title: The pathophysiology of brain swelling associated with subdural hemorrhage: the role of the trigeminovascular system.
abstract: BACKGROUND
  This paper reviews the evidence in support of the hypothesis that the trigeminal system mediates brain swelling associated with subdural bleeding. The trigeminovascular system has been extensively studied in migraine; it may play an important but under-recognized role in the response to head trauma. Nerve fibers originating in trigeminal ganglion cells are the primary sensors of head trauma and, through their collateral innervation of the intracranial and dural blood vessels, are capable of inciting a cascade of vascular responses and brain swelling. The extensive trigeminal representation in the brainstem initiates and augments autonomic responses. Blood and tissue injury in the dura incite neurogenic inflammatory responses capable of sensitizing dural nerves and potentiating the response to trauma.
  
  
  CONCLUSIONS
  The trigeminal system may provide the anatomo-physiological link between small-volume, thin subdural bleeds and swelling of the underlying brain. This physiology may help to explain the poorly understood phenomena of "second-impact syndrome," the infant response to subdural bleeding (the "big black brain"), as well as post-traumatic subdural effusions. Considerable age-specific differences in the density of dural innervation exist; age-specific responses of this innervation may explain differences in the brain's response to trauma in the young. An understanding of this pathophysiology is crucial to the development of intervention and treatment of these conditions. Antagonists to specific neuropeptides of the trigeminal system modify brain swelling after trauma and should be further explored as potential therapy in brain trauma and subdural bleeding.
authors.affiliation: Neuropathology, John Radcliffe Hospital, Oxford, UK. waney.squier@ndcn.ox.ac.uk
authors.forename: Waney
authors.initials: W
authors.lastname: Squier
authors.forename: Julie
authors.initials: J
authors.lastname: Mack
authors.forename: Alex
authors.initials: A
authors.lastname: Green
authors.forename: Tipu
authors.initials: T
authors.lastname: Aziz
mesh_terms: D000293:Adolescent; D001929:Brain Edema / Q000209:etiology* / Q000503:physiopathology*; D001930:Brain Injuries / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D006408:Hematoma, Subdural / Q000150:complications* / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007249:Inflammation / Q000473:pathology; D013353:Subdural Effusion / Q000150:complications; D014276:Trigeminal Nerve / Q000098:blood supply* / Q000473:pathology