Cranial mononeuropathy VI is a disorder that causes double vision, associated with dysfunction of cranial nerve VI, which is responsible for moving the eye to the side.

Alternative Names

Abducens palsy; Lateral rectus palsy

Causes, incidence, and risk factors

Cranial mononeuropathy VI is a mononeuropathy (damage to a single nerve) involving the sixth cranial (abducens) nerve, one of the cranial nerves that controls eye movement. Abducens nerve disorders are often associated with diabetic neuropathy , trauma, infections (like meningitis or sinusitis), infarction (tissue damage from loss of blood flow), cranial aneurysms , tumors, or increased intracranial pressure (pressure within the skull). In some cases, no cause can be found. Because of common pathways through the skull, other cranial nerves (such as the third or fourth cranial nerve) may be affected simultaneously.

Signs and tests

Testing of eye movement shows that one eye has difficulty looking to the side and the other eye moves normally. An eye examination shows the eyes do not align, either at rest or especially when looking in the direction of the weak eye. A complete medical and neurological examination must be done to determine if other parts of the nervous sytem are affected. Depending on the suspected cause, a patient may undergo blood tests, a head imaging study like an MRI or CT scan and possibly a lumbar puncture (spinal tap).

Treatment

In some cases, corticosteroids may reduce swelling and relieve pressure on the nerve, while in others the condition may disappear without treatment. Treatment of the cause (if it can be identified) may relieve the symptoms in many cases. Close control of blood sugar levels in diabetics may be beneficial. Until the nerve heals, an eye patch may alleviate double vision.

Expectations (prognosis)

The outcome depends on the underlying cause. Treatment of the underlying cause may improve the condition, while improvement may occur even if the cause is never determined.

Complications

Some complications include permanent vision changes.

Calling your health care provider

Call your health care provider if double vision occurs.

Prevention

No specific prevention is available, although patients with diabetes may reduce the risk by controlling their blood sugar.