Faculty Bibliography

PURPOSE: To investigate the relation between the number and spatial distribution of language sites and specific patient-and epilepsy-related variables. METHODS: Patients with stimulation-induced reading or naming errors from anterior or inferior temporal cortex (i.e., atypical temporal language sites) were compared with those with language sites confined to Wernicke's area (WA) in the posterosuperior temporal and inferior parietal perisylvian area. In a consecutive series of 44 left hemisphere language dominant patients with complex partial seizures before left temporal lobectomy, correlations were compared between cortical language distribution and measures of cognitive function. RESULTS: Patients with atypical temporal language sites (group 1) had significantly fewer years of education that did patients with language sites in WA (group 2). Patients in group 1 had poorer verbal learning and fluency than did patients in group 2. Patients with IQ <80 were significantly more likely to have multiple sites where stimulation disrupted language than did patients with normal IQ. Number of language sites had significant negative correlations with full-scale IQ, and measures of confrontation naming, verbal fluency, and immediate verbal memory. CONCLUSIONS: Language cortex has a wider spatial distribution in epilepsy surgery patients with lower intelligence, poorer education, and worse verbal and memory skills

The phosphorylation state of the proteins, regulated by phosphatases and kinases, plays an important role in signal transduction and long-term changes in neuronal excitability. In neurons, cAMP-dependent protein kinase (PKA), protein kinase C (PKC) and calcineurin (CN) are attached to a scaffold protein, A kinase anchoring protein (AKAP), thought to anchor these three enzymes to specific sites of action. However, the localization of AKAP, and the predicted sites of linked phosphatase and kinase activities, are still unknown at the fine structural level. In the present study, we investigated the distribution of AKAP79 in the hippocampus from postmortem human brains and lobectomy samples from patients with intractable epilepsy, using preembedding immunoperoxidase and immunogold histochemical methods. AKAP79 was found in the CA1, presubicular and subicular regions, mostly in pyramidal cell dendrites, whereas pyramidal cells in the CA3, CA2 regions and dentate granule cells were negative both in postmortem and in surgical samples. In some epileptic cases, the dentate molecular layer and hilar interneurons also became immunoreactive. At the subcellular level, AKAP79 immunoreactivity was present in postsynaptic profiles near, but not attached to, the postsynaptic density of asymmetrical (presumed excitatory) synapses. We conclude that the spatial selectivity for the action of certain kinases and phosphatases regulating various ligand- and voltage-gated channels may be ensured by the selective presence of their anchoring protein, AKAP79, at the majority of glutamatergic synapses in the CA1, but not in the CA2/CA3 regions, suggesting profound differences in signal transduction and long-term synaptic plasticity between these regions of the human hippocampus.

Right hemisphere functions were examined during cortical stimulation in six patients undergoing epilepsy surgery. Two patients showed mild hemispatial neglect and constructional disability with stimulation of several sites in the inferior parietal lobule and posterior temporal lobe. Two other patients showed no disruption of visuospatial functions with stimulation of similar parietal or posterior temporal sites. Nonverbal acoustic perception of environmental sounds was not disrupted with stimulation of right superior temporal cortex in one patient, and musical abilities were not affected by right superior temporal stimulation in another patient. Nondominant hemisphere functions may be more widely distributed and less localized than linguistic functions in the dominant hemisphere

OBJECT: Because appropriate patient selection is essential for achieving successful outcomes after epilepsy surgery, the need for more robust methods of predicting postoperative seizure control has been created. Standard multivariate techniques have been only 75 to 80% accurate in this regard. Recent use of artificial intelligence techniques, including neural networks, for analyzing multivariate clinical data has been successful in predicting medical outcome. METHODS: The authors applied neural network techniques to 80 consecutive patients undergoing epilepsy surgery in whom data on demographic, seizure, operative, and clinical variables to predict postoperative seizures were collected. Neural networks could be used to predict postoperative seizures in up to 98% of cases. Student's t-tests or chi-square analysis performed on individual variables revealed that only the preoperative medication index was significantly different (p = 0.02) between the two outcome groups. Six different combinations of input variables were used to train the networks. Neural network accuracies differed in their ability to predict seizures: using all data (96%); all data minus electroencephalography concordance and operative side (93%); all data except intra- or postoperative variables such as tissue pathological category (98%); all data excluding pathological category, intelligence quotient (IQ) data, and Wada results (84%); only demographics and tissue pathological category (65%); and only IQ data (63%). CONCLUSIONS: Analysis of the results reveals that several networks that are trained with the usual accepted variables characterizing the typical evaluation of epilepsy patients can predict postoperative seizures with greater than 95% accuracy

PURPOSE: Posterior, 'Wenicke's,' language areas have a high degree of between-subject variability, as shown by electrical-stimulation mapping. We investigated the possibility of an organized structure in the distribution of posterior language areas. METHODS: Extraoperative subdural grid stimulation was performed on 67 left hemisphere-dominant patients before resective epilepsy surgery during counting, naming, and reading. Intersubject-averaged language maps were generated in which stimulation disrupted only one language function and not the others, or combinations of language functions. RESULTS: Language sites, although highly variable between subjects, were not organized randomly and appeared to be arranged into several focal, non-contiguous, higher probability 'nodes' devoted to different aspects of language processing. Speech-arrest sites were concentrated in classic Wernicke's area. Areas where stimulation induced only reading errors were found in the posterior middle temporal gyrus and the inferior parietal lobule. These regions may correspond with an orthographic input lexicon. Areas eliciting only naming errors were found in the posterior inferior temporal gyrus extending into the mid-middle temporal gyrus and may represent a visual-representation input lexicon. Sites where stimulation elicited errors in both naming and reading were more variable in location than sites devoted to only one function, extended farther anteriorly along the temporal neocortex, and may correspond with a semantic lexicon. CONCLUSIONS: The existence of high-probability nodes in posterior language cortex supports a modality-specific modular architecture and the possibility of a conserved, universal structure