Migraine may actually precipitate a stroke, but there is also a variant of migraine, hemiplegic migraine, where unilateral hemiparesis outlasts the headache. This is difficult if not impossible to diagnose correctly at first presentation when it must be regarded as a diagnosis of exclusion; only with recurrent, stereotypic attacks can this be suspected. Cases with alternating hemiplegia have been reported. At times this disorder has been shown to be familial.