation treatment, if desired, and without the use of a skull-affixed stereotactic frame.                             

        Gamma Knife

There are various versions of the Linac machine for providing both single-session Radiosurgery or multiple-session Radiotherapy. The CyberKnife protocol for acoustic neuromas developed at Stanford University has been unique for limiting radiation treatment to three fractions, called hypofractionation to distinguish it from the hyperfractionation of conventional radiotherapy. The recently developed “Edge radiosurgery system” by Varian, for example, uses a Linac for delivering high doses in a small number of fractions. Radiosurgery is beginning to be defined as any radiation treatment involving 1-3 fractions.       

     Proton Beam is a third external beam radiation device that is used for acoustic neuroma but has not been widely available because the technology is very expensive. Proton Beam treatment has typically been by hyperfractionation (e.g., 25-30 sessions over 5 weeks), although this protocol is currently under review.

(See “Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines on the Treatment of Adults with Vestibular Schwannomas,” Neurosurgery (February 2018), Online at www.cns.org/guidelines; D.Larson, “Acoustic Neuroma Today: From Traditional Radiotherapy to Stereo- tactic Radiosurgery,” ANA/NJ Newsletter, vol 16(2) (April 2018); J.D.Lipani, “Acoustic Neuroma Today: Hypofractionated Stereotactic Radiosurgery for Acoustic Neuroma: The CyberKnife,” ANA/NJ News-letter, vol 13(4) (June 2013); D. Smith et al, “Treatment Outcomes and Dose Rate Effects Following Gamma Knife Stereotactic Radiosurgery for VS,” Neurosurgery, vol 85(6) (Dec 2019), free full text at PubMed.gov; O.Persson,J.Bartek et al, “Stereotactic Radiosurgery vs. Fractionated Radiotherapy for Tumor Control in VS Patients: A Systematic Review,” Acta Neurochirurgica, vol 159(6) (April 2017), free full text at PubMed.gov).