thoracic outlet syndrome

definition

· coined by Rob in 1958

· symptoms and signs due to compression of brachial plexus and/or subclavian vessels at root of neck

epidemiology

· age

· 30-50 yrs (80%)

· sex

· F:M = 2:1

· incidence

· varies from rare to common

aetiology

· bony, muscular or ligamentous compresion of neurovascular bundle at thoracic outlet

Anatomic anomalies

· thoracic outlet forms communication at root of neck for passage of vessels and nerves from mediastinum to axilla

· three regions

· superior outlet

· scalenic hiatus

· costoclavicular passage

Bony

Cervical rib

· incidence 5 per 1000

· varies from

· enlarged transverse process

· complete development with cartilage uniting it to cartilage of 1st thoracic rib

· 5-10% are symptomatic

· 10% of TOS have cervical rib

1st thoracic rib

· abnormal curve

· increased size or shape

Clavicle

· posttraumatic callus

· abnormal shape

Musculoligamentous

· most important cause

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

Scalenus muscles

· abnormal insertion

· decreased size of cleft between anterior and medial

Other

Trauma

· precipitates condition in 2/3

Posture

· shoulder sag with middle age

· hypderabduction during sleep

Occupational

· hyperabudction of shoulders

· painters, welders, mechanics

· pressure

· backpacks, soldiers

classification

Neurogenic

· compression of brachial plexus alone

· usually lower trunk (C8,T1)

· by far the most common - 95%

Vascular

· compression of subclavian vessels alone

· usually vein with obstruction

· occasionally artery with insufficiency

· rare - 2%

Combined

· compression of both nerves and vessels

· rare - 3%

clinical features

Symptoms

· most commonly related to compression of plexus rather than vessels

Pain

· intermittent

· gradually worse

· suprascapular area down shoulder and arm

· may be whole arm but more commonly medial arm and ulnar forearm

· radiates to neck

· may be secondary headaches from muscle spasm

· worsened after increased activity (esp. overhead)

Parasthesiae

· mainly ulnar nerve distribution or C8 and T1

· may be whole arm

Weakness

· most noticable is grip

Venous

· duskiness and cyanosis of hand and forearm

Arterial

· cold, pale hand and forearm

· Raynaud’s phenomenon

Signs

East test

· Elevated Arm Stress Test

· shoulder abducted 90^o and externally rotated

· elbows at 90^o

· hands clasped and unclasped for 3 minutes

· positive if

· symptoms reproduced

· arms dropped due to pain and weakness

Plexus pain

· pain from percussion or constant thumb pressure in supraclavicular region

Sensation

· decreased in C8 / T1 distribution

Power

· decreased

· esp. interosseous and grip strength

Vascular

· classical but inaccurate tests

· Adsons and Allens

· obliteration of radial pulse by neck and arm positioning

· Adsons - inhale, elevate chin, turn head to affected side

· Allens - raise and ER arm, turn head away from affected side

investigations

Radiology

Plain x-ray neck

· cervical rib

Chest x-ray

· abnormality of clavicle or 1st rib

CT scan

· gives no extra information

MRI

· may demonstrate fibrous band

· useful to exclude cervical pathology

Angiogram

· difficult to demonstrate intermittent compression

· indicated with

· significant difference in arm BPs

· bruit

· aneurysm

Cervical myelography

· exclude

· cervical disc

· intra or extra dural lesion

Electrodiagnostic studies

· unhelpful

· symptoms intermittent

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

· useful to exclude

· carpal tunnel syndrome

· cubital tunnal syndrome

differential diagnosis

· cervical disc

· carpal tunnel syndrome

· orthopaedic shoulder problem

· impingement

· rotator cuff injury

· ulnar nerve compression at elbow

· spinal cord tumour or disease

· pancoast tumour

· multiple sclerosis

treatment

Nonoperative

· shoulder girdle exercises

· improvement of posture

· analgesia

Operative

· in 10% of patients

Indications

· intolerable pain

· significant loss of function

· significant arterial or venous symptoms

Options

· approach

· supraclavicular

· transaxillary

· posterior

· procedure

· scalenectomy

· resection of 1st rib

· vascular procedures

Complications

· chest problems

· pneumothorax

· empyema

· nerve injury

· phrenic nerve

· T1

· vessel injury

· recurrence of symptoms

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