High-resolution Ultrasound of the Thenar Motor Branch of the Median Nerve

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Congress:

ECR 2016

Poster Number:

C-1727

Type:

Scientific Exhibit

Keywords:

Trauma, Diagnostic procedure, Ultrasound, Neuroradiology peripheral nerve, Musculoskeletal system, Extremities

Authors:

F. Zaottini¹, J. Smith², S. Airaldi¹, C. Martinoli¹; ¹Genova/IT, ²Rochester/US

DOI:

10.1594/ecr2016/C-1727

DOI-Link:

https://dx.doi.org/10.1594/ecr2016/C-1727

Fig. 1: Anatomical views of the ventral aspect of the wrist and hand. After removal of...

Fig. 2: Anatomical views of the ventral aspect of the wrist and hand. Closer look to...

Fig. 3: Ultrasound anatomy of the TMB of the MN.Level of origin and vertical segment....

Fig. 4: Ultrasound anatomy of the TMB of the MN.Distal intrathenar segment. Transverse...

Aims and objectives

The thenar motor branch (TMB) of the median nerve (MN) - which is also referred to as the recurrent motor branch of the median nerve - is a relevant structure within the carpal tunnel region as it supplies the primary motor innervation to the thenar muscles (i.e. opponens pollicis, abductor pollicis brevis and superficial part of flexor pollicis brevis) in most subjects (Figure1-2). As the median nerve courses through the carpal tunnel, it splits into two or three common interdigital nerves. In its typical configuration,...

Methods and materials

Ten unembalmed cadaveric wrist-hand specimens were evaluated by placing 0.2-0.3 ml of diluted colored latex adjacent and into in the presumed TMB using direct 16-7MHz ultrasound visualization. At a minimum of 24 hours post-injection, specimens were dissected to identify the course of the TMB and determine whether the sonographically-guided latex injection had accurately localized the TMB. Presence of latex within and/or around the TMB versus no latex within the TMB, thickness of the vertical nerve segment measured to the nearest 0.1mm, and variations in the...

Results

In the cadaveric study, the presumed vertical segment of the TMB was identified and targeted for latex injection. Subsequent dissection confirmed that n=10 sonographically-guided injections placed latex into and around the TMB of the MN. In this series, all 10 TMBs appeared to travel through a fibrous tunnel formed by the distal edge of the flexor retinaculum and the thenar fascia. No cadaveric specimen demonstrated a true transligamentous course of the TMB. These data are reported elsewhere [1]. In the group of healthy subjects, the...

Conclusion

High-resolution ultrasound can identify the TMB of the MN and characterize its abnormalities, providing unique information about this small nerve branch of the hand.

Personal information

References

Al-Quattan. Variations in the course of the thenar motor branch of the median nerve and their relationship to the hypertrophic muscle overlying the transverse carpal ligament. J Hand Surg Am 2010; 35:1820-1824 Smith J, Barnes DE, Barnes K, Strakowski J, Martinoli C. Sonographic visualization of thenar motor branch of the median nerve: a cadaveric validation study. J Hand Surg (manuscript submitted)