Internuclear ophthalmoparesis (INO), also commonly referred to as internuclear ophthalmoplegia, is
a specific gaze abnormality characterized by impaired horizontal eye movements with weak and slow adduction of the affected eye
, and abduction nystagmus of the contralateral eye.
How would you describe internuclear ophthalmoplegia?
Internuclear ophthalmoplegia (INO) is the
inability to move both your eyes together when looking to the side
. It can affect only one eye, or both eyes. When looking to the left, your right eye will not turn as far as it should. Or when looking to the right, your left eye will not turn fully.
What causes internuclear ophthalmoplegia?
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 happens in ophthalmoplegia?
People affected by ophthalmoplegia
may have double or blurred vision
. They may also experience an inability to position the eyes in sync. Some may also have a hard time moving both eyes in every direction, and many will have drooping of their eyelids.
Why is convergence spared in INO?
If a lesion in the MLF blocks signals from the horizontal gaze center to the 3rd cranial nerve, the eye on the affected side cannot adduct (or adducts weakly) past the midline. The affected eye adducts normally in convergence
because convergence does not require signals from the horizontal gaze center
.
How is internuclear ophthalmoplegia treated?
The majority of patients with persistent internuclear ophthalmoplegia have minimal symptoms. Those with diplopia may benefit from
botulinum toxin injections
or Fresnel prisms. Surgical correction of strabismus may be used for patients with wall-eyed bilateral internuclear ophthalmoplegia.
What causes ophthalmoplegia?
Ophthalmoplegia can be caused by
congenital abnormalities, trauma, complications of viral infections
, or disorders that affect the nervous system, including multiple sclerosis, cerebral tumours, migraines, and vascular (blood vessel) disease such as that associated with diabetes.
What does Internuclear mean?
Medical Definition of internuclear
:
situated or occurring between atomic or biological nuclei
.
What is meant by ophthalmoplegia?
The general textbook definition of ophthalmoplegia is
the paralysis or weakness of one or more of the eye muscles
. Internal ophthalmoplegia refers to paralysis of the intrinsic (iris and ciliary) muscles of the eye, and external refers to the extraocular muscles.
Is ophthalmoplegia curable?
Supranuclear ophthalmoplegia also may be called progressive supranuclear ophthalmoplegia to reflect the fact that the condition is progressive — that means the condition gets worse over time and
there is no cure
.
What happens when your eyes move side to side?
Nystagmus
is a vision condition in which the eyes make repetitive, uncontrolled movements. These movements often result in reduced vision and depth perception and can affect balance and coordination. These involuntary eye movements can occur from side to side, up and down, or in a circular pattern.
What is Webino syndrome?
Wall-eyed bilateral inter nuclear ophthalmoplegia (WEBINO) is a
rare disorder characterized by bilateral exotropia on primary gaze
, bilateral inter nuclear ophthalmoplegia (INO) and impaired convergence. It may also be associated with vertical gaze palsy, up-beat nystagmus and skew deviation.
What causes eyes to not track together?
The causes of eye misalignment are various, and sometimes unknown. Potential causes include high farsightedness, thyroid eye disease,
cataract, eye injuries
, myasthenia gravis, cranial nerve palsies, and in some patients it may be caused by brain or birth problems.
Why is convergence normal in internuclear ophthalmoplegia?
If a lesion in the MLF blocks signals from the horizontal gaze center to the 3rd cranial nerve, the eye on the affected side cannot adduct (or adducts weakly) past the midline. The affected eye adducts normally in convergence
because convergence does not require signals from the horizontal gaze center
.
What does conjugate gaze mean?
Conjugate gaze is
the ability of the eyes to work together or in unison
. It refers to the motion of both eyes in the same direction at the same time. The eyes can look laterally (left/right), upward, or downward. Disorders in conjugate gaze refer to the inability to look in a certain direction with both eyes.
Why is the Trochlear nerve unique?
The trochlear nerve is unique among the cranial nerves in several respects: It is
the smallest nerve in terms of the number of axons it contains
. It has the greatest intracranial length. It is the only cranial nerve that exits from the dorsal (rear) aspect of the brainstem.
