Myasthenia Gravis - Exacerbation/Crisis

VERSION: 1.0 CREATED: January 27, 2026 STATUS: Approved

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DIAGNOSIS: Myasthenia Gravis - Exacerbation/Crisis

ICD-10: G70.01 (Myasthenia gravis with exacerbation)

CPT CODES: 85025 (CBC with differential), 80053 (CMP (BMP + LFTs)), 83735 (Magnesium), 84443 (TSH), 82947 (Blood glucose), 81003 (Urinalysis), 87040 (Blood cultures x2), 85610 (PT/INR), 82803 (ABG), 86235 (AChR binding antibody), 84145 (Procalcitonin), 71046 (Chest X-ray), 83605 (Lactate), 93000 (ECG (12-lead)), 94010 (Bedside spirometry (FVC and NIF)), 71260 (CT chest with contrast), 95937 (Repetitive nerve stimulation (RNS)), 95872 (Single-fiber EMG (SFEMG)), 70450 (CT head), 78816 (PET-CT), 93306 (Echocardiogram), 96365 (IVIG (intravenous immunoglobulin)), 36514 (Plasmapheresis (PLEX))

SYNONYMS: Myasthenic crisis, MG crisis, MG exacerbation, myasthenia exacerbation, myasthenic respiratory failure, acute MG, worsening myasthenia, cholinergic crisis, myasthenia gravis crisis

SCOPE: Acute exacerbation and myasthenic crisis in adults with known or suspected myasthenia gravis. Covers respiratory monitoring, emergent immunotherapy (IVIG/PLEX), cholinesterase inhibitor management, distinguishing myasthenic from cholinergic crisis, and medications to avoid. Excludes new diagnosis workup (see MG - New Diagnosis template), Lambert-Eaton syndrome, and chronic stable management.

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PRIORITY KEY: STAT = Immediate | URGENT = Within hours | ROUTINE = Standard | EXT = Extended/atypical cases | - = Not applicable to this setting

═══════════════════════════════════════════════════════════════ SECTION A: ACTION ITEMS ═══════════════════════════════════════════════════════════════

1. LABORATORY WORKUP

1A. Essential/Core Labs

Test	ED	HOSP	OPD	ICU	Rationale	Target Finding
CBC with differential (CPT 85025)	STAT	STAT	ROUTINE	STAT	Baseline; infection screen (common trigger); leukocytosis suggests infection	Normal
CMP (BMP + LFTs) (CPT 80053)	STAT	STAT	ROUTINE	STAT	Electrolytes, renal/hepatic function for medication dosing; hypokalemia worsens weakness	Normal
Magnesium (CPT 83735)	STAT	STAT	ROUTINE	STAT	Hypomagnesemia worsens NMJ transmission; CONTRAINDICATED to give IV Mg in MG crisis	Confirm normal BEFORE any magnesium replacement
TSH (CPT 84443)	URGENT	ROUTINE	ROUTINE	URGENT	Thyroid disease coexists in 10-15% of MG; thyrotoxicosis precipitates crisis	Normal
Blood glucose (CPT 82947)	STAT	STAT	ROUTINE	STAT	Steroid-induced hyperglycemia management	Normal
Urinalysis (CPT 81003) + urine culture	STAT	ROUTINE	ROUTINE	STAT	UTI as precipitant for exacerbation	Negative
Blood cultures x2 (CPT 87040)	STAT	STAT	-	STAT	If febrile; infection is #1 trigger for crisis	No growth
Pregnancy test (β-hCG)	STAT	STAT	ROUTINE	STAT	Affects treatment choices; MG can fluctuate in pregnancy	Document result
PT/INR (CPT 85610), aPTT (CPT 85730)	STAT	ROUTINE	-	STAT	Coagulation before procedures; PLEX circuit anticoagulation	Normal
ABG (CPT 82803) or VBG (CPT 82800)	STAT	STAT	-	STAT	Respiratory failure assessment; hypercapnia is LATE finding — do not wait for this	Normal; rising pCO2 = imminent failure

1B. Extended Workup (Second-line)

