Consecutive Transcranial Magnetic Stimulation: Phosphene Thresholds in Migraineurs and Controls

Objective.—To characterize the temporal course of transcranial magnetic stimulation‐induced phosphene thresholds in subjects with migraine and in controls. Methods.—Eleven subjects with migraine with aura, 10 subjects with migraine without aura, 9 subjects with menstrual migraine, and 15 controls (no history of migraine and without migraine during the study) were studied. Subjects were not on preventive medication. Transcranial magnetic stimulation was performed, and a phosphene threshold was measured 3 times a week over 3 weeks in a manner timed to incorporate the menstrual period in females. A headache calendar was kept during the study. Results.—Mean transcranial magnetic stimulation thresholds were lower for each migraine group compared with controls (P < .001) for each comparison. There was a trend for lower thresholds among subjects with migraine with aura compared with subjects with migraine without aura (P < .10), but not subjects with menstrual migraine. There was consistent lowering of thresholds from the first to the last stimulation in all migraine groups and in the controls. Maximum and minimum thresholds did not predict headache occurrence, nor did the occurrence of headache predict an ensuing maximum or minimum phosphene threshold. Conclusions.—Transcranial magnetic stimulation thresholds are lower in subjects with migraine compared with controls. The reported phosphene threshold is lowered with repeated measurement. Neither high nor low phosphene thresholds predict a subsequent headache, nor do migraines predict a subsequent high or low threshold.