Syringomyelia: long-term results after posterior fossa decompression.

A retrospective study of the surgical results in 31 adult patients with syringomyelia associated with Arnold-Chiari malformation was carried out. The standard surgical procedure consisted of a posterior fossa craniectomy. The vallecula was opened in 28 patients, with plugging of the central canal in 19. In three patients, severe arachnoidal scarring was present, and dissection was not attempted. The postoperative follow-up period ranged from 5 to 10 years. More than half of the patients considered themselves improved by surgery; however, only five cases showed objective improvement. Despite the operation, six patients experienced progressive neurological deterioration.