A physiologic explanation for distal nerve slowing

Numerous studies have shown that peripheral nerves conduct slower distally than proximally. This slowing is gradual at first, and more pronounced approaching the distal end of the nerve. At first glance, distal slowing appears not to make physiologic sense, as it slows reaction time and coordination compared with a hypothetical nerve that does not slow distally. However, distal slowing decreases energy consumption, crucial in a high energy system. A previous study had shown that exponential slowing correlated well with experimental data, and resulted in significant energy savings. In this study, a series of equations was created to determine the degree of slowing to minimize both conduction time and velocity. The solution, Latency L = kd(.785) where k is a constant and d is the distance from the distal end of the nerve, correlates extremely closely with experimental data. This equation can be easily used to accurately predict normal latencies at different points along a nerve, and to detect subtle distal nerve pathology.