Nerve Injury, Compression Neuropathy, and Microsurgery
Classification drives the plan
Injury classification. Seddon: neurapraxia (demyelination, full recovery), axonotmesis (axonal loss with intact endoneurium, good spontaneous recovery), neurotmesis (transection, no recovery). Sunderland I–V refines this; grade V needs repair. Wallerian degeneration begins within 24–48 hours. An advancing Tinel sign marks regeneration at roughly 1 mm/day (1 inch/month).
Repair principles. Tension-free, atraumatic, epineurial or group fascicular repair under magnification. A gap beyond about 2–3 cm in a sensory nerve, or any gap closing only under tension, needs a nerve graft (sural, medial antebrachial cutaneous). Conduits suit short (<3 cm) sensory gaps in a clean bed. Nerve transfers (anterior interosseous to ulnar motor, Oberlin) are used when the proximal stump is unavailable or regeneration would arrive too late.
Compression. Carpal tunnel syndrome: nocturnal pain, thenar atrophy, provocative tests, EMG confirmation, then division of the transverse carpal ligament while protecting the recurrent motor branch and palmar cutaneous branch. Cubital tunnel syndrome involves the ulnar nerve at the elbow; note subluxation and choose among release, medial epicondylectomy, or transposition.
Traps: attributing a claw hand to a wrist-level ulnar lesion (the ulnar paradox - clawing is worse with distal lesions because FDP to the ring and small fingers remains innervated); confusing anterior interosseous syndrome (pure motor) with carpal tunnel; and missing a double crush.
Rule of thumb: short clean gap → conduit; long or tensioned gap → nerve graft.