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Chapter 60 Disorders of Consciousness in Systemic Diseases J. Claude Hemphill III Copyright © 2014 Elsevier Inc. All rights reserved. 1 Figure 60-1 Neuroanatomy of consciousness. The reticular formation (also known as the reticular activating system [RAS]) is a loosely arranged column of neurons located in the brainstem. Arousal is largely mediated by the RAS through projections to the cerebral cortex through the thalamus. The content of consciousness is localized more diffusely throughout the cerebral cortex. The reticular formation is distinguished from other brain structures associated with induction of sleep. (Netter illustration from www.netterimages.com. © Elsevier Inc. All rights reserved.) Copyright © 2014 Elsevier Inc. All rights reserved. 2 Figure 60-2 Diagnosis of brain death by transcranial Doppler ultrasonography (TCD). A, Normal blood flow velocity and direction in the left middle cerebral artery (LMCA). B, Findings in brain death. Direction of flow is reversed during diastole, indicating cerebral circulatory arrest. For the use of transcranial Doppler ultrasonography as a confirmatory test in brain death, these findings must be present in both anterior circulations as well as in the posterior circulation. Copyright © 2014 Elsevier Inc. All rights reserved. 3