Test	ED	HOSP	OPD	ICU	Rationale	Target Finding
AChR binding antibody (CPT 86235)	-	ROUTINE	ROUTINE	-	Confirm diagnosis if not previously tested; positive in 85% generalized MG	Positive supports MG diagnosis
AChR modulating antibody (CPT 86235)	-	ROUTINE	ROUTINE	-	Additional sensitivity when binding Ab equivocal	Positive supports diagnosis
AChR blocking antibody (CPT 86235)	-	ROUTINE	ROUTINE	-	Part of full AChR panel	Positive supports diagnosis
MuSK antibody (CPT 86235)	-	ROUTINE	ROUTINE	-	If AChR negative; MuSK-positive MG has different treatment implications (poor response to pyridostigmine, PLEX preferred over IVIG)	Check if AChR negative
Anti-striated muscle antibody (anti-titin)	-	ROUTINE	ROUTINE	-	Associated with thymoma; especially in young patients	If positive, image for thymoma
Procalcitonin (CPT 84145)	URGENT	ROUTINE	-	URGENT	Differentiate bacterial infection trigger from other causes of decompensation	<0.5 ng/mL
Chest X-ray (CPT 71046)	STAT	ROUTINE	-	STAT	Aspiration pneumonia, atelectasis; baseline for ventilator	Clear lungs
Lactate (CPT 83605)	URGENT	ROUTINE	-	URGENT	Sepsis screen if febrile	Normal (<2 mmol/L)
Drug level of immunosuppressant (if applicable)	-	ROUTINE	ROUTINE	-	Check azathioprine metabolites (6-TGN), mycophenolate levels, tacrolimus levels if on these agents	Therapeutic range

1C. Rare/Specialized (Refractory or Atypical)

Test	ED	HOSP	OPD	ICU	Rationale	Target Finding
LRP4 antibody	-	EXT	EXT	-	Triple-seronegative MG (AChR-/MuSK-/LRP4+)	Check if double seronegative
Agrin antibody	-	EXT	EXT	-	Emerging biomarker in seronegative MG	Research use
Anti-Kv1.4 antibody	-	EXT	EXT	-	Associated with myocarditis in MG; cardiac risk stratification	Check if cardiac symptoms
Complement levels (C3, C4)	-	EXT	EXT	-	Complement-mediated MG pathophysiology; pre-eculizumab evaluation	Baseline
Quantitative immunoglobulins (IgG, IgA, IgM)	-	ROUTINE	ROUTINE	-	Hypogammaglobulinemia from rituximab or chronic IVIG; IgA deficiency before IVIG	Normal

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2. DIAGNOSTIC IMAGING & STUDIES

2A. Essential/First-line

Study	ED	HOSP	OPD	ICU	Timing	Target Finding	Contraindications
Chest X-ray (CPT 71046)	STAT	ROUTINE	-	STAT	Immediate in ED	Pneumonia, aspiration, atelectasis, mediastinal mass (thymoma)	None significant
ECG (12-lead) (CPT 93000)	STAT	ROUTINE	-	STAT	On admission	Arrhythmia, myocarditis (rare but reported in MG, especially anti-Kv1.4+)	None
Bedside spirometry (FVC and NIF) (CPT 94010)	STAT	STAT	ROUTINE	STAT	Immediately on presentation; serial monitoring	FVC >20 mL/kg; NIF more negative than -30 cmH2O	Patient cooperation required

2B. Extended

Study	ED	HOSP	OPD	ICU	Timing	Target Finding	Contraindications
CT chest with contrast (CPT 71260)	-	ROUTINE	ROUTINE	-	During admission if not recently done	Thymoma (present in 10-15%); thymic hyperplasia	Contrast allergy, renal impairment
MRI chest (alternative to CT)	-	ROUTINE	ROUTINE	-	If CT contraindicated	Thymoma evaluation	Pacemaker, metallic implants
Repetitive nerve stimulation (RNS) (CPT 95937)	-	ROUTINE	ROUTINE	-	If diagnosis not confirmed; avoid during acute crisis (deferred to stable phase)	Decremental response >10% at 2-3 Hz in affected muscle	None significant
Single-fiber EMG (SFEMG) (CPT 95872)	-	-	ROUTINE	-	Most sensitive test (95-99%); defer to outpatient stable phase	Increased jitter, blocking	Patient cooperation
CT head (CPT 70450)	URGENT	ROUTINE	-	URGENT	If altered mental status to rule out other causes	Normal (MG does not affect brain parenchyma)	None significant

