JOHNS HOPKINS
Acoustic Neuroma
Radiosurgery

1. Surgery

   • Surgery for Acoustic Neuromas: Facial Nerve (Facial Strength) Preservation
   • Surgery: Hearing Preservation
   • Surgery: Control of Growth

2. Single Shot Radiosurgery (Gamma Knife)

• Single Fraction Radiosurgery: Facial Nerve (Facial Strength) Preservation
• Single Fraction Radiosurgery: Hearing Preservation
• Single Fraction Radiosurgery: Control of Growth

3. Fractionated Stereotactic Radiosurgery (FSR)

   • Fractionated Radiosurgery: Facial Nerve Preservation
   • Fractionated Radiosurgery: Hearing Preservation
   • Fractionated Stereotactic Radiotherapy: Control

Options: The options for the treatment of the acoustic neuromas include surgery and radiosurgery.

Thousands of patients have received radiosurgery for acoustic neuromas. Radiosurgery is a non-invasive treatment that uses precisely focussed, narrow beams of radiation to both treat the acoustic neuroma and to spare the surrounding normal tissues.

Knowledge: Controversy exists regarding the optimal form of treatment for the acoustic neuromas. The patient and the family should strive to become very knowledgable regarding the options for treatment.

Fractionation: The foundation of Johns Hopkins Radiosurgery for acoustic neuromas is fractionation. Fractionation means giving multiple smaller treatments, one per day, rather than a single large treatment. When compared to single session radiosurgery, fractionation should result in both lower toxicity while maintaining control of the tumor (please see below). The Johns Hopkins Radiosurgery Program employs the fractionated stereotactic radiosurgery (FSR) for the treatment of all patients having acoustic neuromas who elect to receive FSR for treatment.

For surgery, radiosurgery, and fractionated stereotactic radiosurgery (FSR) the important issues in the treatment of the acoustic neuromas are preservation of the facial nerve, preservation of hearing and control of the tumor.

1. Surgery
   
   
   • Surgery for Acoustic Neuromas: Facial Nerve (Facial Strength) Preservation
     
     Most modern surgical series report complete tumor removal with both anatomic and functional preservation of the facial nerve in approximately 90% of patients having surgery for the acoustic neuromas (Buchman CA, Chen DA, Flannagan P, Wilberger JE, Maroon JC. The learning curve for acoustic tumor surgery. Laryngoscope 1996;106:1406-1411.)(Sampath P, Holliday MJ, Brem H, Niparko JK, Long DM. Facial nerve injury in acoustic neuroma (vestibular schwannoma) surgery: etiology and prevention. J Neurosurg 1997;87:60-66.)
     
     

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     • Sampath et. al. (Sampath P, Holliday MJ, Brem H, Niparko JK, Long DM. Facial nerve injury in acoustic neuroma (vestibular schwannoma) surgery: etiology and prevention. J Neurosurg 1997;87:60-66.) report a retrospective analysis of 611 patients surgically treated for acoustic neuroma between 1973 and 1994. Anatomical preservation of the facial nerve was achieved in 596 patients (97.5%). In the immediate postoperative period, 62.1% of patients displayed normal or near-normal facial nerve function (House-Brackmann Grade 1 or 2) after surgery for acoustic neuromas. This number rose to 85.3% of patients at 6 months after surgery and by 1 year, 89.7% of patients who had undergone acoustic neuroma surgery demonstrated normal or near-normal facial nerve function. The surgical approach to the acoustic neuroma appeared to have no effect on the incidence of facial nerve injury.
     
