No Differences in Spinal Cord White and Grey Matter Diffusion Abnormalities between Neuromyelitis Optica Spectrum Disorder and Multiple Sclerosis

OBJECTIVE: To explore microstructural changes of spinal cord grey matter (GM) and white matter (WM) in patients with neuromyelitis optica spectrum disorders (NMOSD) and compare them to those with multiple sclerosis (MS).BACKGROUND: NMOSD and MS may affect the spinal cord differentially. Diffusion tensor imaging (DTI) can reflect in-vivo the pathological involvement of spinal cord.METHODS: We recruited 18 patients with NMOSD (all AQP4-antibody positive except two), 18 with relapsing-remitting MS and 22 healthy-controls (HCs). Mean age was (NMOSD=52 years[±11], MS=42[±10], HCs=34[±10]). Mean disease-duration was (NMOSD=8.9 years[±6.5], MS=8.8[±7.1]). All subjects had 3T MRI with measurement of cord cross-sectional area (CCA) and of DTI metrics (FA:anisotropy of diffusion; AD/RD:amount of diffusion along/across neural fibers; MD:average amount of diffusion) in GM and WM (posterior and lateral-columns). Physical disability was assessed using the expanded-disability-status scale, 9-hole-peg test (HPT), timed-25-foot-walk test, handgrip-strength and vibration-perception. We used ANOVA to compare imaging measures and Spearman-correlation (r) to explore association between DTI and clinical measures. Statistics with p-valuesu003c0.05 were reported as significant.RESULTS: We detected: smaller CCA in NMOSD than HCs (mean=75.6 mm²[±11.4] vs. 85.8[±11.4]) and in MS than HCs (76.5mm²[±11] vs. 85.8[±11.4]), with no significant difference between patient groups; CCA reduced with longer disease-duration (r=-0.58) in NMOSD, and with worse disability (9-HPT test r=-0.51, handgrip-strength r=0.47) in MS. Compared to HCs, NMOSD patients showed reduced FA in GM and posterior-WM; higher RD in posterior-WM and AD in lateral-WM. MS patients had lower FA in the lateral-WM than HC. No difference in diffusion measures between patient groups was seen. In NMOSD, FA and RD of the posterior-WM were associated with worse vibration-perception (r=-0.63 and 0.52, respectively).CONCLUSION: Pathological involvement of spinal cord, as reflected by DTI, does not differ between NMOSD and MS. In NMOSD patients diffusion abnormalities in the posterior-WM may contribute to physical disability. Disclosure: Dr. Cortese has nothing to disclose. Dr. Magnollay has nothing to disclose. Dr. De Angelis has nothing to disclose. Dr. Eshaghi has nothing to disclose. Dr. Grussu has nothing to disclose. Dr. Prados has nothing to disclose. Dr. Ourselin has nothing to disclose. Dr. Yiannakas has nothing to disclose. Dr. Distaso has nothing to disclose. Dr. Miller has nothing to disclose. Dr. Gandini Wheeler-Kingshott has nothing to disclose. Dr. Ciccarelli has received personal compensation for activities with Novartis, Biogen and GE as a consultant.