The benign occipital epilepsies of childhood: an overview of the idiopathic syndromes and of the relationship to migraine.

Benign occipital epilepsy of childhood is an idiopathic partial epilepsy syndrome with elementary visual symptomatology, frequently associated with other ictal phenomena. Seizures are usually followed by postictal headache and are often associated with interictal occipital rhythmic paroxysmal EEG activity that appears only after eye closure. In some children the ictal visual symptoms or the interictal EEG abnormalities may not be demonstrated. The clinical and/or EEG manifestations of other forms of idiopathic partial or generalized epilepsy may be found in association. Occipital spikes in non-epileptic children with defective vision, occipital slow spike-and-wave found in some patients with the Lennox-Gastaut syndrome, focal epilepsy due to occipital lesions, seizures originating in the temporal lobe secondary to an occipital abnormality, and complicated or basilar migraine must be considered in the differential diagnosis. Early-onset benign occipital epilepsy or seizure susceptibility syndrome deserves to be considered separately. It has been defined by Panayiotopoulos as consisting of brief, infrequent attacks or prolonged status epilepticus and characterized by ictal deviation of the eyes and/or head and vomiting, occurring in children usually between the ages of 3 and 7 years. Advances in molecular genetics will help decide whether these two disorders are indeed distinct. Benign occipital and benign rolandic epilepsy are commonly associated with migraine. The selective involvement of the occipital lobe in migraine has not been fully explained. The association between benign occipital epilepsy and migraine is likely related to this underlying mechanism as well. The "fixation off" phenomenon or blocking of occipital epileptic discharges by eye opening is not specific to benign occipital epilepsy of childhood and may be found in symptomatic epilepsies as well. Migraine and epilepsy are distinct disorders, both as far as their pathophysiologic mechanisms and clinical symptomatology are concerned. There is however an overlap in some patients and a causal relationship may exist in some, leading to clinically distinct migraine epilepsy syndromes. Here too, clarification of the molecular basis of migraine and of epilepsy will throw light on the nature of the relationship between the two conditions.