Nerve Injuries
General Information
The median, ulnar, and radial nerves are the terminal branches of the brachial plexus and supply motor, sensory, and sympathetic function to the hand (Appendix 4, Radial, Ulnar, and Median Nerve Anatomy). Hand surgeons commonly evaluate both acute and chronic nerve conditions.
Nerve Lacerations
Diagnostic Criteria
Most peripheral nerve lacerations occur following a penetrating injury (e.g., glass or knife wounds).
History
Patients with median nerve lacerations describe numbness in the thumb, index, long, and ring fingers, and weakness of thumb abduction. Those with ulnar nerve lacerations complain of numbness in the ring and small fingers and have clawing of the ring and small fingers. Those with radial nerve lacerations have weakness of wrist, finger, and digital extension and decreased feeling in the web space between the thumb and index finger.
Physical Examination
Most patients have a Tinel’s sign at the sight of nerve injury. Detailed physical examination shows a neurologic deficit in the distribution of the involved peripheral nerve.
Treatment
Surgical exploration using optical magnification allows anatomic coaptation of the nerve ends. Most repairs approximate the outer layer (epineurium) of the
nerve after alignment of interval nerve fibers (fascicles). Epineural repairs also help prevent disorderly growth of new axons (neuromas). Large nerve gaps require nerve grafting.
nerve after alignment of interval nerve fibers (fascicles). Epineural repairs also help prevent disorderly growth of new axons (neuromas). Large nerve gaps require nerve grafting.
Aftercare
Splint protection of nerve repair is necessary for 3 to 4 weeks. Functional bracing permits proper hand position while motor axons regenerate. Hand therapy is often beneficial.
Results
Microsurgical repairs result in varying return of function based on age and level of laceration, mechanism of injury, the specific nerve involved, and individual health status. Following a laceration, the distal nerve undergoes wallerian degeneration and must be replaced by new axons growing across the repair site. After 30 days, peripheral nerves regenerate at 1 mm per day. Clinically, an “advancing Tinel’s sign” is consistent with nerve regeneration.
Nerve Compression
Nerve compression occurs when increased pressure on a peripheral nerve results in local ischemia and decreased axonal transport. Early symptoms are pain and paresthesias. As compression worsens, patients develop fixed (constant) numbness, loss of dexterity, and weakness.
Carpal Tunnel Syndrome
Carpal tunnel syndrome, or compression of the median nerve beneath the transverse carpal ligament and is the most common entrapment neuropathy.
Diagnostic Criteria
History
Patients describe numbness and tingling in the thumb, index, long, and half of the ring finger. Numbness and pain are worse at night, often causing nocturnal awakening. Daytime activities, such as driving with the wrists extended, may exacerbate the symptoms. Clumsiness and weakness of grip are also common complaints. Pain usually occurs in the distal volar forearm and hand.
Carpal tunnel syndrome is more common in women, and in patients with diabetes mellitus, and rheumatoid arthritis. Other associated conditions are listed in Table 1.
Table 1. Conditions associated with carpal tunnel syndrome | ||
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Physical Examination
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