Early changes following injection injury of peripheral nerves

Using light and electron microscopy and a fluorescent tracer technique, the authors have studied various aspects of injection injuries to nerves in an attempt to elucidate the pathophysiology of this condition and to help establish a rational basis for treatment. In 72 animals 144 nerve injections were carried out, using five drugs in current use and commonly administered by intramuscular injection. The nerves were examined at varying times (10 minutes to 10 weeks) following injection. Pathological alterations in the nerve were evident as early as 30 minutes after injection. The mechanism of injury appears to be a direct neurotoxic effect on the nerve fibre-both axon and Schwann cell-with a breakdown in the blood-nerve barrier.