Long thoracic nerve: anatomy and functional assessment

Area of Science:

• Anatomy and physiology
• Neuroscience
• Orthopedics

Background:

• The precise anatomy and function of the long thoracic nerve remain incompletely understood.
• Existing anatomical representations may not accurately reflect the nerve's course.

Purpose of the Study:

• To elucidate the detailed anatomy of the long thoracic nerve.
• To develop and propose a clinical test for evaluating the function of the long thoracic nerve's upper division.

Main Methods:

• Anatomical dissection of the long thoracic nerve and serratus anterior muscle in 15 fresh cadavera.
• Intraoperative electrical stimulation of the long thoracic nerve in 6 patients undergoing brachial plexus injury surgery.
• Observation of resultant shoulder motion following electrical stimulation.

Main Results:

• The long thoracic nerve originates from C5, C6, and C7 nerve roots, with C5 and C6 forming the upper division.
• The upper division courses superiorly and posteriorly to the brachial plexus upper trunk.
• Electrical stimulation of the upper division branches elicited shoulder protraction, indicating serratus anterior muscle activation.

Conclusions:

• The long thoracic nerve's supraclavicular trajectory parallels the brachial plexus, differing from textbook diagrams.
• Shoulder protraction serves as a viable clinical test for assessing the function of the long thoracic nerve's upper division.