Electrophysiologic recovery of acute conduction block of rat tail nerve

The recovery of experimental compression neuropathy with prolonged conduction block of the caudal nerve was studied electrophysiologically in 48 adult Sprague-Dawley albino rats divided equally into six groups. The pressure applied in groups A, B, C, D, E, and F was approximately 20kg/cm2 for 20 minutes, 20kg/cm2 for 10 minutes, 20kg/cm2 for 5 minutes, 10kg/cm2 for 20 minutes, 20kg/cm2 for 10 minutes, and 10kg/cm2 for 5 minutes, respectively. The motor nerve conduction velocity (NCV) and the amplitude of the evoked compound muscle action potential (CMAP) were measured before and periodically after nerve compression. The period of initial complete block was significantly longer in the high pressure groups than in the lower ones, and also significantly longer in the nerves compressed for 20 minutes than for those compressed for five or ten minutes. Thus, the severity of conduction block seems to be related to both pressure and duration of compression. Once the conduction block began to recover, the recovery rate of conduction block (recovery rate of amplitude ratio of CMAP, proximal/distal) was not significantly different. The recovery rate of demyelinative lesion (NCV recovery rate) was also not significantly different among the six groups. The degree of compression seems to determine the severity of the initial conduction block, but not the subsequent recovery rate of conduction.