Neuropsychologic sequelae of temporal lobe epilepsy and anterior temporal lobectomy

Patients with temporal lobe epilepsy (TLE) frequently have memory complaints, and studies of patients with temporal lobectomy (TL) have become classic for their demonstration of memory problems due to the focal damage. Nevertheless, it has been suggested that these apparent memory problems are not due to memory at all, but instead to concomitant language deficits (Mayeux et al., 1981). The relationship between language dysfunction and memory performance has been difficult to disentangle in prior studies, partly because few such studies have been prospective, and because standardized language testing has not been performed routinely. In the current study, a total of 78 patients undergoing temporal lobectomy (38 left, 40 right) were studied prospectively and longitudinally. Resections were typically anterior temporal lobectomy with variable degrees of hippocampal resection. Neuropsychologic testing was performed preoperatively, at one week (early), and at 6-12 months (late) postoperatively. The neuropsychologic battery included standardized tests of language (Boston Naming Test) and verbal learning and memory (Logical Memory subtest, Rey Auditory Verbal Learning Test or RAVLT). Results can be summarized as follows: Preoperatively, level of language functioning did affect Logical Memory and RAVLT performance, supporting the theory that baseline language deficits are responsible for the memory complaints of TLE patients. Immediately postoperatively, dominant (left) TL patients had declines (as predicted) on the language, verbal learning and memory measures. In the late postoperative period, the cognitive performance of both the dominant and the non-dominant surgical groups returned to baseline levels. For dominant-sided resections, the impairment in the immediate postoperative period in Logical Memory could be attributed to temporary language dysfunction. However, the immediate postoperative impairment in RAVLT performance seems to reflect a true underlying deficit in verbal learning. The finding that language dysfunction affects Logical Memory performance to a greater degree than RAVLT performance has broader implications for the procedures used to measure memory in other language-disordered populations. The fact that impairments in the immediate postoperative period resolved (on the average) by long-term followup is useful outcome information for patients considering TL resection.