title: Aneurysmal subarachnoid hemorrhage causes injury of the ascending reticular activating system: relation to consciousness.
abstract: OBJECTIVE
  Little is known about the pathogenetic mechanism of impaired consciousness following subarachnoid hemorrhage. Using diffusion tensor imaging, we attempted to investigate the presence of injury of the lower portion of the ascending reticular activating system between the pontine reticular formation and the intralaminar thalamic nuclei, and the relation between this injury and consciousness level in patients with SAH.
  
  
  METHODS
  We recruited 24 consecutive patients with spontaneous SAH following aneurysmal rupture and 21 healthy control subjects. Consciousness level was rated by using the Glasgow Coma Scale. Using diffusion tensor tractography, we reconstructed the lower portion of the ascending reticular activating system between the pontine reticular formation and the intralaminar thalamic nuclei. Values of fractional anisotropy, apparent diffusion coefficient, and tract number of the ascending reticular activating system were measured.
  
  
  RESULTS
  A significant difference in the tract number was observed between the patient and control groups (P < .05); however, there was no significant difference in terms of fractional anisotropy and apparent diffusion coefficient values (P > .05). In addition, regarding the tract number of the patient group, the Glasgow Coma Scale showed strong positive correlations with the tract number on the more affected side (r = 0.890, P < .05), the less affected side (r = 0.798, P < .05), and both sides (r = 0.919, P < .05), respectively.
  
  
  CONCLUSIONS
  We found injury of the lower portion of the ascending reticular activating system between the pontine reticular formation and the thalamus in patients with SAH. In addition, we observed a close association between injury of the lower portion of the ascending reticular activating system and impaired consciousness in patients with SAH.
authors.affiliation: From the Department of Physical Medicine and Rehabilitation, College of Medicine, Yeungnam University, Taegu, Republic of Korea.
authors.forename: S H
authors.initials: SH
authors.lastname: Jang
authors.affiliation: From the Department of Physical Medicine and Rehabilitation, College of Medicine, Yeungnam University, Taegu, Republic of Korea. aodwntjr1@naver.com.
authors.forename: H S
authors.initials: HS
authors.lastname: Kim
mesh_terms: D000328:Adult; D016880:Anisotropy; D003244:Consciousness Disorders / Q000209:etiology* / Q000473:pathology; D056324:Diffusion Tensor Imaging; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology*; D065821:Pontine Tegmentum / Q000473:pathology; D013345:Subarachnoid Hemorrhage / Q000150:complications* / Q000473:pathology*; D013787:Thalamic Nuclei / Q000473:pathology