Intra-operative Nerve Stimulation as a Novel Assessment of Rat Median Nerve Function
Matthew J Gluck, BS; Christina M Beck, PhD; Todd A Rubin, MD; Paul J Cagle, MD
Icahn School of Medicine- Mount Sinai, New York, NY
Introduction:Peripheral nerve injuries are difficult to treat and early intervention is of paramount importance. Intra-operative nerve stimulation provides a cost effective and reliable method to both localize and assess nerve function. This study aims to validate the use of nerve stimulation as a functional assessment of rat median nerve damage.
Materials and Methods: Seventeen Sprague-Dawley Rats were used in this study. Approximately 1.5cm of the median nerve was exposed and a Checkpoint surgical nerve stimulator (Checkpoint Surgical, Clevelend, Ohio) was used to assess baseline nerve function. The Checkpoint stimulator provides an adjustable current (0.5mA, 2mA, 20mA) and pulse width (50-200µS). Nerves were first probed at the lowest setting of stimulation, 0.5mA of current at a pulse width of 50µS slowly increasing first pulse width than current until the first twitch of movement (Twitch) and a full paw contraction (Contraction) could be observed. Right median nerves (HS) were then placed in a custom made stretch applicator, and a 20% stretch injury was induced and held over 5 minutes. Left median nerves (SC) were sham control, only being placed in the applicator for 5 minutes with no applied stretch.
Results: All intact values (both SC and HS) exhibited a Twitch of movement at the lowest setting of stimulation, 0.5mA of current with 50µs of pulse width. 14/17 specimens exhibited Contraction at 2mA with 100µs of pulse duration in both right and left nerves. The remaining 3 specimens exhibited intact Contraction values within the 0.5mA range. Following the application of the stretch injury, all HS nerves (17/17) required an increase in stimulation to induce both a Twitch and Contraction. All HS nerves required an increase to 2.0mA to induce a Twitch, though pulse duration varied within this range. 13/17 HS nerves exhibited an increase in pulse width to exhibit Contraction, while 4/17 HS nerves failed to exhibit Contraction in the 2.0mA range. In the sham control (SC) nerves, 14/17 required no change in stimulation to induce a Twitch. 3/17 required an increase to 100µs of pulse width with no increase in current. No SC nerves exhibited an increase in stimulation required for Contraction.
Conclusion: Intra-operative nerve stimulation provides an accurate baseline value to determine median nerve integrity in a rat model. Furthermore, nerve stimulation can reliably detect an acute stretch injury in rat median nerves. Intra-operative nerve stimulation is a useful tool for surgeons to localize nerves and assess their functionality.
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