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Handedness and dominant side of symptoms in Parkinson’s disease

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Abstract

The aim of this retrospective study was to assess the presence of a possible association between handedness and the side of symptom dominance in 963 patients with Parkinson’s disease (PD). In only 287 patients the hand dominance was registered. Out of 254 right-handed patients, 158 (62%) had a right-side dominance of PD symptoms, while 96 patients (38%) had left-lateralized symptom dominance (p < 0.001). For the 33 left-handed subjects, 18 (55%) had left- and 15 (45%) had right-sided symptom dominance (p = 0.602). Right-handedness thus appeared to be associated with right-sided dominance of PD symptoms, while the group of left-handed patients was too small to draw conclusions from. Possible explanations are discussed.

Introduction

Parkinson’s disease (PD) is characterized by asymmetry of symptoms at the onset of disease which is generally maintained during disease progression. Assessment with Positron Emission Tomography (PET) has demonstrated a consistent relation between symptom asymmetry and lateralized cerebral function, in such a way that the dominant side of symptoms significantly correlated with reduced dopamine transporter uptake in the contralateral hemisphere. The cause of symptom lateralization in PD, however, remains to be elucidated [1].

A well-known lateralized function in normal conditions is hand dominance, which is related to asymmetry across brain systems [2]. One might speculate whether such brain asymmetry could provide a clue for a possible explanation for lateralization of PD symptoms. In that case a relation between handedness and such symptom lateralization might be expected. This issue has been addressed in a few previous studies, with varying results. Although these studies generally concerned small groups, a relation between hand dominance was suggested in some studies [3], [4], [5] but not in all [6], [7], [8]. The aim of the present retrospective study was to identify a possible association of handedness with the side of symptom dominance in PD. Moreover, we looked whether a relation could be found between gait-associated disease characteristics and the side of symptom dominance.

Section snippets

Study population

PD patients were retrospectively identified from a database of the Movement Disorders unit from the Neurology Department of the University Medical Centre Groningen. This database contained a total of 1120 patients with the diagnosis PD, seen over a period of about 9 years. After assessment of the patient files, 157 patients were excluded for reasons such as uncertainty about the diagnosis PD, adjustment of the diagnosis, too many missing data or bilateral disease onset. A group of 963 subjects

Results

The study population consisted of 561 (58.3%) males and 402 (41.7%) females. A total of 503 patients (52%) were characterized by right-sided symptom dominance while in 460 patients (48%) symptoms were dominant on the left side. The handedness was reported to be right-sided in 254 patients (26%) and left-sided in 33 (3.4%), while this parameter was unknown in 676 (70%). Right-handed PD patients had significantly more often symptoms on the right than on the left side (p < 0.001) (Table 1).

Discussion

Our results showed a significant excess of right-sided symptom dominance in right-handed patients with PD, while in the smaller group of left-handed patients no significant preference of left-sided symptoms was seen. These results provide support for previous studies that have reported such association [3], [4], [5], which remained a conflicting issue in the literature because absence of this association has been published too [6], [7], [8]. The small number of left-handed subjects in our study

Acknowledgments

No conflicts of interest are present. No funding was obtained for the present study. All authors are employs of the Universitair Medisch Centre Groningen.

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The review of this paper was entirely handled by an Associate Editor, Vincenzo Bonifati.

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