A patient with right internuclear ophthalmoplegia (INO) will show which combination of eye movement findings?
- A Impaired right eye adduction on left gaze; abducting nystagmus of left eye; convergence is often preserved ✓
- B Impaired right eye adduction on left gaze; abducting nystagmus of left eye; normal convergence
- C Impaired right eye abduction on right gaze; nystagmus of right eye; intact convergence
- D Impaired bilateral adduction; preserved abduction bilaterally with intact vestibulo-ocular reflex
Correct answer: A. Impaired right eye adduction on left gaze; abducting nystagmus of left eye; convergence is often preserved
Explanation
INO results from a lesion in the medial longitudinal fasciculus (MLF) ipsilateral to the eye with impaired adduction. Right INO: the right MLF is damaged, causing impaired adduction of the right eye during left conjugate gaze. The left eye shows abducting nystagmus (due to attempted conjugate gaze with increased innervation reaching the intact left lateral rectus). Convergence is typically preserved (supra-nuclear pathway is intact) — a feature distinguishing INO from CN III palsy. Bilateral INO in a young patient suggests MS.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.