Lateralization and Intrahemispheric Localization of Language and Memory During Surgical Therapy of Epilepsy

Abstract

The indications for resections for medically intractable epilepsy include not only the identification of an epileptic focus, but also that the focus be in what Penfield called “dispensible” brain (Penfield and Jasper 1954), that is brain the removal of which is unlikely to lead to a new functional deficit. In practice, this generally means that the focus is not in areas essential for language, that the homologous area of the opposite hemisphere is functionally in-tact, and if the focus is in Rolandic cortex, the patient is willing to accept a sensorimotor deficit, or already has one. For the most common of the resections for epilepsy, in temporal lobe, the functionally essential areas that must be avoided are those for language and recent verbal memory. Areas essential for language provide a posterior limit to temporal lobectomy in the dominant hemisphere. Substantial recent verbal memory deficits have been present in several series of dominant hemisphere temporal lobectomies (Novelly et al. 1984; Rausch and Crandall 1982); indeed it has been suggested that this operation should not be considered for patients whose occupations depend on facile memory (Delgado-Escueta et al. 1983). This chapter reviews the organization of language and memory in the human brain, with particular emphasis on organization in temporal lobe. The techniques used by the author’s group for identifying areas essential for language and memory in individual patients are then discussed.

This study was supported by NIH grants 21724, 17111, and 20482.