A brainstem lesion of any type that involves the medial longitudinal fasciculus ( MLF) can cause internuclear ophthalmoplegia (INO). This primarily affects. Internuclear ophthalmoplegia is an ocular movement disorder caused by a lesion of the medial longitudinal fasciculus. It is characterized by. Internuclear ophthalmoplegia is the inability to move both your eyes together when looking to the side. It can affect one or both of your eyes.
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Residents and Fellows contest rules International Ophthalmologists contest rules. Internuclear ophthalmoplegia Internucleae presents as the inability to perform conjugate lateral gaze and produces an ophthalmoplegia due to damage to the interneuron between two nuclei of cranial nerves CN VI and CN III internuclear.
This interneuron is called the medial longitudinal fasciculus MLF. The MLF can be damaged by any lesion e. The MLF is supplied blood by branches of the basilar artery and ischemia in the vertebrobasilar system can produce an ischemic INO. Thus, demyelinating lesions in the midbrain or pons often produce a unilateral or bilateral INO in young patients.
The INO is characterized clinically by an ispilesional adduction deficit partial or complete with a contralateral, dissociated, horizontal abducting saccade on attempted gaze to the contralesional side. Increased innervation to the underacting adducting muscle would result interhuclear an enhanced stimulus to the contralateral abducting muscle . The INO can be unilateral or bilateral and may present with or without neurologically isolated other brainstem findings.
The most common etiology is infarction of the midbrain in older patients and demyelinating disease in young patients. This syndrome is characterized by having one-and-a-half syndrome and a facial fascicular nerve CN VII palsy. There is conjugate horizontal gaze palsy on looking to one side followed by INO on looking to the opposite side, along with unilateral facial weakness.
The lesion is most often vascular or demyelinating in the dorsal tegmentum of the caudal pons . A syndrome that consists of an INO in one eye combined with an ipsilateral CN VI fascicular involvement with sparing of the sixth nerve nucleus.
This syndrome is a rare ophthalmoplegia, either bilateral or unilateral that exhibits contralateral adducting eye rather than abducting eye nystagmus with abduction restriction on physical exam. It is the reverse of the typical INO, and although the lesion localization is not consistent, it likely is internuclera to CN VI pre-nuclear input asymmetry .
In older people, stroke is a more common etiology. Less common causes for an INO include traumatic, neoplastic, inflammatory e.
Internuclear Ophthalmoplegia – StatPearls – NCBI Bookshelf
Typically, the paramedian pontine reticular formation PPRF receives information from the higher cortical centers such as the frontal eye fields, occipital and parietal lobes and the superior colliculus. The activation of the contralateral medial rectus and ipsilateral lateral rectus muscle produces horizontal conjugate eye movement. In one review of INO, some of the most common causes included: Imaging tests such as a CT scan or MRI are ordered after a diagnosis is made to ophthalmopleggia where the damage internuckear located so that the physician can then assess which.
If the etiology is inflammation or infection, high dose corticosteroids can help. If the etiology is MS and not relapsing-remitting, then treatment becomes harder. Dalfampridine, a potassium channel blocker prescribed for gait impairment was used in in a case series and the authors reported improvement in saccades and ocular motility in patients with INO secondary to demyelination in Multiple sclerosis.
Improved neuronal conduction along MLF has been discussed as a possible explanation for this effect seen . The prognosis of most patients with an INO is good but the final outcome depends in part on treatment of the underlying etiology.
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