Myasthenia gravis: an animated, cited guide

This page needs JavaScript for its animations. The outline and key answers are below, and every claim in the full version carries a numbered citation.

Not medical advice. Myasthenia Gravis Companion is an educational synthesis of published literature. It does not replace a clinician.

What is in it

What myasthenia gravis is Who gets it, the numbers, the muscles it reaches.
The neuromuscular junction One nerve impulse in slow motion, and the safety factor.
Antibodies at the junction AChR, complement, MuSK and LRP4, animated.
Weakness over a day Why muscles tire with use and recover with rest.
Diagnosis Antibodies, nerve tests, single-fibre EMG, a calculator.
MGFA class & scores MGFA classes I to V, MG-ADL and QMG, scored live.
The differential Lambert-Eaton, botulism, ALS, eye and muscle disease.
Pyridostigmine, animated Buying time at the receptor, dose by dose.
The treatment ladder From symptom relief to immunotherapy and biologics.
Thymectomy over the years The thymus, thymoma and the MGTX trial.
Complement & FcRn inhibitors The newer biologics, trial week by trial week.
Myasthenic crisis Triggers, the breathing numbers, ICU care.
Drugs that can worsen MG A cited checker: antibiotics, magnesium and more.
Nursing care Assessment, timing the doses, teaching, documentation.
Living with MG Pregnancy, surgery, exercise, vaccines, work.
Toward a cure CAR-T, B-cell targets and the evidence for each route.
History & people From Willis in 1672 to the biologics.
Flashcards, quiz and glossary Revision for students.
Sources Every reference behind the guide.

Part 1 · The disease

Weakness over a day

In MG, weakness grows with use and through the day, and eases with rest and cold. Press play to run a waking day beside the junction's electrical rundown, then switch between a healthy and an MG junction and try rest breaks, an ice pack and heat.

Fatigability is the hallmark of MG. Weakness fluctuates from day to day and hour to hour, is generally worse later in the day, and can be increased by sustained exercise and a higher body temperature. ²⁷⁶ It eases with rest and recurs with use, and it lessens in the cold. ³⁶⁷ The cause sits at the junction: each nerve impulse releases a little less acetylcholine than the one before, and in MG the margin for that loss has almost gone. ^301,467

Junction

Conditions

Time of day

Panel A is a schematic: no study in our sources publishes an hour-by-hour strength curve, so its shape is modelled from published descriptions (worse with use and later in the day, better with rest; heat worsens and cold improves). ^276,367 In panel B the first-impulse heights use the published mean safety factors, 2.98 healthy and 1.09 MG (filled dots) ⁴⁶⁷; the rundown shape (largest fall from the 1st to the 2nd impulse, lowest at the 4th-5th, slight recovery) follows published descriptions ^301,461, and its size, the spread between fibres, and the effects of the day, ice and heat are modelled (open dots).

The safety factor, in numbers

Bedside tests

Three quick tests use fatigability itself. Sustained upgaze provokes ptosis, an ice pack relieves it, and a rest lets it recover. Pick a test and press play; the accuracy figures are the published ones.

Test time

Illustrative patient. Lid positions are schematic; the 2 mm criterion and the 2.3 mm mean lift are published. ^461,564

What makes it worse

Sudden difficulty breathing or swallowing is an emergency, not ordinary fatigue. See Myasthenic crisis, and for medicines, Drugs that can worsen MG.

Exam hookFatigability is the hallmark. The decrement on repetitive nerve stimulation is the electrical picture of the same rundown: a reproducible fall of 10% or more from the 1st to the 4th or 5th response at 2-5 Hz. ^1,301

In plain wordsEach time a nerve fires in quick succession, it releases a little less messenger. With fewer catchers on the muscle, a few fibres stop responding, and the muscle tires. Rest lets the nerve ending restock.