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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An elderly Scottish lady presented to the emergency department following a fall. Apart from a oophthalmoplegia minor scrapes she came through the ordeal relatively unscathed. However, examination of her ocular movements demonstrated an abnormal finding. Ophthalmolpegia the patient was asked to look right, there was voluntary conjugate deviation of the eyes to the right.

However, when she was asked to look to the left, the left eye abducted but the right eye failed to adduct — it did not move past the midline. In addition, although not shown in these images, horizontal nystagmus was noted in the left eye when the the patient was asked to look to her left. The MLF provides a connection between CN3 nucleus in the midbrain and, therefore, the medial rectus and the CN6 nucleus in the pons abducens on the opposite side and facilitates conjugate eye movements on lateral gaze.

Abduction in either eye is normal, whereas adduction ophthalnoplegia impaired, resulting in dissociation of eye movements — in other words the eyes move independently on lateral gaze. When each eye is tested independently by covering the other internudlear, medial rectus function is shown to still be present.


Saccades may be slow before adduction is impaired. The eye that can abduct may exhibit horizontal nystagmus when it does so. If the INO affects the left eye, the lesion is on the right same side as the eye with the complete conjugate gaze palsy. The PPRF is the brainstem gaze center that controls opythalmoplegia gaze. It innerves the CN6 nucleus and receives projections from higher centers including the contralateral frontal eye fields.

Internuclear Ophthalmoplegia

He has a passion for helping clinicians ophthalmopleggia and for improving the clinical performance of individuals and collectives. After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne.

He has since completed further training in emergency medicine, ophthalmollegia toxicology, clinical epidemiology and health professional education. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. His one great achievement is being the father of two amazing children. On Twitter, he is precordialthump. An interesting presentation of INO.

Internuclear ophthalmoplegia

Adduction of the ipsilateral eye is not affected, however. Conjugate eye movements on attempted lateral gaze are impaired, but convergence is preserved. Medial rectus function is preserved, which can be tested by assessing eye movements in one eye while the other is covered. Or, alternatively, as you state by asking the patient to converge his or her gaze on a near object.

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Learn how your comment data is processed. She was asked to look to her right: And to her left: Describe the clinical finding.

Internuclear Ophthalmoplegia – StatPearls – NCBI Bookshelf

Answer and interpretation When the patient was asked to look right, there was voluntary conjugate deviation of the eyes to the right. Unilateral internuclear ophthalmoplegia INO affecting the right eye. Surprisingly, pateints with INO do not usually complain of diplopia! Causes of internuclear ophthalmoplegia INO include: Vascular brainstem lesion — likely cause in the elderly or people with vascular risk factors; often unilateral. Pontine glioma — more likely cause in children.

Internuclear ophthalmoplegia

Inflammatory encephalitis affecting the brainstem e. One-and-a-half syndrome usually occurs in conjunction with other brainstem symptoms and signs.

The causes of one-and-a-half syndrome include: Brainstem infarction — most common cause in the elderly. Multiple sclerosis — most common cause in young adults. Comments An interesting presentation of INO. Leave a Reply Cancel reply Your email address will not be published.

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