Mechanisms of upper limb amyotrophy in spinal disorders.

Upper limb amyotrophy may occur as an indirect consequence of various spinal disorders, including ventral longitudinal intraspinal fluid collection, Hirayama disease and high cervical cord compression. We present patients who suffer from each of these and review the literature on the three conditions with emphasis on the pathogenesis of amyotrophy. We propose that pathology some distance from the lower cervical spinal cord may affect normal venous drainage, resulting in venous congestion and reduced perfusion pressure which, in turn, could result in anterior horn cell dysfunction in all three disorders.