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Shariatzadeh H, Najd Mazhar F, Abdolahzadeh B, Ghanbari A, Torab R. A Case Report of Carpal Tunnel Syndrome With Median Nerve Anatomical Variation in the Flexor Pollicis Longus Tendon. JROS 2023; 10 (3) :167-172
URL: http://jros.iums.ac.ir/article-1-2238-en.html

Background: Carpal tunnel syndrome (CTS) is an idiopathic or secondary condition. The primary factor contributing to the development of this disorder is the alteration of the median nerve (MN). Two primary categorizations of the median nerve are recognized, referred to as the Lanz and Amadio classification. The Lanz classification is predominantly employed in the surgical literature, and the main contributing factor to CTS development has been group 3 (bifid MN). Moreover, MN’s branches and connections do not align with any specific category. The MN divides into six branches beyond the carpal tunnel in standard anatomical structure. This study reports a case with CTS having anatomical MN variation in the flexor pollicis longus (FPL) tendon. 
Case Presentation: The case was a 43-year-old male teacher presented with complaints of paresthesia and intermittent burning pain in his left arm and hand during the night over the past year. However, neurological examination revealed motor and sensory deficits in the patient’s left hand, specifically affecting the MN. Based on the clinical examination and Phalen’s test results, CTS was diagnosed. Additionally, electromyography and nerve conduction studies confirmed the diagnosis.  During carpal tunnel release (CTR) surgery, the anatomical variation of the MN was observed in the FPL of the tunnel. In the carpal tunnel, the median nerve divides, while at the same time, the FPL tendon traverses the split MN.
Conclusion: The primary factor leading to CTS is the variability of the MN. Understanding the various types of median nerves contributing to CTS is crucial to reducing potential harm during CTR surgery.