Reduced habituation of the retinal ganglion cell response to sustained pattern stimulation in multiple sclerosis patients

Abstract

ObjectiveSustained pattern stimulation in normal subjects induces adaptive changes in pattern electroretinogram (PERG), an effect that has been interpreted as a response of glial cells and retinal ganglion cells (RGC). The aim of this study was to compare the effect in normal subjects and in multiple sclerosis patients without previous optic neuritis. MethodsPERGs were elicited by a 7.5Hz pattern stimulus, presented continuously over 152s. Response cycles were averaged in 20 packets of 60 events each and amplitude and phase of the 2nd harmonic response was measured. Adaptive changes are expressed as amplitude reduction over the full examination time. ResultsIn normal subjects PERG amplitude declined progressively to a plateau (dA=−0.46μV, SE=0.09μV); in patients the effect size was severely reduced (dA=−0.20μV, SE=0.04μV). No significant difference was found in mean amplitude. ConclusionsThe results show reduced RGC habituation in patients, suggesting an abnormal gain and sensitivity control in the inner retina, even in absence of clinical optic neuritis. Recent findings in astrocyte biology and indications drawn from a mathematical model point to a key role of glial cells in this process. SignificanceThe proposed methodology may have implications in the assessment of MS patients and in understanding the pathophysiology of neurological and retinal disorders.