Event Title

Comparison of Motor Unit Activity in Infants with Peripheral vs. Central Neural Lesions

Start Date

19-5-2012 10:45 AM

End Date

19-5-2012 11:00 AM

Description

Background: Upper limb asymmetry after perinatal brachial plexus injury (BPI) is immediately apparent, yet is often identified later after perinatal stroke. This study examined whether spike shape analysis of surface electromyographic (sEMG) activity is a sensitive method to assess group, age and limb differences in motor unit (MU) activation in these infants post-injury.

Methods: Fifteen infants 4 to 6-7 months of age participated; 5 BPI, 5 post-stroke, and 5 controls. We recorded 3 bilateral, isometric, biceps contractions in 90 degrees elbow flexion and neutral forearm rotation, while each infant grasped a dowel. The 5 mean measures of MU activity computed were: spike amplitude (SA), spike frequency (MSF), spike duration (MSD), spike slope (MSS), and number of peaks per spike (MNPPS). Baseline and peak muscle contraction, elicited by tendon tap, were obtained from sEMG. A mixed model ANOVA with repeated measures was used to analyze differences in spike shape data by group, age and limb.

Results: All 5 variables increased from 4 to 6-7 months in infants with BPI and controls. For infants post-stroke, 3 variables decreased in the arm at-risk across age, while MSF increased.

Conclusions: Shape spike analysis of sEMG seems to be a sensitive method to assess MU activation in infants at risk. Infants with BPI and controls recruited higher threshold MU’s during contractions, whereas, infants post-stroke increased the frequency of MU firing perhaps to generate sufficient force due to decreased MU recruitment.

Learning Objectives: At the end of this presentation, participants will:

1. Compare the timeline for presentation of upper limb asymmetry common to infants who sustain perinatal brachial plexus injury vs. those who sustain perinatal stroke.

2. Discuss a unique method to analyze differences in motor unit activation based on isometric surface EMG.

3. Identify the key differences in motor unit activation between infants with a peripheral brachial plexus injury and perinatal stroke and how the results can influence clinical practice.

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May 19th, 10:45 AM May 19th, 11:00 AM

Comparison of Motor Unit Activity in Infants with Peripheral vs. Central Neural Lesions

Background: Upper limb asymmetry after perinatal brachial plexus injury (BPI) is immediately apparent, yet is often identified later after perinatal stroke. This study examined whether spike shape analysis of surface electromyographic (sEMG) activity is a sensitive method to assess group, age and limb differences in motor unit (MU) activation in these infants post-injury.

Methods: Fifteen infants 4 to 6-7 months of age participated; 5 BPI, 5 post-stroke, and 5 controls. We recorded 3 bilateral, isometric, biceps contractions in 90 degrees elbow flexion and neutral forearm rotation, while each infant grasped a dowel. The 5 mean measures of MU activity computed were: spike amplitude (SA), spike frequency (MSF), spike duration (MSD), spike slope (MSS), and number of peaks per spike (MNPPS). Baseline and peak muscle contraction, elicited by tendon tap, were obtained from sEMG. A mixed model ANOVA with repeated measures was used to analyze differences in spike shape data by group, age and limb.

Results: All 5 variables increased from 4 to 6-7 months in infants with BPI and controls. For infants post-stroke, 3 variables decreased in the arm at-risk across age, while MSF increased.

Conclusions: Shape spike analysis of sEMG seems to be a sensitive method to assess MU activation in infants at risk. Infants with BPI and controls recruited higher threshold MU’s during contractions, whereas, infants post-stroke increased the frequency of MU firing perhaps to generate sufficient force due to decreased MU recruitment.

Learning Objectives: At the end of this presentation, participants will:

1. Compare the timeline for presentation of upper limb asymmetry common to infants who sustain perinatal brachial plexus injury vs. those who sustain perinatal stroke.

2. Discuss a unique method to analyze differences in motor unit activation based on isometric surface EMG.

3. Identify the key differences in motor unit activation between infants with a peripheral brachial plexus injury and perinatal stroke and how the results can influence clinical practice.