Neurocognitive efficiency following left temporal lobectomy: standard versus limited resection.

Decreased memory and learning efficiency may follow left temporal lobectomy. Debate exists as to whether the acquired deficit is related to the size of the surgical resection. This study addresses this question by comparing changes in cognitive performance to the extent of resection of both mesial temporal structures and lateral cortex. The authors retrospectively reviewed 47 right-handed patients who underwent left temporal lobectomy for medically intractable seizures. To examine the effects of the extent of mesial resection, the patients were divided into two groups: those with resection at the anterior 1 to 2 cm of mesial structures versus those with resection greater than 2 cm. To examine the effects of the extent of lateral cortical resection, patients were again divided into two groups: those with lateral cortex resections of 4 cm or less versus those with resections greater than 4 cm. Statistical analyses showed no difference in cognitive outcome between the groups defined by the extent of mesial resection. Likewise, no difference in cognitive outcome was seen between the groups defined by the extent of lateral cortical resection. Associated data analyses did, however, reveal a negative correlation of cognitive change with patient age at seizure onset. These results showed that the neurocognitive consequences of extended mesial resections were similar to those of limited mesial resections, and that the neurocognitive consequences of extended lateral cortical resections were similar to those of limited lateral cortical resections. The risk of cognitive impairment depends more on age at seizure onset than on the extent of mesial or lateral resection.