SYRINGOMYELIA ASSOCIATED WITH TYPE-I CHIARI MALFORMATION A 21-YEAR RETROSPECTIVE STUDY ON 75 CASES TREATED BY FORAMEN MAGNUM DECOMPRESSION WITH A SPECIAL EMPHASIS ON THE VALUE OF TONSILS RESECTION

purpose of the present study is to evaluate retrospectively the effect s of several intra-operative manipulations on the results of foremen m agnum decompression (FMD) in patients having syringomyelia associated with type I Chiari malformation. Seventy-five patients having syringom yelia associated with Chiari I malformation were operated on between 1 975 and 1996. This population was grouped into 4 subgroups according t o the surgical protocol: group I = 42 patients with FMD alone; group I I = 16 patients with FMD and third ventricle shunting; group III = 9 p atients with FMD and syringosubarachnoid shunting (SSS); group IV = 8 patients with FMD and cerebellar tonsils resection. Pre- and postsurgi cal magnetic resonance imaging (MRI) studies were analyzed land compar ed). Nine patients were lost to follow-up. The results were evaluated in the 66 remaining patients (mean follow-up: 52 months), using the Bi dzinski's outcome scale (ref). Two patients (3%) died postoperatively, 31 (47%) had very good results (after additional surgery in 7), 16 (2 4,2%) had good results (after additional surgery in 7) and 17 (25,7%) had poor results despite further surgery in 9. A total of 27 reoperati ons were undertaken after primary FMD in 23 patients (35%). Thirty-nin e patients (59%) had both pre- and postsurgical MRI evaluation. In 28 (72%) the syrinx had markedly decreased whereas it had remained stable in 11 (28%). Clinical results were not significantly different betwee n the patients of groups I, II and III. Very good or good results were obtained in 24 patients (64,8%) of group I (after additional surgery in 10), in 8 (61,5%) of group II (after additional surgery in 1) and i n 7 (87,5%) of group III (after additional surgery in 3). Results in g roup IV were as follows: 7 patients (87%) had very good results and on e had a good result. With a mean follow-up of 28 months, no patient re quired additional surgery. Postsurgical MRI syrinx reduction was obser ved in all 8 patients either in the early postoperative course or on d elayed followup. It is suggested that tonsils resection might enhance the results of FMD in individuals having Chiari I-related syringomyeli a.