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The use of frozen section histological analysis in primary obstetrical brachial plexus palsy reconstruction, though widespread, is not universally practiced. Our objective was to develop a histological grading scale that could be used to determine whether further resection of a microscopically suboptimal, though grossly satisfactory stump could lead to a measurable improvement in histological appearance. A 13-point grading tool assessing attributes of the epineurium, perineurium, and endoneurium was tested for interrater reliability. The histological appearance of initial nerve biopsies and of subsequent nerve reexcisions stained with toluidine blue was reviewed retrospectively (n = 52). Specimens were graded in a blinded fashion by a neuropathologist and a medical student. There was high agreement between expert and novice global rating scores with an intraclass correlation coefficient of 0.89 (95% confidence interval 0.85 to 0.93). A comparison of scores between subsequent sections of the same nerve stump revealed a significant decrease of 3.00 (expert) and 2.00 (novice) points ( P < 0.001) in the median global rating score, demonstrating improvement in histological grade. The novel grading tool was used to demonstrate that recutting a microscopically poor, though grossly acceptable nerve stump in obstetrical palsy surgery can yield a significantly improved histological grade.