The aim of this investigation was to define the boundaries of compound motor action potential (CMAP) dispersion, amplitude decay, and area decay in a control population and determine their dependence on external variables such as age and interelectrode distance. Measurements were made from median, ulnar, and common peroneal motor nerves of 110 normal subjects of ages 15-90 years. Significant differences between nerves were found in mean values of each parameter. Dispersion and amplitude decay increased with the square of age in all three nerves, while area decay increased with age in the median nerve. Dispersion was the main cause of amplitude decay. Use of regression equations to predict dispersion and amplitude decay in each nerve significantly tightened confidence limits and should therefore increase the accuracy of these parameters in detecting demyelinating pathology in peripheral nerve.

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The wrinkle test is a reliable test of sympathetic function, is inexpensive and is easy to perform at the bedside. The sweat gland myo-epithelial cells and absence of sebum could play an important role in the wrinkling response. It can be used to select patients who will benefit from sympathectomy, and can adequately evaluate sympathetic blockade.