Choose an answer, then open any option to work its reasoning.
MSK · Neurovascular Compression
Thoracic Outlet Syndrome: Nerve, Vein, or Artery?
Arm overhead narrows the outlet. The pattern tells you which structure is being squeezed: the lower brachial plexus, the subclavian vein, or the subclavian artery.
What this page makes you able to do
- Name the type of TOS from the stem: numb hand = nerve, blue swollen arm = vein, cold pale hand = artery
- Map each type to its bottleneck: interscalene triangle, costoclavicular space, subcoracoid space
- Run and interpret the provocative tests, and know which one is too nonspecific to trust alone
- Separate TOS from cervical radiculopathy, carpal and cubital tunnel, and Pancoast tumor
- Choose the workup and first-line management for each type
- Dr. Fatima Ali, DOPsychiatry residentPrimary reviewer
Last reviewed
From the Attending:
Location plus trigger names the type: numb hand = nerve, blue swollen arm = vein, cold pale hand = artery. Arm up, outlet down. Every time.
Prove it
Opening question
A 31-year-old dental hygienist has 5 months of aching neck and shoulder pain with tingling along the medial forearm, ring finger, and little finger when she reaches overhead at work. Radial pulses are normal, Spurling test and wrist Tinel are negative, and a Roos maneuver reproduces her symptoms with grip fatigue.What is the most likely diagnosis?
- Why this is rightOverhead-provoked paresthesias along the medial forearm and ulnar hand map to the lower trunk C8 to T1; negative distal entrapment tests and a positive Roos push the lesion into the outlet.
- Why this failsCarpal tunnel is median nerve at the wrist: thumb, index, and middle fingers, worse at night, with a positive wrist Tinel, none of which are present here.
- Why this failsCubital tunnel is ulnar nerve at the elbow: ring and little finger symptoms flaring with elbow flexion and a medial epicondyle Tinel, not overhead posture.
- Why this failsA root lesion reproduces with Spurling and often carries reflex or dermatomal motor changes; her Spurling is negative.
- Why this failsVenous TOS is a vascular story: acute swelling, cyanosis, and heaviness after effort with a thrombosed axillosubclavian vein, not tingling with normal pulses.
Work the reasoning
The lower trunk C8 to T1 between the scalenes: the medial forearm, ring, and little finger map to it, and grip fatigue fits its motor fibers.
Negative Spurling, negative wrist Tinel, and a Roos-provoked pattern push the lesion proximal, into the outlet rather than the root, wrist, or elbow.
The medial antebrachial cutaneous territory (C8 to T1) is the most specific clue for neurogenic TOS: neither distal tunnel explains it.
The answer is neurogenic thoracic outlet syndrome: the lower trunk pinched when the arm goes up, with every distal test clean.
CHOOSE THE BOTTLENECK
Nerve, Vein, or Artery?
Name the structure before you pick the test: each type has its own stem clue and its own management.
Three structures thread the same narrow doorway between the neck and the arm, and each one fails in its own signature way. The lower trunk of the brachial plexus (C8 to T1) is the one squeezed in the vast majority of cases; the subclavian vein and the subclavian artery account for the rest, and the artery is the one that can cost a digit.
Frequency: over 90% of TOS cases. Structure: lower brachial plexus C8 to T1 compressed between the anterior and middle scalenes. Stem clue: ulnar-side paresthesia, medial forearm pain, grip fatigue worse with overhead activity, normal distal pulses. Tests: positive Adson (scalene narrowing), positive Roos/EAST (arms at 90 degrees, hands opening and closing for 3 minutes), positive Wright (hyperabduction). Management: posture correction and physical therapy first, unless progressive neurologic deficit or a structural lesion. Two flavors matter: true neurogenic TOS has objective findings (thenar wasting, abnormal electrodiagnostics) and is rare; the common disputed form is subjective, positional, and treated with PT. Rule: neurogenic TOS is the common one, posture and PT first, not surgery.
