title: Atypical Presentation of Aneurysmal Subarachnoid Hemorrhage: Incidence and Clinical Importance.
abstract: BACKGROUND
  The symptoms of sudden severe headache and/or diminished consciousness characterize the onset of aneurysmal subarachnoid hemorrhage (SAH). However, several studies have suggested that some patients show an atypical presentation at the onset: symptoms lacking sudden headache and diminished consciousness. The aim of this study was to investigate the incidence and clinical features of cases with atypical onset.
  
  
  METHODS
  Retrospective observational study based on the data collected prospectively from all patients with SAH admitted to our hospital was performed. Cases with a sudden headache at the onset were classified as the headache onset group, and cases with onset symptoms other than headache were classified as the atypical onset group. The clinical parameters were compared between the two groups.
  
  
  RESULTS
  Of the 368 patients with SAH, 75 (20.4%) showed diminished consciousness from onset, 279 (75.8%) comprised the headache onset group, and 14 (3.8%) comprised the atypical onset group. The main symptoms in the atypical onset group were nausea or vomiting, vertigo or dizziness, and neck pain or back pain. The rate of misdiagnosis of SAH and the rate of rebleeding after misdiagnosis were higher in the atypical onset group (P = .045 and P = .043, respectively). The interval from onset to diagnosis was longer in the atypical onset group (P = .033). The atypical onset group demonstrated a more severe clinical grade on admission (P = .009), a lower rate of ruptured aneurysm repair (P < .001), and a poorer outcome (P = .003).
  
  
  CONCLUSIONS
  Atypical onset is rare but has a great impact on the clinical course through rebleeding exacerbated by misdiagnosis or delayed diagnosis, resulting in poor outcomes.
authors.affiliation: Department of Neurosurgery, Hirosaki University School of Medicine, Hirosaki, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Ogasawara
authors.affiliation: Department of Neurosurgery, Hirosaki University School of Medicine, Hirosaki, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Ito
authors.affiliation: Department of Neurosurgery, Hirosaki University School of Medicine, Hirosaki, Japan. Electronic address: ohkuma@hirosaki-u.ac.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ohkuma
mesh_terms: D000368:Aged; D001416:Back Pain / Q000453:epidemiology; D003244:Consciousness Disorders / Q000453:epidemiology; D057210:Delayed Diagnosis; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D004244:Dizziness / Q000453:epidemiology; D005260:Female; D006261:Headache / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000453:epidemiology; D019547:Neck Pain / Q000453:epidemiology; D019635:Neurosurgical Procedures; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D014717:Vertigo / Q000453:epidemiology; D014839:Vomiting / Q000453:epidemiology
keywords: Subarachnoid hemorrhage; cerebral aneurysm; headache; misdiagnosis; rebleeding