Supplementary motor area activation is impaired in severe traumatic brain injury parkinsonism

A high percentage of survivors of severe traumatic brain injury present diffuse axonal injury and extrapyramidal symptoms. The association between diffuse cerebral damage and parkinsonian symptoms is probably because of the interruption of nigro-striato-frontal pathways. While functional magnetic resonance imaging (fMRI) has been widely used to investigate parkinsonism in idiopathic Parkinson disease, little is known about functional brain modifications related to post-traumatic parkinsonism (PTP). The aim of this study is to assess cerebral activity of the action-related network in patients with PTP comparing these patients to matched healthy controls. In the fMRI scanner, we proposed to 12 PTP patients and 12 healthy control participants a continuum of tasks involving action-related word production, mental simulation of action, and miming of action triggered by external stimuli such as drawings of objects. Patients with PTP showed a main effect similar to that of healthy controls in all the tasks. Direct comparison revealed hypoactivation of areas in the action-related network in patients with PTP for all the tasks. During the mime of action, which involved actual movement, the hypoactivation was localized to the motor network. Our results suggest that patients with PTP showed a cerebral reorganization for motor tasks in agreement with the cerebral reorganization observed in idiopathic Parkinson disease. For patients with PTP, supplementary motor area impairment seems to play a central role in parkinsonism, in line with the brain reorganization of action-related tasks.