Peripheral nerve surgery.

In treating the three main surgical problems of peripheral nerves--nerve sheath tumors, entrapment neuropathies, and acute nerve injuries--the overriding consideration is the preservation and restoration of neurologic function. Because of this, certain other principles may need to be compromised. These include achieving a gross total excision of benign tumors, employing conservative therapy as long as a disease process is not clearly progressing, and delaying repair of a nerve transection until the skin wound has healed. Only three pathophysiologic processes need be considered: neurapraxia (focal segmental dymyelination), axonotmesis (wallerian degeneration caused by a lesion that does not disrupt fascicles of nerve fibers), and neurotmesis (wallerian degeneration caused by a lesion that interrupts fascicles). With nerve sheath tumors and entrapment neuropathies, the goal is minimize the extent to which neurapraxia progresses to axonotmesis. The compressive force is relieved without carrying out internal neurolysis, a procedure that is poorly tolerated, presumably because a degree of nerve ischemia exists with any long-standing compression. When the nerve has sustained blunt trauma (through acute compression, percussion, or traction), the result can be a total loss of function and an extensive neuroma-in-continuity (scarring within the nerve). However, the neural pathophysiology may amount to nothing more than axonotmesis. Although this lesion, in time, leads to full and spontaneous recovery, it must be differentiated from the neuroma-in-continuity that contains disrupted fascicles requiring surgery. Finally, with open nerve transection, the priority is to match the fascicles of the proximal stump with those of the distal stump, a goal that is best achieved if primary neurorrhaphy is carried out.