Elevated levels of TNF are evident in a large number of neurological disorders including ischemia [67,68], traumatic brain injury [69], multiple sclerosis [70-74], Alzheimer's disease [75-77], and Parkinson's disease [78-83], but whether TNF signaling actively contributes to or limits neuronal injury in these disorders has yet to be established. This evidence concerns the gene TNF and Parkinson disease.