Abstract
Aim: The objective of the present study was to develop a method for surface electromyographic (EMG) registration of muscle activity in infants, with the perspective of assessing neuromuscular function/prognosis in infants with obstetric brachial plexus palsy (OBPP).
Method: Fifteen healthy infants, aged 1–4 days, were recruited for the study. EMG signals were registered from the biceps, triceps and palmar portion of thenar muscles on both arms and hands. For this purpose surface electrodes for bipolar recording were developed using two sintered Ag/AgCl pellets that had been cast in silicone rubber. The Moro reflex was used to elicit a standardised motor stimulus. The reflex was elicited 5 times, and during EMG recording the procedure was video taped. To define the onset of muscle activity the running block threshold method was adapted to time signals.
Results: The custom-made electrodes performed well and EMG signals of good quality were obtained from the different sites. The onset algorithm worked automatically, giving stable and visually correct registration. The signals could clearly describe the onset of muscle activity during the Moro reflex with a symmetrical pattern in both arms and hands. The extension/abduction phase of the reflex was characterised by predominant activity in the triceps muscle with concomitant low-grade activity in the antagonistic biceps muscle. During the embracing phase, occurring up to 1 second after onset of abduction, the opposite pattern was seen. Thenar activation, causing flexion/opposition of the thumb, was salient only during the embracing phase.
Conclusion: Surface EMG can be used in infants to objectively assess the normal motor pattern in muscles innervated by different branches of the brachial plexus. This convenient method shall be applied to evaluate the status and possibly the prognosis in infants with OBPP.
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Håkansson, E., Östlund, N., Edström, U. et al. 165 Surface Electromyography for Registration of Infant Neuromuscular Activity. Pediatr Res 58, 383 (2005). https://doi.org/10.1203/00006450-200508000-00194
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DOI: https://doi.org/10.1203/00006450-200508000-00194
