Progression of partial experimental injury to peripheral nerve

Abstract

✓ Isometric measurements of muscle contraction in response to single as well as tetanic volleys of supramaximal stimuli were recorded from the limbs of 32 monkeys with noninjured or partially lacerated tibial nerves. Nerve action potentials (NAP) and muscle action potentials (MAP) were also determined at intervals varying from 1 hour to 52 weeks after injury. Limbs with mobilized noninjured nerve sustained small but definite decreases in muscle contraction strength particularly if the interval between operations was brief. Partially lacerated nerves had immediate averaged decreases in single twitch and supramaximal contraction strengths of 32.8% and 30.4% despite maintenance of NAP velocity. One week following injury, muscle contraction had decreased by another 21.6% and 19.7% respectively while NAP velocity was decreased by 18.5%. Measurements were also reduced at 2, 4, and 8 weeks and to a lesser degree at 12 weeks; at 24 and 36 weeks, muscle contraction was less than preinjury data but not when compared to recordings 15 minutes after injury. Values recorded at 52 weeks reflected partial reinnervation of Achilles musculature. Studies over a 24-hour period following partial laceration demonstrated significant further decreases in muscle power by 8 hours. The authors conclude that nerve activity following partial laceration fluctuates as function diminishes during the early hours to weeks following injury.