Facial nerve preservation after vestibular schwannoma Gamma Knife radiosurgery.

Yang I,  J Neurooncol. 2009 May;93(1):41-8. Epub 2009 May 9. Review.

 a total of 23 published studies reporting assessable and quantifiable outcome data regarding facial nerve function in 2,204 patients who were treated with Gamma Knife radiosurgery for vestibular schwannoma. An overall facial nerve preservation rate of 96.2% was found after Gamma Knife radiosurgery for vestibular schwannoma in our analysis. Patients receiving less than or equal to 13 Gy of radiation at the marginal dose had a better facial nerve preservation rate than those who received higher doses (<or=13 Gy = 98.5% vs. >13 Gy = 94.7%). Patients with a tumor volume less than or equal to 1.5 cm(3) also had a greater facial nerve preservation rate than patients with tumors greater than 1.5 cm(3) (<or=1.5 cm(3) 99.5% vs. >1.5 cm(3) 95.5%). Superior facial nerve preservation was also noted in patients younger than or equal to 60 years of age (96.8 vs. 89.4%).

Gamma knife radiosurgery for vestibular schwannomas: results of hearing preservation in relation to the cochlear radiation dose.

Timmer FC,  Laryngoscope. 2009 Jun;119(6):1076-81.

OBJECTIVES/HYPOTHESIS: This study was designed to evaluate hearing preservation after gamma knife radiosurgery (GKRS) and to determine the relation between hearing preservation and cochlear radiation dose in patients with a sporadic vestibular schwannoma (VS).  A total of 69 patients were included in the study. Mean tumor size was 17 mm. Mean marginal dose at the tumor was 11.0 Gy (range, 9.3 Gy-12.3 Gy), mean maximal dose was 19.7 Gy (range, 16 Gy-25.5 Gy). Mean maximal dose at the cochlea was 10.27 Gy (range, 3.1 Gy-16.1 Gy), and mean minimal dose at the cochlea was 2.6 Gy (range, 0.9 Gy-7.4 Gy). Hearing was considered to be preserved (max +1 class, Tokyo classification) in 52 (75%) of 69 patients. However, only 32 patients had class A, B, or C (serviceable hearing) before GKRS. Within this group, only 13 patients (41%) had a hearing class A, B, or C after GKRS. A significant relation was found between the maximal cochlear dose and the difference in PTA before and after GKRS. CONCLUSIONS: Hearing preservation is correlated to the maximal radiation dose at the cochlea. The purpose of developing GKRS techniques was to avoid collateral damage in healthy tissues. This study emphasizes the need for exact radiation planning to reduce the cochlear radiation dose if the hearing is to be preserved.

Stereotactic radiosurgery for trigeminal schwannoma: tumor control and functional preservation Clinical article.

Kano H, Niranjan A, Kondziolka D, Flickinger JC, Dade Lunsford L. J Neurosurg. 2009 Mar;110(3):553-8.

The median patient age was 49.5 years (range 15.1-82.5 years). Eleven patients had undergone prior tumor resection. Two patients had neurofibromatosis Type 2. Lesions were classified as root type (6 tumors), ganglion type (17 tumors), and dumbbell type (10 tumors) based on their location. The median radiosurgery target volume was 4.2 cm3 (range 0.5-18.0 cm3), and the median dose to the tumor margin was 15.0 Gy (range 12-20 Gy).RESULTS: At an average of 6 years (range 7.2-147.9 months), the rate of progression-free survival (PFS) at 1, 5, and 10 years after SRS was 97.0, 82.0, and 82.0%, respectively. Factors associated with improved PFS included female sex, smaller tumor volume, and a root or ganglion tumor type. Neurological symptoms or signs improved in 11 (33.3%) of 33 patients and were unchanged in 19 (57.6%). Three patients (9.1%) had symptomatic disease progression. Patients who had not undergone a prior tumor resection were significantly more likely to show improvement in neurological symptoms or signs.CONCLUSIONS: Stereotactic radiosurgery is an effective and minimally invasive management option in patients with residual or newly diagnosed trigeminal schwannomas. Predictors of a better treatment response included female sex, smaller tumor volume, root or ganglion tumor type, and the application of SRS as the primary treatment.

Hearing preservation after stereotactic radiosurgery for vestibular schwannoma: a systematic review.

Yang I,  J Clin Neurosci. 2009 Jun;16(6):742-7.

