Neuro-ophthalmology

Myasthenia Gravis

What is myasthenia gravis?

Myasthenia gravis is an autoimmune neuromuscular disease characterised by varying degrees of weakness of the skeletal (voluntary) muscles of the body. The hallmark of myasthenia gravis is muscle weakness that increases during periods of activity and improves after periods of rest. 

What causes myasthenia gravis?

Myasthenia gravis occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control.

What are the symptoms of myasthenia gravis?

Although myasthenia gravis may affect any voluntary muscle, muscles that control eye and eyelid movement, facial expression, and swallowing are most frequently affected. The onset of the disorder may be sudden and symptoms are often not immediately recognized as myasthenia gravis.  In many cases, the first noticeable symptom is weakness of the eye muscles causing a drooping of one or both eyelids (ptosis), blurred or double vision (diplopia). Ocular myasthenia gravis is diagnosed when myasthenia only affects ocular muscles, otherwise myasthenia gravis is considered as systemic myasthenia gravis due to the involvement of other muscles in the body.

Who gets myasthenia gravis?

Myasthenia gravis occurs in all ethnic groups and both genders. It most commonly affects young adult women (under 40) and older men (over 60), but it can occur at any age.

How is myasthenia gravis diagnosed?

The first steps in diagnosing myasthenia gravis include a review of the individual's medical history, and examination by a specialist eye doctor looking for impairment of eye movements or muscle weakness. If the doctor suspects myasthenia gravis, several tests are available to confirm the diagnosis.

How is myasthenia gravis treated?

There is no cure for myasthenia gravis, however it can generally be controlled. There are several therapies available to help reduce and improve muscle weakness. Medications used to treat the disorder include anticholinesterase agents such as neostigmine and pyridostigmine, which help improve neuromuscular transmission and increase muscle strength. Immunosuppressive drugs such as prednisone, azathioprine, cyclosporin, mycophenolate mofetil, and tacrolimus may also be used.

Thymectomy, the surgical removal of the thymus gland (which often is abnormal in individuals with myasthenia gravis), reduces symptoms in some individuals and may cure some people, possibly by re-balancing the immune system.

Treatment for each individual with myasthenia gravis can be quite different. Your eye doctor will devise a  treatment plan specifically for you, which is sometimes carried out in conjunction with a neurologist.

What is the prognosis?

With treatment, most individuals with myasthenia can significantly improve their muscle weakness and lead normal or nearly normal lives. Some cases of myasthenia gravis may go into remission—either temporarily or permanently—and muscle weakness may disappear completely so that medications can be discontinued.