ULTRASONOGRAPHY OF PERIPHERAL-NERVES DURING WALLERIAN DEGENERATION AND REGENERATION FOLLOWING TRANSECTION

Ultrasonography was performed on sciatic, tibial and/or peroneal nerve s and interosseous muscles in 7 dogs using a ultrasound machine with a 7.5 MHz linear array transducer. A tibial nerve was transected near t he distal aspect of the bellies of the gastrocnemius muscle. Serial ne urologic examinations, electromyography, and ultrasonography were perf ormed before and after surgery, Dogs were euthanized at variable inter vals and histopathology performed on nerve samples, In sagittal images , normal nerves had hyperechoic walls with multiple internal linear ec hoes, In transverse images, the nerves were round or oval hyperechoic structures with internal punctate echoes, After transection, the proxi mal stump was consistently seen whereas the distal stump and nerve wer e harder to identify, Neuromas were present in all 5 dogs followed bey ond 2 days and appeared as hypoechoic bulbous swellings most apparent at 3 weeks after surgery, Only 1 dog developed a neuroma large enough to be considered of potential clinical significance. Four dogs were fo llowed beyond 2 months, Regeneration was evidenced by a steady growth of nerve with an irregular outline (2 dogs) or by a knobby connection between the proximal and distal stumps (1 dog). Regeneration was not d etected in 1 dog.