Nerve regeneration--evidence for early sprout formation

Following microneurorrhaphy, sharply transected rat sciatic nerves were harvested 2, 5, 12, 16, 21, and 30 days after repair. Transverse sections of these specimens were made 3, 5, 7, 9 and 11 mm distal to the repair and examined with the scanning electron microscope. Myelinated sprouts were found 3 mm distal to the repair on the fifth day. Sprout migration occurred even though old myelin sheaths were present. Sprouts did not appear in old myelin sheath lumens. Many 5 U myelinated sprouts were found 11 mm distally 21 and 30 days after repair. This study demonstrates that nerve regeneration begins early, before degeneration is complete.