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).

Abducens paralysis; Abducens palsy; Lateral rectus palsy; Vith nerve palsy; Cranial nerve VI palsy

Cranial mononeuropathy VI is damage to the sixth cranial (skull) nerve. This nerve, also called the abducens nerve helps you move your eye sideways toward your temple (laterally).

Disorders of this nerve can occur with:

• Brain aneurysms
• Diabetic neuropathy
• Gradenigo's syndrome (which also causes discharge from ear and eye pain)
• Increased or decreased pressure in the skull
• Infections (such as meningitis or sinusitis)
• Multiple sclerosis
• Pregnancy
• Stroke
• Trauma (caused by head injury or accidentally during surgery)
• Tumors around or behind the eye

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).

When the sixth cranial nerve does not work properly, you cannot turn your eye outwards toward your ear. You can still move your eye up, down, and towards the nose, unless other nerves are affected.

In general symptoms may include:

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

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).

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.

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

Complications may include permanent vision changes.

Call your health care provider if you have double vision.

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

Baloh RW. Neuro-ophthalmology. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 450.

Jensen U, Ulmer S, Tietke M, Jansen O. Double vision. Differentials please! The British Journal of Radiology, 82 (2009), 173–174.