Health Encyclopedia

Cranial mononeuropathy III

Definition

Cranial mononeuropathy III is a nerve disorder. It affects the function of the third cranial nerve. As a result, the person may have double vision and eyelid drooping.

Alternative Names

Third cranial nerve palsy; Oculomotor palsy; Pupil-involving third cranial nerve palsy; Mononeuropathy - compression type

Causes

Mononeuropathy means that only one nerve is affected. This disorder affects the third cranial nerve in the skull. This is one of the cranial nerves that control eye movement. Causes may include:

Brain aneurysm
Infections
Abnormal blood vessels (vascular malformations)
Cavernous sinus thrombosis
Tissue damage from loss of blood flow (infarction)
Trauma (from head injury or caused accidentally during surgery)
Tumors or other growths (especially tumors at the base of the brain and pituitary gland)
Rarely, third nerve palsy can be present at birth (congenital)

In rare cases, people with migraine headaches have a temporary problem with the oculomotor nerve. This is probably due to a spasm of the blood vessels. In some cases, no cause can be found.

People with diabetes may also develop a neuropathy of the third nerve.

Symptoms

Symptoms may include:

Double vision, which is the most common symptom
Drooping of one eyelid (ptosis)
Enlarged pupil that does not get smaller when a light shines on it
Headache or eye pain

Other symptoms may occur if the cause is a tumor or swelling of the brain. Decreasing alertness is serious, because it could be a sign of brain damage or impending death.

Exams and Tests

An eye examination may show:

Enlarged (dilated) pupil of the affected eye
Eye movement abnormalities
Eyes that are not aligned

Your health care provider will do a complete examination to find out if other parts of the nervous system are affected. Depending on the suspected cause, you may need:

Blood tests
Tests to look at blood vessels to the brain (cerebral angiogram, CT angiogram, or MR angiogram)
MRI or CT scan of the brain
Spinal tap (lumbar puncture)

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

Treatment

Some people get better without treatment. Treating the cause (if it can be found) may relieve the symptoms.

Other treatments to relieve symptoms may include:

Corticosteroid medicines to reduce swelling and relieve pressure on the nerve (when caused by a tumor or injury)
Eye patch or glasses with prisms to reduce double vision
Pain medicines
Surgery to treat eyelid drooping or eyes that are not aligned

Outlook (Prognosis)

Some people will respond to treatment. In a few others, permanent eye drooping or loss of eye movement will occur.

Causes such as brain swelling due to a tumor or stroke, or a brain aneurysm may be life threatening.

When to Contact a Medical Professional

Call your provider if you have double vision and it does not go away in a few minutes, especially if you also have eyelid drooping.

Prevention

Quickly treating disorders that could press on the nerve may reduce the risk of developing cranial mononeuropathy III.

References

Rucker JC, Seay MD. Cranial neuropathies. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 103.

Tamhankar MA. Eye movement disorders: third, fourth, and sixth nerve palsies and other causes of diplopia and ocular misalignment. In: Liu GT, Volpe NJ, Galetta SL, eds. Liu, Volpe, and Galetta's Neuro-Ophthalmology. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 15.

Wallenstein J. Brain and cranial nerve disorders. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 91.

Review Date:4/25/2022
Reviewed By:Joseph V. Campellone, MD, Department of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.