Internuclear ophthalmoplegia
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Related on Lably
Through Anatomical terms of motion
Causes
The disorder is caused by injury or dysfunction in the medial longitudinal fasciculus (MLF), a heavily myelinated tract that allows conjugate eye movement by connecting the paramedian pontine reticular formation (PPRF)-abducens nucleus complex of the contralateral side to the oculomotor nucleus of the ipsilateral side.
In young patients with bilateral INO, multiple sclerosis is often the cause. In older patients with one-sided lesions a stroke is a distinct possibility. Other causes are possible.
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Variants
A rostral lesion within the midbrain may affect the convergence center thus causing bilateral divergence of the eyes which is known as the WEBINO syndrome (Wall Eyed Bilateral INO) as each eye looks at the opposite "wall".
If the lesion affects the PPRF (or the abducens nucleus) and the MLF on the same side (the MLF having crossed from the opposite side), then the "one and a half syndrome" occurs, with paralysis of all conjugate horizontal eye movements other than abduction of the eye on the opposite side to the lesion.
Diagnosis
Can be seen in multiple sclerosis, stroke, and other pathologies. Accompanying symptoms include scanning speech, intention tremor, incontinence, and nystagmus.