Thoracic Outlet Syndrome Flashcards
What is thoracic outlet syndrome?
The clinical features that arise from compression of the neurovascular bundle within the thoracic outlet.
What can signs and symptoms be divided into?
Neurological nTOS (most common)
Venous vTOS
Arterial aTOS
Most people affected are between 20-50 yo
When does TOS usually occur?
In setting of hyperextension injuries
Repetitive stress injuries
External compressing factors
Can also be secondary to anatomical abnormalities
Anatomy of structures by thoracic outlet
Brachial plexus and subclavian artery pass through the scalene traingle
Subclavian vein passes anterior to anterior scalene
Brachial plexus can be compressed between anterior and middle scalene or against the 1st rib or a cervical rib.
Typically it is the lower cord that becomes irritated.
Pathophysiology of TOS
Hypertrophy of scalene muscles or abnormality in first rib or presence of a cervical rib can all lead to compression on the brachial plexus or subclavian artery.
Previous clavicle fractures can lead to abnormal bony healing and lead to TOS
Costoclavicular ligmanet can reduce the costoclavicular space leading to vTOS
What is a cervical rib?
An extra rib that arises from the seventh cervical vertebra
Happens in 0.2-0.5% of the poopulation and can be partial or complete.
RIsk factors
Recent trauma
Repetitive motion occupations
Athletes
Anatomical varitations
Clinical features depend on neurological, arterial or venous involvement,
Symptoms may also worsen on certain movements.
Symptoms of nTOS
Paraesthesia and/or motor weakness often in ulnar distribution
Muscle wasting and pain can radiate to the neck and upper part of back.
Clinical features of vTOS
DVT and extremity swelling called Paget-Schrötter syndrome
In untreated severe cases there can be prominent veins over the shoulder due to collateralisation
Clinical features of aTOS
Claudication symptoms or acute limb ischaemia through either occlusion, distal embolisation or aneurysm formation.
Examination findings
Weakness or numbness
Swelling or tenderness
Limb ischaemia features
Tenderness over the scalene muscles
Special tests for TOS
Adson’s manoeuvre
Roo’s test
Elvey’s test
Explain Adson’s
Palpate radial pulse on the affected side with the arm initially abducted 30 degrees
Ask the patient to then turn their head and look at the affected side’s shoulder.
Fully abduct , extend and laterally rotate the shoulder
+ve = Decrease or loss of pulse
Explain Roo’s test
Abduct and externally rotate the shoulder on the affected side to 90 degrees, bend the elbow to 90 degrees and then ask the patient to open and close the hands slowly over a 3 minute period.
+ve = Worsening of symptoms
Explain Elvey’s test
Extend the arm to 90 degrees with the elbow extended and wrist dorsiflexed
Tilt the patients ear to each shoulder
+ve = Loss of radial pulse or worsening symptoms
Initial blood tests
FBC and clotting screen
Initial imaging
CXR to identify any bony abnormalities like
cervical ribs
long transverse cervical processes
Rib/clavicular fracture calluses
Special investigation for vTOS or aTOS
Venous and arterial duplex USS
The patient should be at rest with the arm in stress positions
CT or MRI imaging or a venogram may be used as well.
Investigations for nTOS
Nerve conduction studies to allow detection of decreased action potential conductance due to nerve compression.
Usually used to rule out carpal tunnel and cubital tunnel syndrome rather than diagnose nTOS
nTOS management
First line is physiotherapy for 6 months to improve mobility in the neck and shoudler and strengthen surrounding musculature and relax the scalenes.
Botox can also be effective to help relax the scalenes
vTOS management
Thrombolysis and anti-coagulation
Most cases howevere will require surgical management to decompress the thoracic outlet.
aTOS management with acute limb ischaemia
Urgent vascular input for embolectomy
Most cases are however due to anatomical abnormalities so elective surgery can be done instead.
Indications of surgical management
If conservative measures dont work
Anatomical variations that are symptomatic
Elective surgery in aTOS or vTOS are 90-95% successful
50-70% success in nTOS
Explain vTOS surgery
Decompression of thoracic outlet
Venoplasty
Venous reconstruction or placement of a venous stent
It can be done via a supraclavicular or transaxillary approach.
This allows access to excise the first or cervical rib.
Complications of TOS surgery
Neurological or vascular damage
Haemothorax
Pneumothorax
Chylothorax
Complications of TOS
Further sequelae of the pathology like permanent nerve damage, aneurysma dilation of subclavian artery or loss of limb function
