Thoracic Outlet Syndrome (TOS) Flashcards
What is the most common initial complaint in patients with thoracic outlet syndrome (TOS)?
Paresthesias are the most common initial complaint, present in up to 95% of patients with TOS. Although these paresthesias typically involve the medial arm, forearm, and ulnar two digits, they may also affect the median nerve distribution or the entire hand/arm, making differential diagnosis challenging.
What is Roos test (EAST) and how is it performed in evaluating thoracic outlet syndrome?
Roos test (Elevated Arm Stress Test) involves having the patient hold their arms in 90° abduction with external rotation while rapidly opening and closing the hands for 3 minutes. A positive test occurs when symptoms are reproduced or rapid fatigue develops, typically within 1 minute in patients with positional nerve compression.
How is the Upper Limb Tension Test performed, and what does a positive result indicate?
The Upper Limb Tension Test involves three sequential maneuvers:
1) elevating the arms to the sides with elbows straight;
2) dorsiflexing the wrists with arms still extended; and
3) tilting the head away from the side being evaluated.
Each subsequent maneuver typically elicits increasing discomfort/paresthesias as tension on the brachial plexus increases, suggesting neurogenic TOS.
What is the proper sequence for provocative testing when examining a patient with suspected TOS?
Provocative testing should begin distally and progress proximally, assessing for carpal tunnel syndrome, tendinitis, cubital tunnel syndrome, rotator cuff problems, and cervical radiculopathy before testing for TOS. This sequence prevents false positive results.
What is the role of electrodiagnostic studies in the diagnosis of thoracic outlet syndrome?
Although electrodiagnostic studies are typically normal in disputed/electrically negative TOS (97% of cases), they remain recommended as part of the initial work-up to rule out distal nerve compression syndromes and to identify the rare true neurogenic TOS.
What is the ‘gold standard’ imaging study for evaluating arterial thoracic outlet syndrome?
Angiography remains the gold standard for evaluating arterial TOS, providing the best visualization of arterial anatomy and allowing for therapeutic thrombolysis in acute situations.
What radiographic findings might be present in a patient with true neurogenic thoracic outlet syndrome?
Patients with true neurogenic TOS frequently have visible bony anomalies such as a rudimentary or fully developed cervical rib, abnormal first rib, or elongated C7 transverse process.
What is the diagnostic value of color duplex sonography in TOS evaluation?
Color duplex sonography has been found to be 92% sensitive and 95% specific in diagnosing vascular compromise in patients with TOS.
How should scalene muscle injection be performed and what is its role in TOS management?
Scalene muscle injection should ideally be performed under ultrasound guidance using a long-acting anesthetic and corticosteroid. It is most effective for patients with symptoms of less than 6 months duration.
What is the association between distal nerve compression syndromes and TOS, and how does this impact treatment?
An association between distal nerve compression (carpal tunnel, cubital tunnel) and TOS has been attributed to a ‘double-crush syndrome’ in 21-45% of patients.
What anatomical variations might a surgeon encounter during surgical decompression for thoracic outlet syndrome?
During surgical decompression, a surgeon might encounter cervical ribs, scalenus minimus muscle, subclavius tendon anomalies, and variations in the interscalene triangle dimensions.
What are the key differentiating features between the four subtypes of thoracic outlet syndrome according to Wilbourn’s classification?
Wilbourn’s classification includes:
1) Arterial TOS - involves arterial stenosis or aneurysm formation;
2) Venous TOS - presents with effort-induced thrombosis;
3) True neurogenic TOS - shows objective EMG changes;
4) Disputed/Electrically negative TOS - presents with symptoms but lacks objective findings.
What are the three anatomic triangles of the thoracic outlet and how do they relate to different compression syndromes?
The three anatomic triangles are:
1) Interscalene triangle - site of neurogenic compression;
2) Costoclavicular triangle - site of venous compression;
3) Subcoracoid/pectoralis minor space - site of neurovascular compression.
What occupational factors predispose to the development of thoracic outlet syndrome?
Occupational risk factors include repetitive lifting, uninterrupted arm movements with the hand at or above shoulder level, and awkward or static posture.
What are the key clinical differences between arterial, venous, and neurogenic forms of thoracic outlet syndrome?
Arterial TOS presents with claudication and decreased pulses;
Venous TOS presents with swelling and cyanosis;
Neurogenic TOS presents with pain and weakness without vascular symptoms.
What physical examination findings are characteristic of true neurogenic thoracic outlet syndrome?
True neurogenic TOS typically shows evidence of denervation including wasting of the thenar eminence and intrinsic muscles.
What is Paget-Schroetter syndrome and how does it relate to thoracic outlet syndrome?
Paget-Schroetter syndrome is effort-induced thrombosis of the subclavian or axillary vein, representing a severe manifestation of venous TOS.
