title: A common cause of sudden and thunderclap headaches: reversible cerebral vasoconstriction syndrome.
abstract: BACKGROUND
  Thunderclap headache (TCH) is a sudden headache (SH) with accepted criteria of severe intensity and onset to peak within one minute. It is a well-known presentation for subarachnoid hemorrhage (SAH) but most patients with TCH or SH run a benign course without identifiable causes. Reversible cerebral vasoconstriction syndrome (RCVS), a recently recognized syndrome characterized by recurrent TCH attacks, has been proposed to account for most of these patients.
  
  
  METHODS
  We recruited consecutive patients presenting with SH at our headache clinic. Computed tomography and/or magnetic resonance imaging with angiography were performed to exclude structural causes and to identify vasoconstriction. Catheter angiography and lumbar puncture were performed with patients consent. Reversibility of vasoconstriction was confirmed by follow-up study.
  
  
  RESULTS
  From July 2010 to June 2013, 31 patients with SH were recruited. Twenty-four (72.7%) of these SH patients exhibited headache fulfilling the TCH criteria. The diagnosis of RCVS was confirmed in 14 (45.2%) of patients with SH and 11 (45.8%) of patients with TCH. Other diagnoses were as follows: primary headaches (SH: 41.9%, TCH: 45.8%) and other secondary causes (SH: 12.9%, TCH: 8.3%). Compared with non-RCVS patients, patients with RCVS were older (50.8 ± 9.3 years vs. 40.8 ± 10.0 years, P = 0.006) and less likely to experience short headache duration of < 1 hour (23.1% vs. 78.6%, P = 0.007). Patients with RCVS were more likely to cite bathing (42.9% vs. 0%, P = 0.004) and less likely to cite exertion (0% vs. 29.4%, P = 0.048) as headache triggers.
  
  
  CONCLUSIONS
  Reversible cerebral vasoconstriction syndrome is a common cause of SH and TCH. Considering the potential mortality and morbidity of RCVS, systemic examination of cerebral vessels should be performed in these patients.
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Cheng
authors.forename: Kuei-Hong
authors.initials: KH
authors.lastname: Kuo
authors.affiliation: Section of Neurology, Department of Internal Medicine, Far Eastern Memorial Hospital, No, 21, Sec, 2, Nanya S, Rd,, Ban-Chiao Dist,, New Taipei City 220, Taiwan. laitzuhsien@gmail.com.
authors.forename: Tzu-Hsien
authors.initials: TH
authors.lastname: Lai
mesh_terms: D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D051270:Headache Disorders, Primary / Q000000981:diagnostic imaging* / Q000209:etiology*; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008297:Male; D008875:Middle Aged; D011859:Radiography; D013577:Syndrome; D014661:Vasoconstriction; D020301:Vasospasm, Intracranial / Q000150:complications* / Q000000981:diagnostic imaging*