Ans is 'a' ie Radial Nerve is commonly affected (Ref. S. Das text book of Surgery, 4/e, p 170)Not the Radial nerve, but ulnar nerve is most commonly affected in thoracic outlet syndrome.Thoracic Outlet Syndromeis the collective name which includes -Cervical rib syndromeScalenus anterior syndrome Costoclavicular syndromeHyperabduction syndromePectoralis minor syndromeFirst thoracic rib syndromeThe syndrome is caused by compression of the brachial plexus or subclavian vessels in the region of thoracic outlet. The symptoms may arise from neural, vascular or combined compression.Neurological symptoms (are more common)Compression of the brachial plexus usually affect its lower trunk (C8& T1)Symptoms are - Pain, Paraesthesia and numbness usually in the finger and hands in the ulnar nerve distribution.Symptoms of Arterial Compression are seen less frequently in about 1/4 of the cases.Symptoms are - Pain, numbness, paresthesia, coldness and weakness of the arm or hand. Raynaud's phenomenon may also occur.Venous symptoms are less common and include edema, venous distention, pain and cyanosis.Diagnostic tests or man oeuvres :Adson's test*Costoclavicular compressive test*Hyperabduction test. * Treatment:Before surgical management conservative t/t is given a trialConservative Mx - Weight reduction, Exercise Programme.Operative management differs according to the pathology causing thoracic outlet obstructionExcision of 1st rib (in First thoracic rib syndrome).Excision of cervical rib (in cervical rib syndrome).Scalenotomy (Scalenus anticus syndrome).Division of pectoralis minor (Pectoralis minor syndrome).