Neuropsychological characteristics of parkinsonian patients with lateralized motor impairment

Abstract

Parkinsonians with predominantly unilateral signs provide an interesting experimental means to evaluate if asymmetric nigro-striatal degeneration may affect neuropsychological functions. The aim of our study was to establish if the side of onset of idiopathic Parkinson's disease, right (PDR) or left (PDL), determines a selective pattern of cognitive performances. Furthermore, we verified if PDR and PDL groups show a different frequency of dementia. PDR and PDL patients with at least seven years of disease duration, matched for age, schooling, severity of extrapyramidal symptomatology and index of lateralization, were evaluated by using an extensive neuropsychological battery aimed at assessing hemispheric cognitive asymmetries. Current side of greater motor impairment was the same as the one affected at the onset of the disease. Only subtle differences in the profile of neuropsychological dysfunction emerged from the comparison of PDR and PDL subjects. Moreover, the number of parkinsonians showing dementia syndrome was the same in both groups. Our results suggest that the side of onset of motor impairment does not significantly influence the cognitive performances in PD. Subcortical anatomic and/or functional asymmetries seem to play a less important role in the intellectual functions than in motor activities.

Cognitive Differences Between Patients with Left-sided and Right-sided Parkinson’s Disease. A Review

“…Of the fourteen studies investigating verbal fluency, thirteen used the Controlled Oral Word Association Test (COWAT). Most of these studies (11/13) encountered no differences between LPD and RPD patients (Agniel et al 1991;Bentin et al 1981;Blonder et al 1989;Clair et al 1998;Finali et al 1995;Foster et al 2008;Holtgraves et al 2010;Huber et al 1989;Spicer et al 1988;Starkstein and Leiguarda 1993;Starkstein et al 1987). The two remaining studies yielded opposite results with one reporting lower performance in RPD patients (Cubo et al 2010) and one claiming that patients with a right-sided onset generated more words compared to patients with a left-sided onset (Tomer et al 1993).…”

“…Four studies investigated inhibition and all of them administered the Stroop task. Most studies reported no differences between LPD and RPD patients (Clair et al 1998;Finali et al 1995;Holtgraves et al 2010). One study disclosed a better performance for the RPD patients (Hietanen and Teräväinen 1989).…”

“…Among these, there are further differences in the cutoff-values that were applied. In six studies, the difference between the left and the right score was used (Agniel et al 1991;Cubo et al 2010;Ebersbach et al 1996;Huber et al 1992;Nys et al 2010;Riklan et al 1990), six studies used the ratio between the left-and the right-sided scores (3:1 or 2:1) (Harris et al 2003;Lee et al 2001a, b;Spicer et al 1988;Starkstein and Leiguarda 1993;Starkstein et al 1987) and five other studies used a lateralization index of the symptom severity scores on the left side and on right side (difference/sum) (Clair et al 1998;Dominey et al 1995;Finali et al 1995;Foster et al 2008;Holtgraves et al 2010). Two studies only included patients with exclusively unilateral symptoms (Hietanen and Teräväinen 1989;Huber et al 1989Huber et al , 1989, whereas most of the studies tested patients with bilateral asymmetric symptoms.…”

“…The fact that findings concerning the WCST are conflicting is probably due to the complexity of the task, assessing multiple functions at once, amongst which abstract reasoning and problem solving, mental flexibility, visual pattern recognition and sustained attention. The Trail Making Test, assessing a purer form of switching, was used in two studies (Finali et al 1995;Hietanen and Teräväinen 1989) and revealed no significant differences between LPD and RPD. One study applied the Intradimensional/extradimensional shift task, which is a decomposed version of the WCST to examine the processes involved in the WCST separately.…”

Neuropsychology, neuroimaging or motor phenotype in diagnosis of Parkinson’s disease-dementia: which matters most?

“…For instance, Cooper et al (1991) observed a significant association between right-sided motor impairment and verbal memory, visuoperceptual skills and verbal fluency impairment, while leftsided motor symptoms were not significantly related to any composite cognitive domain. Another study did not find cognitive differences according to the laterality (Finali et al 2005) while a further one found that patients with left onset performed worser than those with right onset (Ibarretxe-Bilbao et al 2009). Male gender is another wellestablished risk factor (Emre 2003a, b).…”