HESI 4 Critical Care MCA 3 Practice Test

As intracranial pressure rises, brain structures become compressed in a way that commonly affects the pupillary reflex. The oculomotor nerve, which carries the parasympathetic fibers that constrict the pupil, is particularly vulnerable. When pressure increases, parasympathetic input is impaired and sympathetic influence dominates, causing the pupil to dilate on the affected side. The light reflex also diminishes as brainstem pathways that mediate constriction become sluggish, so you often see a slower reaction to light. If pressure continues to climb, the pupil can become fixed and dilated, signaling severe herniation and a grim prognosis. Unequal pupils and sluggish or nonreactive pupillary responses fit this pattern of ICP progression.

Constricted pupils are not typical of rising ICP; they usually point to other factors such as opioid effects or different brainstem lesions, not the ICP-related changes described here.