Median nerve: anatomical course and lesions
This issue has not come up in an exam, as yet (at least not since 2000).
However, it may well appear one day. Median nerve injury is a common complication of botched brachial artery cannulation.
Course of the Median Nerve
Lesions of the Median Nerve
Lesions above the elbow
- Motor deficit:
- Loss of pronation of forearm
- Weakness in flexion of the hand at the wrist
- Loss of flexion of thumb, 2nd and 3rd digits
- Loss of abduction and opposition of thumb.
- Fixed hyperextension of index finger, middle finger and thumb
- Sensory deficit:
- Loss of sensation in the thumb, 2nd and 3rd digits, and the thenar area.
Lesions between elbow and wrist
- Motor deficit:
- Loss of pronation of forearm
- Loss of flexion of thumb, 2nd and 3rd digits
- Loss of abduction and opposition of thumb.
- Sensory deficit:
- Loss of sensation in the thumb, 2nd and 3rd digits, and the thenar area.
Lesions proximal to the carpal tunnel
- Motor deficit:
- Loss of flexion of thumb, 2nd and 3rd digits
- Loss of abduction and opposition of thumb.
- Sensory deficit:
- Loss of sensation in the thumb, 2nd and 3rd digits, and the thenar area.
Lesions within the carpal tunnel:
- Motor deficit:
- Loss of flexion of thumb, 2nd and 3rd digits
- Loss of abduction and opposition of thumb.
- Sensory deficit:
- Loss of sensation in the thumb, 2nd and 3rd digits, but excluding the thenar eminence
References
For a reference, I direct the time-rich reader to Sir Sydney Sunderland's "Nerves and Nerve Injuries", from 1968. (Not available as full text in Google, unfortunately.)
For brachial plexus injuries, I recommend Alain Gilbert's book.
For peripheral nerves, there is Haymaker, Webb, and Barnes Woodhall. Peripheral nerve injuries: principles of diagnosis. Thieme, 1998.
Vanderpool, D. W., et al. "Peripheral compression lesions of the ulnar nerve."Journal of Bone & Joint Surgery, British Volume 50.4 (1968): 792-803.