title: Spreading Depression in Primary and Secondary Headache Disorders.
abstract: OBJECTIVE
  Spreading depression (SD) is a wave of simultaneous and near-complete depolarization of virtually all cells in brain tissue associated with a transient "depression" of all spontaneous or evoked electrical activity in the brain. SD is widely accepted as the pathophysiological event underlying migraine aura and may play a role in headache pathogenesis in secondary headache disorders such as ischemic stroke, subarachnoid or intracerebral hemorrhage, traumatic brain injury, and epilepsy. Here, we provide an overview of the pathogenic mechanisms and propose plausible hypotheses on the involvement of SD in primary and secondary headache disorders.
  
  
  RESULTS
  SD can activate downstream trigeminovascular nociceptive pathways to explain the cephalgia in migraine, and possibly in secondary headache disorders as well. In healthy, well-nourished tissue (such as migraine), the intense transmembrane ionic shifts, the cell swelling, and the metabolic and hemodynamic responses associated with SD do not cause tissue injury; however, when SD occurs in metabolically compromised tissue (e.g., in ischemic stroke, intracranial hemorrhage, or traumatic brain injury), it can lead to irreversible depolarization, injury, and neuronal death. Recent non-invasive technologies to detect SDs in human brain injury may aid in the investigation of SD in headache disorders in which invasive recordings are not possible. SD explains migraine aura and progression of neurological deficits associated with other neurological disorders. Studying the nature of SD in headache disorders might provide pathophysiological insights for disease and lead to targeted therapies in the era of precision medicine.
authors.affiliation: Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan.|Department of Neurology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Shih-Pin
authors.initials: SP
authors.lastname: Chen
authors.affiliation: Neurovascular Research Lab, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA. cayata@mgh.harvard.edu.|Stroke Service and Neuroscience Intensive Care Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. cayata@mgh.harvard.edu.
authors.forename: Cenk
authors.initials: C
authors.lastname: Ayata
mesh_terms: D001921:Brain / Q000503:physiopathology; D013181:Cortical Spreading Depression / Q000502:physiology*; D006261:Headache / Q000503:physiopathology*; D006801:Humans
keywords: Intracranial hemorrhage; Ischemic stroke; Migraine aura; Spreading depolarization; Spreading depression; Traumatic brain injury