Treatment failure of syringomyelia associated with Chiari I malformation following foramen magnum decompression: how should we proceed?

The preferred treatment of patients with persistent, recurrent, or progressive syringomyelia after foramen magnum decompression (FMD) for Chiari I (CMI)-associated syringomyelia is controversial, and may include redo FMD, stabilization, or shunting procedures (such as syringopleural or syringo-subarachnoid shunts). We describe our experience in treating these patients and discuss the treatment modalities for these patients. We retrospectively collected data of CMI patients with persistent, recurrent, or progressive syringomyelia after FMD. In addition to baseline characteristics, surgical treatments and neurological and radiological outcomes were assessed. Further, we assessed through uni- and multivariate analyses possible technical, surgical, and radiological factors which might lead to failed FMD. Between 1998 and 2017, 48 consecutive patients (35 females (73%), average age 16.8 ± 11.5 years) underwent FMD for a syringomyelia-Chiari complex. Twenty-four patients (50%) underwent surgical treatment for a persistent (n = 10), progressive (n = 12), or recurrent (n = 2) syringomyelia 21.4 ± 27.9 months (median 14.6 months, range 12 days-134.9 months) after FMD. Of all analyzed factors, only extradural FMD was significantly associated with lower failure rates. Two patients (8%) underwent redo FMD, 18 (75%) underwent 19 syringo-subarachnoid-shunts, and 4 (17%) had 6 cranial CSF diversion procedures. The overall follow-up time was 40.1 ± 47.4 months (median 25 months, range 3-230 months). Based on our results, 50% of the patients undergoing FMD for syringomyelia-Chiari complex may require further surgical treatment due to persistent, progressive, or recurrent syringomyelia. Treatment should be tailored to the suspected underlying pathology. A subgroup of patients may be managed conservatively; however, these patients need close clinical and radiological follow-ups. The technical aspects of FMD in CMI-syrinx complex should be the focus of larger studies, as an effort to improve failure rates.