Hypothesis: the classification of epileptic seizures according to systems of the CNS.

Several comprehensive classifications of the epilepsies and epileptic syndromes have been proposed and the purpose of the last one (1985) was to supplement the International Classification of Epileptic Seizures as accepted by the General Assembly of the International League Against Epilepsy in 1981. These efforts represent a major contribution to a difficult problem, which must be continued as further scientific advances permit. Categorization according to clinical seizure type is a logical approach, inasmuch as response to antiepileptic medication depends more on seizure type than on etiological or other factors. A limitation of this approach, however, has arisen as a result of the Commission's failure to relate clinical seizure types to the underlying neurophysiology that mediates them. This has resulted in the categorization of absence as a generalized form of seizure along with generalized tonic-clonic seizures (GTCS). On the other hand, temporal lobe seizures (including automatisms) have been categorized as a complex form of partial seizures, which emphasizes their focal origin. It is the belief of the authors that a further clarification might be achieved, if a differentiation of seizure types is made with respect to the underlying CNS circuitry which mediates the sustained discharge that determines the clinical manifestations of each type. Focal origins, while significant, assume a secondary importance, since they do not explain the sustained discharge that mediates clinical seizure types, except in the case of elementary partial seizures (EPS) that remain discretely localized. In contradistinction to GTCS that essentially involve the entire CNS, absence and complex partial seizures (CPS) should be categorized as limited forms of seizures, mediated by bilateral, regional systems.(ABSTRACT TRUNCATED AT 250 WORDS)

A neurophysiological basis of developmental dyslexia.

Recent advances in the understanding of the asymmetrical functions of the cerebral hemispheres provide new insight to the mechanisms underlying the developmental language disorders. It is probable that learning to read depends in part upon the ability to establish an association between a seen object (customarily perceived within the right hemisphere) and a verbal symbol (mediated by the left). It is possible that as the reading skill develops, verbal symbol recognition may also become a left hemisphere function. A complex interaction between the two developing hemispheres is involved. A clue to the nature of this problem is that developmental dyslexia is six times more common in boys than in girls. Studies defining differences in cerebral dominance in boys and girls will be reviewed in this context.