Also called: Paget-Schroetter syndrome, effort thrombosis of the axillosubclavian vein. Structure: subclavian vein compressed at the costoclavicular space. Stem clue: acute arm swelling, cyanosis, and heaviness after repetitive overhead effort; duplex shows axillosubclavian thrombosis. Classic patient: young overhead athlete (pitcher, swimmer, rower) with sudden arm swelling after competition. Danger: clot propagation and post-thrombotic syndrome if undertreated. Management: urgent anticoagulation with vascular evaluation for catheter-directed thrombolysis and decompression, not routine stretching. Rule: blue, swollen arm after the game = venous TOS. Anticoagulate, don't stretch.
Frequency: under 5% of TOS, but the most dangerous. Structure: subclavian artery compressed at the scalene triangle, often by a cervical rib or fibrous band. Stem clue: cold pale hand, pulse loss with provocative positioning, digital ischemia, Raynaud-like color changes. Danger: poststenotic dilation leads to aneurysm formation and distal embolization to the digits. Management: vascular imaging and surgical evaluation; anticoagulation alone does not fix the structural compression. Rule: cold + pale + pulse loss = artery. Escalate to vascular evaluation.
Arterial and venous TOS both live in the same doorway, but they announce themselves oppositely.
Lock the classic trigger with a one-liner.
A 20-year-old pitcher wakes after a doubleheader with a swollen, cyanotic, heavy throwing arm and distended shoulder veins. Which type of TOS is this?
Venous TOS (Paget-Schroetter). Sudden swelling with cyanosis after overhead effort in a young athlete is effort thrombosis of the axillosubclavian vein. Neurogenic TOS. That type tingles and fatigues; it does not swell the arm. Arterial TOS. The artery gives a cold pale hand with pulse loss, not a swollen blue arm. Subclavian steal. Steal is dizziness with arm use and blood pressure asymmetry, without arm swelling.
THE REGION TELLS YOU THE TYPE
Tap Where It Hurts
The symptom zone names the structure: neck and medial forearm for nerve, whole arm for vein, hand color for artery.
The outlet is three stacked corridors, and knowing what runs through each one tells you which stem to expect. The interscalene triangle (anterior scalene in front, middle scalene behind, first rib below) carries the brachial plexus and the subclavian artery; the costoclavicular space (between clavicle and first rib) is where the subclavian vein crosses; and the subcoracoid space under the pectoralis minor holds everything as it dives toward the arm. Compression can happen at any of the three, and the structure that gets pinched decides the presentation.
Tap a region.
Now trace the bundle from deep to superficial.
Tap the structures in the order they leave the neck.
THE MOVING DOORWAY
Arm Down, Arm Up
Overhead abduction narrows every corridor: the structure in the tightest spot decides the pattern.
Lifting the arm rotates the clavicle, tightens the scalenes, and narrows the costoclavicular and subcoracoid spaces. That is why every TOS stem carries a positional trigger: hair styling, painting a ceiling, pitching, or carrying a bag on the shoulder.
The four classic provocative tests all exploit that narrowing. Adson: extend the arm, rotate the head to the affected side, and take a deep breath: a fading radial pulse is positive, but many asymptomatic people lose the pulse, so specificity is low and the test should never stand alone. Wright (hyperabduction): abduct and externally rotate the arm: pulse loss or symptom reproduction is positive. Roos elevated arm stress test (EAST): arms abducted 90 degrees with elbows flexed 90 degrees, hands opening and closing for 3 minutes: reproduction of the symptoms is the positive result. Costoclavicular (military): shoulders thrust back and down narrows the space between clavicle and first rib.
Run the bedside exam in the order that keeps you from missing the vascular types.
Match each test to what it provokes.
Match each test to its maneuver.
Which test is too nonspecific to diagnose anything on its own?
Many healthy people lose the radial pulse during this maneuver, so a positive result should never be used alone to diagnose TOS. Which test is it?
Adson test. Pulse obliteration with head rotation and a deep breath occurs in many asymptomatic people, so the Adson test has low specificity and is a supportive sign, not a diagnosis. Roos EAST. EAST is judged by symptom reproduction over 3 minutes, not by pulse loss. Spurling test. Spurling targets the cervical root, not the outlet. Wrist Tinel. Wrist Tinel points to carpal tunnel, a different nerve at a different level.
THE MIMIC ARSENAL
Don't Call Everything TOS
The same hand can be numb from the neck, the elbow, the wrist, or the lung apex: the pattern is the diagnosis.
