Isolated femoral mononeuropathy in the athlete - Anatomic considerations and report of two cases

Atrophy of a single muscle and mononeuropathies are uncommon in a young, he althy population. (1,4,11) Femoral mononeuropathy is most commonly due to c ompression at a proximal level from numerous causes. It may also be associa ted with diabetes, hypotension, drug abuse, neoplastic and paraproteinemic diseases, lumbar spondylosis, lithotomy position, or herpes zoster infectio n. 1,3-9 So far, no explainable pathomechanical or pathophysiologic reason seems to be responsible for the rare phenomenon of isolated vastus lateralis muscle atrophy in healthy athletes when none of the diagnostic categories mentione d can be applied. There have been three previous reports of isolated monone uropathy of the nerve to the vastus lateralis muscle in athletes.(2,5,10) I n one case the atrophy and neuropathy were restricted to the distal-most br anch of the nerve,(10) another involved the entire muscle,(2) and the third case was obviously due to a self-administered injection of testosterone in the thigh and was accompanied by paresthesia.(5) We report two further cases, again in athletes, with the lesion restricted clinically and on MRI to the distal part of the vastus lateralis muscle and its nerve supply. An anatomic study was performed to identify possible ana tomic structures that may cause compression or damage to the branches of th e vastus lateralis muscle.