Why is pupillary asymmetry considered an ominous sign in acute traumatic brain injury?

• A. Potential brain herniation; associated with worse outcomes and higher mortality
• B. It indicates full recovery is imminent
• C. It is unrelated to prognosis in acute TBI
• D. It indicates the patient is ready for discharge

Answer: (A)

Pupillary asymmetry in acute traumatic brain injury signals dangerous brain swelling with potential brainstem compression and herniation. As ICP rises, brain tissue can shift toward the tentorium and compress the oculomotor nerve on the side with the dilated pupil. That pupil becomes large and often nonreactive, and unequal pupils can be an early warning that herniation is developing. This progression is associated with worse outcomes and higher mortality because brain herniation can rapidly impair vital brainstem functions. Recognizing this sign prompts urgent escalation of care to control intracranial pressure and consider surgical intervention. It does not indicate recovery or readiness for discharge; rather, it signals ongoing injury and potential deterioration.