The long thoracic nerve is a slender cord, roughly a millimeter in diameter, that runs from the neck down the side of the chest to power the serratus anterior muscle. When it works properly, you never think about it. When it stops working, the shoulder blade lifts off the ribcage in a visible deformity called scapular winging, and overhead arm movement becomes painful or impossible. The nerve’s unusual length and exposed path make it one of the more injury-prone peripheral nerves in the body, and its damage turns up in contexts ranging from breast surgery to backpacking to weightlifting.
Where It Comes From and Where It Goes
The long thoracic nerve typically forms from three nerve roots leaving the spinal cord in the neck: the fifth, sixth, and seventh cervical roots (C5, C6, and C7). That three-root pattern is the most common, but anatomists dissecting cadavers have documented a wider range, including contributions from C4 or C8 in some individuals, and occasional cases where one of the standard roots is missing entirely.
The upper roots (C5 and C6) usually pass between or through the middle scalene muscle on the side of the neck, while the C7 branch runs in front of it. These branches merge into a single trunk that dips beneath the collarbone and then travels down the lateral chest wall, clinging to the surface of the serratus anterior muscle. Ultrasound studies using high-frequency probes have measured the nerve at just under a millimeter in diameter both where it exits the scalene muscles and where it rides alongside the lateral thoracic artery on the chest wall.
The nerve’s full peripheral length averages about 22 centimeters from the top of the serratus anterior, and it extends roughly 8 centimeters past the bottom tip of the shoulder blade. That makes it one of the longest motor nerves in the upper body, which matters because length means more surface area exposed to stretch, compression, and surgical instruments.
What the Nerve Actually Does
The serratus anterior is a broad, fan-shaped muscle anchored to the ribs on one side and the inner border of the shoulder blade on the other. Its job is to hold the scapula flat against the ribcage and to rotate it upward when you raise your arm. The long thoracic nerve is its sole motor supply, so losing the nerve means losing the muscle.
The relationship is not a simple on-off switch, though. The upper portion of the serratus anterior, which receives branches from multiple nerve roots, stabilizes the scapula’s rotation during shoulder elevation. The middle portion pulls the scapula forward around the ribcage (protraction). The lower portion drives upward rotation, further protraction, and a backward tilt of the scapula that helps clear the shoulder joint for overhead motion. Electrical stimulation of the upper division of the nerve in cadaver studies produced visible shoulder protraction, confirming the nerve’s direct mechanical link to forward scapular movement.
Why It Gets Hurt So Easily
Several features of the nerve’s anatomy set it up for trouble. Its course through the scalene muscles in the neck creates an early pinch point. After exiting the scalene region and passing beneath the clavicle inside the bundle of nerves and blood vessels serving the arm (the axillary sheath), the nerve emerges from that sheath and angles backward toward the ribcage. Anatomical measurements show the nerve makes about a 30-degree bend at this exit point. When you raise your arm, the entire axillary bundle shifts upward, stretching and further angulating the nerve right where it leaves the sheath.
Autopsy studies have also found that the nerve and its blood supply are vulnerable to both compression and stretching where the nerve passes in front of the lower portion of the scapula. This differs from an older theory that positioned the main danger zone at the level of the second rib. Marked differences in the nerve’s exact path from person to person may explain why some people develop paralysis under the same mechanical conditions that leave others unaffected.
Common Causes of Injury
Long thoracic nerve damage shows up in a surprisingly wide range of situations. Broadly, the causes fall into surgical, traumatic, repetitive, and inflammatory categories.
Surgical and Medical Procedures
The nerve is at particular risk during axillary lymph node dissection, a procedure commonly performed in breast cancer staging. In one study of patients who underwent axillary dissection, about 11 percent had electromyography-confirmed long thoracic nerve injury, and most of those injuries involved partial damage to the nerve fibers rather than complete severing. Chest tube placement is another documented culprit; a case report described a patient who developed both scapular winging and chest wall pain after tube thoracostomy, with ultrasound confirming entrapment of the long thoracic nerve at the scar site. The nerve can also be injured during first-rib resection for thoracic outlet syndrome, during cardiac surgery, and during procedures involving the axilla or lateral chest wall.
Athletic and Repetitive Strain
Repetitive overhead movements are a well-recognized trigger. Weightlifters performing overhead presses, swimmers, tennis players, and even people who carry heavy loads on their shoulders (like backpackers) can develop traction injuries to the nerve. A case report documented a patient who developed scapular winging and restricted overhead motion directly from overhead weightlifting, with nerve testing confirming long thoracic nerve damage. The mechanism is usually repeated stretch of the nerve at the vulnerable angulation points described above, rather than a single dramatic event.
