Subcortical structural abnormalities in female neuromyelitis optica patients with neuropathic pain

Neuromyelitis optica (NMO) is a disease characterised by severe relapses of optic neuritis and longitudinally extensive transverse myelitis and it has a strong female predilection. Pain is one of the most typical symptom in NMO. However, few studies have been conducted to examine the neuropathic pain mechanism of NMO patients or gender-specific effects using magnetic resonance imaging technique. A total of 38 female patients with NMO, 28 with pain (NMOWP) and 10 without pain (NMOWoP), were classified using the Brief Pain Inventory (BPI); 22 healthy females were also recruited. We used the FSL Image Registration and Segmentation Toolbox (FIRST) for subcortical region volumes quantifications, and voxel-based morphometry analysis for cortical gray matter (GM) volume, to examine the brain morphology in NMOWP patients. In addition, correlation test between structural measurements of NMO patients and clinical indexes was also performed. The results showed: 1) no significant differences in cortical GM density between the NMOWP and NMOWoP groups; 2) significantly smaller hippocampus and pallidum volumes in the NMOWP group compared with the NMOWoP group; 3) significant negative correlation between the average BPI and volumes of the accumbens nucleus and thalamus in NMO patients. These results revealed that structural abnormality exists in NMO female patients who have pain, with significant implications for our understanding of the brain morphology in NMO patients with pain.