A number of striking differences between generalized and focal convulsive disorders escape present physiological and anatomical explanation. We have considered as generalized epilepsies the warningless seizures of either grand or petit mal type in which a rhythmic bilaterally synchronous 3 cycle per second (cps) spike-wave pattern is recorded on the electroencephalogram (EEG) during the interictal period. In the focal category, we include the seizures with clinical or EEG evidence of localized disturbance or onset, including psychomotor epilepsy. Of particular interest is the marked difference in the EEG response to iterative peripheral stimuli displayed by patients with these two types of seizure disorder. Induction of seizure activity by flickered light tends to be characteristic of the generalized epilepsies as defined above, while subjects with focal cortical seizures rarely demonstrate photic sensitivity. Indeed, in a recent study in our laboratory,19 individuals whose clinical history and EEG's were typical of focal epilepsy usually
STEVENS JR, NAKAMURA Y, MILSTEIN V, OKUMA P, LLINAS R. Central and Peripheral Factors in Epileptic Discharge: Part II. Experimental Studies in the Cat. Arch Neurol. 1964;11(5):463–476. doi:10.1001/archneur.1964.00460230013002
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