200 Section - Brainstem Mechanisms of Yawn-Like Breathing–Induced Arm Elevation in Early Stroke

Objectives : Parakinesia Brachialis Oscitans (PBO) is a rare early-stroke phenomenon featuring yawn-like involuntary arm elevation, possibly reflecting subcortical motor compensation after corticospinal injury. This study used task-based and resting-state fMRI to examine brainstem reticular formation (RF) mechanisms and their links to motor and functional recovery.

Design: Fifteen carefully screened patients with subacute stroke (mean age 47.9 ± 10.2 years; 66.7% male) who met stringent inclusion criteria for PBO-like phenomena were enrolled. Each participant underwent block-designed task-based fMRI comprising simulated PBO-like and simple arm-raising tasks, as well as resting-state fMRI scans acquired before and after the task. Task-related activation was analyzed using a general linear model, and generalized psychophysiological interaction (gPPI) analysis was employed to assess RF-centered functional connectivity. Resting-state RF connectivity was also evaluated. Correlation analyses were performed between RF activation magnitude, upper-limb motor function (Fugl–Meyer Assessment, FMA-UE), and activities of daily living (Modified Barthel Index, MBI).

Results: Simulated PBO-like movements elicited widespread cortical–subcortical activation involving motor cortices, the basal ganglia–thalamic complex, cerebellum, and bilateral RF, whereas simple arm-raising produced restricted activation. gPPI analysis showed enhanced connectivity between bilateral RF and cerebellar and brainstem regions, with reduced connectivity to visual and prefrontal cortices. Simple arm-raising induced only limited RF connectivity changes. At rest, RF connectivity primarily involved the insula, putamen, occipital cortex, and cingulate gyrus. RF activation magnitude positively correlated with both FMA-UE and MBI scores (P < 0.05).

Conclusion: Yawn-like breathing–induced arm elevation in early stroke is characterized by distinctive activation and connectivity patterns centered on the brainstem RF, underscoring the compensatory role of brainstem motor pathways after corticospinal damage. These findings provide novel mechanistic insights into PBO and suggest potential subcortical targets for rehabilitation interventions.