A careful history and physical examination enables proper classification of TOS.

The neurogenic form accounts for the majority of cases in modern series (>95%).² Symptoms of neurogenic TOS, which is more prevalent in women, include paresthesia; pain; and impaired strength in the affected shoulder, arm, or hand along with occipital headaches and neck discomfort. There is commonly an antecedent history of hyperextension neck injury or repetitive neck trauma. Patients frequently manifest tenderness on palpation in the supraclavicular fossa over the anterior scalene muscle. A careful vascular physical examination should confirm the presence of normal circulation.

Approximately 4% of patients with TOS present with venous involvement. Venous TOS patients typically present with acute onset of dull aching pain of the upper extremity associated with arm edema and cyanosis. Paresthesias may be present but are due to hand swelling instead of thoracic outlet nerve involvement. A history of strenuous and repetitive work or athletics involving the affected extremity is common, and most patients are young. This specific condition is also known as Paget-Schroetter syndrome or effort vein thrombosis, as the entrapped subclavian vein has progressed to thrombosis. Some patients will present less acutely with nonthrombotic subclavian vein occlusion or stenosis manifested by intermittent swelling with activity. Regardless, the etiology of venous TOS is mechanical, and treatment is ultimately aimed at eliminating not only the venous obstruction but also the muscular bands and ligaments that have entrapped and damaged the vein.

Arterial TOS typically presents in one of three ways: (1) asymptomatic, (2) arm claudication, and (3) critical ischemia of the hand. The majority of these patients have a cervical rib, which may or may not be fused to the 1st rib and is most commonly posterior to the subclavian artery. The etiology is chronic repetitive injury to the subclavian artery as it exits the thoracic outlet. This injury may cause subclavian artery stenosis but more commonly leads to ectasia or a true aneurysm.

In young patients (<40 years of age) with a classic presentation of neurogenic TOS, there is no need for extensive preoperative testing.

Older patients and those with a history of neck trauma should undergo magnetic resonance imaging (MRI) to rule out cervical disc pathology.

Preoperative physical therapy should be attempted for at least 8 weeks in patients with a diagnosis of neurogenic TOS. The aims of therapy are to improve posture and achieve greater range of motion. Patients with persistent symptoms of neurogenic TOS despite 8 weeks of physical therapy merit surgical intervention. At least 60% of patients will improve with physical therapy and lifestyle alterations.

A radiographically guided anterior scalene block with local anesthetic (lidocaine) injection may provide a few hours of symptomatic relief. Patients with suspected neurogenic TOS often present with a wide constellation of physical complaints, not all of which are directly attributable to the disorder. A scalene block not only helps confirm the diagnosis but also simulates the expected postoperative result, especially in older patients.³ This provides the patient and the surgeon reassurance that surgical intervention will be of benefit and demonstrates which symptoms can be reliably expected to improve.

As an alternative to surgical therapy, patients can then opt for a Botox (Allergan, Irvine, CA) injection. The Botox takes an average of 2 weeks to work and may be repeated. This may provide symptomatic relief for 2 to 3 months, allowing participation in physical therapy. However, not all TOS patients respond to Botox. This practice is especially helpful in patients who have had cervical spine fusions or shoulder operations as they can strengthen the muscles of their neck and back, which may alleviate the TOS symptoms.

Plain film chest x-ray is recommended for all patients undergoing surgical intervention for TOS to rule out a cervical rib.

Nerve conduction studies are typically normal in neurogenic TOS but may be useful in ruling out nerve compression such as carpal tunnel or cubital compression syndrome.

Duplex ultrasonography is the initial diagnostic modality to confirm pathology in patients with arterial TOS. Although useful to confirm axillosubclavian vein thrombosis in patients with suspected venous TOS, venography often supplants it for both diagnostic and therapeutic reasons. Lastly, venous TOS is frequently bilateral.