Table 3. Evidence summary.

Outcomes	Strength of evidence	Conclusions/comments
Question 1: What is the average rate of recurrent or residual syringomyelia following posterior fossa decompression as a result of Chiari malformation with associated syringomyelia?
Recurrent/residual syringomyelia		Rates of recurrent/residual syringomyelia after posterior fossa decompression in adults range from 0–22% with an average across studies of 6.7%. These studies are case series from different populations. Because of the low quality of individual studies and the inconsistency between studies, there is insufficient evidence to establish an expected rate of recurrence; however, we can provide surgeons and patients with a range of estimates to consider.
Question 2: What treatment methods have been reported in the literature for managing recurrent or residual syringomyelia after initial posterior fossa decompression?
Treatments	Not applicable	This was a descriptive key question and therefore an overall strength of evidence is not applicable.