Hippocampal Subfield Abnormalities in Patients With Primary Trigeminal Neuralgia

ABSTRACT Background and Purpose Primary trigeminal neuralgia (PTN) is a prevalent chronic pain disorder whose pathogenesis is not solely confined to the trigeminal system. Although substantial progress has been made in understanding the underlying mechanisms, comprehensive and consistent data concerning the involvement of the hippocampal formation in this process are lacking. The aim of this study was to evaluate structural changes in hippocampal subfields in patients with PTN. Methods Fifty‐nine individuals who were diagnosed with PTN and 28 healthy controls matched for age and sex underwent high‐resolution 3 Tesla MRI. HippUnfold software was used for the segmentation of hippocampal subfields and the extraction of features. Covariance analyses were performed to analyze changes in the volume, thickness, and gyrification index of different subfields in patients with PTN compared to controls. Furthermore, the relationships between MR morphometry data and the severity of nerve root compression, as well as the intensity and duration of pain, were examined in patients with PTN. Results Our analysis demonstrated a decrease in the volume of the right cornu ammonis subfield 1 (CA1)–CA3 and left CA2 hippocampal subfields in patients with PTN compared to healthy controls (adjusted p < 0.05 for all comparisons). No statistically significant associations were found between hippocampal MR morphometry data and clinical metrics. Conclusions Our results suggest the existence of bilateral structural abnormalities in the hippocampal subfields in individuals with PTN, which could contribute to the development and progression of this condition.