Prevalence of Chiari I Malformation and Syringomyelia.

Chiari I malformation (CM) is a common neurosurgical diagnosis and spinal cord syrinx is frequently found in patients with CM. Asymptomatic CM is a common imaging finding. Symptomatic CM is less common. Variation in prevalence estimates may be attributed to differences in sensitivity of CM detection between studies as well as differences in the populations being analyzed. The prevalence of low tonsil position and CM on MRI is higher in children and young adults compared with older adults. Studies that include a large number of older adults find a lower prevalence compared with analyses of children.