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Susan C. Anderson, Pieter Poolman, Jan M. Full, Andrew F. Russo, Ana Recober, Randy H. Kardon; The Light Induced Electromyogram Shows Exaggerated Responses in Migraine. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4844.
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To determine if the photic-electromyogram (photic-EMG), an objective test of light sensitivity, shows an exaggerated response in patients with migraine compared to normal subjects.
Five patients with a diagnosis of migraine headaches (but without headache at the time of testing) and eight normal subjects were tested using red (640nm) and blue (485nm) Ganzfeld, full field light, one second in duration, over a 6 log unit range of intensity (0.5 log unit steps). 2 of the normal subjects were excluded after determining that one had weekly headaches and the other had light sensitivity. Time-stamped, computerized recording of the orbicularis and procerus/corrugator muscle EMG were quantified and the maximum root mean squared (RMS) was compared between the patients with migraine and age matched control subjects.
Subjects with a known diagnosis of migraine had maximum photic-EMG response to the brightest red and blue lights (EMG RMS red mean=7.2+/-2.4 SEM, blue=6.7+/-2.1 SEM) which was significantly greater than normal control subjects (EMG RMS red mean=1.2+/-0.06 SEM, blue=1.5+/-0.23SEM) for either red light (p<0.001) or blue light (p<. 0.03). One migraine patient had near normal EMG responses, but was on pain medications. 2 of the 8 normal subjects appeared to have greater photic-EMGs compared to the remaining 6 subjects. On further questioning, one subject did have a history of weekly headache and the other admitted to light sensitivity.
This preliminary study demonstrated that the photic-EMG shows an exaggerated response in subjects with migraine, headache and light sensitivity. The light induced EMG of the orbicularis and procerus/corrugator muscles may be a useful objective test for classifying migraine patients and their response to treatment.
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