Lateral geniculate nucleus volume changes after optic neuritis in neuromyelitis optica: a longitudinal study

Abstract OBJECTIVES Lateral geniculate nucleus (LGN) volume is reduced after optic neuritis (ON) in neuromyelitis optica spectrum disorders (NMOSD). We aimed at a longitudinal assessment of LGN volume in NMOSD. METHODS Twenty-nine patients with aquaporin 4-IgG seropositive NMOSD (age: 47.8±14.6 years (y), female: n=27, history of ON (NMO-ON): n=17, median time since ON: 3[1.2-12.1]y) and 18 healthy controls (HC; age: 39.3±15.8y; female: n=13) were included. Median follow-up was 4.1[1.1-4.7]y for patients and 1.7[0.9-3.2]y for HC. LGN volume was measured using a multi-atlas-based approach of automated segmentation on 3 Tesla magnetic resonance images. Retinal optical coherence tomography and probabilistic tractography of the optic radiations (OR) were also performed. RESULTS At baseline, NMO-ON patients had lower LGN volumes (395.4±48.9mm3) than patients without ON (NMO-NON: 450.7± 55.6mm3; p=0.049) and HC (444.5±61.5mm3, p=0.025). LGN volume was associated with retinal neuroaxonal loss and microstructural OR damage. Longitudinally, there was no change in LGN volumes in the absence of ON, neither in all patients (B=-0.6, SE=1.4, p=0.670), nor in NMO-ON (B=-0.8, SE=1.6, p=0.617) and NMO-NON (B=1.7, SE=3.5, p=0.650). However, in four patients with new ON during follow-up, LGN volume was reduced at last visit (median time since ON: 2.6 [1.8-3.9] y) compared to the measurement before ON (352±52.7 vs. 371.1±55.9mm3; t=-3.6, p=0.036). CONCLUSION Although LGN volume is reduced after ON in NMOSD, this volume loss is not progressive over longer follow-up or independent of ON. Thus, our findings -at least in this relatively small cohort- do not support occult neurodegeneration of the afferent visual pathway in NMOSD.