In two thirds of patients with myasthenia gravis, the first muscles to be affected are those controlling eye and eyelid movements, and almost all patients have involvement of these muscles at some stage. In some, myasthenia gravis only ever involves the eye muscles (ocular myasthenia gravis) while in the majority there is also involvement of other muscles (generalised myasthenia gravis). Myasthenia gravis itself does not cause pain, but the weakness may lead to non-specific aches and pains. For instance, neck pain may occur because of weakness in the neck muscles.
Ocular myasthenia gravis affects the eye muscles only:
- drooping of the eyelids (ptosis) is often intermittent, and can affect one or both eyes
- double vision (diplopia) may be intermittent, and sometimes occurs only when looking in a particular direction.
Generalised myasthenia gravis usually involves symptoms of ocular myasthenia gravis but there is also involvement of:
- face and throat muscles, affecting smiling, speech (dysarthria), chewing and swallowing (dysphagia)
- neck muscles, causing difficulties in holding the head up
- limb muscles, causing difficulties in walking upstairs, and in holding the arms up (e.g. when brushing hair)
- breathing muscles, causing shortness of breath when exercising or when lying flat.
What is the prognosis?
The prognosis for myasthenia gravis has improved significantly with the introduction of immunosupressive therapy. Most people become symptom-free if they are adequately treated, however they do have to remain on tablets for life as the symptoms generally return if they stop the medication.