Academic journal article Journal of Medical Speech - Language Pathology

A Tailored Approach to Language Mapping in Epilepsy Surgery: Some Preliminary Findings

Academic journal article Journal of Medical Speech - Language Pathology

A Tailored Approach to Language Mapping in Epilepsy Surgery: Some Preliminary Findings

Article excerpt

When anterior temporal lobectomy is used in the treatment of intractable temporal lobe epilepsy there is a subset of patients for whom a postoperative decline in confrontation naming persists. In some language models, Broca's and Wernicke's areas are considered two distinct areas for language production and processing. Other investigations (Damasio et al., 2004) suggest the presence of separable regions within a large cortical network that are recruited in the processing of semantic categories.

Some centers carry out cortical mapping to identify language areas prior to resection in the dominant hemisphere. Requiring the patient to produce rote speech series is commonly used during electricocortical stimulation. The purpose of this pilot project was to determine if an intraoperative protocol based on a model for separation of semantic categories would reveal similar findings during intraoperative cortical stimulation. Two subjects undergoing surgery for temporal lobe epilepsy were administered mapping protocols using traditional rote speech tasks and tasks involving confrontation naming of items from three semantic categories. In both patients, additional naming sites were identified in the temporal lobe, anterior to those found through serial speech production. Possible application of these findings is discussed as they relate to future areas of study.

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According to published estimates, epilepsy affects approximately 5 to 10 people per 1,000 in North America (Hauser & Hesdorffer, 1990). The most common form of epilepsy is of temporal lobe origin, with manifestations including simple partial seizures and complex partial seizures. With simple partial seizures, a number of symptoms may occur, reflected in taste, smell, and other psychic disturbance, without a loss of consciousness. Loss of awareness is associated with complex partial seizures, often accompanied by repetitive motoric behaviors (Wiebe et al., 2001). These seizures, arising from the mesial temporal structures--amygdala, hippocampus, and parahippocampal gyrus--are often linked to early childhood febrile seizures, which can become resistant to medical therapy by adolescence. Frequently, temporal lobe epilepsy is related to magnetic resonance imagery (MRI) hippocampal atrophy or sclerosis. A nonmesial temporal lobe epilepsy group has also been described, with an absence of mass lesions, pathology, hippocampal atrophy, or sclerosis

Anterior temporal lobectomy has become a widely used form of treatment for intractable temporal lobe epilepsy, with benefits that include seizure control and improved quality of life (Wiebe et al., 2001). Variation in surgical protocols is found across centers, with some employing a standard temporal resection (anterior 4 to 4.5 cm, of the lateral cortex, along with resection of the amygdala and a portion of the hippocampus) to remove the epiloeptogenic zone, under general anesthetic (Ojemann, 1993) and others favoring approaches involving additional intraoperative or extraoperative language mapping, in awake patients. Cortical mapping dates back to the work of Penfield (Penfield & Jasper, 1959), who discovered that stimulating the language dominant hemisphere by applying electrodes to perisylivian areas could temporarily disrupt various motor and sensory functions, including speech production. This procedure was further refined over the years, recognizing individual variability among patients in the localization of language beyond the classical areas of Broca and Wernicke and the persistence of aphasia in some patients following resection (Ojemann, 1993; Ojemann et al., 1989).

Language outcome studies, following temporal lobe surgery for epilepsy have yielded conflicting results (Bell et al., 2000; Davies et al., 1998; Hermann et al., 1991; Hermann, et al., 1994; Hermann et al., 1998; Katz et al., 1989; Lutsep et al., 1995; Sabsevitz et al., 2003; Seidenberg et al., 1998; Strauss et al. …

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