Effects of grating spatial orientation on visual evoked potentials and contrast sensitivity in multiple sclerosis

Area of Science:

• Neuroscience
• Ophthalmology
• Clinical Neurology

Background:

• Multiple sclerosis (MS) can affect visual pathways, leading to visual dysfunction.
• Previous research indicates that pattern visual evoked potentials (PVEPs) may be delayed in MS, with findings varying by grating orientation.
• Contrast sensitivity (CS) is also a key measure of visual function potentially impacted by MS.

Purpose of the Study:

• To evaluate the diagnostic utility of PVEPs and CS in detecting cortical structure involvement in MS patients.
• To compare the sensitivity of PVEPs and CS to different grating orientations (vertical vs. horizontal) and spatial frequencies (SF).

Main Methods:

• 14 patients with definite MS underwent PVEP testing using vertical and horizontal gratings at 1 and 4 cycles/degree (c/d).
• Latency and amplitude of P60, N70, and P100 waves were analyzed.
• Contrast sensitivity (CS) was assessed using various SFs for both dark and bright bars.

Main Results:

• PVEP abnormalities were more frequent with vertical gratings, particularly at 4 c/d (up to 42%).
• Horizontal gratings showed lower PVEP alteration rates (up to 35% at 4 c/d).
• CS was more impaired with vertical gratings, peaking at 3.7 c/d SF. CS deficits were observed even with normal PVEPs.

Conclusions:

• Vertical grating orientation is more reliable for both PVEP and CS testing in MS clinical practice.
• CS testing can reveal subclinical visual cortex impairment in MS, even when PVEPs are within normal limits.
• These findings highlight the importance of specific grating orientations for sensitive detection of visual pathway involvement in MS.