Dysnomia after left anterior temporal lobectomy without functional mapping: frequency and correlates

The integrity of language function after a left (dominant) anterior temporal lobectomy performed without the use of functional mapping remains controversial. Much of the controversy concerns the degree to which analyses of group data obscure the identification of surgically induced dysnomia in individual patients. This study investigated postoperative language outcome in our entire series (n = 162) of nonretarded, left hemisphere speech dominant patients with intractable nonlesional epilepsy who underwent a left (n = 85) or right (n = 77) anterior temporal lobectomy without functional mapping. A comparison of preoperative to (6 mo) postoperative performance on a standardized test of nominal speech revealed the following: 1) a statistically significant but clinically modest difference in outcome between left and right anterior temporal lobectomy groups; 2) a subgroup (7%) of left anterior temporal lobectomy patients exhibited a postoperative dysnomia (a decline in nominal speech that exceeded the worst performance in the right anterior temporal lobectomy group); and 3) a postoperative decline in nominal speech after left anterior temporal lobectomy was specifically associated with a later age at the onset of epilepsy. Within the context of group data suggesting minimal risk to language function when functional mapping is not used, a small subgroup of individuals characterized by a later onset of epilepsy can be identified who exhibit a surgically induced dysnomia after a standard left anterior temporal lobectomy. Whether these results differ from the outcome of functional mapping remains to be determined.