Inflammatory and Idiopathic Cases
Sometimes the nerve fails without any obvious trauma. Parsonage-Turner syndrome (neuralgic amyotrophy) is an inflammatory condition that attacks peripheral nerves in the shoulder region, often striking after a viral illness or vaccination. It typically begins with severe shoulder pain followed days or weeks later by weakness. The long thoracic nerve is one of its frequent targets, though the condition can hit other shoulder-area nerves as well. In some patients, no clear cause is ever found, and the palsy is labeled idiopathic.
What Scapular Winging Looks and Feels Like
The hallmark sign is the medial border of the shoulder blade lifting away from the ribcage, creating a wing-like protrusion that becomes more obvious when you push against a wall or reach forward. Pain is common but not universal. Some people notice aching along the shoulder blade or the side of the chest, while others primarily experience weakness and a feeling of instability when trying to use the arm overhead. Forward flexion of the shoulder beyond about 15 degrees can be enough to provoke significant pain in some cases, leading people to simply stop using the arm in that range.
It is worth distinguishing medial winging from lateral winging. Serratus anterior paralysis from long thoracic nerve injury causes the inner (medial) edge of the scapula to lift. Trapezius or rhomboid paralysis, by contrast, causes the outer (lateral) edge to wing out. The distinction matters because the causes, nerve involvement, and treatment strategies differ.
Getting the Diagnosis Right
Visual inspection catches the obvious cases: ask someone to push both hands against a wall, and a winged scapula on one side is hard to miss. But the classic wall push-up test has a significant limitation. A study comparing two clinical tests found that the wall push-up was 100 percent sensitive for picking up winging but had zero specificity for confirming that serratus anterior dysfunction was the actual cause. Many other shoulder conditions can produce some degree of scapular prominence during a wall push-up. A shoulder flexion resistance test, where the examiner resists the patient’s attempt to raise the arm forward, proved both 100 percent sensitive and 100 percent specific for serratus anterior dysfunction in the same study.
Electromyography and nerve conduction studies remain the standard for confirming that the long thoracic nerve itself is damaged. These tests can distinguish partial from complete injury and gauge severity. One research group studying patients referred for “isolated” long thoracic nerve palsy found that more than half had additional electrical abnormalities beyond the long thoracic nerve’s territory, suggesting the injury was part of a broader nerve problem rather than truly isolated. That finding is a reminder that electrodiagnostic testing should survey neighboring nerves, not just the suspected one.
High-resolution MRI at 3 Tesla can now visualize the nerve directly in about three-quarters of cases and shows abnormal findings in roughly 70 percent of patients with confirmed neuropathy on electromyography. When the MRI reveals swelling in the serratus anterior muscle (a sign of nerve-related muscle damage), the nerve itself is visible about 86 percent of the time. MRI adds the most value when trying to identify a structural cause of compression, such as thickening in the scalene muscles or a mass along the nerve’s path.
Waiting It Out Versus Intervening
The traditional teaching has been that most long thoracic nerve palsies recover on their own within about two years. There is truth to this, especially for stretch injuries and inflammatory causes where the nerve is bruised but not severed. Physical therapy during the waiting period focuses on maintaining shoulder range of motion, strengthening the remaining scapular stabilizers, and avoiding movements that further irritate the nerve.
However, the rosy picture of universal spontaneous recovery has been challenged. Evidence shows that a meaningful percentage of patients end up with residual winging, persistent muscle weakness, and easy fatigability even after the two-year window closes. The question of when to move from conservative management to surgery is still debated, but the consensus has been shifting toward earlier investigation and intervention for patients who are not showing signs of recovery on serial nerve testing.
Scapular bracing offers a middle ground during the recovery period. A case series of patients fitted with a custom scapular winger’s brace found that muscle strength increased by one grade with the brace on, and patients who kept wearing it recovered their brace-free shoulder strength or experienced less pain at follow-up.
Surgical Options When the Nerve Does Not Recover
When conservative treatment fails, surgical decisions hinge on whether the nerve can be salvaged or whether the muscle needs to be replaced.
Nerve Decompression and Neurolysis
If the nerve is compressed rather than severed, surgical release of the surrounding tissue (decompression and neurolysis) can restore function. A long-term study of 50 patients who underwent this procedure found improvement in winging in 98 percent of cases, with good or excellent results in 92 percent. Pain relief was good or excellent in 86 percent. Even among the 21 patients who had shoulder instability before surgery, most saw improvement, though five continued to have some instability despite resolution of the winging itself. Separate data showed that shoulder flexion and abduction improved from averages around 104 and 97 degrees before surgery to about 163 and 157 degrees afterward, a gain that was statistically superior to what has been reported for muscle transfer procedures.
