Abstract
Purpose: :
To assess mfVEP amplitude and latency changes over time in MS patients with and without a history of optic neuritis (ON).
Methods: :
MfVEP was recorded with 60-sector pattern-reversal dartboard stimuli (VERIS). Customized software was used to calculate response amplitude (logSNR), latency (ms) and probability plots.1,2 Thirty five MS patients (mean age 43.7±10.8 yrs) had mfVEP twice and mean interval between recordings was 15.5±7.6 months (range 5-37 months). Thirty eyes had a history of ON (ON group). Mean duration between the last ON and 1st mfVEP was 5.3± 8.6 years. Forty eyes without ON history were divided into 2 groups: 18 with ON in fellow eye (no-ONa), 22 without ON in either eye (no-ONb). Bland Altman plots were constructed for each group to examine an eye’s change in mean amplitude and median latency between visits. 95% limits of agreement were obtained from test retest measures of 24 normal subjects. On monocular amplitude and latency probability plots, clusters of abnormal adjacent points meeting our cluster criteria3 were analyzed. Cluster size was defined as the number of abnormal points within a cluster divided by 60 for amplitude and divided by number of sectors with measurable responses for latency, and represented as percentages.
Results: :
Mean logSNR increased in 30% of ON eyes, 33.3% no-ONa and 13.6% no-ONb eyes, with none decreasing. Median latency shortened in 43.3% and lengthened in 16.7% of ON eyes. In the no-ONa and no-ONb eyes, latency of 27.8% and 27.2% shortened while 11.1% and 27.2% lengthened. For eyes with increased logSNR, cluster size reduced, on average, by 20.7%, 10.3% and 21.7% for ON, no-ONa, and no-ONb eyes, respectively. For eyes with shortened latency, the cluster size reduced, on average, by 5.9%, 9.4%, 6.5% for ON, no-ONa, and no-ONb eyes; and for those with longer latencies it increased by 15.6%, and 3.6% for ON and no-ONb eyes. No-ONa eyes with longer latencies had no clusters meeting criteria.
Conclusions: :
MfVEP amplitude and latency measures coupled with cluster analysis indicate long-term longitudinal changes in visual function in MS patients.1.Hood & Greenstein 2003; 2.Fortune et al 2004; 3. Laron et al 2010
Keywords: electrophysiology: clinical • neuro-ophthalmology: optic nerve • visual cortex