Abstract
Purpose: :
To determine if prolonged latency values of multifocal visual evoked potential (mVEP) responses in patients with optic neuritis could be a marker for increased risk of progression to clinically definite Multiple Sclerosis (MS).
Methods: :
68 subjects with optic neuritis (ON) were classified according to the McDonald criteria for as either "not–MS", "possible–MS" and "MS". Each patient then underwent (mVEP) testing using the Accumap V2.0(ObjectiVision, Sydney, Australia) and latency analysis was performed. Latency values determined for sectors showed clear differences between those with definite MS and those with "not–MS" but the "possible MS" group showed a bimodal distribution. The 29 ON patients categorized as "possible–MS" were then followed for one year.
Results: :
Latency values were significantly different between the three groups of patients (p<0.001, ANOVA). The "possible–MS" patients were shown to have a bimodal distribution of latency z–score results: some patients had no latency delay (mirroring results from the "not–MS" patients) whereas other patients had long latency delays similar to those already diagnosed as "MS". Of the possible MS group 7/29 (24.2%) had no latency delay while the remaining 22 (75.9%) had significantly delayed latency results. Over one year 7 patients progressed clinically to a diagnosis of definite "MS". All of these patients had shown a latency delay on initial mVEP testing. Thus the conversion to "MS" was 31.8% in the high latency group, and 0% in the normal latency group. This difference in conversion rates is statistically significant (p<0.01 Chi–squared).
Conclusions: :
This provides evidence to suggest that mVEP latency results in subjects with optic neuritis may have a role in identifying a patient’s risk for future MS.
Keywords: electrophysiology: clinical • neuro-ophthalmology: diagnosis • neuro-ophthalmology: optic nerve