Quantitative motor unit action potential analysis of supraspinatus, infraspinatus, deltoideus and biceps femoris muscles in adult Royal Dutch sport horses.

The research aimed at understanding the normal parameters for the quantitative electromyography (QEMG) – a diagnostic technique for evaluating and recording the electrical activity produced by skeletal muscles, in some specific muscles of adult Royal Dutch sport horses. The values obtained could then be used as benchmarks to identify disorders in those muscles.

Methods

• Seven healthy adult Royal Dutch sport horses participated in this experimental observational study and retrospective case series.
• The researchers carried out a quantitative motor unit action potential analysis on each of the selected muscles (supraspinatus, infraspinatus, deltoideus, and biceps femoris) using commercial electromyography equipment.
• These measurements were taken in line with existing published methods.
• To compare the quantitative motor unit action potential variables between the different muscles, a one-way ANOVA was used, with any significant differences determined by post hoc testing using Bonferroni’s method. The significance was set at P<0.05.
• The researchers then collated and analyzed retrospective QEMG data and clinical information from horses that had previously been diagnosed with lower motor neuron disorders or myopathies.

Results

• The research results delivered a baseline set of values for duration, amplitude, phases, turns, area, and size index for each of the four muscles studied. This represented the 95% confidence intervals for a healthy horse’s muscle parameters.
• Significant differences (P<0.01) were found between muscles; the supraspinatus and infraspinatus muscles had higher values for duration, amplitude, number of phases and turns, area, and size index compared to the deltoideus and biceps muscles.
• Interestingly, four out of the seven normal horses had over 15% polyphasic motor unit action potentials in their supraspinatus and infraspinatus muscles.

Conclusions

• While performing QEMG, differences between muscles should be taken into account to effectively distinguish normal horses from those with suspected neurogenic or myogenic disorders.
• The normative data provided by the study gives a basis for an objective QEMG assessment of shoulder and hindlimb muscles in horses.
• The researchers concluded that QEMG appears to be helpful in diagnosing neuropathies and differentiating these from muscle diseases.