Cranial mononeuropathy III - diabetic type
Diabetic third nerve palsy; Pupil-sparing third cranial nerve palsy
Mononeuropathy means that only one nerve is damaged. This disorder affects the third cranial nerve in the skull. This is one of the cranial nerves that control eye movement.
This type of damage may occur along with diabetic peripheral neuropathy. Cranial mononeuropathy III is the most common cranial nerve disorder in people with diabetes. It is due to damage to the small blood vessels that feed the nerve.
Cranial mononeuropathy III can also occur in people who don't have diabetes.
Symptoms may include:
- Double vision
- Drooping of one eyelid (ptosis)
- Pain in the head or behind the eye
Exams and Tests
An examination of the eyes will determine whether only the third nerve is affected or if other nerves have also been damaged. Signs may include:
- Eyes that are not aligned
- Pupil reaction that is almost always normal
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
- Tests to look at blood vessels in the brain (cerebral angiogram, CT angiogram, 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 nerves in the eye (neuro-ophthalmologist).
There is no specific treatment to correct the nerve injury.
Treatments to help symptoms may include:
- Close control of blood sugar level
- Eye patch or glasses with prisms to reduce double vision
- Pain medicines
- Surgery to correct eyelid drooping or eyes that are not aligned
Some people may recover without treatment.
Many people get better over 3 to 6 months. Some people have permanent eye muscle weakness.
Complications may include:
- Permanent eyelid drooping
- Permanent vision changes
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.
Controlling your blood sugar level may reduce the risk of developing this disorder.
Brownlee M, Aiello LP, Cooper ME, Vinik AI, Plutzky J, Boulton AJM. Complications of diabetes mellitus. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 33.
Rucker JC, Thurtell MJ. Cranial neuropathies. In: Daroff RB, Jankovic J, Mazziotta JC, Pomeroy SL, eds. Bradley's Neurology in Clinical Practice. 7th ed. Philadelphia, PA: Elsevier; 2016:chap 104.
Reviewed By: Amit M. Shelat, DO, FACP, Attending Neurologist and Assistant Professor of Clinical Neurology, SUNY Stony Brook, School of Medicine, Stony Brook, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.