The venous drainage of nerves; anatomical study and clinical implications.

The venous drainage of the peripheral nerves was studied in the upper and lower limbs of two human fresh cadaver subjects after total body perfusion with a radio-opaque lead oxide mixture. Four patterns of extraneural drainage were identified in which the venae nervosa drained: directly to the venae comitantes of the neurovascular bundle; indirectly via nearby veins, derived usually from muscles; to the periarterial venous plexus; or, in the case of the cutaneous nerves, to the perivenous plexus. The various patterns of the drainage along the length of the radial, median, ulnar, sciatic, anterior and posterior tibial nerves were identified. A rich longitudinal plexus of veins exists on and within the nerve which appears to be mainly free of valves. The large venae nervosa usually contained valves, whereas the tiny veins draining the nerves were valveless or exhibited a sentinel valve at their entry point into a larger venous channel. The clinical implications of these results are discussed in relation to the mobilisation of nerves, the use of island nerve flaps, possible donor sites for free arteriolised neurovenous flaps and the compressive nerve syndromes.