Compound Motor Action Potentials During a Modest Nerve Crush

Abstract

Nerve crush injury results in axonotmesis, characterized by disruption of axons and their myelin sheaths with relative sparing of the nerve’s connective tissue. Despite the widespread use of crush injury models, no standardized method for producing these lesions has been established. We characterize a crush model in which a narrow forceps is used to induce a modest and controlled compressive injury. The instantaneous compound motor action potential (CMAP) is monitored in situ and in real-time, allowing the characterization of neuromuscular response during and after injury. The tibial nerves of 11 anesthetized rats were surgically isolated. After the placement of electrodes, CMAPs were elicited and registered using a modular-data-acquisition system. Dumont-#5 micro-forceps were instrumented with a force transducer allowing force measurement via a digital sensor. Baseline CMAPs were recorded prior to crush and continued for the duration of the experiment. Nerve crushing commenced by gradually increasing the force applied to the forceps. At a target decrease in CMAP amplitude of 70%–90%, crushing was halted. CMAPs were continually recorded for 5–20 min after the termination of the crushing event. Nerves were then fixed for histological assessment. The following post-crush mean values from 19 trials were reported: peak CMAP amplitude decreased by 81.6% from baseline, duration of crush was 17 sec, rate of applied force was 0.03 N/sec, and maximal applied force was 0.5 N. A variety of agonal phenomena were evident post-lesion. Following the initial decrease in CMAP, 8 of 19 trials demonstrated a partial and transient recovery, followed by a further decline. Thirteen trials exhibited a CMAP amplitude near zero at the end of the recording. Twelve trials demonstrated a superimposed EMG background response during and after the crush event, with disappearance occurring within 4–8 min. Qualitative histology assessment at the lesion site demonstrated a correspondence between CMAP response and partial sparing of nerve fibers. By using a targeted decline in CMAP amplitude as the endpoint, researchers may be able to produce controlled, brief, and reproducible crush injuries. This model can also be used to test interventions aimed at enhancing subsequent regeneration and behavioral recovery.

Long-term tactile hypersensitivity after nerve crush injury in mice is characterized by the persistence of intact sensory axons

“…The survival and sparing of unmyelinated and smaller diameter myelinated fibers with partial crush nerve injury is consistent with a recently described incremental crush injury. 41 Importantly, this paradigm helps fill a void in the preclinical literature regarding the link between clinically related traumatic nerve “crush” injury and neuropathic pain.…”

Whole body vibration accelerates the functional recovery of motor nerve components in sciatic nerve-crush injury model rats

“…The peripheral nerve injury model animals have been utilized with sciatic nerve, and the injury is made with compression of a surgical clip ( Iwatsuki et al, 2013 ), forceps ( Hamad et al, 2022 ), surgical hemostats ( Wang et al, 2018 ), and a Dead-weight machine ( Mazzer et al, 2008 ). The model animal research are evaluated with compound action potentials ( Hamad et al, 2022 ; Lin et al, 2018 ), behavior ( Alvites et al, 2021 ), gait analysis ( Alvites et al, 2021 ; Wang et al, 2018 ), histological evaluation ( Alvites et al, 2021 ; Wang et al, 2018 ). Further, we also investigated the impact of the nerve wrapping with both sensory thresholds and lumbar magnetic stimulation (LMS)-induced MEPs ( Sonohata et al, 2023 ).…”