Revision carpal tunnel syndrome in the setting of Bifid Median Nerve: A Case Report

Introduction: Carpal tunnel syndrome (CTS) is widely recognized as the most common compressive neuropathy, accounting for 90% of cases. The most common etiologies predisposing to CTS include a history of repetitive wrist movement, obesity, pregnancy, genetic causes, and autoimmune disorders. Less common etiologies of CTS include space occupying anatomic variances to the median nerve. Previous studies have investigated the presence of a bifid median nerve (BMN), noting a prevalence of 1% to 18% among healthy subjects in the United States. The presence of BMN may indeed be a risk factor due to its space-occupying higher cross-sectional area in the carpal tunnel when compared to non-bifid nerves.

Methods: A right-hand dominant 71 y/o female presented to the clinic for pain and paresthesia to her right wrist/hand. The patient underwent bilateral carpal tunnel release twice (once 40 years prior, and again 10-15 years prior). She complained of symptom recurrence over the past 6 months, with constant numbness and tingling in the right hand involving all fingers, particularly worse in the 3rd, 4th, and 5th digits becoming numb, particularly at nighttime. Positive Tinel’s test in both carpal and cubital tunnels, and a positive median nerve compression test were elicited on exam. EMG confirmed severe carpal tunnel syndrome.

Results: Right revision carpal tunnel release and primary cubital tunnel release were performed. During surgery, a bifid median nerve (BMN) and a persistent median artery were incidentally discovered. The patient reported complete resolution of symptoms upon follow up.

Conclusion : Awareness of the presence of such anatomical variations to the median nerve is essential to avoid possible nerve or arterial injuries and/or relapse of carpal tunnel syndrome if decompression of both branches is not executed thoroughly. Furthermore, usage of point-of-care ultrasound and an extensive preoperative assessment of the carpal tunnel and median nerve can assist in determining diagnosis, primary etiological causes, and further treatment planning through conservative or surgical interventions.