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ARTICLES: C.G. Ballard, D. Aarsland, I. McKeith, J. O’Brien, A. Gray, F. Cormack, D. Burn, T. Cassidy, R. Starfeldt, J.-P. Larsen, R. Brown, and M. Tovee Fluctuations in attention: PD dementia vs DLB with parkinsonism Neurology 2002; 59: 1714-1720 [Abstract] [Full text] [PDF]

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Fluctuations in attention: PD dementia vs DLB with parkinsonism

Olivier S Godefroy, Martine Roussel-Pieronne, Annie Routier, and Alain Rosa   (15 January 2003)

Fluctuations in attention: PD dementia vs DLB with parkinsonism 15 January 2003
Olivier S Godefroy, MD, PhD University Hospital, Amiens, France, Martine Roussel-Pieronne, Annie Routier, and Alain Rosa Send Correspondence to journal: Re: Fluctuations in attention: PD dementia vs DLB with parkinsonism godefroy.olivier{at}chu-amiens.fr Olivier S Godefroy, et al.	Ballard et al [1] reported an interesting study showing a similar pattern of attentional deficits in patients with PD dementia and dementia with Lewy bodies, so called ‘parkinsonian dementias’. Using simple (SRT) and Choice (CRT) Reaction Time tests, they showed that both groups were slower, with a disproportionate slowing on CRT (assessed with the SRT-CRT difference), and that their CRTs were more variable (indexed by the individual CRT standard deviation). This pattern seemed different than that of AD and PD without dementia. However, it remains unclear whether these attentional deficits were really specific to ‘parkinsonian dementias’and therefore, if they may improve our diagnosis accuracy. First, the interpretation of SRT-CRT difference in terms of cognitive latency ensures that errors on CRT tests did not differ accross groups [2]. This analysis has probably been performed but does not seem to be reported. Second, the additional slowing on CRT test was assessed using the SRT-CRT difference. Since the SRT-CRT difference is usually correlated to the overall RT slowing [3], its analysis requires the use of a transformation (usually a logarithmic transformation). The present study only provides the coefficient of variation (that is presumably used as transformation) for two groups (PD dementia and dementia with Lewy bodies). Was the additional slowing of AD patients on CRT test significantly higher than that of controls using an appropriate transformation? Third, the interpretation of RT variability in terms of attentional fluctuation implies that errors did not differ across groups, otherwise fluctuating RTs may be due to difficulty in performing the task [4]. Again, this analysis does not seem to be reported. These informations seem to be critical to determine whether these RT impairments are specific to vs more severe in patients combining dementia with movement disorders. The finding of a specific attentional deficit would be very useful to improve the diagnosis of dementia with Lewy bodies. In clinical practice this is a common difficulty especially in patients with some degree of cognitive fluctuation reported by caregivers. References 1.Ballard CG, Aarsland D, McKeith I et al. Fluctuations in attention. PD Dementia vs DLB with parkinsonism. Neurology 2002; 59: 1714-1720. 2.Godefroy O, Rousseaux M. Binary choice performance in patients with prefrontal or posterior brain damage. A relative judgement theory analysis. Neuropsychologia 1996; 34: 1029-1038. 3.Luce DR. Response times. Their role in inferring elementary mental organization. Oxford: Oxford University Press, 1986. 4.Godefroy O, Lamy-Lhullier C, Rousseaux M. SRT lengthening: role of an alertness deficit in frontal damaged patients. Neuropsychologia 2002; 40: 2234–2241.