Limits of variation of fiber distribution in the sural nerve of man

Although the sural nerve is the most extensively studied nerve in man, there is a dearth of data regarding the normal variations in the size-frequency distribution of axons in normal subjects; criteria for assessing the normality of a given individual are not available. Therefore, in everyday practice, the surgical pathologist may meet with difficulty in interpreting the biopsy of one particular individual, in whom the distribution is slightly different from the curves published. The object of this work is to detect the normal limits of variation in the distribution of diameters of myelinated and unmyelinated fibers in normal subjects and to establish the criteria that permit the calculated curves to be used in everyday clinical practice. Normal sural nerves of 19 patients were analyzed. Ages ranged between 18 months and 55 years. Morphometric analysis was performed with the Histoscan X automatic image processing analyzer, and, for statistical analysis, mixtures of lognormal distributions were fitted and tested with Pearson's statistics. Nerves of three diabetic patients were used for testing the method. They were clearly classified as abnormal. The curves, therefore, have been proven useful for everyday surgical pathology practice.