[Rare and atypical forms of migraine]

The rare forms of migraine should be studied so that they can be recognized, thereby avoiding diagnostic errors and unnecessary complementary investigations. These rare forms can be divided into three categories: 1) atypical auras, characterized by the following: their semiology (visual or sensory illusions or hallucinations); their manner of onset (sudden onset of aura, with development of migraine in under four minutes); their duration (aura prolonged for between 60 minutes and seven days); aura with absence of accompanying cephalgia. This form of migraine could be confused with a case of partial epilepsy or AIT and raises a problem of differential diagnosis requiring an etiological investigation to ensure correct diagnosis; 2) clinical forms which are for the most part recognized by the International Headache Society's (IHS) classification, i.e., basilar artery migraine, familial hemiplegic migraine, ophthalmoplegic migraine and the rare occurrence of retinal migraine. Confusional migraine, a disorder which is mainly encountered in childhood, has not been categorized by the IHS but may be part of the symptomatology of the above-described forms; and 3) secondary migraines, in which a triggering mechanism causes migraine attacks to appear in a subject who was not previously affected by this disorder. This category covers post-traumatic migraine, migraine of cervical origin, the co-morbidity of migraine and epileptic seizures, and rare cases of symptomatic migraine which are indicative of underlying general disease or an intracranial lesion, i.e., a tumor or arteriovenous malformation.