Objective: Our objective was to study the long-term prognosis of sporadic hemiplegic migraine (SHM).
Methods: We performed a longitudinal follow-up study in 18 patients who were diagnosed with SHM between 1993 and 1996. Follow-up time between the first and second survey ranged from nine to 14 years. These patients were included as part of a genetic study in which we systematically analysed the role of the three known familial hemiplegic migraine (FHM) genes.
Results: In 12 out of 18 patients the clinical diagnosis was unchanged. In two of the six remaining patients the attacks were no longer associated with hemiplegia; one of them had an ATP1A2 gene mutation (E120A). In the four other patients, the diagnosis changed into FHM, because a family member had developed hemiplegic migraine since the initial diagnosis was made. In two of the four patients a mutation was demonstrated (CACNA1A [R583Q] and ATP1A2 [R834X]).
Conclusion: This study shows that the diagnosis of SHM changes into FHM in a considerable percentage of patients (22% [4 of 18]), almost a decade after the initial diagnosis. This indicates that a careful follow-up of SHM patients and their families is advisable for optimal care and counseling. Diagnostic screening of FHM genes in SHM patients can be of value. Our genetic and clinical follow-up studies reinforce the evidence that FHM and SHM are part of the same spectrum of migraine.