History and exam
Key diagnostic factors
common
muscle strength fatigability
The weakness worsens with activity or repetition (fatigable weakness) and improves on rest. Fluctuations often, but not always, show diurnal variation (better in the morning than in the evening).
ptosis
Drooping eyelids and double vision occur early in the majority of patients.[22] The pupils are spared. [Figure caption and citation for the preceding image starts]: Ptosis of the left upper eyelid in a patient with myasthenia gravisForoozan R, Sambursky R. Ocular myasthenia gravis and inflammatory bowel disease: a case report and literature review. Br J Ophthalmol. 2003 Sep;87(9):1186-7. [Citation ends].
Pulling up on the upper eyelid may induce ptosis in the contralateral lid.
Cooling of the eyelid for 2 to 5 minutes with an ice pack (ice test) improves ptosis in more than 95% of patients.[70][71] It may not improve severe ptosis.
diplopia
Double vision occurs early in the majority of patients.[22]
dysphagia
Difficulties in chewing or swallowing occur when the facial and oropharyngeal muscles are affected. Patients describe being unable to finish chewing their food or complete their meal, and may switch to softer foods. Patients with marked weakness of the tongue may describe difficulty manoeuvring food in their mouth.
dysarthria
Changes in speech occur when the oropharyngeal muscles are affected and there may be a characteristic nasal speech. Tongue and facial weakness may also cause problems with speech.
facial paresis
Changes in expression occur when the facial muscles are affected and there may be a characteristic flattened or transverse smile.
proximal limb weakness
Difficulty in getting out of chairs or climbing stairs, or sustaining proximal upper limb functions. There is no evident muscle wasting. Reflexes are normal. Sensations are intact.
Characteristically the limb weakness worsens with activity or repetition (fatigable weakness) and improves on rest, and fluctuations often, but not always, show diurnal variation (better in the morning than in the evening).
Less commonly, patients may present with predominant or exclusive weakness of the limbs, sometimes called limb-girdle MG.
uncommon
shortness of breath
If shortness of breath becomes severe enough to require mechanical ventilation, the patient is said to be in myasthenic crisis.[23]
Risk factors
weak
family history of autoimmune disorders
genetic markers
Use of this content is subject to our disclaimer