Myasthenia gravis(MG) is an autoimmune disease which results from antibodies that block acetylcholine receptors at the junction between the nerve and muscle. This prevents nerve impulses from triggering muscle contractions.
About half of patients with MG present with visual complaints of droopy eyelids or double vision, and many will remain with purely ocular muscle weakness without generalized weakness, defined as Ocular Myasthenia(OM). OM may be confused with disorders of the brainstem, ocular motor nerves, and eye muscles.
Ocular myasthenia gravis only affects the muscles that move the eyes and eyelids.
The symptoms of ocular myasthenia gravis include
On the other hand, generalized myasthenia gravis affects muscles throughout the body that may cause trouble speaking, trouble swallowing, and weakness in the arms or legs.
A detailed history taking from the patient andperforming a physical examination to carefully test the eyelids and eye movements, to see what happens to the muscles when they are fatigued and when they have rested.
Additional tests to confirm a diagnosis of myasthenia gravis.
A blood test can check if the immune system is blocking the signals that travel from the nerves to the muscles (antibodies against acetyl choline receptors). In patients with ocular myasthenia gravis (who have visual symptoms only) this blood test has lower accuracy, so a negative result might require additional testing.
One important test to help diagnose myasthenia gravis is called a nerve conduction study/electromyogram.
The most accurate test to diagnose myasthenia gravis is called a single fiber electromyogram (SFEMG). Both the EMG and SFEMG tests can reveal a pattern of responses that suggests myasthenia gravis.
Treatment is by medication and/or surgery. Medication consists mainly of acetylcholinesterase inhibitors to directly improve muscle function and immunosuppressant drugs to reduce the autoimmune process. Thymectomy is a surgical method to treat MG
Double vision is most often treated by blocking the vision from one eye.
Certain medications can worsen the symptoms of myasthenia and should be avoided. These medications include specific antibiotics (called aminoglycosides and quinolones), beta-blockers, calcium channel blockers, and phenytoin (Dilantin).
If a patient with myasthenia gravis requires a surgical procedure, the anesthesiologist should be aware and in order to use the proper medications.