Quantification of Neuromotor Control in STXBP1-Related Disorders With Wearable Sensors

STXBP1-related disorders (STXBP1-RD) are a spectrum of neurodevelopmental conditions that present with motor impairments, which include involuntary movements, ataxia, and tremor that have been difficult to measure. The objective of this study was to use wearable sensors to characterize motor control abnormalities in individuals with STXBP1-RD, a spectrum of neurodevelopmental conditions that present with motor impairments affecting motor development.

In this study, an exploratory analysis to quantify the clinical features of motor control impairment, including tremor, in 23 individuals with STXBP1-RD was conducted and compared these features with those of 18 typically developing control participants using inertial sensors during a reaching task. Clinical relevance of the sensor-derived metrics of motor control was evaluated in the context of traditional developmental clinical assessments collected during a prospective natural history study.

Individuals with STXBP1-RD demonstrated slower reaching time, decreased arm acceleration intensity, less smooth reaching, and tremor frequency characteristics consistent with an unstable or irregular rhythmic movement pattern. More than 65% of individuals with STXBP1-RD presented with tremor in our sample. Combining features from all 4 upper limb sensors predicted tremor with the highest accuracy (area under the curve = 0.87), and multiple motor control metrics were significantly related to developmental assessment scores with reaching duration having the strongest correlation.

Our study provides an understanding of motor control in a rare neurodevelopmental disorder and establishes a paradigm to quantify neuromotor control in individuals with developmental differences. Our observations demonstrate significant relations between motor control measures and developmental function, and a tremor prevalence that exceeds twofold what has been reported in historical, retrospective data sets.