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Lateral Rectus Palsy

What are the causes of a lateral rectus palsy and how is it investigated and treated?

Video Transcript:

Almost all lateral rectus palsies are acquired in later life and are caused by conditions that have damaged the VIth cranial nerve, which supplies the lateral rectus muscle.

What are the causes of a lateral rectus palsy?

  • - Poor blood supply to the VIth nerve caused by a combination of factors such as high blood pressure, diabetes, high cholesterol and smoking. This is known as a microvascular palsy.
  • - Direct pressure on the VIth nerve caused by tumours, middle ear infections or swelling of neighbouring blood vessels can damage the VIth nerve. Lateral rectus palsies can also be a sign of raised intracranial pressure.
  • - Head injuries can cause a lateral rectus palsy, but this is usually due to raised intracranial pressure.
  • - Occasionally inflammation in the region of the nerve can cause a lateral rectus palsy.

What are the features of a lateral rectus palsy?

Typical features of a lateral rectus palsy include:
  • - Sudden onset of horizontal double vision, which is worse when the patient looks to the affected side.
  • - Limited outward movement of the affected eye. Patients often compensate for this by turning their head to the affected side.
  • - A convergent squint that is large when the patient tries to look at an object in the distance.

Investigations

All patients will be seen by an Orthoptist and an Ophthalmologist. A detailed history will be taken and specific tests carried out to measure the squint and assess the range of eye movements. A chart may be plotted to measure the size of the area of single vision and to measure the movements of the eyes in different directions. Blood tests and an MRI scan are carried out to investigate what could have caused the palsy.

What are the treatment options?


Observation

Most (80%) microvascular superior oblique palsies will resolve within 3-6 months. However spontaneous recovery is less likely to occur if the lateral rectus palsy has been caused by a head injury or a tumour.

Prisms

In adults it may be possible to have temporary plastic prisms fitted to the patient’s glasses that will reduce or in some cases completely correct the squint and double vision. If the angle of the squint is too large to correct with prisms Botox treatment can be considered.

Botox

Botox injections into the medial rectus muscle will reduce the size of the convergent squint. It will also prevent the medial rectus from contracting and shortening which can cause reduced outwards movement of the eye, even if the lateral rectus muscle starts to work normally again.