Thoracic Outlet Syndrome: Diagnosis, Causes, Symptoms, and Treatment

Thoracic Outlet Syndrome (TOS) is a diagnosis of exclusion, primarily based on clinical history and symptoms. It is a neurovascular compression syndrome affecting the brachial plexus within the thoracic outlet, located in the retroclavicular region. TOS can have either a neurogenic or vascular etiology and is more common in females. Anatomy of the Thoracic Outlet The thoracic outlet is a space created by the following structures: Clavicle First rib Subclavius muscle Costoclavicular ligament Anterior scalene muscle This space contains: Subclavian vessels Thoracic duct Lower trunk of the brachial plexus (C8 and T1 nerve roots) Types of Thoracic Outlet Syndrome Neurogenic TOS (most common): Caused by compression of the brachial plexus as it passes over the first rib or through the scalene muscles. Vascular TOS: Caused by compression of the subclavian artery or vein, sometimes due to an aneurysm. Causes of Compression in Thoracic Outlet Syndrome Cervical rib or an elongated C7 transverse process Anomalous insertion of scalene muscles First rib malunion Fibrous bands Repetitive shoulder movements Extreme arm positions Abnormal pectoralis minor muscle Athletic activities (e.g., weightlifting, rowing, swimming) Common Sites of Compression Scalene Triangle (Most common site) Formed by the anterior scalene (anteriorly), middle scalene (posteriorly), and first rib (inferiorly). Structures compressed: Brachial plexus and subclavian artery (subclavian vein does not pass through this triangle). Causes: Fibrous bands, elongated C7 transverse process, or cervical ribs. Under the Clavicle Compression by the subclavius tendon. Under the Conjoined Tendon Compression occurs at its insertion into the coracoid process. Clinical Presentation of Thoracic Outlet Syndrome Neurogenic Symptoms Shoulder and neck pain, often radiating to the forearm and hand Paresthesia in the upper limb Sensory loss in the ring and little fingers Intrinsic muscle weakness of the hand Vascular Symptoms Arterial ischemia (cold hands, pale discoloration, weak pulse) Venous congestion (swelling, cyanosis) Raynaud’s phenomenon (color changes in hands with cold exposure) Chronically diminished pulse Differential Diagnoses C8 radiculopathy (rule out if no neck pain and no radicular pain but C8-T1 sensory and motor changes are present) Ulnar nerve compression at the elbow Double Crush Syndrome (concurrent compression at the thoracic outlet and carpal tunnel) Medial antebrachial cutaneous nerve compression (sensory loss in the medial forearm and medial third of the hand; arises from the medial cord of the brachial plexus) Provocative Tests for Thoracic Outlet Syndrome (These tests have high false-positive rates and should not be used in isolation.) Adson’s Test (Most commonly used) Position: Abduction, extension, and external rotation of the arm while monitoring the radial pulse. The patient rotates their head towards the testing arm and may extend the neck. Positive test: Diminished pulse and symptom reproduction. Wright’s Test Position: Abduction and external rotation of the arm while the neck is rotated away. Positive test: Loss of pulse and symptom reproduction. Roos Test (Elevated Arm Stress Test – EAST) Position: Arms raised to 90° abduction and externally rotated. The patient rapidly opens and closes their fingers for 3 minutes. Positive test: Pain, numbness, or fatigue. Imaging and Diagnostic Studies Cervical spine X-ray: May show a cervical rib. Chest X-ray: Helps rule out a Pancoast tumor (apical lung tumor compressing the brachial plexus). Electromyography (EMG) and nerve conduction studies: Usually not helpful for diagnosis. Vascular studies: Can confirm a vascular subtype of TOS. Management of Thoracic Outlet Syndrome Non-Surgical Treatment (First-Line Therapy) Physical therapy: Strengthening of shoulder girdle muscles. Postural correction: Avoid shoulder sagging and maintain proper alignment. Activity modification: Avoid repetitive overhead arm movements. Surgical Treatment (Indications) Severe pain refractory to conservative management Neurological deficits Persistent vascular insufficiency Surgical Options First rib resection (or resection of a cervical rib, if present) Release or excision of the anterior and middle scalene muscles Excision of any abnormal fibrous bands Surgical approaches: Transaxillary approach (90% success rate for first rib resection) Supraclavicular approach Vascular procedures may be necessary in vascular TOS cases. Quizzes with answers. 1) What is the most common cause of neurogenic thoracic outlet syndrome? Cervical rib First rib fracture Clavicle malunion Pancoast tumor Correct answer: Cervical rib Explanation: A cervical rib or scalene muscle anomaly is the most common cause of neurogenic TOS. 2) Which structure does NOT pass through the scalene triangle? Subclavian artery Subclavian vein Brachial plexus C8 nerve root Correct answer: Subclavian vein