Qualitative neuropsychological performance characteristics in frontotemporal dementia and Alzheimer's disease.
BACKGROUND
Frontotemporal dementia (FTD) and Alzheimer's disease are clinically distinct disorders, yet neuropsychological studies have had variable success in distinguishing them. A possible reason is that studies typically rely on overall accuracy scores, which may obscure differences in reasons for failure.


OBJECTIVE
To explore the hypothesis that analysis of qualitative performance characteristics and error types, in addition to overall numerical scores, would enhance the neuropsychological distinction between FTD and Alzheimer's disease.


METHODS
38 patients with FTD and 73 with Alzheimer's disease underwent assessment of language, visuospatial abilities, memory, and executive function, using a neuropsychological screening instrument and standard neuropsychological tests. In each of these cognitive domains, performance characteristics and error types were documented, in addition to numerical scores on tests.


RESULTS
Whereas comparison of neuropsychological test scores revealed some group differences, these did not occur consistently across tests within cognitive domains. However, analysis of performance characteristics and error types revealed qualitative differences between the two groups. In particular, FTD patients displayed features associated with frontal lobe dysfunction, such as concrete thought, perseveration, confabulation, and poor organisation, which disrupted performance across the range of neuropsychological tests.


CONCLUSIONS
Numerical scores on neuropsychological tests alone are of limited value in differentiating FTD and Alzheimer's disease, but performance characteristics and error types enhance the distinction between the two disorders. FTD is associated with a profound behavioural syndrome that affects performance on cognitive assessment, obscuring group differences. Qualitative information should be included in neuropsychological research and clinical assessments.
Thompson
J C
JC
Cerebral Function Unit, Greater Manchester Neuroscience Centre, Hope Hospital, Salford M6 8HD, UK. jennifer.thompson@manchester.ac.uk
Stopford
C L
CL
Snowden
J S
JS
Neary
D
D
D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000523:psychology; D003704:Dementia / Q000175:diagnosis* / Q000523:psychology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis / Q000523:psychology; D008609:Mental Status Schedule; D008875:Middle Aged; D009460:Neurologic Examination / Q000706:statistics & numerical data; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D011594:Psychometrics / Q000706:statistics & numerical data; D015203:Reproducibility of Results