A 45-year-old man has a lesion in the right paramedian pontine reticular formation (PPRF). What eye movement deficit would be expected?
- A Inability to deviate both eyes to the left (left gaze palsy)
- B Loss of upward gaze only
- C Inability to deviate both eyes to the right (right gaze palsy) ✓
- D Right internuclear ophthalmoplegia
Correct answer: C. Inability to deviate both eyes to the right (right gaze palsy)
Explanation
The PPRF is the horizontal gaze center for ipsilateral conjugate gaze. It drives the ipsilateral CN VI nucleus and, via the MLF, the contralateral CN III medial rectus subnucleus. Right PPRF damage therefore causes right horizontal gaze palsy — the eyes cannot conjugately deviate to the right. Left gaze palsy would result from a left PPRF lesion. Upward gaze palsy is controlled by the rostral interstitial nucleus of the MLF (riMLF) in the midbrain.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.