The long thoracic nerve is a purely motor nerve that arises from the supraclavicular part of the brachial plexus. It contains fibers from the spinal cord segments C5 to C7.
Function
The long thoracic nerve provides motor innervation to the serratus anterior muscle.
Course
The long thoracic nerve passes through the middle scalene muscle and then runs dorsal to the brachial plexus toward the lateral thoracic wall, where it lies against the serratus anterior muscle, which it also innervates. From there, the long thoracic nerve continues caudally along the lateral thoracic wall to the inferior border of the serratus anterior muscle, approximately at the level of the 9th rib.
Clinical relevance
In the event of long thoracic nerve palsy, the arm can no longer be elevated above the horizontal, and the scapula protrudes posteriorly. This phenomenon is referred to as winged scapula.