Effects of head trauma from motor vehicle accidents on Parkinson's disease. During 1 year we monitored changes in clinical disability scores in 10 patients with Parkinson's disease (PD) who sustained head trauma from motor vehicle accidents. Disability significantly increased immediately after trauma, but returned to baseline levels in subsequent weeks. These patients' signs deteriorated over the subsequent year, but this decline was equivalent to that of a matched control group with PD who did not have a motor vehicle accident or trauma. Based on these data, we conclude that trauma or stress caused by motor vehicle accidents can transiently exacerbate parkinsonian dysfunction without causing persistent increased disability or an alteration in disease course. 