Neurocirculatory Scalenus Anticus Syndrome in the Presence of Developmental Defects of the First Rib *

In years past, a rather voluminous literature has accumulated dealing with certain neurologic and circulatory deficits that occur in the upper extremities. Cervical rib syndrome, scalenus anticus syndrome, Naffziger syndrome, and scalenus neurocirculatory compression syndrome are among the names applied to the variable symptom complex found present in a small percentage of individuals with abnormal morphologic developments about the region of the thoracic operculum. Because so few of those with developmental defects in that region have symptoms attributable to them, and these usually develop their symptoms relatively late in life, various hypotheses have been suggested as the mechanisms for production of the symptoms. Among these are: 1. Alteration in the relative positions of the subclavian structures and the first dorsal rib due to the gradually increasing dependency of the shoulder girdle as one grows older; with a resultant angulation of the vessel over the rib and a pressure of the rib upward against the brachial plexus.7 2. An abnormal development of the first rib or a cervical rib causing pressure upon the plexus.3 3. Variations in the constitution of the brachial plexus whereby the second dorsal segment takes a greater than normal part in the formation of the plexus.4 4. Theories taking into account the scalenus anticus muscle as a factor in compressing the nerves and artery against the abnormal rib or the normal first rib in cases where the relative positions of the rib and shoulder girdle are altered.3 " 6 While some would attribute the circulatory manifestations to direct compression of the subclavian artery, others believe them due to interference with the vascular innervation.2