What exam signs suggest impending uncal herniation?

• A. Bilateral pinpoint pupils.
• B. Ipsilateral sensory loss in face.
• C. Ipsilateral pupil dilation and poor reactivity; contralateral motor weakness.
• D. Normal pupil light reflex and stable consciousness.

Answer: (C)

Uncal herniation classically starts with pressure on the oculomotor nerve on the side of the herniation, producing an ipsilateral pupil that is dilated and poorly reactive to light (often with ptosis). As the process progresses and the brainstem is further compromised, the nearby motor pathways can be affected, leading to contralateral weakness. So the combination of an on-the-same-side dilated, poorly reactive pupil with opposite-side motor weakness is the pattern that most reliably signals impending uncal herniation. Signs like pinpoint pupils, ipsilateral facial sensory changes, or a normal pupil reflex with stable consciousness don’t fit this progression as well.