Abstracts

Rationale: Electrical stimulation mapping to identify essential language cortex is typically performed prior to cortical resection involving the language dominant hemisphere. Within the past decade, several studies have shown that in childhood, the number of language sites identified via ESM increases with age. This has been interpreted to reflect the establishment of language areas associated with maturation. However, beyond adolescence, the influence of age on the number and topographical distribution of language sites has not been explored. Behavioral studies of naming across the age span have shown that naming is relatively unchanged until approximately the seventh decade of life. Given the relative stability of naming ability, we hypothesized that the number and distribution of naming sites identified by ESM would also show no significant change across the adult age span, below age 70. Methods: Subjects were 49 pharmacologically refractory temporal lobe epilepsy patients (age range: 19-64 years, mean age = 35.3, SD = 10.6) who underwent ESM for language mapping prior to surgical resection for seizure control (21 intraoperative, 28 extraoperative). Naming was assessed during stimulation using both visual picture naming and auditory description naming at each site. A mean of 26 cortical sites per patient was tested (range: 15-55). Preoperative baseline naming tasks included the Boston Naming Test and the Visual and Auditory Naming tests. Pearson correlations assessed the relations between age, number of naming sites, and naming performance. Independent sample t-tests assessed differences between groups. Results: Age and number of visual naming sites were not correlated (r = -.02, P = .85); however, increasing age was significantly associated with a greater number of auditory naming sites (r = .33, P = .03). Restricting this analysis to extraoperative cases, which received more extensive mapping, the correlation between auditory naming sites and age was stronger (r =- .49, P = .01), whereas the correlation between visual naming sites and age remained nonsignificant (r = .21, P = .27). Similarly, mean number of auditory naming sites per patient was greater in patients over 30 years relative to those below age 30 (< age 30 mean = .62, SD = .96; > age 30: mean = 1.76, SD=1.5; P =.02), whereas there was no group difference for number of visual naming sites (P = .12). Importantly, there was no relation between age and total number of sites tested (r = -.09, P = .63). Spatially, older patients had significantly more auditory naming sites in the anterior temporal region and more diffuse representation of visual naming sites relative to younger patients. Conclusions: At odds with our hypothesis, these results suggest an increase in stimulation-identified auditory naming sites with increasing age. It is unlikely this increase represents the establishment of new naming areas in older adults. Rather, we speculate that language, and perhaps, auditory naming in particular, becomes more susceptible to disruption over the adult age span.