Study Design?Systematic review. Study Rationale?One of the most consistent indications for a Chiari decompression is tonsillar descent meeting the radiographic criteria and an associated syrinx in a symptomatic patient. In counseling patients about surgery, it would be advantageous to have information regarding the expected outcome with regard to the syrinx and other possible treatments available if the result is suboptimal. Clinical Questions?The clinical questions include: (1) What is the average rate of recurrent or residual syringomyelia following posterior fossa decompression as a result of Chiari malformation with associated syringomyelia? (2) What treatment methods have been reported in the literature for managing recurrent or residual syringomyelia after initial posterior fossa decompression? Materials and Methods Available search engines were utilized to identify publications dealing with recurrent or residual syrinx after Chiari decompression and/or management of the syrinx. Rates of residual or recurrent syrinx were extracted and management strategies were recorded. Overall strength of evidence was quantified. Results?Of the 72 citations, 11 citations met inclusion criteria. Rates of recurrent/residual syringomyelia after decompression in adults range from 0 to 22% with an average of 6.7%. There were no studies that discussed specifically management of the remaining syrinx. Conclusion?Rates of recurrent/residual syringomyelia after Chiari decompression in adults range from 0 to 22% (average 6.7%). Although no studies describing the optimal management of residual syrinx were found, there is general agreement that the aim of the initial surgery is to restore relatively unimpeded flow of cerebrospinal across the craniocervical junction. Large holocord syrinx may induce a component of spinal cord injury even with adequate decompression and reduction in the caliber of the syrinx, resulting in permanent symptoms of injury.