Cranial mononeuropathy III - diabetic type
Diabetic third nerve palsy; Pupil-sparing third cranial nerve palsy
Causes, incidence, and risk factors
Cranial mononeuropathy III - diabetic type is a mononeuropathy, which means that only one nerve is damaged. It affects the third cranial (oculomotor) nerve, which is one of the cranial nerves that controls eye movement.
This type of damage may occur along with diabetic peripheral neuropathy. It is due to damage to the small blood vessels that feed the nerve.
Cranial mononeuropathy III is the most common cranial nerve disorder in people with diabetes.
Causes may include:
- Infarction of the nerve (tissue damage from loss of blood flow)
- Mononeuritis multiplex
- Double vision
- Drooping of one eyelid (ptosis)
- Pain in the head or behind the eye
Signs 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 (dysconjugate gaze)
- 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 nervous system (neuro-ophthalmologist).
There is no specific treatment to correct the nerve injury.
Treatments may include:
- Close control of blood sugar levels
- Eye patch or glasses with prisms to reduce double vision
- Pain medications
- Surgery to correct eyelid drooping or eyes that are not aligned
Some people may recover without treatment.
Many patients get better over 3 - 6 months, although some have permanent eye muscle weakness.
- Permanent eyelid drooping
- Permanent vision changes
Calling your health care provider
Call your health care provider if you have double vision and it doesn't go away in a few minutes, especially if you also have eyelid drooping.
Control of blood sugar levels in people with diabetes may reduce the risk of developing this disorder.
Baloh RW. Neuro-ophthalmology. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 450.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.