     
     
     • Gormley et. al. (Gormley WB, Sekhar LN, Wright DC, Kamerer D, Schessel D. Acoustic neuromas: results of current surgical management. Neurosurgery 1997;41:50-58; discussion 58-60.) reported the preservation of postoperative facial nerve function and showed preserved function (House Brackman grade I or II [11]) in 96% of small tumors (less than 2 cm diameter), 74% of medium tumors (2.0 - 3.9 cm), and 38% of large tumors (4.0 cm and greater). Further, a "fair" postoperative function (Grade III or IV) was achieved in 4% of small tumors, 26% of medium tumors, and 58% of large tumors. Other studies have corroborated this inverse relationship between size of the tumor and preservation of the facial nerve function (Lalwani AK, Butt FY, Jackler RK, Pitts LH, Yingling CD. Facial nerve outcome after acoustic neuroma surgery: a study from the era of cranial nerve monitoring. Otolaryngol Head Neck Surg 1994;111:561-570.).
       
       
     • With continuous intraoperative monitoring of the facial nerve, however, Sterkers et. al. (Sterkers JM, Morrison GA, Sterkers O, El-Dine MM. Preservation of facial, cochlear, and other nerve functions in acoustic neuroma treatment. Otolaryngol Head Neck Surg 1994;110:146-155.) reported that the percentage of preserved facial function (grade I or II) improved from 20% to 52% for large tumors (larger than 3 cm), from 42% to 81% for medium tumors (2 to 3 cm in diameter) and from 70% to 92% for small tumors (up to and including 2 cm in diameter).

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   • Surgery: Hearing Preservation
     
     
     • The preservation of hearing following surgery has presented a greater challenge and ranges from 30 to 50 percent following the retrosigmoid approach (Gormley WB, Sekhar LN, Wright DC, Kamerer D, Schessel D. Acoustic neuromas: results of current surgical management. Neurosurgery 1997;41:50-58; discussion 58-60.). In this series, functional hearing preservation defined as Gardner-Robertson Class I or II was achieved in 48% of small tumors and only 25% of medium tumors. Hearing was not preserved in that series in any of the patients with large tumors in whom hearing preservation was attempted.
       
       
     • Sterkers et. al. report that hearing was preserved in 38.2% of cases operated on by means of the retrosigmoid route and 36.4% of cases after the middle fossa approach (Sterkers JM, Morrison GA, Sterkers O, El-Dine MM. Preservation of facial, cochlear, and other nerve functions in acoustic neuroma treatment. Otolaryngol Head Neck Surg 1994;110:146-155.).
       
       
     • Cerullo et. al. (Cerullo LJ, Grutsch JF, Heiferman K, Osterdock R. The preservation of hearing and facial nerve function in a consecutive series of unilateral vestibular nerve schwannoma surgical patients (acoustic neuroma). Surg Neurol 1993;39:485-493.) showed that for the 64 patients with functional preoperative hearing, 13 patients retained hearing postoperatively: five had normal hearing (PTA < 25 dB, SD > 70%), five had near normal hearing (PTA < 45 dB, SD > 70%), four patients had preserved hearing (PTA < 50 dB, SD > 50%), and three patients had preserved cochlear nerve function (PTA > 50 dB, SD < 50%) after surgery.
       
       

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   • Surgery: Control of Growth
     
     
     • The rates of control following surgery are high and range from 94 to 100 percent (Buchman CA, Chen DA, Flannagan P, Wilberger JE, Maroon JC. The learning curve for acoustic tumor surgery. Laryngoscope 1996;106:1406-1411.) (Sampath P, Holliday MJ, Brem H, Niparko JK, Long DM. Facial nerve injury in acoustic neuroma (vestibular schwannoma) surgery: etiology and prevention [see comments]. J Neurosurg 1997;87:60-66.)

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2. Single Fraction Radiosurgery



• Single Fraction Radiosurgery: Facial Nerve (Facial Strength) Preservation
  
  The rates of facial neuropathy after single fraction radiosurgery have been published as well. The results suggest that single "shot" radiosurgery may result in low preservation of normal cranial nerve function. The science of "radiobiology" predicts low preservation of normal tissues when single large radiation treatments are given. This treatment is very different when compared to the fractionated stereotactic radiosurgery (FSR) (please see below). The FSR offers multiple smaller treatments (fractions) rather than one large treatment, and may preserve normal cranial nerve function better than single "shot" radiosurgery.
  
