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Visuospatial dysfunction in Alzheimer's disease and behavioural variant frontotemporal dementia
Shirin Salimi1, Muireann Irish2, David Foxe2
1Faculty of Medicine, University of New South Wales, Sydney, Australia.
Journal of the Neurological Sciences
|May 24, 2019
Summary
Visuospatial tests can help differentiate Alzheimer's disease (AD) from behavioural variant frontotemporal dementia (bvFTD), but only when accounting for disease severity. AD patients showed greater visuospatial deficits than bvFTD patients, suggesting targeted tests are needed for accurate diagnosis.
Area of Science:
- Neuroscience
- Cognitive Neurology
- Dementia Research
Background:
- Alzheimer's disease (AD) is often misdiagnosed due to overlapping symptoms with other dementias, particularly behavioural variant frontotemporal dementia (bvFTD).
- Visuospatial abilities, linked to parietal lobe function, are affected early in AD and may serve as diagnostic markers.
- Distinguishing AD from bvFTD is clinically challenging, necessitating improved diagnostic tools.
Purpose of the Study:
- To investigate the utility of visuospatial tests in differentiating AD from bvFTD.
- To determine if visuospatial performance differs between AD and bvFTD patients, considering disease severity.
Main Methods:
- Evaluated visuospatial abilities using the Addenbrooke's Cognitive Examination (ACE) visuospatial subtask, Rey-Osterrieth Complex Figure (RCF) task, and Visual Object and Space Perception (VOSP) battery.
- Assessed 55 AD patients, 51 bvFTD patients, and 54 healthy Controls.
- Conducted subgroup analysis using Pittsburgh Compound B positron emission tomography (PiB-PET) data to control for disease severity.
Main Results:
- Both AD and bvFTD patients exhibited visuospatial impairments compared to Controls.
- AD patients performed significantly worse than bvFTD patients on drawing tasks (ACE pentagons/loops copy, cube copy, RCF scores) and spatial orientation tasks (VOSP cube analysis) after controlling for disease severity.
- Visuospatial measures alone showed limited diagnostic power without considering disease severity.
Conclusions:
- Visuospatial function is disproportionately impaired in AD compared to bvFTD when disease severity is accounted for.
- Current visuospatial tests have limited ability to distinguish AD from bvFTD without adjustments for disease severity.
- Development of targeted visuospatial measures is crucial for improving the differential diagnosis of AD and bvFTD.