title: Subarachnoid hemorrhage of unknown etiology along the cortical convexity.
abstract: BACKGROUND
  Only 8% to 22% of cases of subarachnoid hemorrhage (SAH) are of nonaneurysmal origin. Among these, perimesencephalic nonaneurysmal SAH is a distinct clinical and radiologic entity with normal angiographic findings and a good prognosis. In contrast, SAH of nonaneurysmal origin occurring along the cortical convexity is rare and poorly understood. We report 2 cases of subarachnoid hemorrhage along the cortical convexity and discuss their possible etiologies.
  
  
  METHODS
  In a retrospective analysis of 234 patients with SAH, we identified 2 patients with a typical computed tomographic pattern of convexity SAH that was associated with no known etiology.
  
  
  RESULTS
  In these 2 cases, the source of hemorrhage could not be identified with computed tomography, magnetic resonance imaging, or digital subtraction angiography, although neurovascular outcomes were good. The patients reported such incidents as coughing or exertion immediately before headache developed. These incidents may have caused increased intracranial pressure.
  
  
  CONCLUSIONS
  We suggest the possible involvement of a brief increase in intracranial pressure, such as that accompanying coughing or exertion, in the occurrence of SAH along the cortical convexity.
authors.affiliation: Department of Neurosurgery, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan. ymurai@nms.ac.jp
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Murai
authors.forename: Shiro
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Akira
authors.initials: A
authors.lastname: Teramoto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015901:Angiography, Digital Subtraction; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000209:etiology*; D014057:Tomography, X-Ray Computed