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Abstract
Objective: To test the hypothesis that patients with multiple sclerosis (MS) with intereye asymmetry on low contrast letter acuity, and thickness of the retinal nerve fiber layer (RNFL), would exhibit corresponding changes in cortical timing and amplitude responses on pattern reversal multifocal visual evoked potentials (mfVEP), contingent upon variable stimulus contrast.
Methods: In a cross-sectional study, we investigated a cohort of 11 normal subjects and 40 patients with MS, 21 of whom had a history of acute optic neuritis (MS-AON) with an intereye asymmetry with respect to RNFL thickness, and on low contrast letter acuity performance. Pattern reversal mfVEP was performed at high (100%), low (33.3%), and very low (14.2%) Michelson-contrast levels.
Results: Compared to baseline measures at 100% contrast, the mean amplitude of the mfVEP was reduced in MS-AON eyes, upon pattern-reversal stimulation at the 2 lower contrast levels (p < 0.0001). With respect to changes in timing responses, the intereye asymmetry was increased in the MS-AON patients upon lower contrast pattern-reversal stimulation (p < 0.0001 for 33.3% compared to 100%, and p < 0.001 for 14.2% compared to 100%). The fellow eye in 12 (57%; p < 0.001) of the patients with an abnormal eye, and a history of AON, revealed abnormal amplitude and timing responses upon low contrast stimulation (signifying unmasking of occult damage).
Conclusions: Our findings support the hypothesis that mfVEP metric abnormalities are contingent upon contrast magnitude during pattern reversal stimulation. Further, this paradigm was capable of unmasking occult abnormalities in a significant number of apparently unaffected eyes.
GLOSSARY
- AON=
- acute optic neuritis;
- mfVEP=
- multifocal visual evoked potential;
- MS=
- multiple sclerosis;
- MS-AON=
- multiple sclerosis with a history of acute optic neuritis;
- MS-FON=
- unaffected fellow eye;
- OCT=
- optical coherence tomography;
- RNFL=
- retinal nerve fiber layer;
- VEP=
- visual evoked potential
Footnotes
Study funding: National Multiple Sclerosis Society (RG 3780A3/3 to Elliot M. Frohman. RG 4091A3/1 to Robert Fox subcontracted to E.M.F., TR 3760-A-3 to P.A.C., and RG 4212-A-4 to Laura J. Balcer subcontracted to P.A.C. and E.M.F.), National Eye Institute (R01 EY 014993 and R01 EY 019473 to Laura J. Balcer subcontracted to P.A.C. and E.M.F.), Dale Energy Corporation (to Elliot M. Frohman and Benjamin Greenberg), and Braxton Debbie Angela Dillon and Skip (DADS) Donor Advisor Fund (to Elliot M. Frohman and subcontracted to P.A.C., L.J.B.).
Editorial, page 732
Supplemental data at www.neurology.org
- Received October 17, 2011.
- Accepted March 8, 2012.
- Copyright © 2012 by AAN Enterprises, Inc.
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