Nerve Transfer
When the nerve is too damaged for simple decompression, surgeons can reroute a nearby donor nerve to take over the serratus anterior’s motor supply. The thoracodorsal nerve, which powers the latissimus dorsi, is a common donor because of its proximity and compatible function. In a small series, three patients who received a thoracodorsal-to-long thoracic nerve transfer regained full forward shoulder flexion at an average of about two and a half months, a remarkably fast recovery that reflects the short distance the regenerating nerve fibers need to travel.
Tendon Transfer
For chronic cases where nerve repair is no longer viable, surgeons can redirect a functioning muscle to substitute for the paralyzed serratus anterior. The pectoralis major transfer is the most commonly described procedure. The sternal head of the pectoralis major, sometimes extended with tendon graft material, is detached from its normal insertion and reattached to the lower scapula. This effectively tethers the scapula to the chest wall through a different muscle, reducing the winging and restoring some overhead function. Scapulothoracic fusion, where the scapula is surgically fixed to the ribs, is a last-resort option reserved for patients in whom soft-tissue procedures have failed or are not feasible.
Anatomical Variations That Complicate Things
One reason this nerve trips up clinicians and surgeons alike is that its anatomy is not the same from person to person, or even from side to side within the same person. A cadaver study documented the nerve arising from as few as two roots and as many as five (C4 through C8). Case reports have described individuals in whom one side followed the textbook three-root pattern while the opposite side was missing the C5 contribution entirely, with the nerve forming solely from C6 and C7 and taking a different path relative to the scalene muscles.
These variations have real consequences. A surgeon who expects the nerve to pass through the middle scalene muscle may not recognize it if it runs behind or in front of the muscle on that particular patient. A nerve block targeting a standard anatomical landmark could miss or inadvertently damage a variant nerve. High-frequency ultrasound has made preoperative mapping more practical; studies with 24-MHz probes have shown that the C5 and C6 components of the nerve can be reliably visualized above the collarbone in the vast majority of people, which helps surgeons plan their approach.
Children and the Long Thoracic Nerve
Long thoracic nerve palsy is less commonly discussed in children, but it does happen. Falls are a typical trigger. A case report described a four-year-old boy who developed acute scapular winging after falling onto his back. In another documented case, a nine-year-old girl experienced long thoracic nerve palsy twice: the first episode followed a fall and resolved completely with rehabilitation within six months, but the nerve was injured again later. The fact that a child’s nerve recovered fully after one episode and then failed again highlights both the regenerative capacity of young nerves and their continued vulnerability to re-injury.
Diagnosis in children can be tricky because young kids may not articulate their symptoms clearly, and scapular winging can be subtle in a small frame. Clinicians who see a child with unexplained shoulder weakness or asymmetry after a fall should keep this nerve on their differential.
When “Isolated” Palsy Is Not Really Isolated
A finding that deserves more attention is how often long thoracic nerve palsy turns out to be part of a broader nerve injury. In a series of seven patients initially diagnosed with isolated long thoracic nerve palsy, four had additional electrodiagnostic abnormalities outside the nerve’s territory, and five had MRI evidence of nerve enlargement or muscle wasting in areas the long thoracic nerve does not supply. These patients did not have any obvious compression of the nerve in the scalene muscles, suggesting the underlying process was more diffuse, possibly an inflammatory neuropathy or a brachial plexopathy masquerading as a single-nerve problem.
The clinical takeaway is that scapular winging with a confirmed long thoracic nerve lesion should prompt testing of neighboring nerves, particularly the spinal accessory nerve and the suprascapular nerve. A broader workup avoids the trap of treating one nerve while missing a more widespread condition that might require different management. Electrodiagnostic examination ideally includes bilateral nerve conduction studies of both the long thoracic and spinal accessory nerves, along with needle testing of their target muscles.
Ultrasound-Guided Treatment
High-resolution ultrasound is not just useful for diagnosis; it is increasingly used to guide treatment. Hydrodissection, a technique where fluid is injected around a nerve under ultrasound guidance to free it from surrounding scar tissue, has been applied to long thoracic nerve entrapment. In one reported case involving entrapment at a chest tube scar site, ultrasound-guided hydrodissection of the long thoracic nerve relieved both the scapular winging and the chest wall pain. The advantage of ultrasound guidance is that the clinician can watch the needle tip in real time and confirm that the injectate is spreading around the nerve, reducing the risk of inadvertent nerve puncture. This approach is still emerging and has not been studied in large trials, but it offers a minimally invasive option for patients whose nerve is trapped in scar tissue rather than severed.