Neurogenic TOS is a diagnosis of exclusion that lives on the ulnar side of the forearm and hand with an overhead trigger. Before committing to it, walk the mimic list. Cervical radiculopathy radiates from the neck along a dermatome, reproduces with Spurling, and shows a disc on MRI. Carpal tunnel is median at the wrist: nocturnal thumb, index, and middle finger tingling with a positive wrist Tinel and Phalen. Cubital tunnel is ulnar at the elbow: ring and little finger numbness worse with elbow flexion, a Tinel at the medial epicondyle, and numbness over the dorsal ulnar hand: the dorsal cutaneous branch is spared in wrist-level ulnar lesions but not in elbow lesions. Pancoast tumor is the one that kills: an apical lung mass invading the lower plexus and the sympathetic chain in a smoker, with Horner syndrome and weight loss. Rotator cuff disease aches at the shoulder but never causes distal paresthesias.
Route the symptom pattern to its home.
Choose a pattern to route it.
Two ulnar-flavored tunnels, one key difference.
This mimic is a tumor, not a pinch.
A 62-year-old smoker has shoulder and medial arm pain, 8 kg weight loss, ptosis and miosis of one eye, and intrinsic hand weakness. What is the most likely diagnosis?
Pancoast tumor. Weight loss plus Horner syndrome (ptosis, miosis, anhidrosis) plus an apical lung mass plus lower plexus hand weakness is the Pancoast triad. Neurogenic TOS. TOS is mechanical and positional; it never causes weight loss or eye signs. Subclavian steal. Steal gives dizziness with arm use and blood pressure asymmetry, with no Horner. Rotator cuff tear. Cuff disease aches at the shoulder and spares the sympathetic chain.
THE WORKUP
The Two Tests That Matter
Each type has exactly one imaging question worth asking: ask the right one.
Neurogenic TOS is clinical first: if the story and exam fit and there is no red flag, electrodiagnostics and cervical MRI exist to exclude a root lesion, not to make the diagnosis. In true neurogenic TOS, ulnar motor and sensory studies and the medial antebrachial cutaneous nerve are the most often abnormal. Venous TOS is confirmed with duplex ultrasound of the axillosubclavian vein, then venography or CT venography for intervention planning. Arterial TOS needs arterial imaging (CTA or MRA) of the subclavian artery, a chest radiograph hunting for a cervical rib or elongated C7 transverse process, and bilateral arm blood pressures.
Order the workup for a swollen arm after effort.
Tap the workup steps in order.
The radiograph already pointed the way.
A chest radiograph shows a cervical rib, and the hand is cool with a diminished radial pulse during head rotation. Which study confirms the diagnosis?
CTA or MRA of the subclavian artery. Cold, pale hand with positional pulse loss beside a cervical rib is arterial TOS; arterial imaging shows stenosis, poststenotic dilation, or aneurysm. Duplex of the subclavian vein. The vein is the wrong vessel: there is no swelling or thrombosis story. Cervical spine MRI. Spine imaging addresses radiculopathy, not a pulseless hand. EMG/NCS. Electrodiagnostics address the nerve type and never image the artery.
MANAGEMENT
PT First, Surgery for the Real Thing
The treatment is set by the type: stretch the nerve type, thrombolyse the vein, operate on the artery.
Uncomplicated neurogenic TOS starts with physical therapy: posture correction, scalene and pectoralis minor stretching, and scapular strengthening. Surgery (first rib resection with scalenectomy, often via a supraclavicular approach) is reserved for true neurogenic TOS with progressive deficit or wasting, and for the vascular types. Effort thrombosis is treated with anticoagulation plus catheter-directed thrombolysis, followed by delayed first rib resection to decompress the costoclavicular space and prevent recurrence. Arterial TOS is a surgical disease: embolectomy or arterial repair with cervical rib resection: anticoagulation alone never fixes the structural pinch, and a delayed diagnosis can cost digits.
Route the type to its management.
Choose a type to route its management.
Pearl. The artery never waits for physical therapy. Cold, pale, pulseless means vascular surgery, full stop.
Prove it
Walkthrough: name the mechanism
Original practice scenarios, one at a time. Work each option to see why it wins or fails.
Clinical walkthrough
