Clinical features

The clinical features of myasthenia gravis are: (1)

• external ocular muscles - affected in over 90% of cases, and are the muscles first affected in 65% of cases; diplopia or ptosis, often asymmetrical, are typical; ocular myasthenia describes myasthenia confined to the eyes.
  
  
• limb weakness - characteristically, increased by exercise, i.e. easily fatigued; shoulder girdle is commonly affected - patient may complain of difficulty in raising their arms above their head, or of brushing their hair; arm flexion is often more strong than extension; tone is normal and reflexes are often brisk; lower limbs are rarely affected; muscle wasting may occur in chronic disease.
  
  
• bulbar - loss of facial expression - patient appears unable to smile and may seem to snarl; inability to whistle; dysarthria - often, slurring speech; difficulty in chewing and swallowing; weakness of the neck muscles may force the patient to sit with their jaw propped by a hand
  
  
• respiratory - shortness of breath; may be exacerbated by lying down.

Reference

1. Narayanaswami P, Sanders DB, Wolfe G, et al. International consensus guidance for management of myasthenia gravis: 2020 update. Neurology. 2021 Jan 19;96(3):114-22.