Multiple system atrophy (MSA) is a term used to describe a progressive neurological condition incorporating a parkinsonian syndrome (striatonigral degeneration), often accompanied by autonomic failure (Shy-Drager syndrome) or cerebellar and/or pyramidal signs (olivopontocerebellar atrophy— OPCA) (179,180).
Cognitive deterioration is not generally considered to be an integral feature of MSA (181). Indeed, lack of dementia throughout the course of the disease has been proposed as a feature that might help to differentiate between MSA and PD premortem (182).
However, routine neuropsychological assessment often reveals multiple cognitive deficits suggesting a prominent involvement of the frontal lobe (183). MSA patients perform normally on tasks of spatial and pattern recognition, which are sensitive to deficits in patients with AD and medicated PD (183,184). On the contrary, Robbins et al. (183) demonstrated that MSA patients are impaired in comparison with matched controls on test of visual memory and learning but in specific and unusual ways. Thus on a matching-to-sample test they were significantly impaired at the simultaneous stage, when no memory was involved, but showed normal delayed matching performance. This particular pattern of deficit is distinct from that reported in PD patients (184). Moreover, on the test of visual learning, unlike PD patients (184), the MSA subjects performed surprisingly well at the more difficult levels of the task but were inefficient at the early stages.
Taken together, this pattern of performance is suggestive of problems in attention and orientation rather than of primary visual learning or memory deficits. Visuospatial contrast thresholds are also unimpaired in MSA, unlike PD patients, who normally exhibit a reduction in contrast sensitivity (185). This finding suggests that reduced contrast sensitivity is related to a dopaminergic pathology, possibly at the level of retinal amacrine cells, which might be affected in PD (186-188) but not in MSA (185).
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