[The neurological forms of thoracic outlet syndrome: the role of the middle scalene].

The authors discuss the pathogenesis of neurological involvement in the thoracic outlet syndrome. They emphasise a factor which has been neglected up until now: the tendon of scalenus medius, around which the primary inferior trunk of the brachial plexus forms a curve with a postero-inferior concavity. An anatomical study reveals this close relation which is only apparent in the horizontal plane. Thirteen clinical cases of pure neurological forms, confirmed by Aran-Duchenne amyotrophy of the hand, illustrate the role of scalenus medius in this nerve lesion. The therapeutic application of this new concept consists of middle scalenectomy and posterior release of the nerve trunks by cervicotomy.