Visual cortex excitability in migraine with and without aura

Previous research using transcranial magnetic stimulation has produced equivocal findings concerning thresholds for the generation of visual phosphenes in migraine with aura. These studies were methodologically varied and did not systematically address cortical excitability in migraine without aura. We therefore studied magnetophosphene thresholds in both migraine with aura and migraine without aura compared with headache-free controls.

Sixteen subjects with migraine with aura and 12 subjects with migraine without aura were studied and compared with 16 sex- and age-matched controls. Using a standardized transcranial magnetic stimulation protocol of the occipital cortex, we assessed the threshold stimulation intensity at which subjects just perceived phosphenes via a method of alternating course and fine-tuning of stimulator output.

There were no significant differences across groups in the proportion of subjects seeing phosphenes. However, the mean threshold at which phosphenes were reported was significantly lower in both migraine groups (migraine with aura=47%, migraine without aura=46%) than in controls (66%). Moreover, there was no significant correlation between individual phosphene threshold and the time interval to the closest migraine attack.

Our findings confirm that the occipital cortex is hyperexcitable in the migraine interictum, both in migraine with and without aura.