Vascularized muscle fibers: etiopathogenesis and clinical significance.

Contrary to common assumption, internal vascularization of muscle fiber occurs independent of muscle fiber splitting. Review of 1091 cases who underwent muscle biopsies demonstrated muscle fibers with internal blood vessels in a wide variety of chronic neuromuscular disease states, predominantly in patients with chronic neurogenic diseases. Many of these cases show evidence of internal disorganization or focal degeneration of muscle fibers, in particular, formation of targets, targetoids or similar structural alterations. Internal vascularization of muscle fiber probably occurs as a "healing" or "reparative process" in such fibers. Myopathic features, especially secondary myopathic changes (as seen in chronic denervation-reinnervation) are common and appear to be a necessary accompaniment of this phenomena. The vascularized muscle fiber is more likely to be seen in a distal lower extremity muscle than in a proximal limb muscle biopsy.