Distribution of Auditory and Visual Naming Sites In Patients With and Without Temporal Lobe Lesions
Shearwood McClelland III M.D.1, Marla J. Hamberger Ph.D.1, Guy M. McKhann II M.D.2, Robert R. Goodman M.D., Ph.D.2
Departments of 1Neurology and 2Neurological Surgery, Columbia University, College of Physicians and Surgeons, New York, NY
Previous work has shown a modality-based topographic distinction in naming sites in the lateral temporal region. Specifically, anterior temporal stimulation tended to disrupt only auditory naming, whereas posterior temporal stimulation disrupted both auditory and visual naming. Most patients in these studies were nonlesional; thus, it is unclear whether space-occupying lesions might alter this configuration. As structural lesions can displace functional areas of cortex, we compared the topographical distribution of auditory and visual naming sites in patients with and without temporal lobe lesions.
Subjects were 25 nonlesional TLE patients (mean age = 35.2; 13 with mesial temporal sclerosis) and 21 lesional patients (mean age = 33.0; 14 temporal tumors, 5 cavernous malformations, and 2 arteriovenous malformations; 9 patients had epilepsy) who underwent cortical language mapping utilizing visual and auditory naming tasks. The superior temporal gyrus (STG) and middle temporal gyrus (MTG) were reliably mapped in all subjects. A mean of 20.5 naming sites (range = 5-46) was tested per patient. The proportion of auditory and visual naming sites in the STG versus the MTG was compared in lesional and nonlesional patients using Fishers exact test or Chi-square analysis depending on cell sizes. T tests were used for comparisons of demographic and patient related data.
There was a significant difference in positive naming sites found between groups, as 23/25 nonlesional patients had at least one positive naming site, compared to only 11/21 lesional patients (p = .005). Although fewer sites overall were identified in the lesional compared to the nonlesional group, the pattern of auditory naming sites anterior to visual/dual auditory-visual sites was similar in both groups. However, the distribution of positive naming sites on the STG and MTG, regardless of modality, differed between groups. In the nonlesional group, 24 sites were found on the STG and 22 sites were found on the MTG, whereas in the lesional group, 25 sites were found on the STG and only 3 sites were found on the MTG (p = .001). Further analyses indicated that these results were not influenced by intra vs. extraoperative mapping, a diagnosis of epilepsy, or overall number of sites tested.
These results suggest that auditory naming sites are likely to be anterior to visual/dual sites, regardless of the particular temporal lobe pathology. However, patients with temporal lobe lesions might be less likely to have positive naming sites identified overall, and might also be less likely to have positive naming sites on the MTG. This pattern might reflect reorganization of language in response to a space-occupying lesion.
Cortical Mapping Surgery, Temporal Lobe Epilepsy, Temporal Tumors, Cavernous Malformations, Stimulation