Objective: Chiari I malformation is complicated by syringomyelia in many cases. Hindbrain decompression remains first-line surgical treatment; however, the incidence, time course, and predictors of syrinx resolution remain unclear. We set out to determine predictors of syrinx improvement after hindbrain decompression for Chiari I- associated syringomyelia.
Methods: Forty-nine consecutive pediatric patients undergoing posterior fossa decompression for Chiari I-associated syringomyelia were followed with serial magnetic resonance imaging evaluations postoperatively. Clinical, radiological, and operative variables were assessed as predictors of syrinx improvement as a function of time using Kaplan-Meier plots and log-rank analysis.
Results: Mean patient age was 11 +/- 5 years. Syringomyelia was symptomatic in 39 (80%) and asymptomatic in 10 (20%) cases. Twenty-one (54%) patients experienced symptom resolution (median, 4 mo postoperatively). Twenty-seven (55%) patients experienced radiographic improvement in syringomyelia (median, 14 mo postoperatively). After hindbrain decompression, motor symptoms were associated with a 2.35 increased hazard ratio for symptom improvement (P = 0.031) versus all other symptoms. Among patients with sensory deficits, dysesthesia was associated with a 3.12 increased hazard ratio for symptom improvement (P = 0.032) versus symptoms of paresthesia or anesthesia.
Conclusion: In our experience, just more than one-half of patients with Chiari- associated syringomyelia demonstrated clinical and radiographic improvement after hindbrain decompression. Median time to radiographic improvement lagged behind clinical improvement by 10 months. Motor symptoms were more likely to improve with hindbrain decompression. Paresthesia or anesthesia symptoms were less likely to improve with hindbrain decompression. These findings may help guide surgical decision making and aid in patient education.