What is a possible cause of unilateral pupil dilation?

Unilateral pupil dilation, also known as mydriasis, can occur due to various neurological conditions, and one significant cause is a head injury. When a head injury occurs, it can result in increased intracranial pressure, which may affect the oculomotor nerve that controls pupil constriction. If this nerve is damaged or compressed, it can lead to dilation in one pupil while the other remains normal.

Head injuries can also cause the brain to shift within the skull, potentially leading to a condition known as uncal herniation, where part of the brain pushes against the oculomotor nerve, causing the affected pupil to dilate. Monitoring pupils in the context of head trauma is an essential part of assessing for serious neurological issues, making this option a relevant cause of unilateral dilation.