NEUROPSYCHOLOGICAL CONSEQUENCES OF EPILEPSY SURGERY IN FRONTAL-LOBE EPILEPSY

The present study investigated the effect of frontal lobe surgery on ' 'cognitive functions'', which have previously been shown to be discrim inative in the evaluation of non-resected patients with frontal lobe e pilepsy (FLE). The cognitive outcome was evaluated with particular con sideration of the side (left/right), the site (lateral, orbital, mesia l, premotor/SMA), the type of surgery (resections vs. resections plus multiple subpial transections; MST), and seizure outcome. The evaluati on is based on 33 patients with left (n = 17) or right (n = 16) fronta l surgery. Forty-five patients who underwent successful left (n = 21) or right (n = 24) temporal lobectomy served as controls. The neuropsyc hological examination covered speed/attention, motor sequencing/coordi nation, response maintenance/inhibition, short-term memory, and langua ge. With the exception of short-term memory, the chosen tests were dis criminative in determining preoperative frontal lobe dysfunctions but they did not differentiate patients with a different lateralization or localization of the frontal focus. At the 3 month follow-up examinati on, patients with temporal lobectomy had improved frontal functions, w hereas patients with frontal lobe surgery showed a mild deterioration. Within the frontally resected group, completely seizure-free patients had significantly improved short-term memory. Further consideration o f the side, site and the type of the frontal resection indicated that patients with premotor/SMA surgery and patients with precentral/centra l MST had additional impairment after surgery. Premotor/SMA resections led to a deterioration in response maintenance/inhibition and if perf ormed left sided also to deteriorated language functions. The latter i mpairment could be clearly related to transient aphasia directly after surgery. Irrespective of pareses observed immediately after surgery, patients with MSTs of the precentral/central areas displayed additiona l problems in motor coordination at the follow-up examination. In this group the seizure outcome was also less favourable. In summing up, fr ontal lobe surgery does not cause any considerable additional impairme nt in the short-term followup. However, caution is recommended when su rgery or MST affect functional relevant cortex (here the prefrontal/SM A and precentral/central area). Finally, a release of functions associ ated with frontal areas not affected by surgery is suggested, when sei zures are successfully controlled by surgery. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.