gms | German Medical Science

61st Annual Meeting of the German Society of Neurosurgery (DGNC) as part of the Neurowoche 2010
Joint Meeting with the Brazilian Society of Neurosurgery on the 20 September 2010

German Society of Neurosurgery (DGNC)

21 - 25 September 2010, Mannheim

Relevant anatomical variations of the origin of the thenar muscles for the operation of carpal tunnel syndrome

Meeting Abstract

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  • Francisco Marin - Klnik für Neurochirurgie, Klinikum Amberg, Deutschland
  • Richard Megele - Klnik für Neurochirurgie, Klinikum Amberg, Deutschland
  • Andrea Kleindienst - Klnik für Neurochirurgie, Universitätsklinikum Erlangen-Nürnberg, Deutschland

Deutsche Gesellschaft für Neurochirurgie. 61. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC) im Rahmen der Neurowoche 2010. Mannheim, 21.-25.09.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocP1815

doi: 10.3205/10dgnc286, urn:nbn:de:0183-10dgnc2861

Published: September 16, 2010

© 2010 Marin et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The carpal tunnel syndrome (CTS) is the most frequent entrapment syndrome of peripheral nerves. Within the carpal tunnel, a mismatch between width and content of the tunnel causes a pressure damage of the median nerve. With open surgery und midline incision, beneath the palmar fascia there is sometimes muscle tissue, which has to be transsected before reaching the retinaculum. We wanted to see how often this muscle tissue is present and if there is any correlation to gender, age, electrophysiology und clinical outcome after surgery.

Methods: In our previous autopsy series, the existence of muscle tissue between thenar and hypothenar mostly associated with a variation of very ulnar origin of thenar muscles was confirmed. In 100 consecutive patients diagnosed with CTS and operated on, we examined incidence of muscle origin variations. We recorded patient’s characteristics in order to verify predisposing factors, and followed the patients clinically and neurologically after 1 week and 3 months. Statistical analysis was performed by a rank sum test: CTS patient with variations (CTS+V) versus CTS patient without variations (CTS-V).

Results: In 20 percent of patients, we confirmed the muscle origin variation. One of these patients was operated on both hands, and a bilateral the variation was present. Women (70%) were more often affected than men. Postoperative assessment revealed a higher incidence of symptom relief in the CTS+V groups at 1 week and 3 months. However, neurological function and electrophysiological function did not differ significantly.

Conclusions: We report for the first time about a muscular anomaly of the wrist present in 20% of CTS patients. The surgical minimal incision allows an optimal inspection of the anatomical structures of the CT and the subsequent therapy. Endoscopic methods have to consider the variations to avoid bleeding. The better outcome of CTS-patients with a broad origin of the thenar muscles at the retinaculum may be explained by keeping the tunnel more open with muscle tension.