  

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  • Flickinger et. al. (Flickinger JC, Lunsford LD, Linskey ME, Duma CM, Kondziolka D. Gamma knife radiosurgery for acoustic tumors: multivariate analysis of four year results. Radiother Oncol 1993;27:91-98.) studied results of gamma knife radiosurgery (single "shot") in 136 acoustic tumors having a median follow-up was 24 months. The minimum tumor doses varied from 12 to 20 Gy (median = 17 Gy) (The "Gy" is an abbreviation for "Gray" and is equal to 100 "rad", the unit of radiation dosage. The incidences of postradiosurgery facial (facial strength) and trigeminal (facial sensation) neuropathies (loss of nerve function) were 29.0 +/- 4.4% and 32.9 +/- 4.5%, respectively.
    
    
  • Mendenhall et. al. (Mendenhall WM, Friedman WA, Buatti JM, Bova FJ. Preliminary results of linear accelerator radiosurgery for acoustic schwannomas. J Neurosurg 1996;85:1013-1019.) studied fifty-six patients who had single "shot" stereotactic radiosurgery via the linear accelerator for acoustic neuromas. Most patients received 12.5 to 15 Gy. Facial neuropathy developed in 6 patients (about 10 percent). The likelihood of complications was proportionate to the radiation dose and treatment volume in that study.
    
    
  • To determine whether cranial nerve complications after single session radiosurgery could be reduced by lowering the dose, Miller et. al. (Miller RC, Foote RL, Coffey RJ, Sargent DJ, Gorman DA, Schomberg PJ, Kline RW. Decrease in cranial nerve complications after radiosurgery for acoustic neuromas: a prospective study of dose and volume. Int J Radiat Oncol Biol Phys 1999;43:305-311.) studied forty-two consecutive patients who were prospectively treated using progressively decreasing radiation doses of 20, 18, or 16 Gy. With a median follow-up of 2.3 years for 80 of 82 patients, the cumulative incidence of facial neuropathy was 31% after one year and 38% after two years for the high dose regimen. The incidence of facial neuropathy reached 8% after one year and was unchanged (8%) after two years for the reduced dose protocol. The cumulative incidence of trigeminal neuropathy was 24% after one year and was 29% after two years for the high dose regimen. The incidence of trigeminal neuropathy reached 15% after one year was was unchanged after two years for the reduced dose protocol. These results show that lowering the dose for the single "shot" technique may be safer, but longer follow up after these lower doses is needed to be sure that the acoustic neuroma will not grow back after these lower treatments.
    
    
  • In a very large study Kondziolka et. al. (Kondziolka D, Lunsford LD, McLaughlin MR, Flickinger JC. Long-term outcomes after radiosurgery for acoustic neuromas. N Engl J Med 1998;339:1426-1433.) noted normal facial function was preserved (House-Brackmann grade 1) in 79 percent of the 162 consecutive patients five years after gamma knife radiosurgery. This means that about 21 percent of patients had new facial weakness.

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• Single Fraction Radiosurgery: Hearing Preservation
  
  
  • The rates of hearing preservation after single fraction radiosurgery have been described. Niranjan et. al. (Niranjan A, Lunsford LD, Flickinger JC, Maitz A, Kondziolka D. Dose reduction improves hearing preservation rates after intracanalicular acoustic tumor radiosurgery. Neurosurgery 1999;45:753-762; discussion 762-755.) described 29 patients with intracanalicular acoustic tumors who had stereotactic radiosurgery using the gamma knife. Fifteen assessable patients had serviceable pre-radiosurgery hearing (pure tone average > 50 dB) (the "dB" is the "decibel" or the unit of loudness for the hearing tests). The authors retrospectively analyzed the hearing results and compared hearing preservation in patients who received a minimal tumor dose of 14 Gy or less versus those who received more than 14 Gy to the tumor margin. Long-term follow-up showed serviceable hearing preservation in 10 (100%) of 10 patients who received marginal tumor doses of 14 Gy or less but in only one of five patients who received more than 14 Gy.
    
