In vivo visualization of the neuromuscular junction before and after autologous nerve transfer in the rat.

In vivo visualization of the neuromuscular junction with epifluorescence imaging techniques has become a successful method of observing the ongoing process of re-occupation by regenerating motor axons of former post-synaptic sites after nerve injury. By using a light-integrating video camera for digital documentation, all parts of the neuromuscular junction can be visualized, as detailed as when documented with high-speed film, but with a minimum light intensity to prevent damage of neural or muscular structures. Results from comparisons of pre- and post-synaptic staining indicate a non-reoccupation rate up to 37 percent at a 55-day interval after nerve transfer, and up to 34 percent at a 66-day postoperative interval. Morphologic findings suggest that these high non-reoccupation rates are caused jointly by intramuscular missprouting, an insufficient intramuscular guidance apparatus, and intramuscular microneuroma formation at the insufficient neuromuscular junction.