Establishing the electrical physiological feasibility of the rabbit median nerve as an experimental model for carpal tunnel syndrome.

Backround: Rabbits are appropriate models for experimental carpal tunnel syndrome (CTS) studies. This study aimed to explore whether the distribution and innervation area of the nerves supplying the thenar muscles of rabbits are similar to those in humans using anatomical, electrophysiological, and histopathological methods.

New Method: 20 New Zealand rabbits were used to establish reference conduction values for the median and ulnar nerves. Median nerve denervation was performed on the left forelimb of six rabbits, and changes were assessed 33 days post-surgery. Normative data from healthy rabbits were compared with those from denervated rabbits, and comparisons were made between the right and left forelimbs of the denervated rabbits. Thenar and interosseous (2nd, 3rd, and 4th) muscles were used for histopathology. Dissections focused on the thenar muscles and branches of the median and ulnar nerves.

Results: Thenar muscles were 2.5-3mm in width and 7-8mm in length), innervated by both the median and ulnar nerves. Normative latency and amplitude values of 1.85±0.30 ms and 7.71±3.50mV for the median nerve and 1.85±0.19 ms and 6.14±2.50mV for the ulnar nerve, respectively. Denervation reduced thenar muscle CMAP amplitude (2.51±2.16mV, p=0.047) on ulnar nerve stimulation, indicating dual innervation. The median sensory nerve conduction latency (2.55±0.20 ms) was successfully performed for the first time. Histopathological analysis revealed localized atrophy and degenerative changes in the denervated thenar muscles.

Comparison With Existing Methods: The new method including novel normative data will significantly enhance the evaluation of CTS in experimental rabbit models, paving the way for more accurate and reliable future research.

Conclusion: The innervation patterns of rabbit thenar muscles were similar to those in humans. This data can aid CTS understanding in rabbit models.