Abstract
The ascending reticular activating system (ARAS) is known to play an essential role in maintaining arousal and consciousness. In this report, we describe the case of a patient with impaired consciousness due to injury of the ARAS after bilateral pontine infarction. A 73-year-old female patient presented with anterior chest pain to the Emergency Department of our university hospital. She was diagnosed with chronic stable angina pectoris, three-vessel disease, and chronic total occlusion of the left anterior descending artery by coronary angiography and received conservative treatment. After five days, she showed deep drowsy mentality and brain MRI revealed bilateral paramedian pontine infarction. Four weeks after the pontine infarction, she showed severely impaired consciousness, with a Glasgow Coma Scale score of 7 (eye-opening: 2, best verbal response: 2, and best motor response: 3). Coma Recovery Scale-Revised score was 10 (auditory function: 2, visual function: 3, motor function: 2, verbal function: 2, communication: 0, and arousal: 1). Results of diffusion tensor tractography (DTT) for the ARAS showed decreased neural connectivity in the left lower dorsal ARAS, both lower ventral ARAS, and both upper ARAS. To the best of our knowledge, this is the first report of injury to the ARAS in bilateral pontine infarction diagnosed by DTT. We presume that our report would provide clinicians a better understanding of the mechanism of impaired consciousness in patients with pontine infarction.
Highlights
The ascending reticular activating system (ARAS) is known to play an essential role in maintaining arousal and consciousness [1,2]
To reconstruct the ARAS, which plays an essential role in maintaining arousal and consciousness, the regions of interest were the pontine reticular formation at the level of trigeminal nerve entry zone and intralaminar thalamic nucleus at the level of the commissural plane for the lower dorsal ARAS [7], pontine reticular formation at the mid-pons level where the trigeminal nerve is seen and hypothalamus including the mammillary body, which was identified by the optic
Three portions of the ARAS were injured in both hemispheres: the lower dorsal ARAS – narrowing in the left side compared to the right and that of a normal subject, the lower ventral ARAS – non-reconstruction on both sides, and the upper ARAS – decreased neural connectivity to the right prefrontal cortex, right basal forebrain, and both basal ganglia and thalami
Summary
The ascending reticular activating system (ARAS) is known to play an essential role in maintaining arousal and consciousness [1,2]. The association between injury of the ARAS and impairment of consciousness has been reported in patients with various brain pathologies including stroke, traumatic brain injury, and hypoxicischemic brain injury [3]. Impaired consciousness is one of the clinical symptoms that can occur following pontine infarct [11]. Pontine infarcts have been reported to account for 8% of ischemic stroke cases, which caused impaired consciousness [11]. Several previous studies have reported the association between injury of the ARAS and impaired consciousness in patients with pontine hemorrhage, intracerebral hemorrhage, traumatic brain injury, and hypoxic-ischemic brain injury using DTT [12,13,14,15,16,17]. There are limited studies evaluating the ARAS using DTT in patients with impaired consciousness following pontine infarction. Injury of ARAS after pontine infarction 265 consciousness and injury of the ARAS after bilateral pontine infarction
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