THORACIC OUTLET SYNDROME
TOS or TOCS (Compression) is the most commonly litigated condition in thoracic surgical practice[1]. The thoracic outlet is a narrow channel between collarbone and ribs, at the top of the armpit, through which the major arteries, veins and nerves to the arm pass.
There is no major dispute about the entities of the Arterial, Venous and (True) Neurogenic forms, all of which are rare and defined by demonstrable anatomical abnormalities.
PRACTICE POINT Diagnostic features of undisputed TOS:
Cervical rib or long transverse process of C7.
Wasting of hand and forearm muscles.
Venous/arterial thrombosis or aneurysm.
Even so, causation may be disputed. Cervical rib occurs in about 1 in 200 people, and 90% of them are asymptomatic. Since the anatomical abnormality has been present from birth, Defence perusal of pre-accident clinical records may reveal recurrent symptoms which have not been acknowledged.
PRACTICE POINT Even in True TOS, traumatic causation may be in doubt.
Major controversy surrounds the existence and surgical treatment of the commonly diagnosed Symptomatic (= Nonspecific Neurogenic, Atypical or Disputed) variety. Sufferers complain of pain in the neck and arm, weakness and numbness or tingling in the hand. They often have tender points in muscles of the upper back but no truly objective findings.
Researchers[2] have recently indicated that their ongoing comparison with normal cadavers will probably define more subtle anatomical abnormalities in Symptomatic TOS.
There are a large number of conditions which mimic, and have been misdiagnosed as, nonspecific neurogenic TOS. Two neurologists[3] collected a series of 14 postoperative patients whose correct diagnosis would in their view have been established by fuller clinical assessment and diagnostic imaging.
The performance and interpretation of tests of blood-vessel compression varies between clinicians. Adson's is one of a number of provocative manoeuvres designed to detect abnormal arterial compression at the thoracic outlet. Critics[4]have claimed significant obstruction by at least one manoeuvre in up to 60% of normal subjects, bilaterally in 33%.
Nonspecific TOS has no unassailable clinical findings and is sometimes a substandard misdiagnosis.
The majority of patients with this diagnosis will improve with weight reduction and muscle strengthening exercises[5]. A variety of surgical approaches have success rates between 50% and 90% and the potential for serious complications such as major nerve and blood-vessel damage[6].
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