Arm Swing while Walking and Running: A New Clinical Feature to Separate Parkinson's Disease from Functional Parkinsonism.

BACKGROUND: Functional parkinsonism is an important differential diagnosis of Parkinson's disease (PD). Based on anecdotal experience, we hypothesized that arm swing while walking and running could differentiate these two conditions, but this assumption has not been previously explored systematically. OBJECTIVES: To examine differences in arm swing while walking and running between patients with PD and functional parkinsonism. METHODS: We analyzed blinded video assessments of arm swing and other gait parameters in patients with asymmetrical PD (n = 81) and functional parkinsonism (n = 8) while walking and running. The groups were matched for age, sex and disease duration. RESULTS: In contrast to those with PD, patients with functional parkinsonism (i) were more likely to have a marked asymmetry in arm swing while walking (5/8 vs. 25/81; P = 0.06), (ii) were less likely to improve arm swing while running with full effort (3/8 vs. 72/81; P < 0.001) and (iii) demonstrated normal passive arm swing even when asymmetry of arm swing was marked during running/walking (6/6 vs. 9/33; P = 0.002). CONCLUSIONS: Assessment of arm swing while walking and running and passive arm swing could be important differentiating clinical features between functional parkinsonism and PD.

Movement Disorders and Renal Diseases.

Movement disorders often emerge from the interplay of complex pathophysiological processes involving the kidneys and the nervous system. Tremor, myoclonus, ataxia, chorea, and parkinsonism can occur in the context of renal dysfunction (azotemia and electrolyte abnormalities) or they can be part of complications of its management (dialysis and renal transplantation). On the other hand, myoglobinuria from rhabdomyolysis in status dystonicus and certain drugs used in the management of movement disorders can cause nephrotoxicity. Distinct from these well-recognized associations, it is important to appreciate that there are several inherited and acquired disorders in which movement abnormalities do not occur as a consequence of renal dysfunction or vice versa but are manifestations of common pathophysiological processes affecting the nervous system and the kidneys. These disorders are the emphasis of this review. Increasing awareness of these conditions among neurologists may help them to identify renal involvement earlier, take timely intervention by anticipating complications and focus on therapies targeting common mechanisms in addition to symptomatic management of movement disorders. Recognition of renal impairment in a patient with complex neurological presentation may narrow down the differentials and aid in reaching a definite diagnosis.