A total of 254 published studies reported assessable and quantifiable outcome data of patients undergoing radiosurgery for vestibular schwannomas. American Association of Otolaryngology-Head and Neck Surgery (AAO-HNS) class A or B and Gardner-Robertson (GR) classification I or II were defined as having preserved hearing. A total of 5825 patients (74 articles) met our inclusion criteria. Practitioners who delivered an average dose of 12.5 Gy as the marginal dose reported having a higher hearing preservation rate (12.5 Gy=59% vs. >12.5 Gy=53%, p=0.0285). Age of the patient was not a significant prognostic factor for hearing preservation rates (<65 years=58% vs. >65 years=62%; p=0.4317). The average overall follow-up was 41.2 months. Our data suggest that an overall hearing preservation rate of about 57% can be expected after radiosurgical treatment, and patients treated with 12.5 Gy were more likely to have preserved hearing.

Predictors of hearing preservation after stereotactic radiosurgery for acoustic neuroma.

Kano H, Kondziolka D, Khan A, Flickinger JC, Lunsford LD. J Neurosurg. 2009 Mar 13.

The authors of this study evaluated tumor control and hearing preservation as they relate to tumor volume, imaging characteristics, and nerve and cochlear radiation dose following stereotactic radiosurgery (SRS) using the Gamma Knife. Methods Seventy-seven patients with ANs had serviceable hearing (Gardner-Robertson [GR] Class I or II) and underwent SRS between 2004 and 2007. This interval reflected more recent measurements of inner ear dosimetry during the authors' 21-year experience. The median patient age was 52 years (range 22-82 years). No patient had undergone any prior treatment for the ANs. The median tumor volume was 0.75 cm(3) (range 0.07-7.7 cm(3)), and the median radiation dose to the tumor margin was 12.5 Gy (range 12-13 Gy). At diagnosis, a greater distance from the lateral tumor to the end of the internal auditory canal correlated with better hearing function. Results At a median of 20 months after SRS, no patient required any other additional treatment. Serviceable hearing was preserved in 71% of all patients and in 89% (46 patients) of those with GR Class I hearing. Significant prognostic factors for maintaining the same GR class included (all pre-SRS) GR Class I hearing, a speech discrimination score (SDS) >/=80%, a pure tone average (PTA) < 20 dB, and a patient age < 60 years. Significant prognostic factors for serviceable hearing preservation were (all pre-SRS) GR Class I hearing, an SDS >/=80%, a PTA < 20 dB, a patient age < 60 years, an intracanalicular tumor location, and a tumor volume < 0.75 cm(3). Patients who received a radiation dose of < 4.2 Gy to the central cochlea had significantly better hearing preservation of the same GR class. Twelve of 12 patients < 60 years of age who had received a cochlear dose < 4.2 Gy retained serviceable hearing at 2 years post-SRS. Conclusions As currently practiced, SRS with the Gamma Knife preserves serviceable hearing in the majority of patients. Tumor volume and anatomy relate to the hearing level before radiosurgery and influence technique. A low radiosurgical dose to the cochlea enhances hearing preservation.

Vestibular schwannoma: surgery or gamma knife radiosurgery? A prospective, nonrandomized study.

Myrseth E, Møller P, Pedersen PH, Lund-Johansen M. Neurosurgery. 2009 Apr;64(4):654-61;

OBJECTIVE: To conduct a prospective, open, nonrandomized study of treatment-associated morbidity in patients undergoing microsurgery or gamma knife radiosurgery (GKRS) for vestibular schwannomas. METHODS: Ninety-one patients with vestibular schwannomas with a maximum tumor diameter of 25 mm in the cerebellopontine angle were treated according to a prospective protocol either by GKRS (63 patients) or open microsurgery (28 patients) using the suboccipital approach. Primary end points included hearing function, according to the Gardner-Robertson scale, and facial nerve function, according to the House-Brackmann scale at 2 years. Clinical data included a balance platform test, score for tinnitus and vertigo using a visual analog scale, and working ability. Patients responded to the quality-of-life questionnaires Short-Form 36 and Glasgow Benefit Inventory. RESULTS: Three elderly GKRS patients withdrew; all remaining patients were followed for 2 years. Both primary end points were highly significant in favor of GKRS (P < 0.001). Evidence of reduced facial nerve function (House-Brackmann grade 2 or poorer) at 2 years was found in 13 of 28 open microsurgery patients and 1 of 60 GKRS patients. Thirteen of 28 patients who underwent surgery had serviceable hearing (Gardner-Robertson grade A or B) preoperatively, but none had serviceable hearing postoperatively. Twenty-five of 60 GKRS patients had serviceable hearing before treatment, and 17 (68%) of them had serviceable hearing 2 years after treatment. The tinnitus and vertigo visual analog scale score, as well as balance platform tests, did not change significantly after treatment, and working status did not differ between the groups at 2 years. Quality of life was significantly better in the GKRS group at 2 years, based on the Glasgow Benefit Inventory questionnaire. One GKRS patient required operative treatment within the 2-year study period. CONCLUSION: This is the second prospective study to demonstrate better facial nerve and hearing outcomes from GKRS than from open surgery for small- and medium-sized vestibular schwannomas.