Left/right asymmetry of atrophy in semantic dementia - Behavioral-cognitive implications

Objective: To characterize presenting symptomatology in patients with semantic dementia (SD) and to investigate whether left and right temporal variants of the disease have distinct behavioral and cognitive profiles. Methods: Retrospective examination of case notes was performed in 47 consecutive referrals of patients with a clinical diagnosis of SD. Patients (and informants) were interviewed and underwent neuropsychological testing within 6 months of assessment. Patients were designated as having predominantly left (L>R; n=36) or right (R>L; n=11) temporal lobe atrophy based on MRI or CT of the brain. Results: R>L and L>R SD groups did not differ in terms of presenting age (mean 63.4+/-7.4 years), symptom duration (3.6+/-2.3 years), or Mini-Mental State Examination scores (22.1+/-6.7). The most frequently reported behavioral symptoms were food fads, irritability, depression, and preoccupation with puzzles; cognitive deficits included word-finding difficulties, reduced comprehension, difficulty with person identification, and reduced conversation. The frequency of several symptoms differed significantly between groups. The following aspects were more likely to be associated with major right temporal atrophy: social awkwardness, job loss, loss of insight, and difficulty with person identification. Word-finding difficulties and reduced comprehension were more salient features of L>R patients. Both groups showed deficits on semantic memory tests, as expected for this syndrome, but several items yielded greater impairment for L>R than R>L. Conclusions: Patients with left and right predominant SD present with distinct behavioral cognitive profiles. Characterization of these features may assist in the early and accurate diagnosis of SD.