872 Natural History of Conservatively Managed Patients With Chiari Malformation Type I and Syringomyelia

Abstract

INTRODUCTION: Chiari malformation type 1 (CM1) describes caudal ectopia of the cerebellar tonsils. Though often asymptomatic earlier in life and found incidentally on imaging, CM1 can disturb cerebrospinal fluid (CSF) flow and generate an array of symptoms. Surgical treatment for CM1 centers around procedures to increase the posterior fossa volume and improve CSF circulation. Many surgeons elect to operate on CM1 patients in the setting of a syrinx, making it difficult to understand the natural history of these patients. METHODS: Retrospective study of 37 CM1 patients with syrinx who were managed conservatively at our institution. All patients had initial and follow-up clinic visits with a neurologist or neurosurgeon. Of the 37 patients, 27 had initial and follow-up MRI images at least six months apart. Student t-tests were used to compare radiological parameters. RESULTS: A total of three patients saw complete resolution of their syrinxes. Regarding clinical symptomatology, 19 out of 32 patients who were initially symptomatic saw clinical improvement by follow up, while 13 remained stable, and five declined. Of the five patients that declined, three had worsening neurological conditions not attributed to the syrinx or CM1 while the remaining two patients were the only patients that declined surgery despite recommendation. A total of 16 patients saw decreases in both syrinx size and tonsillar descent. There were no statistically significant differences between tonsillar descent, syrinx size, and number of vertebral bodies spanned by syrinx between the initial and latest follow up. The presence of tonsillar pegging was predictive of decrease in syrinx size. Tonsillar descent and syrinx size were not predictive of clinical outcomes. CONCLUSIONS: Although the surgical treatment of the CM1 patient successfully resolves the syrinx, the natural history of the syrinx can be benign.