Multifocal bioelectrical cortical responses in Leber Hereditary Optic Neuropathy

Abstract

Purpose: To assess visual cortical bioelectrical responses in Leber’s Hereditary Optic Neuropathy (LHON) by means of multifocal visual evoked potentials (mfVEPs)

Methods: Seventeen patients carrying LHON mutation (mean age 33.35 ± 8.4 years, 17 LHON eyes) and 22 age-matched healthy control subjects (mean age 38.2 ± 6.0 years, 22 Control eyes) were studied by mfVEPs in response to 61 M-stimuli presented to the central 20 degrees of the visual field. MfVEPs P1 implicit time (P1 IT, ms) and response amplitude density of the N1-P1 components (N1-P1 RAD, nV/deg2) of the second- order binary kernel were measured for five retinal eccentricities in areas between the fovea and midperiphery: 0-2.5 (R1), 2.5-5 (R2), 5-10 (R3), 10-15 (R4), and 15-20 (R5) degrees

Results: LHON patients showed statistically significant (ANOVA, p<0.01) differences in mean mfVEPs P1 ITs and N1-P1 RADs at all five foveal eccentricities (R1-R5, 0-20 degrees) compared to Controls. In both Control and LHON eyes, mean mfVEPs responses obtained from R1 to R5 showed a progressive shortening of P1 ITs (linear fitting, LHON: R=-0,95; C:R=-0,98) and decreasing of N1-P1 RADs (exponential fitting, LHON: R2= 0,94; C: R2= 0,93). The progressive decay of mean mfVEPs P1 ITs resulted about three times greater in LHON patients than in Controls (LHON: y = -13,33x +182,03; C: y = -4,528x +108,1)

Conclusions: Our findings confirm the presence of an impairment of the neural conduction along the visual pathways in LHON. This dysfunction is more evident for the axons driving responses from the central retinal areas with respect to the axons driving responses from the peripheral retinal regions

Keywords: 613 neuro-ophthalmology: optic nerve • 600 mitochondria • 507 electrophysiology: clinical