Narrow Foramen Ovale and Rotundum: A Role in the Etiology of Trigeminal Neuralgia.

Primary trigeminal neuralgia (TN) may occasionally occur in absence of neurovascular compression. A mechanism other than nerovascular compression may play a role in TN. High-resolution computed tomographies (CTs) of 21 consecutive TN patients without vascular compression during surgery and 30 healthy volunteers were retrospectively performed. Measuring parameters (length, width, and aspect ratio) were obtained in the axial plane for foramen ovale, and in the reconstructed coronal plane for foramen rotundum on both sides in each subject. The right-sided foramen ovale is slightly narrower than the left-sided, but no difference was observed between the sides. No correlation was found between the foramen size and the gender in both groups. The affected side with a narrower ovale foramen (>0.5 mm) and a significantly greater aspect ratio compared with the unaffected side may contribute to TN. Meanwhile, no significant correlation, but more likely a tendency, was found between the right and left sides in size of foramen rotundum (P = 0.09). This study has speculatively suggested that a narrow skull foramen may be etiologically important in a small percentage of TN patients. If recurrent or residual TN was encountered in cases of TN without vascular compression during surgery, high-resolution CT may help to evaluate the anatomical morphology of skull foramen in great detail.