Differential diagnosis of visual aura in migraine and epilepsy

Visual phenomena like lightnings, disturbed contours of objects, or skotoma , can be due to ophthalmological diseases, but can also occur as symptoms g enerated by the central nervous system ("aura'') in migraine or epilepsy. A subsequent hemicrania is considered as a hallmark of migraine, but in many cases does not, allow for a certain distinction from postictal headaches i n patients with focal epilepsy. A detailed analysis of the aura does, howev er, provide sufficient information for classifying the disorder as an aura in migraine or as a. simple partial epileptic seizure in most cases. The higher degree of differentiation of visual phenomena including colour, movement, and complex visual phenomena, is characteristic of the activation of neuronal circuits during an epileptic aura. The higher speed of transsy naptic propagation of epileptic discharges and postictal inactivation cause s a more rapid time-course of the epileptic aura as compared to a migraine aura resulting from a depolarization spreading by diffusion. Clinically, th e diagnosis of epilepsy is supported by additional positive motor phenomena or by a transition into a complex partial seizure, e. g. when epileptic ac tivity spreads into a temporal lobe. Secondarily generalized seizures, howe ver, may also occur in patients with migraine. Interictal and ictal EEG recordings can be important to prove an epileptic origin, but their sensitivity is low if ictal discharges remain limited to a small brain area. In rare cases, measurements of ictal cerebral perfusion can contribute to the differential diagnosis.