Thoracic Outlet Syndrome

1. Interscalene Triangle

• Borders: Anterior Scalene (Anterior), Middle Scalene (Posterior), First Rib (Inferior).
• Contents: Brachial Plexus (Trunks) and Subclavian Artery.
• Note: The Subclavian Vein passes ANTERIOR to the Anterior Scalene (outside the triangle). Thus, scalene hypertrophy affects Artery/Nerve but spares Vein.

The C8/T1 roots are most vulnerable at the base of the triangle.

2. Costoclavicular Space

• Borders: Clavicle (Superior), First Rib (Inferior), Costoclavicular Ligament (Anterior).
• Contents: Artery, Vein, and Nerve.
• Compression: Clavicle fracture callus, first rib anomalies.

"Nutcracker" mechanism between clavicle and first rib.

3. Subcoracoid (Pectoralis Minor) Space

• Borders: Pectoralis Minor tendon (Anterior), Chest wall (Posterior), Coracoid (Superior).
• Compression: Hyperabduction of the arm stretches the bundle under the Pec Minor.

This is rarer than scalene compression.

Neurogenic TOS (NTOS)

• Prevalence: Greater than 95% of cases.
• Demographics: Women affected more than men (approximately 3:1), age 20-50.
• Pathology: Scarring of scalenes, whiplash, repetitive stress.
• Symptoms: Pain in neck/trapezius/arm. Paresthesia in C8/T1 distribution (Ulnar forearm/hand). Weakness (late).

The diagnosis is often clinical, supported by exclusion of other causes.

Venous TOS (VTOS)

• AKA: Paget-Schroetter Syndrome. "Effort Thrombosis".
• Prevalence: ~3-4%.
• Demographics: Young athletic men (pitchers, swimmers, weightlifters).
• Pathology: Compression of vein between clavicle/1st rib + repetitive endothelial damage leads to DVT.
• Symptoms: Sudden swelling, cyanosis, heaviness, dilated collateral veins (Urschel's sign).

Urgent referral to vascular surgery is required.

Arterial TOS (ATOS)

• Prevalence: ~1% (Rare).
• Pathology: Almost always a bony abnormality (Cervical Rib or anomalous 1st rib) causing post-stenotic dilation leading to aneurysm and emboli.
• Symptoms: Ischemia, pallor, coldness, claudication, distinct from Raynaud's.

Look for a palpable pulsatile mass.

Disputed/Nonspecific TOS

• Definition: Subjective pain without objective NCS/EMG findings.
• Controversial: Many surgeons do not operate unless objective signs exist.

Psychosocial factors often play a major role.

Neurogenic TOS

• First Line: Conservative.
• PT: Postural correction, strengthening trapezius (elevate shoulder girdle), stretching scalenes/pec minor.
• Meds: Gabapentin/pregabalin, NSAIDs.
• Scalene block: Local anaesthetic injection into the anterior scalene is mainly diagnostic/prognostic (a positive response is part of the SVS NTOS criteria and predicts surgical benefit). Note: a placebo-controlled RCT (Finlayson 2011) found scalene Botox gave no therapeutic pain benefit, so it should not be relied on as a treatment.
• Surgery: If conservative measures fail (typically over 3-6 months). First Rib Resection plus Scalenectomy.

Surgery is reserved for refractory cases with significant disability.

Venous TOS (Paget-Schroetter)

• Urgent: Catheter-directed Thrombolysis (within 14 days).
• Anticoagulation: Heparin/Warfarin for 3 months.
• Surgery: First Rib Resection is MANDATORY to prevent recurrence. Usually done same admission or shortly after lysis.
• Balloon: Venoplasty AFTER decompression (never before, or it ruptures).

Timing is critical (within 2 weeks of clot).

Arterial TOS

• Urgent: Embolectomy / Thrombolysis if ischemic.
• Surgery: Cervical Rib Resection + First Rib Resection.
• Reconstruction: Arterial bypass/graft if aneurysm exists.

Distal embolectomy may also be needed.

Approaches

• Transaxillary: Most common. Cosmetically superior. "Roos Approach". Access to 1st rib. Hard to see C-rib or reconstruct vessels.
• Supraclavicular: Best for Nerve visualization and Cervical Rib. Standard for NTOS/ATOS.
• Infraclavicular: Good for Venous (Vein exposure).

Robotic First Rib Resection is emerging.

First Rib Resection (Supraclavicular)

1. Exposure: Transverse incision 2cm above clavicle.
2. Scalene: Identify Phrenic Nerve (on Ant Scalene). Medial retraction.
3. Release: Divide Anterior Scalene (protect Phrenic).
4. Rib: Expose 1st Rib. Protect Subclavian Artery (Posterior) and Vein (Anterior).
5. Excision: Divide rib anteriorly and posteriorly. Remove Middle Scalene attachment.
6. Neurolysis: External neurolysis of plexus.

Complete removal of the rib back to the transverse process is key.

Intraoperative Complications

• Pneumothorax: Pleura is attached to the undersurface of the 1st rib via Sibson's fascia (15-30% risk). Chest X-ray in recovery is mandatory.
• Vascular Injury: Subclavian artery or vein laceration - requires immediate vascular repair.
• Brachial Plexus Injury: Direct trauma or excessive traction during first rib resection.
• Phrenic Nerve Palsy: Lies on anterior scalene - must protect during scalenectomy. Results in diaphragm paralysis.
• Long Thoracic Nerve: Injury causes scapular winging - avoid excessive retraction.
• Thoracic Duct Injury: Chylothorax (left-sided approach) - requires drainage and dietary modification.

