Clinical features of fatigable weakness in myasthenia gravis by region of involvement
| Muscle group/region | Manifestation of fatigable weakness in myasthenia gravis |
|---|---|
| Ocular | Fluctuating ptosis (often asymmetrical, worsened by sustained upgaze) with or without variable diplopia Ptosis may improve with application of an ice pack to the eyes, ie, the bedside ice-pack test |
| Bulbar | Dysarthria with or without dysphonia; worse at the end of long conversations, when especially nasal-sounding, “mushy,” or “wet” speech is significant Painless dysphagia, which may include nasal regurgitation, sialorrhea, and frequent throat-clearing, with or without coughing; may range from weak to frank choking Masticatory or chewing weakness; when severe, the mouth may hang open, and the patient may use a hand to close or manipulate the jaw |
| Facial | Bilateral weakness with “sagging and expressionless” face and a horizontal smile Inability to close eyes firmly Drooling from poorly sealed lips Inability to whistle, pucker lips, or use a straw |
| Axial Weak | Weak flexion or extension of the neck, “dropped” head when severe Occasional stooped posture with anteroposterior truncal flexion (camptocormia) or lateral trunk flexion (“Pisa syndrome”) |
| Limb or appendicular | Weakness that affects proximal more than distal upper and lower limb groups Difficulty getting up from low-seated positions, using arms for overhead activities like washing hair; worse with repeated and sustained actions |
| Respiratory | Orthopnea Dyspnea on exertion or with increased intra-abdominal pressure as when bending forward to tie shoelaces, or when trunk is immersed in a pool Classic features of accessory respiratory muscle use during respiratory distress may be blunted with significant myasthenic weakness of these muscles Decreased counts (< 20) on a single-breath counting test suggest significant respiratory muscle weakness and risk for respiratory failure |