Chap 125-128 Thoracic Outlet Syndrome Flashcards
What is TOS?
Constellation of symptoms that occur from compression of the neurovascular bundle
What is usual age of onset?
20-50
Is there a sex predominance? Why?
70% are female
likely because 70% of cervical rib happen in women
Which form of TOS is most common? Least common?
nTOS 95%
aTOS <1%
What injuries cause nTOS?
hyperextension injury, whiplash, repetitive stress injury, falls
What are anatomical predisposing factors for nTOS? (3)
Cervical rib
Congenital band
Scalene triangle muscle variations
What are the histopathological findings in nTOS? (4)
Predominance of Type I muscle fibers (slow twitch)
Endomysial fibrosis (thickened tissue around individual muscle finer)
2fold increase in CT
Mitochondrial abnormalities
What is the usual composition of type I and II muscle fibbers?
usually 50% each but become 80% in nTOS
What are symptoms of nTOS? (5)
Extremity pain paresthesia weakness + neck pain and occipital headache raynaud's CP for pec minor syndrome
Why remove the first rib in nTOS?
Prevents lower trunk of plexus from getting fixed to the rib with scarring
How does a neck injury cause nTOS?
Underlying narrowed scalene triangle
Asympto until neck trauma tears scalene muscle
Swelling and bleeding result in swelling, scarring and compression
How many patients with nTOS have a predisposing neck injury?
> 80%
What is the double crush syndrome?
get distal neurapathy from proximal axonal injury
What is the treatment for nTOS?
Conservative therapy is physical therapy for 4-6weeks
If fails then surgical approach
What are findings of nTOS on CT/MRI?
negative findings support diagnosis of nTOS
What can findings be on EMG for nTOS?
usually negative
What is necessary for diagnosis of nTOS?
Physical findings
What is the path of the phrenic nerve?
lateral border of scalene, passes lateral to medial as it descends along anterior surface of the scalene, then passes behind the subclavian into the mediastinum
What is the path of the long thoracic nerve?
passes through the belly of the middle scalene where the components form a single nerve
what does the long thoracic nerve supply? what happens if you injure the nerve?
serratus anterior, winged scapula
what proportion of patients have abnormal scalene anatomy?
2/3
What syndrome can develop in long-standing severe nTOS?
complex regional pain syndrome type I
What are symptoms of CRPS-I
persistent vasospasm, disuse edema, extreme hypersensitivity
What investigations to do for nTOS?
CXR, CT/MRI, EMG
What can you do to see if patient will respond to surgical decompression?
Scalene muscle block
What are some differential diagnoses for nTOS?
Carpel tunnel syndrome, ulnar nerver compression, rotator cuff tendonitis, cervical spine strain, fibromyositis, cervical disk disease, cervical arthritis, brachial plexus injury
What are advantages/disadvantages for transaxillary approach for nTOS?
cosmetic incision, adequate to remove first rib
incomplete exposure of scalene triangle, limited for vascular reconstruction
What are advantages/disadvantage of supraclavicular approach?
wider exposure, compete resection of scalene muscles, direct visualization of nerve roots, vascular reconstruction
first rib resection may need additional incision