Ulnar nerve injury in the wrist

1. What are the borders of Guyon's canal?
2. What are common causes of injury to the ulnar nerve in Guyon's canal?
3. What are the symptoms of ulnar injury at the wrist?
4. What are the NCS/EMG findings?

Answers:
1. Guyon's canal is formed by the pisiform and the hook of the hamate bones, covered by the pisohamate ligament. The ulnar nerve splits into its superficial and deep branches as it enters the canal.
2. Cycling activity, wrist ganglions, rheumatoid arthritis.
3. Weakness in all ulnar innervated hand muscles (dorsal interossei, palmar interossei, lumbricals, adductor pollicis, FPB, hypothenar muscles, opponens digiti minimi, ADM, FDM), wasting of FDI, severe claw hand.
4. SNAP: normal for DUC, abnormal to 5th digit. CMAP abnormal. EMG abnormal in all ulnar-innervated hand muscles.