Gait speed in Parkinson disease correlates with cholinergic degeneration

Abstract

Objective: We investigated dopaminergic and cholinergic correlates of gait speed in Parkinson disease (PD) and non-PD control subjects to test the hypothesis that gait dysfunction in PD may result from multisystem degeneration.

Methods: This was a cross-sectional study. Subjects with PD but without dementia (n = 125, age 65.6 ± 7.3 years) and elderly subjects without PD (n = 32, age 66.0 ± 10.6 years) underwent [¹¹C]dihydrotetrabenazine dopaminergic and [(11)C]methyl-4-piperidinyl propionate acetylcholinesterase PET imaging, and cognitive and clinical testing, including an 8.5-m walk in the dopaminergic "off" state. The fifth percentile of cortical cholinergic activity in the elderly without PD was used to define normal-range activity in the subjects with PD.

Results: Normal-range cortical cholinergic activity was present in 87 subjects with PD (69.6%). Analysis of covariance using gait speed as the dependent variable demonstrated a significant model (F = 6.70, p < 0.0001) with a significant group effect (F = 3.36, p = 0.037) and significant slower gait speed in the low cholinergic PD subgroup (0.97 ± 0.22 m/s) with no significant difference between the normal-range cholinergic PD subgroup (1.12 ± 0.20 m/s) and control subjects (1.17 ± 0.18 m/s). Covariate effects were significant for cognition (F = 6.58, p = 0.011), but not for striatal dopaminergic innervation, sex, or age.

Conclusion: Comorbid cortical cholinergic denervation is a more robust marker of slowing of gait in PD than nigrostriatal denervation alone. Gait speed is not significantly slower than normal in subjects with PD with relatively isolated nigrostriatal denervation.

Figures

Figure 1. Distribution of cortical cholinergic innervation in the different groups

Group scatter plot of distribution of cortical acetylcholinesterase activity (k3 hydrolysis rate, min−1) in non–Parkinson disease control (Non-PD), relatively isolated dopamine (Low DA PD), and combined DA and acetylcholine (Low DA & Low ACH PD) degeneration PD groups.

Figure 2. Distribution of nigrostriatal dopaminergic innervation in the different groups

Group scatter plot of distribution of striatal vesicular monoamine type 2 distribution volume ratio in non–Parkinson disease control (Non-PD), relatively isolated dopamine (Low DA PD), and combined DA and acetylcholine (Low DA & Low ACH PD) degeneration PD groups. Although 7 subjects with PD had average striatal binding values in the low normal range, these subjects had evidence of more posterior putaminal dopaminergic denervation patterns consistent with the diagnosis of PD.