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. 2021 May 18:14:1259-1269.
doi: 10.2147/JPR.S303142. eCollection 2021.

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

Dougho Park  1 , Byung Hee Kim  1 , Sang-Eok Lee  1 , Dong Young Kim  2 , Yoon Sik Eom  2 , Jae Man Cho  3 , Joong Won Yang  3 , Mansu Kim  3 , Heum Dai Kwon  3
Affiliations

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

Dougho Park et al. J Pain Res. .

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 mm2, slightly larger than 15.1±4.2 mm2 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 mm2 and 6.0 mm2, 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.

Keywords: bifid median nerve; carpal tunnel syndrome; diagnostic ultrasound; electrodiagnosis; pain measurement.

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Conflict of interest statement

The authors report no conflicts of interest in this work.

Figures

Figure 1
Figure 1
Flow chart of this study.
Figure 2
Figure 2
CSA measurement of the bifid median nerve at the scaphoid and pisiform level. After detecting the scaphoid and pisiform bones, the CSA measurement (dotted lines) is carried out at the proximal carpal tunnel level.
Figure 3
Figure 3
Measurement of flexor retinaculum bowing (arrow heads). After drawing a line connecting the hook of the hamate and tubercle of the trapezium where the flexor retinaculum is attached (transverse dotted line), the distance from the line to the top of the flexor retinaculum is measured (vertical dotted line). The radial and ulnar sides branch of the bifid median nerve (arrows) passes beneath the flexor retinaculum.
Figure 4
Figure 4
Identification of the persistent median artery (arrow) between the radial and ulnar sides branch of the bifid median nerve (arrow heads) by ultrasonography.
Figure 5
Figure 5
Comparison of CSA between the radial and ulnar side branches of the median nerve. The radial branch shows a significantly larger CSA than the ulnar branch. ***Means P-value <0.001.
See this image and copyright information in PMC

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