Incidence of Asymptomatic Chiari Malformation

Aim The aim of this study is to define the incidence of asymptomatic Chiari malformation in an Irish population. Methods MRIs performed over 24 months were analysed. Exclusion criteria include: space occupying lesion, hydrocephalus, Chiari symptoms and inadequate views. Data were analysed to give incidence of asymptomatic Chiari and to analyze the relationship between symptom and position of the cerebellar tonsils (Chi square and Fishers exact test). Results Sample Characteristics: 147 patients (Male = 65: Female = 82), age range 15 to 93 years (M age = 53.35, SD= 16.67). 2%had a Chiari malformation (n=2). There was no significant association between symptom and tonsil position (Fishers exact test, ² (8) = 9.98, p = .23.) Conclusion This study shows an asymptomatic Chiari Malformation rate of 2%. This study supports the idea that in asymptomatic patients, a tonsil herniation of up to 5 millimeters may be an incidental and inconsequent finding.