The effects of dopaminergic medication and task load on trembling and akinetic freezing of gait in Parkinson's disease.

Abstract

Background: In people with Parkinson's disease (PD), freezing of gait (FOG) can manifest as an absence of leg movement (akinetic) or a presence of high-frequency leg trembling. FOG is triggered most often during turning or dual-tasking when OFF-medication, but it is unclear whether the same holds true for akinetic and trembling FOG.

Objectives: To investigate the effects of dopaminergic medication and cognitive and motor tasks on trembling and akinetic FOG.

Method: Sixty-three PD patients with daily FOG performed a home-based FOG-provoking protocol OFF and ON-dopaminergic medication. FOG was video-annotated based on pre-specified definitions. We compared the % time in trembling and in akinetic FOG between OFF and ON. We also analyzed these outcomes during various motor tasks and with- and without a cognitive dual task. To identify subgroups, an exploratory k-means cluster analysis was performed.

Results: Trembling and akinetic FOG co-occurred in most patients (82.5%), although trembling was observed most frequently. Both manifestations were ameliorated by medication, but we identified four different patterns: a responsive mild group (n = 32), an unresponsive akinetic-dominant group (n = 8), and two trembling-dominant groups with (n = 12) and without (n = 11) a response to medication. Task load also affected the manifestations differentially, as dual-tasking and gait initiation induced more akinetic FOG compared to other conditions.

Conclusions: Trembling and akinetic FOG respond similarly to dopaminergic medication (except for a specific trembling subgroup), yet they are differentially influenced by FOG triggers. Altogether, we suggest that "trembling" may represent a milder form of FOG, although "trembling" as a distinct FOG-variant cannot be rule out.