The long thoracic nerve is a purely motor nerve that arises from the pars supraclavicularis of the brachial plexus. It contains fibers from the C5 to C7 spinal cord segments.
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 posterior to the brachial plexus to the lateral thoracic wall, where it lies against and innervates the serratus anterior muscle. 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 raised above the horizontal, and the scapula protrudes posteriorly. This phenomenon is referred to as scapula alata.