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. Classically, TOS has been attributed to anomalous cervical ribs, muscles, fractured clavicles or scar that passes through the nerve bundles squeezing them. Another important cause for TOS is automobile accident producing severe stretching or direct compressive trauma of the brachial plexus. Currently, at least in my practice, the overwhelming majority of cases are caused by repetitive work injury due to keyboard use. Characteristically, symptoms appear after an especially intense period of keyboard use due to various time pressures and, since they are initially mild in nature and disappear with rest, are easy to discount or ignore. However, after this initial appearance of symptoms, repetitive or forceful movements at work or normal activities of daily life cause these symptoms to reappear and worsen. Rest produces less relief, and stressful activities bring about pain more quickly and to a more intense degree.   .