A unilateral sluggish pupil is most commonly caused by which condition?

• A. Increased ICP
• B. Opiate poisoning
• C. Brain Death
• D. Diabetes mellitus

Answer: (A)

A unilateral sluggish pupil points to impaired parasympathetic input to the pupil on that side, most often from compression of the oculomotor nerve as intracranial pressure rises. When ICP increases, the oculomotor nerve can be compressed (often with impending herniation), disrupting the nerves that constrict the pupil. The result is a pupil that is slower to react to light and may appear dilated on the affected side. This is a classic sign of raised ICP or early herniation.

Opiate poisoning typically causes pinpoint pupils that are constricted bilaterally, not a unilateral sluggish response. Diabetes mellitus can cause various autonomic changes but does not classically produce a unilateral sluggish pupil. Brain death features fixed, nonreactive pupils rather than sluggish reactivity.