A patient with a midline pontine lesion at the level of the abducent nucleus develops convergent squint and inability to abduct both eyes, but vertical gaze is intact. The most likely structure damaged besides the abducent nucleus is the:
- A Paramedian pontine reticular formation (PPRF) ✓
- B Medial longitudinal fasciculus (MLF)
- C Superior salivatory nucleus
- D Nucleus of Darkschewitsch
Correct answer: A. Paramedian pontine reticular formation (PPRF)
Explanation
The paramedian pontine reticular formation (PPRF) is the horizontal gaze centre; damage abolishes ipsilateral horizontal saccades. A combined abducent nucleus + PPRF lesion produces complete ipsilateral horizontal gaze palsy. MLF damage produces internuclear ophthalmoplegia (failure of adduction ipsilaterally with intact abduction). The nucleus of Darkschewitsch is in the midbrain and is involved in vertical gaze via the posterior commissure.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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