This chapter discusses the retrospective data found in 285 patients with syringomyelia associated with Chiari abnormality and collected from 18 neurosurgical departments. A pre and postoperative MRI study and a minimum follow up of at least 2 years were required. A scale of severity was fixed and tested before and after treatment. The size of the cyst, the degree of the foraminal obstruction were analyzed. The mean age at diagnosis was about 39 years and the duration of symptoms about 6.7 years. Sensory disorders were present in 91% of cases, pain in 66% and motor deficit in about 60%. According to our functional classification, the majority of our patients were moderately disabled and only 10.8% showed a severe impotence. Results of the two major surgical procedures, foramen magnum decompression (FMD) (88% of cases) and cyst shunting procedures (SP) (32% of cases) were evaluated with a mean follow-up period of 6.7 years (ranged from 2 to 14 years). Better clinical and morphological results (87% of stabilization or improvement for FMD versus 71% for SP) were obtained by FMD procedure comparing to SP, with the same rate of complications.
