Electrodiagnostic, Sonographic, and Clinical Features of Carpal Tunnel Syndrome with Bifid Median Nerve

Abstract

Purpose: A bifid median nerve (BMN) is not a rare variant. This study aimed to investigate the features of carpal tunnel syndrome (CTS) accompanied by BMN. Patients and Methods: In this retrospective study, we defined a BMN group as CTS with BMN and a non-bifid median nerve (NMN) group as CTS without BMN. All hands were assigned to four severity grades according to the findings of electrodiagnosis (EDx): very mild, mild, moderate, and severe. The cross-sectional area (CSA) of the median nerve, palmar bowing of the flexor retinaculum, and persistent median artery (PMA) were assessed by ultrasonography. Numerical pain rating scale (NRS) and symptom duration were assessed as clinical variables. Results: Sixty-four hands (57 patients) and 442 hands (341 patients) were enrolled in the BMN and the NMN groups, respectively. BMN was prevalent in 12.6% of all CTS hands. The distribution of EDx severity grade was milder in the BMN group than in the NMN group (P<0.001). The CSA of the BMN group was 16.2±4.1 mm 2 , slightly larger than 15.1±4.2 mm 2 in the NMN group (P=0.056). The BMN group showed higher NRS than the NMN group (5.5±1.5 and 4.4±1.7, respectively; P<0.001). In the subgroup analysis, NRS was significantly higher in the BMN group than in the NMN group at all EDx severity grades. In the BMN group, the PMA group showed greater EDx severity (P=0.037) and higher NRS (6.0 and 5.0, respectively; P=0.012) than the non-PMA group. The radial side branch's CSA was larger than that of the ulnar side branch (10.0 mm 2 and 6.0 mm 2 , respectively; P<0.001). Conclusion: CTS with BMN presented more severe symptoms and relatively milder EDx severity. When assessing the severity of CTS with BMN, the clinical symptoms should primarily be considered, as well as we should complementarily evaluate the EDx and ultrasonography.

Application of digital infrared thermography for carpal tunnel syndrome evaluation

“…The moderate (S3) group included cases with abnormal transcarpal latency or sensitivity test findings, with abnormalities of the compound motor nerve action potential, and without abnormal findings of needle electromyography of the APB muscle. The severe (S4) group included those with abnormal transcarpal latency or sensitivity test findings and abnormal findings of needle electromyography of the APB muscle 24 .…”

“…Patients were asked to assume an upright sitting position and instructed to bend their elbows at 90° and fully supinate their forearms. The pisiform and scaphoid were identified at the level just proximal to the carpal tunnel, and transverse images were acquired to measure the cross-sectional area (CSA) of the median nerve 24 , 25 .…”

Coexistence of anomalous muscle, persistent median artery, bifid median nerve causing carpal tunnel syndrome: A case report and literature review

“…Previous studies show that the prevalence of BMN in CTS is about 18%–18.5%, while the prevalence in normal control is approximately 9.4%–15.4%, they believed that BMN was not a rare variant and did not support its etiological relationship with CTS ( 10 , 25 ). However, Park et al ( 26 ) demonstrated that CTS with BMN showed more severe symptoms and relatively mild electrophysiological diagnosis.…”

Characteristics of diabetic and non-diabetic carpal tunnel syndrome in terms of clinical, electrophysiological, and Sonographic features: a cross-sectional study

“…In contrast, the moderate-to-severe group included patients with abnormal findings in the motor nerve conduction studies. The detailed methods for the electrodiagnosis of CTS have been described previously [ 18 , 19 ].…”