Peak CSF velocities in patients with symptomatic and asymptomatic Chiari I malformation.

BACKGROUND AND PURPOSE PCMR is used to evaluate the Chiari I malformation. We compared quantitative PCMR in symptomatic and asymptomatic patients with Chiari I. MATERIALS AND METHODS PCMR image data in an axial section near the foramen magnum in a consecutive series of patients with Chiari I malformations were evaluated. Patients were classified as symptomatic for a Chiari I if they had apnea spells and/or exertional headaches and as asymptomatic if they had symptoms not considered specific for a Chiari I malformation. The PCMR CSF flow study was obtained with the same protocol for all patients and with the neck in neutral, flexed, and extended positions. Images were inspected for CSF flow jets and synchronous bidirectional flow. Peak CSF flow velocities were calculated with commercial software. Differences between the 2 groups were tested with mixed-effects ANOVA and Wilcoxon rank sum or Fisher exact probability tests with significance set at the .05 level. RESULTS Twenty-six patients with Chiari I were classified as symptomatic, and 24, as asymptomatic. Abnormal flow jets tended to occur more often in the symptomatic than in the asymptomatic patients (P = .054). Peak CSF velocities ranged from 2 to 20 cm/s in the symptomatic and the asymptomatic groups and did not differ significantly between the 2 groups or with neck position. CONCLUSIONS Peak CSF flow velocities near the foramen magnum did not differentiate symptomatic and asymptomatic patients with Chiari I.