Altered interictal saccadic reaction time in migraine: a cross-sectional study.
Chandna A., Chandrasekharan DP., Ramesh AV., Carpenter RHS.
AIMS: The underlying mechanisms of migraine remain poorly understood, partly because we lack objective methods for quantitative analysis of neurological function. To address this issue, we measured interictal saccadic latency in migraineurs and controls. METHODS: In a cross-sectional study, we compared interictal saccadic latency distributions of 12,800 saccades in 32 migraineurs with 32 age- and sex-matched controls. RESULTS: The variability of migraineurs' reaction time distributions was significantly smaller (σ = 1.01 vs. 1.13; p < 0.05) compared with controls. In addition, a smaller proportion of migraineurs generated 'early' saccades (31% vs. 56%: p < 0.05). Sensitivity/specificity analysis demonstrated the potential benefit of this technique to diagnostic discrimination. CONCLUSIONS: The migraineur's brain behaves significantly differently from that of a control during the interictal period. By analysing whole distributions, rather than just means, data can be related directly to current neurophysiological models: specifically, the observed decrease in variability suggests a functional deficit in the noradrenergic systems influencing the cerebral cortex. From a clinical perspective, this novel method of characterising neurological function in migraine is more rapid, practicable, inexpensive, objective and quantitative than previous methods such as evoked potentials and transcranial magnetic stimulation, and has the potential both to improve current diagnostic discrimination and to help guide future research into the underlying neural mechanisms.