Altered mental status pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Pratik Bahekar, MBBS [2]



Although the neural science behind alertness, wakefulness, and arousal are not fully known, the reticular formation is known to play a role in these. The ascending reticular activating system is a postulated group of neural connections that receives sensory input and projects to the cerebral cortex through the midbrain and thalamus from the retucular formation. Since this system is thought to modulate wakefulness and sleep, interference with it, such as injury, illness, or metabolic disturbances, could alter the level of consciousness.

Normally, stupor and coma are produced by interference with the brain stem, such as can be caused by a lesion or indirect effects, such as brain herniation. Mass lesions in the brain stem normally cause coma due to their effects on the reticular formation.[1] Mass lesions that occur above the tentorium cerebelli (pictured) normally do not significantly alter the level of consciousness unless they are very large or affect both cerebral hemispheres.


  1. Tindall SC (1990). "Level of consciousness". In Walker HK, Hall WD, Hurst JW. Clinical Methods: The History, Physical, and Laboratory Examinations. Butterworth Publishers. Retrieved 2008-07-04. Mass lesions within the brainstem produce coma by virtue of direct effects on the reticular formation