title: Mechanisms of disease: the blood-brain barrier.
abstract: OBJECTIVE
  The blood-brain barrier (BBB) is often perceived as a passive membrane. However, evidence has demonstrated that the BBB plays an active role in normal homeostasis and in certain disease processes.
  
  
  METHODS
  Approximately 300 peer-reviewed publications that discussed normal or abnormal BBB function were reviewed.
  
  
  RESULTS
  The role of the BBB and how it contributes to disorders of the central nervous system vary, depending on the specific disease process.
  
  
  CONCLUSIONS
  In health and disease and extending to old age, endothelial cells, neurons, and glia constitute a neurovascular unit that regulates the BBB. Advances toward penetrating the BBB must account for both normal and abnormal functions of the neurovascular unit.
authors.affiliation: Department of Neurology, Oregon Health & Science University, Portland, Oregon 97201, USA. neuwelte@ohsu.edu
authors.forename: Edward A
authors.initials: EA
authors.lastname: Neuwelt
mesh_terms: D001812:Blood-Brain Barrier / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D002493:Central Nervous System Diseases / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D011859:Radiography