Visual phenomena and headache in occipital epilepsy: a review, a systematic study and differentiation from migraine

This is a systematic-prospective study of occipital seizures with elementary visual hallucinations in 18 patients with symptomatic occipital epilepsy. Qualitative and chronological analysis showed that visual seizures usually lasted for seconds to 1-3 minutes. Three patients also had longer visual seizures of 20-150 minutes. Elementary visual hallucinations mainly consisted of coloured and small circular patterns flashing or multiplying in a temporal hemifield. Flashing lights or non-circular patterns were rare. Three patients experienced achromatic flickering lights. None of the patients had the over 4 minute, linear, zigzag, and achromatic or black and white patterns characteristic of migraine visual aura. Blurring of vision could precede visual hallucinations. Visual seizures were usually frequent, often occurring in multiple clusters daily or weekly. They usually occurred alone but they often advanced to other occipital and extra-occipital ictal symptoms. In 7 patients they progressed to temporal lobe seizure manifestations, and in 6 to motor partial seizures or ipsilateral hemiconvulsions. All but 2 had secondary generalised tonic clonic convulsions. Ictal blindness ab initio occurred in 2 and ictal, mainly orbital headache in another 2 patients. One patient had ictal vomiting as an occasional symptom. Postictal headache, often severe and indistinguishable from migraine, occurred in two thirds of the patients, even after brief visual seizures without convulsions. Despite relevant structural lesions in brain imaging, 10 patients had a normal mental and neurological state. In 8 patients, EEG was also normal or nonspecific. Misdiagnosis of visual seizures as visual aura of migraine was common and 3 patients were misdiagnosed as suffering from migraine. The differential diagnosis between migraine and the occipital epilepsies is reviewed. It is concluded that elementary visual hallucinations, blindness or both, alone or followed by headache and vomiting of symptomatic occipital epilepsy are identical to those of idiopathic occipital epilepsy. Progress to temporal lobe structures is different and consistent with symptomatic occipital lobe epilepsy. The clinical diagnosis of visual seizures is easy if individual elements of duration, colour, shape, size, location, movement, speed of development and progress are identified. They are markedly different from visual aura of migraine, although they often trigger migrainous headache, probably by activating trigeminovascular or brain stem mechanisms.