Multifocal VEP provide electrophysiological evidence of predominant dysfunction of the optic nerve fibers derived from the central retina in Leber’s hereditary optic neuropathy
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).
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).
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: r 2 = 0.94; C: r 2 = 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.
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.
KeywordsMultifocal visual evoked potentials Leber’s hereditary optic neuropathy LHON Retinal ganglion cells function Mitochondrial optic neuropathy
Research for this paper was financially supported partially by the Italian Ministry of Health (grant number: 2006 RF-FGB-2006-368547) and partially by Fondazione Roma. The authors acknowledge Dr. Valter Valli Fiore for technical help in electrophysiological evaluations.
Conflict of interest
Each author states that he/she has no proprietary interest in the development or marketing of the instruments used in the present study, and no conflict of interest.
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