You’re treating a patient who nails their first sit-to-stand, then can barely rise from the chair by the fifth repetition. That rapid, fatigue-dependent decline is the signature of myasthenia gravis—a condition you must recognize, respect, and plan around as a physical therapist.
What is Myasthenia Gravis?
Myasthenia gravis (my-uh-THEE-nee-uh GRAV-is) is an autoimmune neuromuscular junction disorder in which antibodies block or destroy acetylcholine receptors on the postsynaptic muscle membrane. The result is fatigable weakness: muscle strength declines with repeated use and improves with rest. It most commonly affects the ocular, bulbar, and proximal limb muscles.
Why Myasthenia Gravis Matters in Physical Therapy Practice
MG directly impacts your Plan of Care because exercise has the potential to worsen weakness if not carefully dosed. Functional mobility, safety, and endurance all hinge on energy conservation and pacing. You also need to screen for red flags like worsening respiratory function, which can signal a myasthenic crisis requiring immediate medical referral.
What You’ll See in the Clinic
Your patient may present with drooping eyelids (ptosis), double vision, nasal or slurred speech, difficulty chewing or swallowing, and proximal muscle weakness that worsens as the session progresses. You might document:
“Patient completed 3 repetitions of sit-to-stand with good form, then demonstrated progressive trunk collapse and needed two-person assist by the 8th repetition. Strength testing of bilateral hip flexors declined from 4/5 to 3-/5 after repeated testing. Patient reports symptom onset 20 minutes after morning medication.”
Common Pitfall & Pro Tip
⚠️ Pitfall: Pushing through fatigue to “build endurance.” In MG, overexertion can trigger prolonged post-exercise weakness and, in severe cases, respiratory compromise.
💡 Pro Tip: Schedule PT sessions during the patient’s medication peak, typically 1–2 hours after pyridostigmine, and use short rest breaks. Objective measures like the MG-ADL scale or repeated sit-to-stand counts are excellent—but stop before the patient’s strength bottoms out.
Memory Aid for Myasthenia Gravis
Think “MG = Muscle Gives out.” The weakness is not constant—it comes with use and recovers with rest. If a patient’s strength seems to improve as you test it again, that’s not MG; that’s more like Lambert-Eaton syndrome, which improves briefly with activity.
NPTE Connection
This term commonly appears in questions about neuromuscular junction disorders, medication side effects, and when to hold therapy due to a myasthenic crisis. Watch for differential diagnosis between MG, Lambert-Eaton, and anticholinesterase toxicity (cholinergic crisis).
Related Physical Therapy Concepts
Understanding MG ties directly into neuromuscular re-education, energy conservation techniques, and respiratory muscle weakness. It also overlaps with Guillain-Barré syndrome and multiple sclerosis when considering fatigue-driven functional decline, though the underlying mechanisms differ substantially.
Quick Reference
✓ Key findings: Fatigable weakness, ocular/bulbar symptoms, improvement with rest ✓ Priority level: High/Critical – recognize respiratory red flags ✓ PT Interventions/Considerations: • Session timing around medication peak • Pacing and high-frequency, low-duration exercise • Energy conservation and activity modification • Monitor vital capacity and cough strength • Avoid overtiring; refer immediately for respiratory distress
Bottom line: In MG, your best clinical move is knowing when to push—and when to stop.