Axillary nerve entrapment in the quadrilateral space

The quadrilateral space syndrome is a recently established entity with seemingly consistent pathological and radiographic features. An example of this syndrome is reported. In this patient, entrapment of the axillary nerve by fibrous bands in the quadrilateral space caused shoulder pain with paresthesias in the upper extremity. Subclavian angiography provided the diagnosis by demonstrating that the posterior humeral circumflex artery, which was normal when the arm was in a neutral position, was occluded when the arm was abducted and externally rotated. Axillary neurolysis through a posterior approach resulted in relief of symptoms.