1. Subjects who have clinically unstable medical disease (cardiovascular, renal, gastrointestinal, pulmonary, metabolic, endocrine, other); CNS disease deemed progressive; moderate or severe traumatic brain injury (TBI). Patients with mild TBI, however, will not be excluded from study participation. The ACRM definition of mild TBI will be utilized for this study (Kay et al., 1993). That definition will be operationalized using the INTRuST TBI Screening Instrument.