The VER as a diagnostic marker for childhood abdominal migraine. Abdominal migraine is a common childhood migraine equivalent, for which diagnostic criteria have not been defined. As in other children with migraine equivalents this leads to difficulties in diagnosis and determination of prevalence. By recording the fast wave activity (beta rhythmn) in the visual evoked response (VER) to red and white flash, the pattern stimulation, 27 out of 28 children with clinically diagnosed abdominal migraine revealed significant differences compared with normal controls, outside the attack phase. Comparisons with children diagnosed as migraine with or without aura revealed, from the VER findings of higher amplitude fast wave activity and the presence of paroxysmal sharp wave activity, that abdominal migraine appears to be a specific form of childhood migraine. We found that both clinically and electrophysiologically, abdominal migraine changes with age; older children exhibiting a shorter duration of abdominal pain during attacks, and less evidence of sharp wave activity in the VER. 