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 26.93±16.03 years and 50 healthy subjects (29 men/21 women) with a mean age of 33.13±21.40 years 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 3.62±1.64 mm, 4.91±1.31 mm, 2.71±1.06 mm, and 43.45±5.62 mm, respectively. In controls, FN-L, FN-W, FN-D, and CL were measured as 4.95±1.18 mm, 3.42±0.97 mm, 1.98±1.22 mm, and 48.01±3.51 mm, 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.