title: Thunderclap headache and normal computed tomographic results: value of cerebrospinal fluid analysis.
abstract: OBJECTIVE
  To determine the sensitivity, specificity, and negative and positive predictive values of cerebrospinal fluid (CSF) xanthochromia for detection of ruptured cerebral aneurysms in patients with thunderclap headache (sudden and severe headache with maximal intensity at onset).
  
  
  METHODS
  We identified patients who presented to our emergency department with symptoms of thunderclap headache between January 1, 1998, and January 1, 2008. Those with normal results on computed tomography (CT) of the head were selected for inclusion in the study. All consenting adult patients had undergone a lumbar puncture procedure for CSF analysis. Xanthochromia was assessed by visual inspection. All patients with a normal CT result were further evaluated by conventional 4-vessel catheter angiography. If no aneurysms were detected in the initial study, the procedure was performed again within 7 to 14 days. All patients were followed up clinically for a mean period of approximately 29 months.
  
  
  RESULTS
  A total of 152 patients were identified (mean +/- SD age, 44.7+/-15.8 years; 53 men). Cerebrospinal fluid xanthochromia was present in 18 patients (12%), 13 (72%) of whom were ultimately diagnosed as having aneurysmal subarachnoid hemorrhage. A single patient who tested negative for xanthochromia and had a normal CT result was subsequently found to have a ruptured middle cerebral artery aneurysm. The sensitivity, specificity, positive predictive value, and negative predictive value of CSF xanthochromia for detection of cerebral aneurysms were 93%, 95%, 72%, and 99%, respectively.
  
  
  CONCLUSIONS
  Although not perfect, visual inspection of CSF in patients with a history suggestive of subarachnoid hemorrhage remains a highly valuable and simple test to detect a recently ruptured aneurysm.
authors.affiliation: Department of Neurology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA. dupont.stefan@mayo.edu
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Dupont
authors.forename: Eelco F M
authors.initials: EF
authors.lastname: Wijdicks
authors.forename: Edward M
authors.initials: EM
authors.lastname: Manno
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Rabinstein
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003124:Colorimetry; D005260:Female; D051270:Headache Disorders, Primary / Q000134:cerebrospinal fluid* / Q000209:etiology; D006801:Humans; D002532:Intracranial Aneurysm / Q000134:cerebrospinal fluid* / Q000150:complications / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013129:Spinal Puncture; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid* / Q000150:complications / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed