Symptoms attributable to brachial plexus nerve compression include pain, numbness, and tingling (paresthesia) in the neck, shoulder, arm, and hand. The distribution of symptoms in the hand often extends beyond that expected for either the median or ulnar nerves, involving all fingers. Patients with NTOS attributable to compression at the pectoralis minor tendon often describe upper anterior chest and axillary pain. The intensity of symptoms of NTOS can vary with the extent of upper extremity activity and are usually reliably exacerbated with arm elevation and abduction.

Many NTOS patients experience relatively mild symptoms, with gradual progression in severity punctuated by periodic exacerbations. Others experience steady, progressive worsening of symptoms and related disability. Hand muscle weakness and atrophy (Gilliatt-Sumner hand) are rare, typically following long-standing brachial plexus compression due to an associated cervical rib or similar bony anomaly.

Physical examination typically identifies reproducible tenderness to palpation over the supraclavicular scalene triangle and/or the infraclavicular subcoracoid space (FIG 2).

Most NTOS patients experience recurrent upper extremity symptoms in response to provocative positional maneuvers, such as the upper limb tension test (ULTT) or the 3-minute elevated arm stress test (EAST) (FIG 2). Positional dampening of the radial artery pulse at the wrist during arm abduction and external rotation (Adson’s test) is nonspecific and inaccurate and is generally not useful in establishing or excluding a diagnosis of NTOS.

Directed physical examination is performed to determine the presence of cervical spine degenerative disease or peripheral nerve compression (carpal tunnel and cubital canal syndromes) as potential alternative sources of NTOS-like symptoms as well as evidence of arterial or venous compromise to the affected extremity. Signs of increased upper extremity sympathetic tone are also sought, including digital swelling, discoloration, and skin hypersensitivity (allodynia).

Documentation of patient-reported symptoms and quantification of disability prior to treatment are accomplished by completion of standardized outcomes measurement tools such as the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire and quality-of-life instruments.¹⁴ Repeated use of these instruments at various intervals before and after treatment has provided increasing insight into the relative value of alternative management strategies.¹⁵

Although imaging and other diagnostic studies may provide helpful ancillary information, there is no definitive test to confirm or exclude the diagnosis of NTOS. Diagnosis remains quintessentially clinical and dependent on experienced pattern recognition.

Plain anteroposterior chest radiographs will identify a cervical rib when present. No other currently available imaging study adds significant value to the clinical diagnosis of NTOS (FIG 3).

Conventional electrophysiologic tests (electromyography and nerve conduction studies) are often performed to exclude peripheral nerve compression disorders or cervical radiculopathy. These tests are usually negative or nonspecific in NTOS and cannot be used to establish or exclude the diagnosis.

Vascular laboratory studies (Duplex ultrasound) may detect alterations in upper extremity blood flow attributable to subclavian artery compression during arm elevation. However, positional subclavian artery compression may represent an incidental and unrelated vascular finding and does not establish a diagnosis of neurogenic or arterial TOS. As they do not assess the presence or severity of brachial plexopathy, vascular laboratory studies add little specificity beyond the clinical diagnostic criteria.

Performance of image-guided anterior scalene and/or pectoralis minor muscle anesthetic blocks may assist the clinical diagnosis of NTOS.¹⁶ A positive block, characterized as temporary relief or improvement in the presenting
symptoms, strongly supports the clinical diagnosis of NTOS. A positive block may predict symptomatic relief from surgical decompression and is therefore highly useful in selecting candidates for 1st rib resection. Unfortunately, however, failure of temporary symptom resolution following muscle blockade does exclude the diagnosis of NTOS and should not preclude consideration of surgical management in otherwise compelling clinical candidates.

Initial treatment for NTOS is based on physical therapy to relieve scalene/pectoralis minor muscle spasm, improve
posture, enhance functional limb mobility, strengthen associated shoulder girdle musculature, and diminish repetitive strain exposure in the workplace. Incorrect approaches to physical therapy can result in worsening of symptoms and failure of conservative management. In many NTOS patients, significant symptomatic improvement may be experienced in response to physical therapy, particularly in the first 4 to 6 weeks. Because NTOS is commonly chronic, however, and subject to acute symptomatic “flare ups” (often related to overuse activities or new injury), such patients should continue prescribed physical therapy exercises during long-term follow-up. Patients that fail a conscientious and effective physical therapy, as well as alternative conservative measures, are referred for consideration of surgical intervention.

Supraclavicular decompression (scalenectomy, 1st rib resection, and brachial plexus neurolysis) is recommended on the basis of (1) sound clinical diagnosis of NTOS, (2) substantial resulting disability (interference with daily activities and/or work), and (3) an inadequate response to standard physical therapy. Supraclavicular decompression may also provide relief from persistent or recurrent NTOS symptoms following prior surgery, particularly when continued conservative measures prove ineffective.

For patients with symptoms referable to the subcoracoid space, release of the pectoralis minor tendon should be included in the supraclavicular thoracic outlet decompression procedure. Pectoralis minor tenotomy may also be performed as a stand-alone procedure when nerve compression symptoms are limited to this area.^17,18

Decompression should be performed as a staged, sequential procedure in patients with bilateral NTOS symptoms. The initial supraclavicular decompression, with or without pectoralis minor tenotomy, is performed on most symptomatic or dominant extremity. If symptoms remain present or progress, contralateral supraclavicular decompression may be performed within 6 to 12 weeks of the initial procedure. Normal phrenic nerve function should be verified on the side of the previous procedure, by chest fluoroscopic examination, before contralateral intervention.