The Ascending Reticular Activating System in a Patient With Severe Injury of the Cerebral Cortex: A Case Report

We reported on the ascending reticular activating system (ARAS) finding of a patient in whom severe injury of the cerebral cortex was detected following a hypoxic-ischemic brain injury (HIBI). A 67-year-old female patient who suffered from HIBI induced by cardiac arrest after surgery for lumbar disc herniation underwent cardiopulmonary resuscitation approximately 20 to 30 minutes after cardiac arrest. The patient exhibited impaired alertness, with a Glasgow Coma Scale (GCS) score of 4 (eye opening: 2, best verbal response: 1, and best motor response: 1). Approximately 3 years after onset, she began to whimper sometimes and showed improved consciousness, with a GCS score of 10 (eye opening: 4, best verbal response: 2, and best motor response: 4) and Coma Recovery Scale-Revised score of 9 (auditory function: 1, visual function: 1, motor function: 2, verbal function: 2, communication: 1, and arousal: 2). Results of diffusion tensor tractography for the upper connectivity of the ARAS showed decreased neural connectivity to each cerebral cortex in both hemispheres. The right lower ARAS between the pontine reticular formation and the thalamic intralaminar nuclei (ILN) was thinner compared with the left side. Severe injury of the upper portion of the ARAS between the thalamic ILN and cerebral cortex was demonstrated in a patient with some level of consciousness.