Visual field effects of classical migraine.

Although classical migraine is known to produce lateralized sensory disturbances (e.g., visual "fortification" structures), its effect on higher order processes is unknown. Here four lateralized visual tasks were repeatedly presented to a single subject (the author) over a 2 1/2-year span, during both classical migraine attacks and headache-free periods. Attacks varied as to inferred hemispheric locus. All four tasks ("words," "typing," "bar graphs," and "locations") produced significant or marginally significant visual field (VF) by condition interactions, results generally consistent with a phasic impairment of function in the migrainous hemisphere. A content analysis of notes made during the attacks suggests that among other symptoms, alphabetic indistinctiveness and spatial disturbances are characteristics of left and right hemisphere attacks, respectively. Aspects of the results argue against any major influence of demand characteristics.