Incidence and Size of the Fossa Navicularis in Chiari Type I Malformation

Introduction: This study aimed to compare the morphology of the fossa navicularis (FN) in patients with Chiari type I malformation (CIM) and healthy subjects.Methods: Radiologic views of 50 CIM patients (21 men/29 women) with a mean age of 26.9316.03years and 50 healthy subjects (29 men/21 women) with a mean age of 33.1321.40years were included in this computed tomography study.The presence or absence of FN was noted, and the depth (FN-D), width (FN-W), and length (FN-L) of FN, as well as the clivus length (CL), were measured.Results: FN was observed in 14 CIM patients (28%) and in eight controls (16%).In CIM patients, FN-L, FN-W, FN-D, and CL were measured as 3.621.64mm, 4.911.31mm, 2.711.06mm, and 43.455.62mm, respectively.In controls, FN-L, FN-W, FN-D, and CL were measured as 4.951.18mm, 3.420.97mm, 1.981.22mm, and 48.013.51mm, respectively.CIM subjects had greater FN-W (p=0.008) but smaller CL (p=0.042).FN-L (p=0.059) and FN-D (p=0.070) were similar between the groups.In CIM patients, all parameters were similar between sexes.In controls, men had greater FN-L compared to women (p=0.029).Discussion and Conclusion: CIM patients had greater FN-W compared to controls.FN incidence was not affected by CIM.These findings may help clinicians better understand clivus anatomy in CIM patients.