One and a half syndrome

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
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One and a half syndrome
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Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Horizontal gaze palsy, internuclear ophthalmoplegia
Complications	Diplopia, nystagmus
Onset	Sudden
Duration	Variable
Types	N/A
Causes	Pontine stroke, multiple sclerosis, brainstem tumor
Risks	Hypertension, diabetes mellitus, smoking
Diagnosis	Clinical examination, MRI
Differential diagnosis	Internuclear ophthalmoplegia, sixth nerve palsy
Prevention	N/A
Treatment	Physical therapy, prism glasses, botulinum toxin
Medication	N/A
Prognosis	Variable, depends on underlying cause
Frequency	Rare
Deaths	N/A

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SVG representation of the one and a half syndrome.

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Image related to the fabrication process in a medical context.

One and a Half Syndrome is a rare neurological condition characterized by a combination of ocular dysmetria and internuclear ophthalmoplegia. It is caused by a lesion in the paramedian pontine reticular formation and the medial longitudinal fasciculus on the same side of the brain.

Etiology

The most common cause of One and a Half Syndrome is a stroke, specifically a brainstem stroke. Other causes can include multiple sclerosis, brain tumor, brain abscess, and neurodegenerative diseases.

Clinical Presentation

Patients with One and a Half Syndrome present with a unique set of ocular motility disturbances. They have a horizontal gaze palsy in one direction and an internuclear ophthalmoplegia (INO) in the other direction. This means they are unable to move the eye on the side of the lesion horizontally (either medially or laterally), and they have a limited ability to adduct the eye on the opposite side during lateral gaze.

Diagnosis

Diagnosis of One and a Half Syndrome is primarily clinical, based on the characteristic ocular motility disturbances. Magnetic resonance imaging (MRI) can be used to confirm the diagnosis and identify the underlying cause.

Treatment

Treatment of One and a Half Syndrome is primarily aimed at managing the underlying cause. This may involve anticoagulation therapy for stroke, immunomodulatory therapy for multiple sclerosis, or surgery for brain tumors or abscesses.

Prognosis

The prognosis of One and a Half Syndrome varies depending on the underlying cause. In cases caused by stroke, some improvement may be seen over time with appropriate therapy. In cases caused by neurodegenerative diseases, the condition may be progressive.