1. The scalenus anterior syndrome, a lesion of combined vascular and neurological signs and symptoms in the shoulder, the arm, and the hand, may be dependent upon an anatomical type plus a lesser trauma or strain of the shoulder girdle.
2. Lesions of the cervical spine may induce spasm of the scalenus anterior muscle with the resultant syndrome.
3. Traumatic and infectious lesions of the shoulder girdle may induce or be associated with the scalenus anterior syndrome.
4. When cervical or shoulder-girdle lesions are amenable to therapy, the scalenus anterior syndrome may subside without specific therapy.
5. In the anatomical type, or in the long-standing scalenus anterior syndrome from other causes, with hypertrophy or contracture of the scalenus anterior muscle, scaleniotomy is indicated.
6. Indiscriminate scaleniotomy in all cases of the scalenus anterior syndrome is not indicated, as conservative therapy has resulted in the cure of cases in the past and will continue to do so in the future if the etiological factor is removed in a reasonable period of time.