Study Design. This study was designed to investigate prospectively a series of patients with syringomeylia-Chiari I complex operated on by a minimally invasive procedure. Objective. The objective was to determine whether a relatively simple and low-risk osteo-dural decompression would obtain as good clinico-radiological results as those observed after the commonly used, more complex posterior fossa surgery. Summary of Background Data. The majority of hypotheses concerning the pathogenesis of syringomyelia line it to the existence of some derangement of the cerebro-spinal fluid flow at the cranio-spinal level and, consequently, surgical procedures are directed toward decompressing the cranio-cervical junction; however, there is no clear-cut evidence that simple osteo-dural decompression should be associated with manipulation of nervous tissue for the purpose of restoring to normal an altered cerebro-spinal fluid flow dynamic. Methods. The procedure consisted of a small subocipital craniectomy and laminectomy of C1 (when necessary C2 as well), followed by dura mater opening. Exploration and plugging of the obex, resection of arachnoid adherences, or amputation of the amygdala(e) were never performed. Every effort was made to keep the arachnoid intact. The series included 20 patients with progressive disease treated according the above-mentioned criteria. Results. Mortality and morbidity were nil and MRI controls showed shrinkage of the syrinx in all cases. At long-term follow-up (average, 2.4 years), 8 patients were considered improved, 11 stabilized, and 1 patient continued to deteriorate despite the collapse of the cord cavity. Conclusion. Considering that the results of this ''conservative'' cranio-cervical decompression are at least comparable to those obtained with other surgical procedures, this procedure, which was not associated with mortality or morbidity, currently should be considered the first option in the treatment of syringomyelia-Chiari I complex.
