Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classic Trigeminal Neuralgia

Abstract

A small posterior fossa (PF) has been hypothesized to explain the increased incidence of trigeminal neuralgia (TN) in females and could make microvascular decompression (MVD) more challenging. The aim of this study was to investigate the association between the PF volume and dimensions in relation to biological sex, type of neurovascular conflict (NVC), and outcome after MVD in classical TN. In this observational study, 84 TN patients operated with MVD with a preoperative head computed tomography (CT) scan were included. 82 adults without TN who had done a head CT for other reasons were included as controls. PF volume and dimensions (X-, Y-, and Z-axis) were evaluated on the CT scans. For the TN patients, Barrow Neurological Institute (BNI) grade was evaluated 6 months after MVD. There was no difference in PF volume or dimensions between the TN patients and controls. Females exhibited a smaller volume and narrower (X-axis) than males, but these differences did not manifest when comparing TN patients and controls within each sex. Patients with a NVC involving the superior cerebellar artery (SCA) had a narrower (X-axis) and shorter (Y-axis) PF than patients with a NVC caused by other arteries. PF volume or dimensions were not associated with BNI after MVD. PF anatomy was related to the NVC type, but did not differ between TN patients and controls, and was not related to surgical outcome following MVD.