    
  • Ogunrinde et. al. (Ogunrinde OK, Lunsford LD, Flickinger JC, Kondziolka D. Stereotactic radiosurgery for acoustic nerve tumors in patients with useful preoperative hearing: results at 2-year follow-up examination. J Neurosurg 1994;80:1011-1017.) studied 20 patients who received radiosurgery via the gamma knife. Useful hearing (defined as Gardner and Robertson Class I or II) preservation was obtained in 100% of cases immediately postoperatively, but only 50% at 6 months, and 45% at both 1 and 2 years.
    
    

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• Single Fraction Radiosurgery: Control of Growth
  
  
  • The rates of control of the acoustic neuromas after single "shot" radiosurgery have been published. Flickinger (Flickinger JC, Lunsford LD, Linskey ME, Duma CM, Kondziolka D. Gamma knife radiosurgery for acoustic tumors: multivariate analysis of four year results. Radiother Oncol 1993;27:91-98.) showed that the 4-year tumor control rate was 89.2 +/- 6.0%.
    
    
  • Mendenhall (Mendenhall WM, Friedman WA, Buatti JM, Bova FJ. Preliminary results of linear accelerator radiosurgery for acoustic schwannomas. J Neurosurg 1996;85:1013-1019.) showed that fifty-five patients (98%) achieved local control after single fraction radiosurgery.
    
    
  • Similarly, Kondziolka et. al. (Kondziolka D, Lunsford LD, McLaughlin MR, Flickinger JC. Long-term outcomes after radiosurgery for acoustic neuromas . N Engl J Med 1998;339:1426-1433.) showed that following an average single fraction dose of 16 Gy, the rate of control of tumors was 98%.

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3. Fractionated Stereotactic Radiosurgery (FSR)
   
   To reduce the morbidity of treatment for acoustic neuromas while maintaining efficacy, fractionated stereotactic radiosurgery (FSR) offers radiobiological sparing of normal tissues with escalation of the total dose when compared to single "shot" techniques.
   
   
   • Fractionated Radiosurgery: Facial Nerve Preservation
     
     The rates of preservation of the facial nerve function after fractionated radiosurgery have been described as well.
     
     
     • Williams et. al. (Song DY, Williams JA. Fractionated stereotactic radiosurgery for treatment of acoustic neuromas. Stereotact Funct Neurosurg 1999;73:45-49.) showed preservation of the facial nerve in all 30 patients receiving the FSR.
       
       
     • Andrews et. al. (Andrews DW, Silverman CL, Glass J, Downes B, Riley RJ, Corn BW, Werner-Wasik M, Curran WJ, Jr., McCune CE, Rosenwasser RH, et al. Preservation of cranial nerve function after treatment of acoustic neurinomas with fractionated stereotactic radiotherapy. Preliminary observations in 26 patients. Stereotact Funct Neurosurg 1995;64:165-182.) showed preservation of the facial nerve in all 26 patients receiving fractionated radiosurgery.
       
       
     • Lederman et. al. (Lederman G, Lowry J, Wertheim S, Fine M, Lombardi E, Wronski M, Arbit E. Acoustic neuroma: potential benefits of fractionated stereotactic radiosurgery. Stereotact Funct Neurosurg 1997;69:175-182.) showed that only one patient of 38 treated patients receiving 2000 cGy in 4 or 5 fractions had temporary seventh nerve palsy.

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   • Fractionated Radiosurgery: Hearing Preservation
     
     The rates of preservation of hearing after fractionated stereotactic radiotherapy have been described as well.
     
     
     • Williams et. al. (Song DY, Williams JA. Fractionated stereotactic radiosurgery for treatment of acoustic neuromas. Stereotact Funct Neurosurg 1999;73:45-49.) showed preservation of the hearing. Of the 12 patients with useful hearing (PTA < or = 50 dB) prior to treatment, 9 patients retained useful hearing following FSR.
       
