Unilaterality of headache in classic migraine

The localization of a headache is a matter of importance for the diagnosis. Migraine is considered to be a unilateral headache. There is, however, only limited information available on the constancy of the unilaterality: how frequently is the pain locked to one side? This aspect is of importance in the differential diagnosis vs. cervicogenic headache, where the pain persistently seems to occur on the one side. In the present study, 31 cases (26F, 5M with a mean age of 40 years; range: 17-63) with a diagnosis of classic migraine were questioned with regard to laterality of headache at the first consultation. A unilaterality as such was present in 42%; unilaterality alternated with bilaterality in 42% of the cases; unilaterality in some form was therefore found in 84% of the cases. In classic migraine, unilaterality thus seems to outweigh bilaterality. In every case of unilaterality there was a sideshift. A side-locked unilaterality thus seems to be a rare phenomenon in classic migraine. These patients were followed-up after between 3 and 9 years; they then filled in a questionnaire (response rate: 81%). The consistency between the two sets of information in the responders was good. Only one case (possibly two) showed a side-locked unilaterality at the time of the questionnaire.