The spatial tuning of steady state pattern electroretinogram in multiple sclerosis.

Area of Science:

• Neuroscience
• Ophthalmology
• Clinical Electrophysiology

Background:

• The pattern electroretinogram (PERG) in healthy individuals exhibits a band-pass spatial tuning, peaking at intermediate spatial frequencies.
• Low spatial frequency attenuation in PERG is linked to center-surround interactions in inner retinal neurons.
• Multiple Sclerosis (MS) can affect the visual pathways, but early retinal changes in patients without optic neuritis are less understood.

Purpose of the Study:

• To investigate the spatial tuning characteristics of the steady-state PERG in MS patients without a history of optic neuritis.
• To compare PERG spatial tuning in MS patients with and without optic neuritis history, and with healthy controls.
• To explore potential early retinal dysfunction in MS.

Main Methods:

• Recorded steady-state PERGs using counterphase-modulated sinusoidal gratings at various spatial frequencies (0.6-4.8 c/deg).
• Studied 18 MS patients without optic neuritis history (ON-), categorized as asymptomatic or symptomatic.
• Compared results with 10 MS patients with optic neuritis history (ON+) and 21 age-matched controls.

Main Results:

• Asymptomatic ON- MS patients showed reduced PERG amplitudes at medium-high spatial frequencies compared to controls.
• Symptomatic ON- and ON+ MS patients exhibited reduced PERG amplitudes across all spatial frequencies, with greater losses at medium-high frequencies.
• All MS patient groups displayed a low-pass spatial tuning function, deviating significantly from the controls' band-pass tuning.

Conclusions:

• Altered PERG spatial tuning is present in MS patients even without optic neuritis or subclinical demyelination.
• These findings suggest early retinal dysfunction in MS, possibly due to inner retinal neuron loss or altered lateral interactions.
• PERG spatial tuning abnormalities correlate with other visual function deficits in MS patients.