Efficacy analysis of Gamma knife for the treatment of different types of acoustic neuroma

Abstract

Objective To analyze the efficacy of Gamma knife for the treatment of different types of acoustic neuroma. Methods From April 1997 to June 2013, 123 patients with acoustic neuroma (<3 cm) treated with Gamma knife in Xiangya Hospital, Central South University were enrolled retrospectively. Hasegawa classification: type A 5 cases, type B 38 cases, type C 47 cases, and typed D 33 cases. Different types of tumor growth and complications after treatment were analyzed and the related factors of influencing the effective tumor control rate were investigated. Results The follow-up time of 123 patients ranged from 6 to 135 months (median, 41 months). The 5-year effective tumor control rate was 92.1%. The tumor control rate of type D was lower than A+ B+ C types (74.1% and 96.1% respectively; P<0.01). Multivariate Cox model analysis showed that the tumor type was an independent factor for affecting tumor control rate (RR, 12.172, 95% CI 2.584-57.348; P=0.002). In the 123 patients, the incidence of radiation-induced brain edema was 12.2% (n=15), and the type A, B, C, and D were 0%, 2.6% (n=1), 10.6% (n=5), and 27.3% (n=9), respectively. The incidences of type C and D were higher than those of type A and B (P=0.014). The incidence of hydrocephalus was 2.4% (n=3, all type D). Of the patients with complete assessment data, the incidence of facial palsy was 10.8% (n=8), and the type A, B, C, and D were 1/4 (n=1), 8.0% (2/25), 4.2% (1/24), and 19.0% (4/21), respectively. The incidence of rigeminal nerve dysfunction was 29.7% (n=22), and type A, B, C, and D were 0%, 4% (1/25), 37.5% (9/24), and 57.1% (12/21), respectively. The incidences of type C and D were higher than those of type A and B (P=0.001). Conclusions The effective control rate of Gamma knife for the treatment of <3 mm acoustic neuroma and the neurological retention rate were closely associated with the tumor typing. The prognoses of type A and B were better, and those of type C and D were poor. Key words: Neuroma, acoustic; Gamma knife; Tumors categories; Complications