Patient handout

Myasthenic Crisis

PRODUCTION

1. Your condition

This handout is for myasthenic crisis. Your care team identified this based on: bulbar weakness — dysphagia / dysarthria / dysphonia (aan 2024).

Other reasons your team may use this plan: respiratory failure / paradoxical breathing (aan 2024); rapidly worsening weakness in known mg (aan 2024); fluctuating fatigable weakness with diurnal pattern (aan 2024).

2. Your medications

Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.

Medication	Starting dose	How	When	What it does
ivig	2 g/kg total over 5 days (typically 0.4 g/kg/d × 5 d)	IV	daily × 5 d	2020 MGFA — IVIG and PLEX equivalent for AChR; check IgA before infusion (anaphylaxis risk in IgA deficient)
plasmapheresis	5 sessions over 7–10 days (every other day)	IV/large-bore	5 sessions q2 days	PLEX favoured in MuSK + when faster onset needed (response within 24–72 h vs 5–10 d for IVIG) (AAN 2024)

Plan: Myasthenic crisis immunomodulation + airway + chronic IS (AAN 2024)

3. Your action plan

Use these zones to know what to do based on how you feel.

GREEN — At baseline (AAN 2024)

If you have:

Stable strength (AAN 2024)
Normal swallow + speech
Adequate breathing

Do this:

Take pyridostigmine and immunosuppressant as prescribed
Avoid known offending meds (fluoroquinolones, aminoglycosides, macrolides, β-blockers, magnesium)
Carry MGFA emergency wallet card
Keep follow-up appointments

YELLOW — Caution — worsening symptoms (AAN 2024)

If you have:

Increased fatigability
New mild dysphagia or slurred speech
Mild dyspnea on exertion
Recent infection / fever
Started new medication

Do this:

Contact neurology team within 24 h
Review medication list for offenders
Treat infection promptly with safe antibiotics
Monitor breathing carefully
Do NOT increase pyridostigmine without team guidance (cholinergic crisis risk)

Call your provider if:

Any change persisting >24 h
New medication exposure
Fever or infection

RED — Medical alert — myasthenic crisis warning signs (AAN 2024)

If you have:

Severe difficulty breathing or shortness of breath at rest
Cannot swallow saliva / drooling / aspiration
Cannot speak above a whisper
Cannot lift head off pillow
Sudden generalised severe weakness
Weak cough / cannot clear secretions

Do this:

Call 911 / go to ED immediately
Bring MGFA wallet card and medication list
Tell ED team: "myasthenic crisis suspected — avoid succinylcholine, magnesium, aminoglycosides"
Sit upright; do not lie flat

Call your provider if:

Any red zone symptom — ED now

4. When to seek emergency care

Call 911 or go to the nearest emergency room right away if you have:

Impending myasthenic crisis — FVC 15–20 mL/kg AND/OR NIF magnitude 20–30 cmH2O AND/OR bulbar progression with single-breath count <15; act BEFORE mechanical ventilation required (MGFA 2020 Update Int Consensus PMID 33144515)
Full myasthenic crisis — FVC <15 mL/kg OR NIF magnitude <20 cmH2O OR severe bulbar weakness with aspiration OR hypercapnia → mechanical ventilation indicated (MGFA 2020 Update PMID 33144515)(life-threatening)
Cholinergic crisis from pyridostigmine overdose — SLUDGE (Salivation, Lacrimation, Urination, Defecation, GI cramping, Emesis) + fasciculations + miosis + bradycardia mimicking myasthenic weakness (MGFA 2020)
Severe bulbar weakness with cough / swallow failure / drooling — leading cause of MG mortality (MGFA 2020)
MuSK-Ab positive MG (~5–8% of generalised MG) — predominantly bulbar / respiratory / facial / neck flexor weakness; less response to AChE-I; rituximab first-line per international consensus
Anti-AChR-Ab positive MG (~80% of generalised MG) — thymus pathology common (hyperplasia or thymoma); responsive to AChE-I, IVIG, PLEX, steroids, eculizumab, efgartigimod, rozanolixizumab, zilucoplan
Seronegative MG (~5–10%) — standard AChR + MuSK Ab tests negative; clustered-AChR cell-based assay positive in subset; clinical features match generalised MG
Refractory MG — failed ≥2 prior therapies (typically prednisone + a steroid-sparing IS or PLEX/IVIG); persistent generalised disease despite maximal conventional therapy
MG in pregnancy — disease course unpredictable (1/3 improve, 1/3 stable, 1/3 worsen); risk of transient neonatal MG from passive antibody transfer (~10–20% of infants)
Crisis precipitant — recent exposure to an MG-aggravating medication: fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin), aminoglycosides (gentamicin, tobramycin, amikacin), macrolides (azithromycin, erythromycin, telithromycin), magnesium IV (especially obstetric), β-blockers (esp. propranolol, timolol), immune-checkpoint inhibitors (nivolumab, pembrolizumab), procainamide, quinidine, D-penicillamine, succinylcholine
MG in pregnancy / peripartum — disease course unpredictable (~1/3 worsen, peak first trimester + first postpartum month); IV magnesium sulfate for pre-eclampsia/eclampsia is CONTRAINDICATED (potent NMJ block → precipitates crisis); transient neonatal MG in ~10–20% of infants from transplacental maternal-antibody transfer (onset within 72 h, resolves 2–4 wk)
Acute neuromuscular respiratory failure differential — the load-bearing pivot is cholinergic-vs-myasthenic crisis (both cause weakness + respiratory failure in a known-MG patient on pyridostigmine); the discriminating cluster is muscarinic excess (SLUDGE + miosis + fasciculations + bradycardia → cholinergic) vs its absence (→ myasthenic). When the post-test probability of a non-MG mimic dominates, route by engine_id with carryover state (accumulated findings, current FVC/NIF, time-since-onset, therapy stack)

5. Follow-up

Long-term immunosuppression (steroid + steroid-sparing — azathioprine, MMF, rituximab; new agents efgartigimod/rozanolixizumab/zilucoplan); thymectomy if thymoma or AChR + age <65 (AAN 2024)

6. Sources

Guideline: International Consensus Guidance for Management of Myasthenia Gravis: 2020 Update (Narayanaswami, Sanders, Wolfe et al, Neurology 2020;96(3):114-122, PMID 33144515) — primary guideline floor; trial-grade anchors MGTX (Wolfe NEJM 2016), REGAIN (eculizumab), ADAPT (efgartigimod), MycarinG (rozanolixizumab), RAISE (zilucoplan), Díaz-Manera 2012 (MuSK rituximab), Barth 2011 (IVIg vs PLEX), Vivacity-MG3 (nipocalimab 2025)