Bifid Median Nerve Causing Carpal Tunnel Syndrome: MRI and Surgical Correlation

Abstract

Carpal tunnel syndrome can be secondary in some patients, and vascular anomalies (usually a persistent median artery), median nerve variations, or both are among the etiologic factors. High division of the median nerve proximal to the carpal tunnel (known as a bifid median nerve) is a median nerve anomaly that has an incidence rate of 2.8%. This rare entity is often associated with various abnormalities that are clinically relevant, such as vascular malformations (persistent median artery), aberrant muscles, and carpal tunnel syndrome. The bifid median nerve is one cause of carpal tunnel syndrome because of its relatively higher cross-sectional area compared with a nonbifid median nerve. Obtaining magnetic resonance imaging and ultrasounds of bifid median nerves has helped surgeons avoid potential surgical hazards.This article describes 3 men with 4 bifid median nerves associated with a persistent median artery. Mean patient age was 38 years (range, 37-40 years). Mean follow-up was 7 years (range, 3-11 years). Patients were diagnosed with carpal tunnel syndrome and underwent open carpal tunnel release. To reveal a morphological etiology in patients in whom it the possibility of having idiopathic carpal tunnel syndrome is unlikely, preoperative imaging studies should be obtained. Bifid median nerves associated with a persistent median artery in the carpal tunnel are important to understand for their clinical and surgical significance. A secondary nature should be suspected in patients with unilateral symptoms, especially those with a history of symptoms and when the symptomatic hand shows severe neurophysiologic impairment but the contralateral hand is neurophysiologically intact. Inadvertent injury to the median nerve during carpal tunnel surgery can be minimized if the variations of the median nerve are recognized.

Sonographic Findings of the Bifid Median Nerve and Persistent Median Artery in Carpal Tunnel: A Preliminary Study in Chinese Individuals

“…Previous studies and several case reports have suggested that bifid median nerve occurs relatively frequently in patients with CTS 4-7. However, this conclusion is controversial.…”

“…Thus, it is important for surgeons to be aware of these structural variations when planning carpal tunnel release or other surgeries associated with carpal tunnel syndrome (CTS). Several studies have implicated bifid median nerve and persistent median artery as potential risks for CTS 4-7. However, this hypothesis has been disputed.…”

Three-dimensional display of peripheral nerves in the wrist region based on MR diffusion tensor imaging and maximum intensity projection post-processing

“…Occasionally, we met a healthy case with a bifid median nerve variation caused by the persistent median artery, which was regarded as a potential etiology for CTS [15] (Fig. 11).…”

Acute carpal tunnel syndrome caused by thrombosed persistent median artery associated with bifurcated median nerve in a pregnant woman

“…Several studies have showed that bifid median nerve and PMA association is a potential risk for CTS 5. A bifid median nerve and PMA are anatomic variants that have been reported widely in the surgical literature.…”