Multiple sclerosis with normal neuro-ophthalmological work-up: results of focal stimulations induced by a scanning laser ophthalmoscope

Objective - Visual evoked potentials (VEPs) are a very useful tool in diagn osis of multiple sclerosis (MS). Nevertheless, in some cases of the disease , VEPs are normal. The aim of this study was to evaluate the diagnostic val ue of focal checkerboard reversal stimulation based on opto-acoustic modula tion generated by a scanning laser ophthalmoscope (SLO) in patients whose s tandard neuro-ophthalmological work-up was normal. Methods - We prospective ly studied 185 MS patients. In this cohort we found 30 patients with defini te MS and normal neuroophthalmological work-up and we studied the diagnosti c yield of focal visual stimulation in these patients. We performed focal S LO-elicited VEPs with two different spatial distributions: a central 8 x 8 degrees square field and a central 8 x 8 degrees exclusion square. The resu lts were analysed in terms of age of the patient, course of the disease, an d disability evaluated on the Expanded Disability Status Scale (EDSS). Resu lts - Mean latencies of focal VEPs were increased in MS patients compared t o controls. In MS, focal stimulation allowed dysfunction of the visual syst em to be detected in 50% of patients who have been classified as normal acc ording to conventional VEPs. VEP abnormalities were found to be correlated with the EDSS score (P < 0.001) and the course of the disease (P < 0.05). C onclusion - We have demonstrated the value of focal VEPs in MS diagnosis us ing SLO-based techniques. Further prospective work in patients with possibl e and probable MS should enable an evaluation of the sensitivity and specif icity of this method in the early diagnosis of MS.