A 35-year-old woman is evaluated for numbness, tingling, and weakness in her left arm that radiates from the shoulder to the fingers. Her symptoms began 3 months ago and appear to be worsening. They occur with repetitive use of the arm, especially with overhead activities. She has been painting a ceiling mural for the past 6 months. She has no history of arm or shoulder trauma. She takes no medications.
On physical examination, vital signs are normal. When the patient holds her arms above her head for several minutes during the examination, the symptoms are reproduced. The neck demonstrates full range of motion, and muscle bulk and tone in the upper extremities are normal bilaterally. Neurologic examination is normal, and all upper extremity pulses are full and equal.
Results of electrodiagnostic studies are normal.
Which is the most appropriate therapy for this patient?
B. Interscalene injection of botulinum toxin type A
C. Physical therapy
D. Surgical decompression
MKSAP Answer and Critique
The correct answer is C. Physical therapy. This content is available to MKSAP 18 subscribers as Question 116 in the General Internal Medicine section. More information about MKSAP is available online.
Physical therapy aimed at shoulder girdle muscle strengthening and improving posture would be the best therapeutic option for this patient with thoracic outlet syndrome (TOS). TOS is caused by compression of the brachial plexus, subclavian artery, or subclavian vein as these structures pass through the thoracic outlet. There are three main clinical subtypes of TOS, defined by the primary structure involved (nerve, artery, vein). Neurogenic TOS is the most common subtype and is caused by compression of the brachial plexus nerve roots as they exit the triangle formed by the first rib and the scalenus anticus and medius muscles. Symptoms include paresthesias and pain that typically worsen with activities that involve continued use of the arm or hand, especially those that include elevation of the arm. This patient's presentation is most consistent with neurogenic TOS. In most patients, there are no abnormal neurologic findings. Electrodiagnostic studies frequently fail to reveal any abnormalities. Although imaging studies are often obtained, they are not required to make the diagnosis; they may, however, reveal the presence of a structural abnormality, such as an anomalous cervical rib. First-line therapy for neurogenic TOS includes improving posture and strengthening shoulder girdle muscles.
Although neurogenic TOS is caused by intermittent compression of the brachial plexus within the thoracic outlet, the role of gabapentin in managing this condition has not been well studied. Gabapentin is not considered to be first-line therapy.
Observational studies have supported the use of interscalene injection of anesthetic agents, glucocorticoids, or botulinum toxin type A in patients with neurogenic TOS. However, in a randomized, double-blind clinical trial, patients treated with botulinum toxin did not show improvement in function, pain, or paresthesias compared with patients treated with placebo.
Surgical decompression is not considered to be first-line therapy for neurogenic TOS, especially in patients who lack neurologic abnormalities. The procedure is reserved for patients who do not respond to conservative measures or for those with progressive or disabling neurologic symptoms.
- Symptoms of neurogenic thoracic outlet syndrome include paresthesias and pain that typically worsen with activities that involve continued use of the arm or hand, especially those that include elevation of the arm; first-line therapy includes improving posture and strengthening the shoulder girdle muscles.