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as this large nerve bundle exits the neck region. The LTN is directly adjacent to the major nerve bundles that comprise the brachial plexus. Often, when there is brachial plexus compression, the LTN can be compressed, but symptoms from other nerves likely dominate, so LTN compression may go undetected. Other causes of nerve compression in this region include falls or blows directly on top of the shoulder, especially those that may include clavicular fracture. 1 You see injuries like these in football. Heavy straps such as those in backpacks, knapsacks, shoulder bags, or even bra straps can also compress the nerve. If you are a massage therapist who carries your table around with a strap over your shoulder, this is something to consider. Rapid tensile loading on the nerve can also cause damage and dysfunction. The rapid stretch of the nerve is most common in sudden lateral flexion movements of the cervical region, such as those that happen in contact sports or in lateral whiplash injuries from automobile accidents. 2 There are also some associations of LTN injury with sports activities that have a strong single-arm dominance, such as bowling, tennis, or golf. LTN injuries are most frequently associated with an activity. However, nerve compression can occur from inactivity if the body is in a position that compresses the nerve for long periods, such as awkward sleeping positions or postural strain from a challenging workstation or occupational activity. There are also reports of LTN injury resulting from surgeries in which the patient was placed in a position on the surgical table for hours at a time. 3 Surgery can also be implicated in LTN damage from direct trauma of the nerve during the surgical procedure. There are reports of LTN injury from mastectomy, first rib resection to treat thoracic outlet syndrome, cardiac surgery, and even spinal fusion surgery to treat scoliosis. 4 In addition to the more common causes of nerve injury described above, some anatomical variations can contribute to LTN pathology. An anatomical anomaly can occur in which there is a connecting branch between the dorsal scapular nerve and the long thoracic nerve (Image 2). When a connection exists between two nerves, each is less mobile and more susceptible to tension injury. 5 DYSFUNCTIONAL BIOMECHANICS As noted earlier, the LTN is the motor supply nerve for the serratus anterior muscle. The serratus anterior's function is to hold the scapula firmly against the thoracic rib cage and contribute to upward rotation of the scapula. However, this function should not be oversimplified because it plays a key role in scapulothoracic mechanics. When the shoulder is moved in abduction, there is a coordinated movement between the scapula and humerus called the scapulo-humeral rhythm. This coordinated pattern is such that for every three degrees of abduction, two degrees occur at the glenohumeral joint and one occurs at the scapulothoracic articulation. This coordinated movement allows the shoulder to abduct as fully as possible. The upward rotation of the scapula helps make a greater range of motion than would be possible with just glenohumeral abduction alone. In a situation of LTN compression, weakness of the serratus anterior means that full upward rotation of the scapula does not occur during abduction. Consequently, range of motion in abduction is diminished. However, when the scapula does not move in full upward rotation, the lateral edge of the humeral head is more likely to contact the underside of the acromion process during abduction, leading to shoulder impingement and potential damage to soft tissues in the subacromial region, including the bursa, supraspinatus, or joint capsule. SYMPTOMS OF LTN PATHOLOGY Because the LTN is primarily a motor nerve, it does not have many sensory fibers. Thus, the usual indicators of nerve compression, such as sharp pain or paresthesia, are not always present or may be diminished. Those with LTN injury may report weakness in the shoulder along with pain sensations. Keep in mind shoulder pain can result from impingement problems that are directly caused by the biomechanical dysfunction. Attempting to address shoulder impingement and not recognizing the contribution of LTN involvement can lead to poor results and continual problems. Sometimes people describe weakness with various shoulder motions. The weakness might be accompanied with pain, but could also occur without any pain or sensory deficit. The client may also describe some difficulty performing activities overhead, as these motions usually involve a significant degree of scapular upward rotation to complete. C h e c k o u t A B M P 's l a t e s t n e w s a n d b l o g p o s t s . Av a i l a b l e a t w w w. a b m p . c o m . 99 2 Long thoracic nerve Dorsal scapular nerve Proximity of the LTN to the dorsal scapular nerve. Their close proximity sometimes allows for a connecting branch between them. Image courtesy 3D4Medical's Essential Anatomy 5 application.