A case of occurrence of superficial ulnar artery along with retrobrachial median nerve has been reported previously (Latha VP et al 2002). However, the present case differed from the previous in that the ulnar artery has a high origin and a caliber much smaller than that of the normal artery in the contralateral limb. The termination of the brachial artery into radial and common interosseous artery is a similarity between these two cases. This arterial variation along with absence of any muscular abnormality makes it one of its kinds. Such an artery may present a superficial pulse and a hazard to venipuncture (Hazlett 1949).
Development of arteries of upper limb in 5 stages has been proposed (Senior 1926 and Singer 1933). An axial system represented in the adult by axillary artery, brachial artery and interosseous artery develops first while other branches develop later from the axial system. In stage 2, median artery branches from the anterior interosseous artery, while the ulnar artery branches from the brachial artery in stage 3. Formation of a superficial brachial artery from axillary artery and its continuation as radial artery marks the stage 4. Regression of the median artery and an anastomosis between the brachial artery and superficial brachial artery with regression of the proximal segment of the latter gives rise to definitive radial artery.
The present anomaly can be explained by the persistence of embryological vessels, which may be due to hemodynamic persistence of superficial system over deep system at the origin of ulnar artery. Genetic influences are deemed to be prevalent causes of such variation, although factors like fetal position in utero, first limb movement or unusual musculature cannot be excluded.
Variation in the branching pattern of the brachial artery is of significance in cardiac catheterization for angioplasty, pedicle flaps, or arterial grafting.
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