Long thoracic neuropathy and dorsal scapular

Occurs in many sports, but especially tennis. Its due to acute and/or repetitive use when the arm is raised and head is turned in the other direction. It can be due to compression of C5-6 roots as they travel through the scalene muscles, bow-stringing of the nerve across a fascial band, or traction injury. Non traumatic causes include brachial neuritis (idiopathic, postviral, or post surgical). Other causes are stab wounds, direct pressure from a heavy shoulder bag or shoulder braces during surgery, including thoracotomy, axillary node resection, resection of the first rib for TOS, and radical mastectomy. Blows to the sholder or lateral thoracic wall during falls or injuries can cause it. Its reported as the sole presentation of lyme disease.

The serratus anterior stabilizes the scapula against the chest wall, and long thoracic neuropathy causes weakness and difficulty moving the shoulder and arm, especially abduction or flexion above shoulder level. Patients may have a dull ache around the shoulder girdle. The shoulder looks funny due to winging. Clinical signs include scapular winging with arm outstretched against the wall. The superior angle of the scapula flips medially whereas the inferior angle swings laterally (opposite of that seen in axillary neuropathy). In contrast to trapezius weakness, in which winging is exaggerated with abduction of the arm, in LT neuropathy, its worse with outstretched arm thrust forward. Arm abduction beyong 110 degrees may be impossible. Acutely there may be shoulder pain but chronically it may be painless. Besides axillary neuropathy, differential includes scapular winging due to muscular dystrophy, C7 radiculopathy, and separation of serratus from insertion in a fracture of the scapula (easy to repair). See pictures of long thoraic and axillary neuropathy in Stewart, p 160 and 90 respectively.

Evaluation is x rays of shoulder, chest and shoulder to rule out a compressive lesion such as an osteochondroma. EMG is needed to confirm that the weak muscle is the serratus anterior as the trapezius also can produce scapular winging. It is formed directly from nerve roots C5-7 and will be NORMAL in plexopathy, abnormal with root lesion. EMG of serratius anterior is done with patient lying on the opposite side, arm adducted across the chest. It can be done by looking at medial scapular border , lower aspect below rhomboids. In the mid axillary line, isolate a rib, anterior to the lattissmus dorsi, posterior to the breast tissue in a woman. Treatment is rest, bracing and PT for ROM and strengthening of the shoulder girdle. Braces maintain scapula against the thorax to prevent further winging. Surgery for long thoracic palsy not due to penetrating trauma is only after 1-2 years of observation as natural history favors recovery. The current procedure of choice is transfer of the sternal head of the pectoralis major to the inferior angle of the scapula.