Internuclear ophthalmoplegia (INO)

a. Normal primary position

b. Left impaired adductionn on right gaze

c. Normal left abduction on left gaze

d. Normal convergence

Left internuclear ophthalmoplegia
The most common scenario in the examination is young female with history of multiple sclerosis. However, it can also be 
seen in older patients with cerebrovascular accident. The main feature of this condition is impaired adduction. A favourite 
question is the site and side of the lesion (see question below).

In unilateral case, the affected eye shows failure (or impaired) adduction (failure of conjugate eye movement). The abducting 
eye shows jerk nystagmus with the quick phase towards the opposite side (this is called ataxic nystagmus but may not be 
obvious and  can be absent). The horizontal saccade is abnormal with the affected eye lagging behind the normal eye. The 
vertical saccade and convergence are normal.

Left saccade abnormality.
This may be the only sign present in patient 
with recovered internuclearophthalmoplegia.

In the examination:

  • there may be strabismus in the primary position
  • the internuclear ophthalmoplegia may be bilateral with or without asymmetry
  • if ask for further examination, mention that you would like to examine the patient for signs of demyelination:
    • fundal examination for pale disc (from previous optic neuritis which may be in either eye)
    • afferent pupillary defect (again from previous optic neuritis)
    • cerebellar signs (for example scanning speech, disdianochokinesia, intentional tremor, 

    • past-pointing in finger nose test)


1. What is the mechanism of internuclear ophthalmoplegia?

2. A patient with internuclear ophthalmoplegia has problem with left adduction, which side is the lesion located?

3. Is convergence ever affected in lesion of the medial longitudinal fasciculus?

4. What is the mechanism of one and a half syndrome?

5. What is wall eyed syndrome?

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