Objective: To evaluate the prevalence and clinical features of transient visual disturbances (TVDs) during migraine without aura (MO) attacks and to point out any similarities with the disturbances listed among the diagnostic criteria of the International Headache Society (IHS) classification for migraine with aura (MA).
Methods: We studied a sample of 191 patients (145 women and 46 men) with MO and no other associated forms of primary headache who had been referred to the University of Parma Headache Centre between December 1, 1999 and December 1, 2000.
Results: A total of 165 patients reported that they had never experienced TVDs during their MO attacks. In the remaining 26 patients (19 women and 7 men), MO attacks were at times accompanied by TVDs, which were present in over 30% of MO attacks in 65.4% of patients. In about 60% of cases, TVDs lasted less than half a minute. TVDs consisted of phosphenes in most patients, general blurring of vision in about one-fourth, and scintillating scotomas in 15%. In 73% of cases, TVDs occurred during the headache phase, whereas in the remainder they preceded it. Strict application of the IHS diagnostic criteria would have led to a diagnosis of MA in 12 cases, corresponding to 46% of our MO patients with TVDs and to 6.3% of all patients with an established clinical diagnosis of MO.
Conclusion: The results of our study suggest that current IHS diagnostic criteria for MA may lead to an overestimation of MA cases.