Poster Q8 - FUNCTIONAL CHANGES IN HYPOXIC NEONATAL BRACHIAL PLEXUS AFTER STRETCH

Introduction: Neonatal Brachial Plexus Palsy (NBPP) is a serious condition affecting infants during their delivery and often accompanied by hypoxia. It is characterized by either a stretch or rupture of the brachial plexus [1-7]. Brachial Plexus comprises of C5-T1 spinal roots and depending on the root injured is classified into different types of palsy; Erb’s Palsy being the most common one affecting C5 and C6 roots. In vivo electrophysiology data of hypoxic neonatal brachial plexus and its association to the stretch response does not exist. This study focuses on reporting the normal, post-stretch and one-hour post stretch latency in the compound action potentials of hypoxic brachial plexus nerves (ulnar and median) in neonatal piglets.

Materials and

Methods: Four neonatal brachial plexus nerves were put through mechanical stretching by clamping the nerve and pulling it to a fixed strain as shown in Fig.1. All procedures were according to the approved IACUC protocol, Drexel University.

The electrophysiology and data acquisition set up consisted of an amplifier, stimulator, DAQ system, bipolar stimulating and recording cuff electrodes, ground electrode and a laptop with LabView software as shown in Fig.2 [8-9].

The brachial plexus segment was stretched at known strains and compound action potential was acquired at sampling rate of 20,000 Hz, acquisition time of 1 sec, gain of 10K and duration of 0.1 msec before, after and one-hour post stretch. The stimulus applied was 0-2V with increments of 0.5V. A ZED camera was placed over the nerve being tested to capture the distance between the stimulating and recording electrodes to determine the conduction velocity (CV) and amplitude of the compound action potentials. Eq. 1 show how to calculate percentage change in latency post-stretch.

% change in latency post-stretch = [latency before stretch – latency after stretch] / [latency before stretch] Eq(1)

A customized MATLAB code was used to determine the latency of compound action potentials recorded for before stretch, post-stretch and one-hour post stretch conditions to check for recovery or conduction block.

Results, Conclusions, and Discussions: Electrophysiological recordings reported immediate conduction block when subjected to a 20% strain (Fig.3). No spontaneous recovery was observed at 1 Hr or 3 Hr. At a 15% strain, the nerve continued to conduct however, a 100% increase in latency immediately post stretch, which did not recover. No data is available on the mechanical, and related functional changes in the hypoxic neonatal BP subjected to stretch. This study is the first to a direct correlation between subjected strain and observed functional changes. Data from the study confirms that the extent of stretch directly affects the injury outcomes and spontaneous recovery responses. Strains of 20% or more leads to significant conduction block in hypoxic tissues. Obtained data helps better understand the mechanism of NBPP and can help with prognosis and identification of optimal treatment options., especially in complicated cases including hypoxia.

Acknowledgements (Optional): This research was supported by funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under Award Number R15HD093024 and R01HD104910A and NSF CAREER Award Number 1752513.