Careful anatomical dissection and nerve identification prevents most complications.

Postoperative Complications

• Haematoma: Supraclavicular wound - may require evacuation.
• Wound Infection: Rare but treat aggressively given proximity to vessels.
• Horner's Syndrome: Sympathetic chain injury - ptosis, miosis, anhidrosis.
• Recurrence: Due to incomplete rib resection (stump too long) or reformation of scar tissue.
• Persistent Symptoms: Consider incomplete decompression or incorrect diagnosis.
• Winging: Long thoracic nerve injury.

Most complications are preventable with meticulous surgical technique.

Late Complications

• Recurrent TOS: Incomplete first rib resection, fibrous band reformation, or scalene muscle regrowth.
• Chronic Pain: May indicate incorrect initial diagnosis or neuropathic pain.
• Winged Scapula: Long thoracic nerve injury - may require tendon transfer.
• Functional Limitation: Some patients have persistent weakness despite decompression.

Re-operation success rates are lower than primary surgery.

Surgical Outcomes by Type

• NTOS: 80-90% good outcomes if diagnosis is correct and confirmed by positive scalene block response. Poorer results in "Disputed" TOS or workers' compensation cases.
• VTOS: Excellent outcomes with early thrombolysis and first rib resection. Greater than 90% long-term vein patency if treated within 2 weeks.
• ATOS: Good outcomes if arterial reconstruction is patent and no embolic sequelae. May require staged procedures.

Conservative management for NTOS achieves 50-70% improvement with dedicated physiotherapy.

Favorable Prognostic Factors

• Objective positive NCS/EMG findings
• Positive response to scalene block (Botox or local anaesthetic)
• Clear anatomical cause (cervical rib, first rib anomaly)
• Short duration of symptoms before surgery
• Absence of workers' compensation or litigation

Poor Prognostic Factors

• Disputed/Nonspecific TOS without objective findings
• Long symptom duration (greater than 2 years)
• Previous failed neck or shoulder surgery
• Significant psychosocial factors or secondary gain
• Double crush syndrome (concurrent CTS or cubital tunnel)

Patient selection is critical for surgical success.

Recurrence Rates

• Primary Surgery: 5-15% recurrence rate.
• Causes: Incomplete first rib resection, scalene muscle regrowth, fibrous band reformation.
• Re-operation: Success rates lower than primary surgery (60-70%).

Meticulous surgical technique and complete rib excision minimize recurrence.

Global Epidemiology

• Distribution: Neurogenic TOS makes up roughly 90-95% of cases, venous ~3-5%, arterial ~1%.
• Sex/age: NTOS predominantly affects women (about 3:1) aged 20-50; venous (effort) thrombosis predominantly affects young athletic men.
• Cervical rib: Present in approximately 0.5-1% of the general population (radiographic studies), more common in women; only a minority ever become symptomatic. Arterial TOS is almost always associated with a bony anomaly.
• Provoking factors: Repetitive overhead work and sport (throwers, swimmers, weightlifters), prior clavicle fracture/malunion, and post-whiplash scalene scarring.

The true incidence of NTOS is unknown worldwide because there is no gold-standard diagnostic test.

Guidelines Side-by-Side

• SVS (Society for Vascular Surgery, 2016): Reporting standards defining NTOS by 3 of 4 criteria including a positive scalene block; the global reference framework.
• AANEM / neurology bodies: Emphasise that EMG/NCS (especially reduced MABC sensory response) confirm only true neurogenic TOS; normal studies do not exclude the disputed form.
• AAOS / hand-surgery consensus: Conservative therapy and postural rehabilitation first-line for NTOS; surgery reserved for objective deficit or refractory disabling symptoms.
• Vascular consensus (ESVS-aligned practice): Venous TOS - early catheter-directed thrombolysis then first rib decompression; arterial TOS - urgent revascularisation plus bony decompression.

Across all societies the unifying message is the same: discipline the NTOS diagnosis and treat the vascular subtypes urgently.

Registry & Outcome Data

• Unlike arthroplasty, TOS has no dedicated international implant/procedure registry - evidence comes from institutional series and meta-analyses.
• Best pooled venous data: Lugo (2015, 12 series) and Karaolanis (2021, 25 studies/1511 patients) consistently favour thrombolysis followed by first rib resection.
• Reported recurrence after first rib resection is roughly 5-15%, usually from incomplete posterior rib removal or fibrous-band re-formation.
• The lack of a registry and absence of randomised trials is itself a recognised limitation driving calls for prospective multicentre collaboration.

Interpret all surgical "success rates" cautiously given heterogeneous, mostly retrospective data.

High- vs Limited-Resource Settings

• High-resource: Duplex ultrasound, CT/MR angiography, dedicated brachial plexus MRI, neurophysiology, catheter-directed thrombolysis and elective first rib resection (open, thoracoscopic or robotic) all available.
• Limited-resource: Diagnosis leans on history, examination and plain radiographs (cervical rib, apical chest film to exclude Pancoast); systemic anticoagulation may substitute where thrombolysis/interventional radiology is unavailable, accepting higher recurrence.
• Universal first steps: Plain cervical-spine and chest radiographs to identify a cervical rib or apical mass are cheap, available everywhere and high-yield.
• Referral: Venous and arterial TOS are vascular emergencies and warrant urgent transfer to a centre with vascular/interventional capability wherever feasible.

Whatever the setting, excluding Pancoast tumour and confirming the subtype precede any decompression.