American Society for Peripheral Nerve

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Anatomic Variations of Brachial and Lumbosacral Plexus Models in Different Rat Strains.
Adam Bobkiewicz, MD1; Joanna Cwykiel, MSc2; Maria Siemionow, MD PhD DSc1,2
1Poznan University of Medical Sciences, Poznan, Poland, 2University of Illinois at Chicago, Chicago, IL

Purpose: The selection of an appropriate model for preclinical assessment of new methods of peripheral nerve injury management should consider parameters, such as nerve course, diameter, length and type. This report presents anatomic variations within brachial and lumbosacral plexuses in three selected rat strains of Sprague Dawley (Hsd:Sprague Dawley®SD®), Athymic Nude (Hsd:RH-Foxn1rnu) and Lewis (LEW/SsNHsd) rats.

Methods: Eighteen cadaver rats were divided into three groups, based on their strain. The rats' mean age was 17.1±0.8 weeks (Sprague Dawley), 17.8±0.8 weeks (Lewis) and 16.6±0.8 weeks (Athymic Nude). A total of 90 brachial plexus nerves (axillary, musculocutaneous, median, ulnar, and radial nerves) and 72 lumbosacral plexus nerves (sciatic, tibial, common peroneal and sural nerves) were analyzed for the length, diameter and correlation with the animals body weight. A detailed anatomic course of each nerve within the brachial and lumbosacral plexuses was outlined.

Results: The sural nerve was the longest nerve in all studied rat strains (Sprague Dawley-38.61±0.82mm, Athymic Nude-42.31±1.5mm, Lewis-34.94±1mm), whereas the sciatic nerve had the largest diameter (Sprague Dawley-1.64±0.1mm, Athymic Nude-1.63±0.05mm, Lewis-1.59±0.07mm). Comparison of all the nerves' length demonstrated that the Lewis rat sciatic and sural nerves were significantly shorter (p<0.05). The ulnar nerve remained the longest measured nerve within the brachial plexus in all tested strains (Sprague Dawley - 25.6±1.03mm, Lewis - 26.43±1.05mm and Athymic Nude rats - 25.83±1.63mm). No significant differences in nerve diameters were found among the analyzed rat strain groups. Significant correlation was revealed between the length of sciatic nerve and the rats' weight, which is irrelevant to the rats' genetic background. However, there was no correlation found in any of the experimental groups between nerve diameter and body weight.

Conclusions: To the best of our knowledge, this study is the first to compare the anatomic variations of nerves within the brachial and lumbosacral plexuses in different rat strains. Similar results of length values for respective nerves among tested strains confirmed that nerve length within rat's brachial and lumbosacral plexus depends on the inter-individual variations within the rat strains rather than on the differences in the peripheral nerve development, which is inherent to the specific rat strain. Correlation between the nerve length and body weight suggests that bigger rats should be considered for studies requiring access to long nerves. This study will facilitate the optimal selection of the rat strain and nerve model for researchers in the field of novel nerve conduits, biopolymers, or nerve grafts materials.

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