AREA MEASUREMENTS WITHIN THE FORAMEN MAGNUM: COMPARISON OF 171 PATIENTS WITH SYMPTOMATIC AND ASYMPTOMATIC CHIARI MALFORMATION TYPE 1

Objective: In previous studies, different radiological measurement techniques could not reliably distinguish patients with symptomatic Chiari type 1 malformation (CMI) from those with asymptomatic CMI. We aimed to develop a new perspective to select patients with CMI for surgery by calculating the brainstem area (BA), cerebellar tonsillar area (CTA), foramen magnum area (FMA), and CTA/BA ratio in T2 MR axial imaging at the foramen magnum level. Materials and Methods: Eighty six symptomatic and 85 asymptomatic patients evaluated by neurosurgeons were included in the study. The patients' BA, CTA, FMA, and CTA/BA ratios were calculated by two neuroradiologists. In addition, the measurements of the operated patients in the postoperative period were re-made, and the pre-operative and postoperative measurements were compared. Results: The mean BA was 1.57 cm2 and 1.76 cm2 in symptomatic and asymptomatic patients, respectively (p<0.05). The cut-off value between symptomatic patients with BA and asymptomatic patients was 1.74 cm2. The results of our study were found to be statistically significant in such a way that BA measurements can show the amount of compression on the brainstem. The mean postoperative BA (1.73±0.32) was higher than the mean pre-operative BA (1.58±0.35; p<0.001). There was no difference between the mean postoperative BA of symptomatic patients (1.73±0.33) and the mean BA of asymptomatic patients. Symptomatic patients' CTAs were wider than asymptomatic patients. In addition, FMA was different between symptomatic and asymptomatic patients (p<0.001). Conclusion: BA and FMA may provide a new perspective on the distinction between symptomatic and asymptomatic CMI.