Median nerve penetration by a muscular branch of the brachial artery.

Arterial variations in the distal half of the arm are common (Anagnostopoulou and Venieratos 1999, J. Anat. 195:471-476). We observed a rare variant of a muscular branch of the brachial artery that penetrated the median nerve in the lower part of the arm. After its origin from the posteromedial surface of the brachial artery, the muscular branch passed through a nervous loop in the median nerve to enter and supply the brachialis muscle. At the site of arterial penetration, the nerve displayed perineurial thickening and increased fasciculation and interfascicular connective tissue. Three small branches of the artery supplied the nerve fascicles. We did not observe nerve compression or muscular changes, but the possibility of altered clinical symptoms produced by irritation from arterial pulsation cannot be ruled out. This variation may be clinically important because symptoms of median nerve compression arising from similar variations are often confused with more common causes, such as radiculopathy and carpal tunnel syndrome.