Objective: To evaluate the cognitive contribution of a dual task (DT) or motor plan updating while turning on the akinetic and trembling freezing of gait (FOG) manifestations in Parkinson’s disease (PD).

Background: FOG is a very disabling yet highly prevalent symptom in PD. FOG manifests itself typically through trembling of the knees (TR-FOG) but can also present as akinetic FOG without any observable movement in the legs or feet (AK-FOG). Decoupling between basal ganglia and cognitive control networks led to motor arrests during a foot pedaling task in complex conditions.¹ These motor arrests resembled AK-FOG. Therefore, we hypothesized that AK-FOG would occur more often under cognitive load or when updating the motor plan.

Method: Participants performed 360° turns in place after >12h withdrawal of dopaminergic medication (OFF), and 1 hour after medication intake (ON) and this with (DT) and without (ST) a cognitive dual task (serial 3 subtraction). FOG onset was based on expert video ratings and expressed as the relative time point (percentage of the turn duration while excluding the FOG duration). A generalized linear mixed model with a logit link and random intercept was used to investigate the likelihood of AK-FOG compared to TR-FOG. Task (ST or DT) and FOG onset and their interaction were included as predictors. As motor plan updates occur early and late in the turn, FOG onset was entered as a quadratic term.

Results: A total of 968 (601 trembling & 367 akinetic) FOG episodes were collected from 56 PD patients with FOG. When pooling ON & OFF, a near significant interaction was found between FOG onset and task (F=3.58; p=0.06) showing that akinetic manifestations were consistently present during DT turns while mostly present at the beginning of the ST turns, i.e. when the cognitive load increased to update the motor plan. Furthermore, there was a main effect for task (F=14.79; p<0.001) indicating that akinetic FOG was significantly more likely than trembling FOG during DT turns compared to ST turns.

Conclusion: We found that while turning in place, the akinetic FOG manifestation were more frequently induced under cognitive load from either a secondary task or at the start of the turn when motor plan updating was required. This suggests that akinetic FOG is associated with cognitive overload and decoupling motor planning from motor execution.

References: 1 Shine JM, Matar E, Ward PB, Frank MJ, Moustafa AA, Pearson M, Naismith SL, Lewis SJ. Freezing of gait in Parkinson’s disease is associated with functional decoupling between the cognitive control network and the basal ganglia. Brain. 2013 Dec;136(Pt 12):3671-81. doi: 10.1093/brain/awt272.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/contribution-of-cognitive-load-to-akinetic-and-trembling-freezing-of-gait-manifestations-in-patients-with-parkinsons-disease/