Microsurgical fenestration of perineural cysts to the thecal sac at the level of the distal dural sleeve

Background Surgery for symptomatic sacral perineural cysts remains an issue of discussion. Assuming microcommunications between the cyst and thecal sac resulting in a valve mechanism and trapping of CSF as a pathomechanism, microsurgical fenestration from the cyst to the thecal sac was performed to achieve free CSF communication. Methods In 13 consecutive patients (10 female, 3 male), MRI revealed sacral perineural cysts and excluded other pathologies. Micro-communication between the thecal sac and the cysts was shown by delayed contrast filling of the cysts on postmyelographic CT. Surgical fenestration achieved free CSF communication between the thecal sac and cysts in all patients. The patient histories, follow-up examinations and self-assessment scales were analyzed. Symptoms at initial presentation included lumbosacral pain, pseudoradicular symptoms, genital pain and urinary dysfunction. Mean follow-up was 10.7±6.6 months. Findings Besides one CSF fistula, no surgical complications were observed. Five patients did not improve after surgery; in four of these cases multiple cysts were found, but small and promptly filling cysts remained untreated. Seven patients reported lasting benefit following surgery; three of these had single cysts, and all had cysts >1 cm. One patient initially benefited from cyst fenestration but experienced recurrent pain within 2 months postoperatively. Re-myelography revealed delayed contrast filling of the recurrent cyst; however, surgical revision did not lead to an improvement despite successful fenestration and collapse of the cyst revealed by postoperative imaging. Conclusions Microsurgical fenestration of sacral perineural cysts to the thecal sac is a surgical approach that has shown success in the treatment of lumbosacral pain, pseudoradicular symptoms, genital pain and urinary dysfunction associated with sacral perineural cysts. Our analysis, however, shows that mainly patients with singular large cysts benefit from this treatment.