There were 16 men and 20 women who met imaging-supported criteria for SD (). Most SD patients had asymmetric anterior temporal involvement. On MRI analysis, there were 21 with left-sided predominance and 11 with right-sided predominance. An additional 4 were not sufficiently asymmetric for this study, and are described but not compared with the left-sided and right-sided predominant groups. There were no differences between the males and females on the MRI rating scores. There were no correlations between years of education, Mini-Mental State Examination scores, age of onset or age of presentation, and the MRI rating scores.
In comparing the right and left-sided predominant patients, there were no group differences in age, sex, duration of illness, or activities of daily living on the FTLD-modified Clinical Dementia Rating (). All patients, regardless of temporal lobe asymmetry, had semantic anomia, but, on the face identification test, only 4 (19.0%) of the left-predominant patients had 3 or fewer correct facial identifications, compared with all 11 (100%) of the right-predominant patients (χ2=15.89, P<0.001).
The results of the naming tests also showed laterality differences. On the mBNT, the left-predominant patients were significantly more impaired in total scores and inanimate naming than the right-predominant patients (). In contrast, the right-predominant patients had lower mean animate naming scores, and significantly greater animate-inanimate differences, than the left-predominant patients, consistent with disproportionate difficulty with animate naming. Similarly, the left-predominant patients had worse letter, but not category (animal), fluency. Only 10 (47.6%) of the left-predominant patients missed all 5 of the “animate” items, compared with 8 (72.7%) of the right-predominant patients. When the single plant item (ie, cactus), was excluded, 13 (61.9%) of the left-predominant patients missed all 4 of the animal items, compared with all 11 (100%) of the right-predominant patients (χ2=3.74, P=0.05). Floor effects in animate naming were unlikely to explain the smaller animate-inanimate difference scores for the left-predominant patients as their animate naming was larger than for the right-predominant patients.
This study further compared the responses with semantic knowledge for items and the word recognition portion of the mBNT (). Semantic knowledge was significantly better than word recognition for the left-predominant group (t=2.49, P<0.05), but not for the right-predominant group. Within the left-predominant group, semantic knowledge for both animate and inanimate items was significantly better than word recognition (animate: t=4.84, P<0.001; inanimate: t=3.20, P<0.01). Within the right-predominant group, semantic knowledge was not significantly better than word recognition for either the animate or the inanimate items.
An evaluation of word frequency of the animate compared with the inanimate words indicated much greater frequency of the inanimate items (www.americancorpus.org
). Consequently, the 2 patient groups were compared on a subgroup of words matched for raw word frequencies [beaver (1654) with comb (1725); unicorn (383) with stethoscope (417); and octopus (592) with hammock (771)]. This subgroup comparison found no significant differences between left and right-predominant groups on the 3 animate words [0.43 (0.81) vs. 0.18 (0.40)], respectively; however, the inanimate word difference persisted [0.62 (0.86) vs. 1.45 (1.13), t
<0.05]. There were no animate-inanimate differences in the left-predominant group, but the right-predominant group had significantly worse animate compared with inanimate naming (t
Individual responses to the misnamed animal items were compiled for the right-predominant SD patients. Examples of responses to the Octopus item were: “one of those funny animals,” “a bug on the beach,” “a ghost” (described by 2 patients), “not a dog,” and “a bunch of extra hands.” Examples of responses to the Beaver item were: “some kind of animal,” “something that can bite you,” “a rat,” “a little animal with a tail,” “a giraffe,” “a beetle,” and “a wild thing.” Examples of responses to the Unicorn item were: “a halloween horse,” “a dog,” “some sort of animal,” and “a cat.” Examples of responses to the Sphinx item were: “a person’s face” (described by 2 patients), “an animal with a human person,” and “a dog.” Among these right-predominant patients, one mistook stuffed animals for living animal, and another, a rancher, could not tell his ranch animals apart.