Structural Changes in the Neonatal Brachial Plexus at Varying Degrees of Stretch
Author(s): Virginia Orozco, Jasmin Jerry, Rachel Magee, Sriram Balasubramanian, Anita Singh
Neonatal brachial plexus palsy (NBPP) is a common brachial plexus (BP) injury resulting from overstretching of the BP complex during complicated birthing scenarios. Mechanical stretch induced structural changes in nerve tissue include axonal injury, causing cytoskeletal alterations, axonal swelling, and impaired axonal transport and are directly related to dysfunction and degeneration. Limited research exists on the structural changes in the neonatal BP when stretched. This study addresses this gap using a neonatal piglet animal model and investigates the extent of vascular and fiber damage as well as the extent of impaired axoplasmic transport at varying strains in neonatal BP. BP terminal nerves (musculocutaneous, median, ulnar, and radial) were stretched to three strain ranges, namely <10% (mild), 10-20% (moderate), and >20% (severe) strains. All stretched BP terminal nerves had significant changes in their vascular and nerve fiber structure when compared to sham that only underwent surgical procedure. Modified scoring systems for vascular and nerve fiber changes reported vascular and nerve fiber changes to increase with increasing strains. Furthermore, the area of nerve fibers decreased with increasing strain. Axoplasmic transport impairment, measured by beta-amyloid precursor protein (βAPP) accumulation at the injury site, also increased with strain. Also, the stretched nerves were significantly differed from sham. This study provides critical insights into straininduced structural changes in the neonatal BP nerves, highlighting strain dependency in vascular damage, nerve fiber changes, and axoplasmic transport impairments thereby enhancing our understanding of injury severity during NBPP injury.