The temporal variant of frontotemporal dementia

Frontotemporal dementia is a dementia syndrome with diverse clinical characteristics. Based upon clinical parameters and single photon emission computed tomography, we identified 47 frontotemporal dementia subjects. In 10 of these 47 the primary site of brain dysfunction was anterior temporal and orbital-frontal with other frontal regions relatively spared. In this temporal lobe variant (TLV) of frontotemporal dementia, five of the subjects had more severe left-sided, and five had more right-sided, hypoperfusion. The clinical, neuropsychological and neuropsychiatric features of predominantly left-sided (LTLV) and right-sided (RTLV) TLV subjects are discussed and contrasted with more frontal presentations of frontotemporal dementia. In LTLV, aphasia was usually the first and most severe clinical abnormality RTLV patients presented with behavioural disorders characterized by irritability, impulsiveness, bizarre alterations in dress, limited and fixed ideas, decreased facial expression and increased visual alertness. These findings suggest that: (i) frontotemporal dementia is clinically heterogeneous with bitemporal and inferior frontal lobe dysfunction contributing to the clinical presentation; (ii) behavioural disturbance and aphasia are the most prominent features of predominantly temporal subtypes of frontotemporal dementia; (iii) the right and left anterior temporal regions may mediate different behavioural functions. The results of this study suggests that TLV offers a valuable source of information concerning the behavioural disorders seen with combined anterior temporal and inferior frontal lobe dysfunction.