Prevalence of Chiari type I malformation on cervical magnetic resonance imaging: a retrospective study.

Objectives: Chiari malformation is characterized by caudal herniation of cerebellar tonsils from foramen magnum into the cervical canal on radiological images. Type I Chiari malformation is the herniation of cerebellar tonsils more than 3 mm which does not cause any symptoms until adulthood. In this study, we aimed to investigate the prevalence of Chiari type I malformation. Methods: In this retrospective study, cervical magnetic resonance images taken between 2013 and 2015 were retrospectively analyzed. The patients were 18-70 year old males and females. Type I Chiari malformation was defined as an inferior displacement of the cerebellar tonsils more than 3 mm below the opisthion-basion line. The patients with intracranial lesions, hydrocephalus or previous craniotomy were excluded from the study. Results: The prevalence of Chiari type I malformation was found as 4% when both genders were taken into consideration. The prevalence was 3.3% in females and 0.7% in males. Chiari type I malformation was associated with syringomyelia in 0.5% of females and 0.2% of males. In the present study, concomitant syringomyelia was observed in 0.7% of the patients. On the other hand, incidence of Chiari type I malformation was found relatively higher in the patients with scoliosis (15.4%). The ratio of this co-occurrence was higher in females (11.4%) when compared to the males (4%). Conclusion: In the present study, the prevalence of Chiari type I malformation was investigated in a large population, consisting of 2480 individuals, and its association with syringomyelia and scoliosis. [ABSTRACT FROM AUTHOR]