title: [Chronic daily headache: I. Diagnosis and pathophysiology].
abstract: BACKGROUND
  Chronic daily headache (CDH), or headache more than 15 days/month or over 180 days/year, is one of the main reasons for visits to specialised headache centres and accounts for up to 5% of primary headaches.
  
  
  OBJECTIVE
  Our objective was to determine the classification, epidemiology, risk factors and pathophysiology of CDH by reviewing the literature.
  
  
  METHODS
  CDH has a prevalence of 2 to 3% in the general population and is subdivided into two groups according to the headache duration. The first group (more than four hours) represents over 90% patients; includes chronic migraine (60 to 87.4%), chronic tension-type headache (0.9 to 28.8%), new daily persistent headache (0.8 to 20%) and hemicrania continua (2.2%), which represents over 90% of patients. The second group (less than four hours) is made up of cluster, chronic paroxysmal hemicranial, idiopathic stabbing-type headache and cranial neuralgias. The pathophysiology of CDH is multifactorial; it has been suggested that genetic factors, peripheral and central neuronal dysfunction derived from the alteration of protein and receptor synthesis, inadequate release of inhibitory and excitatory neuropeptides, imbalance, excitatory and inhibitory neuropeptides concentration imbalance, in association with abuse of analgesics, high comorbidity with psychiatric disorders (anxiety, depression and panic) and sleep disorders may all be involved.
  
  
  CONCLUSIONS
  CDH is a frequent cause of headache and chronic migraine is the main presenting symptom. Pathophysiology is multifactorial; there is a strong association with analgesic abuse, high comorbidity with psychiatric disorders and sleep disorders.
authors.affiliation: New England Center for Headache, Stamford, Connecticut 06902, USA. medvol98@yahoo.com
authors.forename: M
authors.initials: M
authors.lastname: Volcy-Gómez
mesh_terms: D000700:Analgesics / Q000627:therapeutic use; D015897:Comorbidity; D020773:Headache Disorders / Q000145:classification / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D001523:Mental Disorders / Q000503:physiopathology; D009474:Neurons / Q000378:metabolism; D012307:Risk Factors; D012677:Sensation / Q000502:physiology; D012701:Serotonin / Q000378:metabolism
chemical_list: D000700:Analgesics; D012701:Serotonin