Anomalous nerve anatomy at the wrist?

Background And Aims: The common course of the ulnar and median nerve in the carpal tunnel has been described previously on two occasions. The aim of the study was to explain the cause of two main nerve trunks in the carpal tunnel found at an operation.

Material And Methods: A patient was treated with open reduction and internal fixation for a volar Barton's fracture of the distal radius. Later, compression syndrome of the ulnar and median nerves developed. At operation, two nerves were found in the carpal tunnel. Electroneuromyography (ENMG) and magnetic resonance imaging (MRI) confirmed a divided median nerve.

Result And Conclusion: No anomaly of the ulnar nerve was confirmed. Deviation from the common clinical and ENMG picture of the carpal tunnel syndrome should result in thorough evaluation of possible anomalous nerve anatomy at the wrist. When at operation findings are suspicious of anomalous anatomy of the median or ulnar nerves in the carpal tunnel, Guyon's canal should also be explored to clarify the anatomy of the nerves. In cases with previous carpal collapse or other space occupying lesions we recommend division of the whole transverse carpal ligament in connection with a volar osteosynthesis, because the operative trauma may cause elevation of pressure in both the carpal and Guyon's canals.