Vascular compression of the trigeminal nerve is generally accepted as the primary source causing TN. To date, skull base bone deformity associated with ITN has been reported in only a number of case reports. The aim of the present study was to investigate one such skull base deformity, platybasia, in ITN patients in comparison with a randomized control population.Basal angle values reflecting the development of platybasia were measured in 25 patients with ITN and compared with the measurements in 25 control subjects.Basal angle measured to investigate the existence of platybasia was found significantly wider in the ITN group (t = 3.90; P < .001), although platybasia was present in only 10 patients. Moreover, the average angle was also greater in the study group than in the control group, and the difference was statistically significant. Platybasia was found in 10 patients, whereas it was detected in only 2 control individuals; difference in platybasia incidence between the 2 groups was also statistically significant (chi(2) = 7.01; P < .01).Our data demonstrated that platybasia affecting the bony walls of the posterior fossa may play an important role in the pathogenesis if vascular abnormalities causing TN.