       
     • For 26 patients having fractionated radiosurgery, Andrews et. al. (Andrews DW, Silverman CL, Glass J, Downes B, Riley RJ, Corn BW, Werner-Wasik M, Curran WJ, Jr., McCune CE, Rosenwasser RH, et al. Preservation of cranial nerve function after treatment of acoustic neurinomas with fractionated stereotactic radiotherapy. Preliminary observations in 26 patients. Stereotact Funct Neurosurg 1995;64:165-182.) showed preservation of hearing in 5 of 7 patients who had serviceable pre-treatment hearing.
       
       
     • Sakamoto et. al. [24] studied preservation of hearing in twenty-four patients with acoustic neuroma who received fractionated stereotactic radiotherapy. The irradiation schedule varied from 36 Gy given in 20 fractions in 5 weeks up to 44 Gy given in 22 fractions in 6 weeks, each followed by a single 4 Gy boost. The median follow-up time was 22 months. Fifty percent of patients showed a change in the pure tone average (PTA) of less than 10 dB, 79.2% of patients showed a change in PTA of less than 20 dB and 20.8% of patients showed a change in PTA of more than 21 dB at the last follow-up. Further, the pre-treatment size of the tumor was not related to the change in PTA in that study.
       
       
     • Following 21 Gy in 3 fractions given over 1 day for 32 acoustic neuromas, Adler et. al. (Poen JC, Golby AJ, Forster KM, Martin DP, Chinn DM, Hancock SL, Adler JR, Jr. Fractionated stereotactic radiosurgery and preservation of hearing in patients with vestibular schwannoma: a preliminary report. Neurosurgery 1999;45:1299-1305; discussion 1305-1297.) noted preservation of useful hearing (GR Class 1-2) in 77% of the treated patients.
       

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   • Fractionated Stereotactic Radiotherapy: Control
     
     The rates of control of the acoustic neuromas after fractionated stereotactic radiotherapy have been described.
     
     
     • Williams et. al. (Song DY, Williams JA. Fractionated stereotactic radiosurgery for treatment of acoustic neuromas. Stereotact Funct Neurosurg 1999;73:45-49.) showed no growth of the treated acoustic neuromas following the fractionated stereotactic radiosurgery (FSR). The current data show no failures to date, with maximal follow up of 8 years.
       
       
     • Lederman et. al. (Lederman G, Lowry J, Wertheim S, Fine M, Lombardi E, Wronski M, Arbit E. Acoustic neuroma: potential benefits of fractionated stereotactic radiosurgery. Stereotact Funct Neurosurg 1997;69:175-182.) described 38 who received 2,000 cGy in divided weekly doses of 400 or 500 cGy. With follow-up of 27.1 months, all tumors were controlled. Of 23 tumors smaller than 3 cm, 14 (61%) decreased in size, and 9 showed cessation of growth. Thirteen of 16 (81%) large acoustic neuromas (3-5 cm) diminished in size. The remaining 3 showed cessation of growth. Unfortunately, recently there have been documented recurrences requiring surgery of the treated acoustic neuromas after these decreased doses.
       
       
     • Similarly Varlotto et. al. (Varlotto JM, Shrieve DC, Alexander E, 3rd, Kooy HM, Black PM, Loeffler JS. Fractionated stereotactic radiotherapy for the treatment of acoustic neuromas: preliminary results. Int J Radiat Oncol Biol Phys 1996;36:141-145.) studied twelve patients with acoustic neuroma who were treated with fractionated radiosurgery using doses of 54 Gy in 30 fractions. After a median follow-up of 26.5 months, local control was obtained in 12 out of 12 tumors.
       
       
     • Adler et. al. (Poen JC, Golby AJ, Forster KM, Martin DP, Chinn DM, Hancock SL, Adler JR, Jr. Fractionated stereotactic radiosurgery and preservation of hearing in patients with vestibular schwannoma: a preliminary report. Neurosurgery 1999;45:1299-1305; discussion 1305-1297.) noted tumor regression or stabilization in 30 of 31 patients (97%) following 21 Gy given in 3 fractions over one day.
       
       

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