An epidemiological analysis of cranio-vertebral morphometrics other than tonsillar position in symptomatic, adult, female Chiari malformation type I.

Adult, symptomatic Chiari malformation Type I (CMI) is a painful, often debilitating, neurological condition which is defined by the herniation, or extension, of the cerebellar tonsils below the skull. Research has shown that Chiari patients on average exhibit a number of anatomical variations, or morphometric differences, from healthy controls in the cranio-vertebral region; however the potential contribution of these differences to CMI's pathophysiology is not clear. This case-control study looked at nine representative morphometric measures (MM) in 432 adult, female CMI subjects and 148 adult, female controls. Each measure was dichotomized at three increasing distances from the control mean to represent exposures in an odds ratio analysis with CMI as the outcome. In addition, logistic regression modeling was used to determine the overall predictive ability of the MMs. Finally, disease severity was compared across three CMI subgroups with varying degrees of morphometric severity. We found that a reduced fastigium height demonstrated the largest increase in both crude and adjusted odds ratios at every level with an exposure-response pattern. Logistic regression correctly identified 87% of the CMI subjects as CMI based on the MMs. On average, CMI subjects had more than 3 MMs that were at least one standard deviation from the control mean, but there was no association between morphological and disease severity. These results suggest that further studies into anatomical variations such as fastigium height in CMI patients are warranted.