Low-contrast visual evoked potential and early detection of optic demyelination.

Visual Evoked Potential (VEP) is a useful tool in identifying abnormality relative to the integration of optic pathways, and aids the diagnosis of central nervous system demyelinating disorders, such as multiple sclerosis (MS). However, the sensitivity of VEP in detecting early optic abnormality as a visual function surrogate remains questionable. Recent studies showed that low-contrast VEP increases sensitivity in early detection of optic demyelination. In order to evaluate the applicability of low-contrast VEP to our electrodiagnostic protocol, we tested whether low-contrast VEP may provide an improved sensitivity in identifying early optic demyelination. We performed low-contrast VEP with different stimulation intensities in 42 subjects. Twenty-three were patients (age: 44.0 ± 13.6 year-old, range 26-69) with a clinical diagnosis of clinically isolated syndrome, a subtype of MS, and 19 subjects were normal volunteers (age: 34.4 ± 14.3 year-old, range: 18-59) without any neurological disorders. Neither of them had a history of optic neuritis. Our preliminary data indicate that the low-contrast VEP is not superior over the conventional high-contrast VEP, and may not provide improved sensitivity in early detection of optic demyelination.