Definition of Cranial mononeuropathy VI:

Cranial mononeuropathy VI is a nerve disorder. It prevents some of the muscles that control eye movements from working well. As a result, people may see two of the same image (double vision).

Causes, incidence, and risk factors:

Cranial mononeuropathy VI is damage to the sixth cranial (skull) nerve. This nerve, also called the abducens nerve, helps control eye movement to the left or right.

Disorders of this nerve can occur with:

• Brain aneurysms
• Diabetic neuropathy
• Increased pressure in the skull (intracranial pressure)
• Infections (such as meningitis or sinusitis)
• Pregnancy
• Tissue damage from loss of blood flow (infarction)
• Trauma (caused by head injury or accidentally during surgery)
• Tumors

In some people, there is no obvious cause.

Because there are common nerve pathways through the skull, the same disorder that damages the sixth cranial nerve may affect other cranial nerves (such as the third or fourth cranial nerve).

Symptoms:

Symptoms may include:

• Double vision when looking to one side
• Headaches
• Pain around the eye

Signs and tests:

Tests typically show that one eye has trouble looking to the side, while the other eye moves normally. An examination shows the eyes do not line up -- either at rest, or when looking in the direction of the weak eye.

Your health care provider will do a complete examination to determine the possible effect on other parts of the nervous system. Depending on the suspected cause, you may need:

• Blood tests
• Head imaging study (such as an MRI or CT scan)
• Spinal tap (lumbar puncture)

You may need to be referred to a doctor who specializes in visual problems related to the nervous system (neuro-ophthalmologist).

Treatment:

If your health care provider diagnoses swelling or inflammation of, or around the nerve, medications called corticosteroids will be used.

Sometimes, the condition may disappear without treatment. People with diabetes may benefit from close control of blood sugar levels.

Until the nerve heals, wearing an eye patch will relieve double vision.

Expectations (prognosis):

Treating the cause may improve the condition. Most people in whom no cause is found recover completely.

Complications:

Complications may include permanent vision changes.

Calling your health care provider:

Call your health care provider if you have double vision.

Prevention:

There is no way to prevent this condition. However, people with diabetes may reduce the risk by controlling their blood sugar.