Quantitative evaluation of trunk function and the StartReact effect during reaching in patients with cervical and thoracic spinal cord injury

Yolanda Castillo-Escario,Raimon Jané,Hatice Kumru,Josep Valls-Solé,Joan Vidal,Loreto García-Alen

doi:10.1088/1741-2552/ac19d3

Abstract

Objective. Impaired trunk stability is frequent in spinal cord injury (SCI), but there is a lack of quantitative measures for assessing trunk function. Our objectives were to: (a) evaluate trunk muscle activity and movement patterns during a reaching task in SCI patients, (b) compare the impact of cervical (cSCI) and thoracic (tSCI) injuries in trunk function, and (c) investigate the effects of a startling acoustic stimulus (SAS) in these patients. Approach. Electromyographic (EMG) and smartphone accelerometer data were recorded from 15 cSCI patients, nine tSCI patients, and 24 healthy controls, during a reaching task requiring trunk tilting. We calculated the response time (RespT) until pressing a target button, EMG onset latencies and amplitudes, and trunk tilt, lateral deviation, and other movement features from accelerometry. Statistical analysis was applied to analyze the effects of group (cSCI, tSCI, control) and condition (SAS, non-SAS) in each outcome measure. Main results. SCI patients, especially those with cSCI, presented significantly longer RespT and EMG onset latencies than controls. Moreover, in SCI patients, forward trunk tilt was accompanied by significant lateral deviation. RespT and EMG latencies were remarkably shortened by the SAS (the so-called StartReact effect) in tSCI patients and controls, but not in cSCI patients, who also showed higher variability. Significance. The combination of EMG and smartphone accelerometer data can provide quantitative measures for the assessment of trunk function in SCI. Our results show deficits in postural control and compensatory strategies employed by SCI patients, including delayed responses and higher lateral deviations, possibly to improve sitting balance. This is the first study investigating the StartReact responses in trunk muscles in SCI patients and shows that the SAS significantly accelerates RespT in tSCI, but not in cSCI, suggesting an increased cortical control exerted by these patients.

Highlights

Trunk stability is a complex sensorimotor function necessary to maintain a balanced upright posture, both under static and dynamic loading conditions [1]
In one of the cervical SCI (cSCI) patients (SCI 15), the channels corresponding to the PECT and the response time (RespT) could not be recorded
For this patient, we had no measures of the EMG amplitudes

Summary

Introduction

Trunk stability is a complex sensorimotor function necessary to maintain a balanced upright posture, both under static and dynamic loading conditions [1] This requires an accurate control by the central nervous system to integrate proprioceptive information and coordinate abdominal, pelvic, and spinal muscle groups against extrinsic or intrinsic destabilizing forces [1, 2]. Trunk stability is essential for sitting and standing balance, and to support functional limb movements [5, 6], being a necessary component in activities of daily living (ADLs) such as eating, dressing, and transferring [7] For these reasons, impaired trunk control sustained by patients with SCI constitutes a major cause of motor disability, which affects their independence and quality of life, and increases the healthcare costs [8]. One of the reasons is the lack of objective, standardized measures to assess trunk function

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