What are the other Names for this Condition? (Also known as/Synonyms)

• Abducens Palsy
• CNVI Palsy
• Cranial Nerve VI Palsy

What is Cranial Mononeuropathy VI? (Definition/Background Information)

• The nerves that originate directly from the brain and brainstem are called the cranial nerves. Cranial nerves are found in the ventral part of the brain. Generally, a human body has 12 pairs of cranial nerves that are connected to various body organs to perform several functions
• The sixth cranial nerve is called the abducens nerve and it is responsible for the lateral movement of the eye. When, as a result of any disorder, the abducens nerve is affected, the condition is termed as Cranial Mononeuropathy VI
• Common causes of Cranial Mononeuropathy VI are brain infections, brain aneurysms (dilatation of vessel wall in the brain), diabetes, and high pressure within the brain (hydrocephalus). This condition generally leads to double vision and an inability to move the eyes sideways. The condition can lead to permanent vision loss
• Diagnosis of Cranial Mononeuropathy VI may include a thorough eye examination and the use of imaging studies, such as CT scan and MRI scan of the brain
• Sometimes the condition may disappear on its own. However, if there is swelling around the nerve, steroids may be helpful. The nerve palsy resolves once the underlying cause is treated
• There is no effective prevention of Cranial Mononeuropathy VI, since it is caused by variety of factors that may be unrelated to each other
• The prognosis of Cranial Mononeuropathy VI depends upon the cause of the condition

Who gets Cranial Mononeuropathy VI? (Age and Sex Distribution)

• Cranial Mononeuropathy VI may affect individuals of any age group
• There is no gender predilection observed; both male and female sexes are equally affected
• This condition occurs worldwide; all racial and ethnic groups are affected

What are the Risk Factors for Cranial Mononeuropathy VI? (Predisposing Factors)

The following individuals are at risk for Cranial Mononeuropathy VI:

• Individuals with brain aneurysm; a condition in which blood vessel walls in the brain becomes dilated, putting pressure on the nerve
• Those having brain infections such as meningitis or encephalitis
• A condition causing buildup of excess fluid in the brain (hydrocephalus)
• Individuals affected by diabetes
• Those with high blood pressure (hypertension) 

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Cranial Mononeuropathy VI? (Etiology)

The abducens nerve (also called the abducent nerve or sixth cranial nerve) may be affected due to disorders or infections leading to Cranial Mononeuropathy VI. Since this cranial nerve is damaged, it can cause double vision and headaches.

The disorders or infections that could cause Cranial Mononeuropathy VI include:

• Brain aneurysms: A condition in which the blood vessel walls weaken and become dilated, thus putting pressure on the cranial nerve
• Vasculitis: An inflammatory disorder of the blood vessels
• Hydrocephalus; a condition causing increased pressure in the  brain
• Infections such as meningitis (condition where the membranes around the brain and spinal cord are infected) and sinusitis (sinus infection)
• Diabetic neuropathy: A condition where high blood sugar levels cause damage to the nerves
• Pregnancy
• Ischemia: Tissue damage from loss of blood flow
• Tumors that are located behind the eye or around the eye
• Stroke
• Multiple sclerosis: A disorder affecting the central nervous system
• Gradenigo’s syndrome: A condition that relates to complications arising from otitis media (infection of the middle ear)

In some cases, the cause of Cranial Mononeuropathy VI is unknown (termed idiopathic).

What are the Signs and Symptoms of Cranial Mononeuropathy VI?

The signs and symptoms of Cranial Mononeuropathy VI may include:

• Inability to move the eye sideways
• Double vision
• Headaches
• Pain around the eyes

How is Cranial Mononeuropathy VI Diagnosed?

A diagnosis of Cranial Mononeuropathy VI may include the following:

• A complete physical examination and evaluation of medical history including a history of diabetes
• The physical exam shall include a thorough eye examination that may reveal improper alignment of the eyes and reaction of the pupil to light to check for other cranial nerves that control eye movements

Other tests may include:

• Blood tests to determine sugar levels in blood
• MRI scan of the brain
• CT scan of the brain
• Lumbar puncture or spinal tap test 

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Cranial Mononeuropathy VI?

Cranial Mononeuropathy VI can lead to permanent vision loss.

How is Cranial Mononeuropathy VI Treated?

The treatment for Cranial Mononeuropathy VI may include:

• Corticosteroids may be administered if swelling or inflammation is found in the affected area
• Monitoring blood sugar levels and taking steps to keep it under control
• Glasses with prisms can be used to reduce the effect of double vision
• Sometimes, Cranial Mononeuropathy VI may spontaneously disappear on its own

How can Cranial Mononeuropathy VI be Prevented?

• There are no effective prevention measures for Cranial Mononeuropathy VI, since it is caused by a variety of unrelated factors
• Maintaining blood sugar at normally required levels can help reduce the risk of cranial mononeuropathy VI in diabetics

What is the Prognosis of Cranial Mononeuropathy VI? (Outcomes/Resolutions)

• The prognosis of Cranial Mononeuropathy VI depends upon the cause of the condition
• The nerve palsy resolves once the underlying cause is treated
• In idiopathic cases (where there is no cause), it typically resolves within 2-3 months

Additional and Relevant Useful Information for Cranial Mononeuropathy VI:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/health-topics/neurological-institute/