To delineate if the change in cortical excitability persists across migraine attacks, visual evoked magnetic fields (VEF) were measured in patients with migraine without aura during the interictal (n = 26) or peri-ictal (n = 21) periods, and were compared with 30 healthy controls. The visual stimuli were checkerboard reversals with four different check sizes (15', 30', 60' and 120'). For each check size, five sequential blocks of 50 VEF responses were recorded to calculate the percentage change of the P100m amplitude in the second to the fifth blocks in comparison with the first block. At check size 120', interictal patients showed a larger amplitude increment than controls [28.1 +/- 38.3% (s.d.) vs. 8.7 +/- 21.3%] in the second block and a larger increment than peri-ictal patients in the second (28.1 +/- 38.3% vs. -3.2 +/- 19.2%), fourth (22.7 +/- 31.2% vs. -5.7 +/- 22.3%) and fifth (20.5 +/- 30.4% vs. -10.8 +/- 30.1%) blocks (P < 0.05). There was no significant difference at other check sizes or between peri-ictal patients and controls. In conclusion, there may be peri-ictal normalization of visual cortical excitability changes in migraine that is dependent on the spatial frequency of the stimuli and reflects a dynamic modulation of cortical activities.

Persistent visual aura without infarction is rare. Its pathogenic mechanism is unknown, and the response to migraine prophylactic agents varies. A systematic analysis of 29 patients (23 from the literature and six in the present report; 6M/23F, mean age 37.6 years) was carried out in terms of demographics, headache and visual symptom profiles, treatment regimens and outcomes. Patterns of visual disturbances (VDs) were re-assessed with the Visual Aura Rating Scale (VARS, score 0-10). Even though the majority of patients had headache improvement, only eight (27.6%) had complete resolution of persistent VD, without definite relevance to any specific agent. Patients with complete resolution of VD tended to have scotoma (50.0% vs. 0%; P = 0.003), unilateral/homonymous involvement (62.5% vs. 9.5%; P = 0.008), higher VARS scores (1.88 +/- 1.73 vs. 0.10 +/- 0.30; P < 0.001) and shorter duration of illness (10.0 +/- 12.9 vs. 60.2 +/- 90.9 months, P = 0.008) compared with those without. These findings remained even when the six current patients were not included for analyses. In conclusion, the prognosis of persistent VD was poor, and higher VARS scores, i.e. more typical of migraine visual aura, predicted a better outcome. For those with a potential for complete resolution, improvement would occur early in the course.

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