Review Question - QID 212018

The clinical picture described is most consistent with lumbrical muscle weakness secondary to neuropraxia of the proper palmar digital nerve to the index finger (D).

Carpal tunnel release (CTR) remains the gold standard for the management of persistent symptoms from carpal tunnel syndrome (CTS) despite conservative management. Overall, complications from the surgery are uncommon (~1%). These complications include incomplete release, wound complications, and nerve-related injuries. The most common nerve injury is the recurrent motor branch due to the variable anatomy associated with the nerve leaving the median nerve proper. Injury to the proper digital nerve of the index finger has also been reported and this generally leads to a lumbrical minus deformity of the index finger due to lumbrical weakness.

Seiler et al. reviewed the complications associated with open CTR due to anatomic variations. The authors note that understanding both normal and variant anatomy, including anomalies in neural, vascular, tendinous, and muscular structures about the carpal tunnel, is fundamental to achieving both safe and efficacious surgery. The authors noted that although no true internervous plane exists during the approach for CTR, the long-ring webspace axis does appear to pose the lowest risk to damage to important structures such as the recurrent motor branch, the index finger proper digital nerve, and Guyon's canal.

Karl et al. review the etiology of complications after CTR. The complications discussed include intraoperative technical errors, postoperative infection and pain, and persistent or recurrent symptoms. The authors noted that patients with continued complaints after CTR should be carefully evaluated with a detailed history and physical examination in addition to electrodiagnostic testing. The authors conclude that for those with persistent or recurrent symptoms, a course of nonoperative management including splinting, injections, occupational therapy, and desensitization should be considered prior to revision surgery.

Figure A is a schematic of the various distal branches of the median nerve proper

Incorrect Answers:
Answer 1: A is the median nerve proper. Injury to this nerve would manifest as weakness and sensory changes to the thumb, index finger, middle finger, and radial half of the ring finger
Answer 2: B is the recurrent motor branch of the median nerve which innervates the thenar musculature and its injury would mannifest as thenar weakness.
Answer 3: C is the common palmar digital nerve that innervates the radial half of the middle finger and the ulnar half of the index finger. Injury to this nerve would manifest as both lumbrical weakness and sensory loss to both the middle and index finger.
Answer 5: E is the ulnar digital nerve to the thumb. Injury to this nerve wound manifest as a sensory loss to the ulnar half of the thumb.