Multifocal VEP provide electrophysiological evidence of predominant dysfunction of the optic nerve fibers derived from the central retina in Leber’s hereditary optic neuropathy

Purpose: To differentiate the bioelectrical cortical responses driven by axons from central and mid-peripheral retina in Leber’s hereditary optic neuropathy (LHON) by using multifocal visual evoked potentials (mfVEP). Methods: Seventeen genetically confirmed LHON patients (33.35 ± 8.4 years, 17 eyes) and 22 age-matched controls (C) (38.2 ± 6.0 years, 22 eyes) were studied by mfVEP and optical coherence tomography. MfVEP 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 concentric retinal areas between the fovea and mid-periphery: 0–20 degrees (R1 to R5). Results: Mean mfVEP P1 ITs and N1-P1 RADs at all five foveal eccentricities were significantly different (p <0.01) in LHON when compared to controls. In both groups, mean mfVEP responses obtained from R1 to R5 showed a progressive shortening of P1 ITs (linear fitting, LHON: r = −0.95; C: r = −0.98) and decrease of N1-P1 RADs (exponential fitting, LHON: r² = 0.94; C: r² = 0.93). The slope of the linear fitting between mean mfVEP P1 ITs in the two groups was about three times greater in LHON than in controls (LHON: y = −13.33x +182.03; C: y = −4.528x +108.1). MfVEP P1 ITs detected in R1 and R2 (0–5 degrees) were significantly correlated (p <0.01) with the reduction of retinal nerve fiber layer thickness of the temporal quadrant. Conclusions: MfVEP identifies abnormal neural conduction along the visual pathways in LHON, discriminating a predominant involvement of axons driving responses from the central retina when compared to those serving the mid-peripheral retina.