What is one-and-a-half syndrome?

One-and-a-half syndrome is a syndrome characterized by horizontal movement disorders of the eyeballs, which was first reported and named by Fisher in 1967. It presents a combination of ipsilateral conjugate horizontal gaze palsy (one) and ipsilateral internuclear ophthalmoplegia (INO) (a half).

What causes one-and-a-half syndrome?

One-and-a-half syndrome is most often caused by multiple sclerosis (MS), brain stem stroke, brain stem tumors, and arteriovenous malformations.

Is internuclear ophthalmoplegia a disease?

Internuclear ophthalmoplegia (INO) is a disorder of eye movements caused by a lesion in an area of the brain called the medial longitudinal fasciculus (MLF). The most common causes of INO are multiple sclerosis and brainstem infarction.

What is 8 and a half syndrome?

Eight-and-a-half syndrome describes a constellation of symptoms that occur due a lesion involving the abducens (cranial nerve (CN) VI) nucleus, the fascicular portion of the facial (CN VII) nerve, and the medial longitudinal fasciculus (MLF).

What does internuclear ophthalmoplegia mean in medical terms?

Internuclear ophthalmoplegia (INO) describes a clinical syndrome of impaired adduction in one eye with dissociated horizontal nystagmus of the other abducting eye, due to a lesion in the medial longitudinal fasciculus (MLF) ipsilateral to the eye unable to adduct. It is a common finding in multiple sclerosis, but has a number of other etiologies.

How is internuclear ophthalmoplegia related to multiple sclerosis?

How does one and a half eye syndrome work?

One-and-a-half syndrome results when the disorder that causes internuclear ophthalmoplegia also damages the center that coordinates and controls horizontal eye movements (horizontal gaze center). When the person tries to look to either side, the affected eye remains motionless in the middle. The other eye can turn outward but not inward.

What kind of eye condition is one and half?

In this syndrome, patients present with a combination of an ipsilateral conjugate horizontal gaze palsy (referring to the ‘one’ horizontal gaze palsy) and an ipsilateral internuclear ophthalmoplegia (INO) (referring to the ‘half’ of a horizontal gaze palsy) .