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Home » Vision Therapy in Old Bridge, NJ » Sixth Nerve Palsy (VI Palsy)

Sixth Nerve Palsy (VI Palsy)

This is a copy of an email that was sent to me:

"I have been diagnosed with sixth nerve palsy in my left eye. I have been told it will take 3-6 months for it to cure itself. I know there are glasses made to help in the interim. I have had this before two years ago in my right eye and it lasted 9 weeks. I had a very hard time with an eye patch then and I am having the same difficulty now. I can't drive or feel comfortable anywhere but home. Can something be done?"

The Short and the Long Of It

The short answer is yes, most often we can help.  It is important to gather some important information, such as is there Diabetes, Lyme Disease, Stroke, especially if the palsy has occured more than once.  did this occur spontaneously or was it due to trauma, for example, a motor vehicle accident.  An MRI is also important in order to ensure that there is no brain tumor.

It is common for many doctors to simply tell their patients that it will take 6-9 months to go away and to just use a patch.  This is usually unreasonable and frustrating to most people.  Driving and simple common activities are affected.

How can we Relieve Symptoms & Maintain Binocular Vision?

We can often help you function using special prisms called Fresnel prism. This enables you to be able to function at the same time that you heal.  As the palsy improves, the prism can be changed to help the individual see without having double vision.  These are attached to the patient's glasses, or to glasses without prescription.  The prisms compensate for the inward misalignment of the affected eye. The misalignment may vary in degree in different eye positions, for example, there may be a different misalignment at distance than at near, or different in the straight ahead position than when looking to the sides.  The prisms are available in different strengths and can be changed and modified as the indivudual goes through recovery phases.  Rarely, we may need to occlude (totally cover) one eye temporarily. Occlusion would never be used in infants though because of the risk of inducing stimulus deprivation amblyopia (lazy eye).

Longer Term Management

Where full recovery has not occurred after a certain amount of time, then Vision Therapy should be considered.  Surgery should be a last resort.

The Longer Answer

Sixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI (the abducens nerve), which is responsible for contracting the lateral rectus muscle to abduct (i.e., turn out) the eye. The inability of an eye to turn outward results in a convergent strabismus or esotropia of which the primary symptom is double vision or diplopia in which the two images appear side-by-side. The condition is commonly unilateral (one eye) but can also occur bilaterally (both eyes).

The unilateral abducens nerve palsy is the most common of the isolated ocular motor nerve palsies.

Abducens palsy Limitation of abduction of the right eye. This individual tries to look to his right, but the right eye fails to turn to the side.

The affected individual will have an esotropia or convergent squint on distance fixation. On near fixation the affected individual may have only a latent deviation and be able to maintain binocularity or have an esotropia of a smaller size. Patients sometimes adopt a face turn towards the side of the affected eye, moving the eye away from the field of action of the affected lateral rectus muscle, with the aim of controlling diplopia and maintaining binocular vision.

Diplopia is typically experienced by adults with VI nerve palsies, but children with the condition may not experience diplopia due to suppression. The neural plasticity present in childhood allows the child to 'switch off' the information coming from one eye, thus relieving any diplopic symptoms. Whilst this is a positive adaptation in the short term, in the long term it can lead to a lack of appropriate development of the visual cortex giving rise to permanent visual loss in the suppressed eye; a condition known as amblyopia.

In general terms, the most common causes of 6th nerve palsy in adults are:

  • More common: Vasculopathic (diabetes, hypertension, atherosclerosis), trauma, idiopathic.
  • Less common: Increased intracranial pressure, giant cell arteritis, cavernous sinus mass (e.g. meningioma, multiple sclerosis, sarcoidosis/vasculitis, stroke (usually not isolated).

In children, it could be caused by trauma, tumor, or at times, of unknown origin. It could be brought on by an ear, nose and throat infections.

Whether in a child or in adults, it is important to identify and treat the cause of the condition, where this is possible, and to relieve the symptoms of double vision.  Children rarely notice double vision and often can't report it to others because they either suppress (within the brain they turn off) the the image from the turning eye.  It is important to maintain binocular vision and thus, promote proper visual development.

Some palsies will recover without the need for surgery.

 

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