Visual cortex excitability in migraine evaluated by single and paired magnetic stimuli

Objective. - To determine the excitability of the visual cortex by phosphene thresholds (PT) in patients with migraine using transcranial magnetic stimulation (TMS) with single- and paired-pulses. Methods. - Nineteen patients with migraine with aura(MWA), 19 patients with migraine without aura(MWoA), and 22 control subjects were included. Patients were free from preventive anti-migraine treatment and were investigated within 3 days before or after an acute migraine attack. In each subject, PT were assessed by single- pulse and paired-pulse TMS with an interstimulus interval of 50 ms. Results. - The main effect of diagnosis indicated that mean PT were significantly lower in migraine patients than in control subjects (P = .001). Using single- pulse TMS, mean PT tended to be lower in MWoA-patients (57.7 +/- 11.8%) compared with control subjects (64.4 +/- 10.5%) (P = .064). In MWA-patients, mean PT (53.1 +/- 5.7%) were significantly lower compared with controls (P < .001). Using TMS with paired pulses, mean PT were significantly reduced in MWoA-patients (40.3 +/- 4.9%, P = .017) as well as in MWA-patients (39.6 +/- 4.2%, P =. 005) compared with controls (44.6 +/- 6.0%). The main effect of stimulation type indicated that mean PT were lower determined with paired-pulse stimulation than with single pulses (P < .001). Conclusions. - PT are reduced in patients with migraine in the interictal state suggesting an increased excitability of visual cortical areas. Compared with single- pulse TMS, paired-pulse magnetic stimulation is more efficient to elicit phosphenes. This technique provides the opportunity to evaluate visual cortex excitability with lower stimulus intensities and less discomfort.