Thoracic Outlet Syndrome

Definition

 

Symptoms & signs due to compression of brachial plexus & /or subclavian vessels at root of neck

 

Epidemiology

 

80% 30-50 years 

 

F:M = 2:1 

 

Incidence

 

Uncommon

 

Anatomy

 

Thoracic Outlet forms communication at root of neck 

- for passage of nerves and vessels from mediastinum to axilla 

- vein is anterior to Scalenus Anterior

 

Boundaries

 

Anterior:  Scalaneus Anterior

Posterior: Scalaneus Medius

Floor:      First Rib

Roof:       Prevertebral fascia & clavicle

 

Aetiology

 

Bony / muscular / ligamentous compression of neurovascular bundle at Thoracic Outlet

 

Bony

 

1.  Cervical Rib

- 5 / 1000 

- only 10% of cervical ribs are symptomatic

- 10% of TOS have cervical rib

 

Varies from 

- enlarged TP 

- complete developed with cartilage uniting it to cartilage of 1st thoracic rib 

 

2.  1st Thoracic Rib

-  abnormal curve 

-  increased size or shape

 

3.  Clavicle

-  posterior fracture callus 

-  abnormal shape / malunion

 

Musculo-ligamentous

 

Most important cause

 

1.  Fibrous Band

 

Cervical rib joined to 1st rib by congenital fibrous band 

-  elevates lower part of brachial plexus 

-  makes it more susceptible to scissor compression by clavicle from above 

-  9 variants recognised

 

2.  Scalenus Muscles

 

Abnormal insertion 

Decreased size of cleft between S Anterior & S Medius

 

Other

 

Trauma

- Precipitates condition in 2/3

 

Posture

- shoulder sags with middle age 

- hyperabduction in sleep

- scapular winging secondary to trapezius palsy

 

Occupational

- hyperabduction of shoulders (painters, welders) 

- pressure (backpacks, soldiers)

 

Classification

 

1. Neurogenic

 

Compression of brachial plexus alone 

-  usually lower trunk C8,T1

-  most common 95%

 

2. Vascular

 

Compression of subclavian blood vessels alone 

- usually vein obstruction 

- occasionally arterial insufficiency 

- rare 2%

 

3. Combined

 

Compression of both nerves & vessels 

- rare 3%

 

Symptoms

 

2° compression of Plexus > Vessels

 

Pain

-  intermittent

-  suprascapular area and neck

-  may be whole arm

-  more common medial arm & ulnar forearm 

-  radiates to neck 

 

Worse after activity

- overhead

- carrying heavy weight

 

Paraesthesia

- C8 & T1 (mainly ulnar nerve distribution)

- may be whole arm

 

Weakness

- most noticeable is grip

 

Venous

- duskiness & cyanosis of hand 

 

Arterial

- cold, pale hand & forearm

- Raynaud's 

 

Signs

 

Pain from percussion or constant thumb pressure in supraclavicular region over plexus

 

Listen for bruit / compare arm BP

 

Sensation

-  decreased in C8 / T1 distribution

 

Power

-  decreased especially grip strength

 

1. Elevated Arm Stress Test (EAST)

- shoulder abducted 90° & ER 

- elbows at 90° 

- hands clasped / unclasped for 3min

- positive if symptoms reproduced or arms drop 2° pain & weakness

 

2.  Adson Manoeuvre

- head toward side tested, neck extended

- arm by side

- palpate radial pulse of extended arm

- patient inhales deeply

- positive test if decrease or obliteration in pulse with concomitant reproduction of symptoms

 

3.  Wright's Manoeuvre

- head turned away from tested arm, neck extended

- arm abducted and ER

- breath in

- loss of pulse or reproduction of symptoms

- highly sensitive

 

Xray neck / CXR

 

Cervical rib

Clavicle fracture

 

CT 

 

MRI

 

May show fibrous band 

- exclude cord pathology

 

Angiogram

 

Must do with arms abducted and by side

- will show compression of subclavian vein

 

NCS

-  unhelpful as symptoms intermittent 

-  stimulus cannot be placed proximal to site of compression or irritation 

-  exclude CTS / cubital tunnel Syndrome

 

DDx

 

Cervical Disc (C8/T1) / spinal cord lesion

Ulna nerve entrapment

Shoulder pathology

Pancoast tumour

MS

 

Management

 

Non-operative

 

Explanation & reassurance

- shoulder girdle exercises 

- posture improvement 

- analgesia

 

Operative

 

 

Indications

 

10% of patients

- intolerable pain 

- significant loss of function

- significant arterial or venous symptoms

 

Options

 

Resection of cervical rib

Scalenectomy 

Resection first rib

Clavicular osteotomy

 

Complications

 

Chest

- pneumothorax 

- empyema 

 

Nerve injury 

- phrenic nerve 

- T1 

 

Vessel injury 

 

Recurrence of symptoms