Aneurysmal Subarachnoid Hemorrhage Causes Injury of the Ascending Reticular Activating System: Relation to Consciousness

Abstract

BACKGROUND AND PURPOSE: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.

Evolution of diffusion tensor imaging parameters after acute subarachnoid haemorrhage: a prospective cohort study

“…Some reports exist on FA changes in SAH, namely regarding the mammillothalamic tract [15], the corticospinal tract [16] and the ascending reticular activating system [14]. However, these reports focused only at the chronic stages of SAH, thus probably reflecting the late secondary injury to the neuronal tracts and not any acute changes.…”

“…DTI analysis is known to be operator dependent, and regions where fibres cross may modify FA values [24]. We did not analyse tract volume, which has been shown to be associated with lesion of white matter tracts [14,15], sometimes more significantly than FA values. Our interest was more on measuring whole-brain DTI and different regions of interest in the brain, other than analysing specific tracts.…”

“…Regarding FA measurements in SAH patients, however, the literature is scarce, with only a few studies that refer to specific tracts and that studied patients several weeks or months after SAH [14][15][16].…”

Injury of the Contralateral Lower Ascending Reticular Activating System by an Intracerebral Hemorrhage

“…The seed ROI was placed at the reticular formation of the pons, and the target ROI was placed at the intralaminar nuclei of the thalamus. [1][2][3] Fractional anisotropy (FA) and tract volume (TV) of the lower portion of the ascending reticular activation system (ARAS) were measured. In the patient, TV of the left ARAS was decreased Ͼ2 SDs compared with that of control subjects.…”

Early Prediction of Delayed Ischemia and Functional Outcome in Acute Subarachnoid Hemorrhage

“…13 However, there are only few studies in the literature reporting on FA measurements in SAH patients. 11,[14][15][16] Because DTI can provide data on the cerebral injury induced by SAH, we hypothesized that DTI changes could be an independent prognostic factor for the main outcomes of SAH. To our knowledge, no other studies addressed this question using DTI in the acute phase in SAH patients.…”