Quantitative analysis of motor evoked potentials in the neonatal lamb

Abstract

Evoking motor potentials are an objective assessment method for neuromotor function, yet this was to our knowledge never done in neonatal lambs. There is neither a method for standardized quantification of motor evoked potentials (MEPs). We first aimed to evaluate the feasibility of MEP recording in neonatal lambs and test its validity. Second we aimed to develop an algorithm for its quantification and test its reliability since manual input is required. We recorded myogenic MEPs after transcranial motor cortex stimulation in 6 lambs aged 1–2 days. MEPs were also measured in one lamb undergoing Neuro-Muscular Blockade (NMB) and another undergoing lumbar spinal cord (SC) transection, both serving as controls. We computed 5 parameters using a custom-made algorithm: motor threshold, latency, area-under-the-curve, peak-to-peak amplitude and duration. Intra- and inter-observer reliability was analyzed. MEPs could be easily recorded, disappearing after NMB and SC transection. The algorithm allowed for analysis, hence physiologic readings of the parameters in all 4 limbs of all lambs were obtained. Our method was shown to have high intra- and inter-observer ( ≥70%) reliability for latency, area-under-the-curve and peak-to-peak amplitude. These results suggest that standardized MEP recording and analysis in neonatal lambs is feasible, and can reliably assess neuromotor function.

Validation of the Fetal Lamb Model of Spina Bifida

“…All lambs were delivered by cesarean section through flank incision around term (145 days of gestation) under spinal anesthesia as described earlier 38 . On day two of life, general anesthesia was induced using intravenous propofol.…”

“…Our MEP protocol has been described previously 38 . Briefly, MEPs were recorded between two needle electrodes inserted in the distal forelimb and hindlimb muscles following a contralateral motor cortex transcranial stimulation using skull screw electrodes (Fig.…”

Vagus Nerve Stimulation-Induced Laryngeal Motor Evoked Potentials: A Possible Biomarker of Effective Nerve Activation

“…Different methods can be applied to quantify the amplitude of a motor EP, based on either peak sizes or signal integration (area) measurements. Different metrics are widely accepted (Lavoie et al, 1995; Cacchio et al, 2009; Joyeux et al, 2017). We compared the results of the LMEP amplitude evaluation using a P2P metric, a single peak amplitude (N1 prominence) and the integral AUC measurements.…”

“…For each measure, we calculated the mean values per train of stimulation based on the grand average (average over the maximum number of epochs available in a train). We first measured the mutual agreement of the three different amplitude measurements, as an indication of their inter-exchangeability and of the overall reliability of EP measures (Joyeux et al, 2017). We calculated the ICC(3,k) for inter-rater reliability, in which each method is considered as a different rater, and their consistency across trials is tested (McGraw and Wong, 1996; Koo and Li, 2016; Joyeux et al, 2017).…”

Safety and efficacy of fetal surgery techniques to close a spina bifida defect in the fetal lamb model: A systematic review

“…As new clinical techniques are introduced, it would seem logic to preclinically validate them against this experimental standard in the SB fetal lamb model. Such experiments should use standardized methods for both timing of the experiments, ie, induction and closure of the lesion, and objectively evaluating the effects of surgical closure …”