2C. Rare/Specialized

Study	ED	HOSP	OPD	ICU	Timing	Target Finding	Contraindications
PET-CT (CPT 78816)	-	EXT	EXT	-	If thymoma on CT; staging	Metabolic activity, metastatic disease	Pregnancy
Echocardiogram (CPT 93306)	-	ROUTINE	ROUTINE	ROUTINE	If cardiac symptoms or anti-Kv1.4 positive	Myocarditis, cardiomyopathy	None significant
Pulmonary function tests (formal) (CPT 94010)	-	-	ROUTINE	-	Outpatient baseline after recovery	FVC baseline for future comparisons	Patient cooperation

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3. TREATMENT

3A. Acute/Emergent

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
IVIG (intravenous immunoglobulin) (CPT 96365)	IV	-	0.4 g/kg :: IV :: daily x 5 days :: 0.4 g/kg/day IV x 5 days (total 2 g/kg) OR 1 g/kg/day x 2 days (faster option). Start within 24h of crisis recognition	IgA deficiency (anaphylaxis risk — use IgA-depleted product); renal failure; thrombotic risk	Vital signs q15min first infusion; renal function daily; headache (aseptic meningitis); thrombotic events	-	STAT	-	STAT
Plasmapheresis (PLEX) (CPT 36514)	-	-	N/A :: - :: once :: 5 exchanges over 10-14 days (every other day); 1-1.5 plasma volumes per exchange. PREFERRED for MuSK-positive MG. Faster onset than IVIG (days vs 1-2 weeks)	Hemodynamic instability, severe sepsis, heparin allergy, poor vascular access	BP continuous during exchange; Ca2+ (citrate toxicity); fibrinogen; electrolytes; line infection	-	STAT	-	STAT
Intubation and mechanical ventilation	-	-	20 mL/kg :: - :: - :: Indications: FVC <20 mL/kg, NIF >-30 cmH2O (weaker), >30% FVC decline, clinical distress, inability to handle secretions. Use NON-DEPOLARIZING agents at REDUCED DOSE (MG patients are sensitive). Avoid succinylcholine (unpredictable response)	N/A (life-saving)	Ventilator per ICU protocol; daily SBT when improving	STAT	STAT	-	STAT
Hold pyridostigmine during crisis	-	-	N/A :: - :: per protocol :: HOLD cholinesterase inhibitors during intubation/crisis — excess cholinergic stimulation increases secretions and complicates ventilator management. Resume at reduced dose during weaning	N/A	Secretion management; restart when extubation approaching	STAT	STAT	-	STAT
Supplemental oxygen	-	-	94% :: - :: - :: As needed for SpO2 <94%	N/A	SpO2 monitoring	STAT	STAT	-	STAT
IV fluids (isotonic)	IV	-	N/A :: IV :: per protocol :: NS maintenance; hydration for IVIG renal protection	Volume overload	I/O, electrolytes	STAT	STAT	-	STAT

3B. Symptomatic Treatments

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
Pyridostigmine (when stable/recovering)	PO	Symptomatic weakness improvement	30 mg :: PO :: q4h :: Resume at 30 mg PO TID during recovery; titrate by 30 mg/dose q3-5 days to 60 mg PO q4-6h; max 120 mg q4h (rarely needed). Take 30-60 min before meals for dysphagia	Cholinergic crisis (excessive dosing), mechanical bowel obstruction	GI symptoms (diarrhea, cramping, salivation = cholinergic excess); reduce dose if muscarinic symptoms	-	ROUTINE	ROUTINE	ROUTINE
Glycopyrrolate	IV	Cholinergic side effects of pyridostigmine	1-2 mg :: IV :: BID :: 1-2 mg PO BID-TID; or 0.2 mg IV PRN for excessive secretions	Angle-closure glaucoma, urinary retention, tachycardia	Heart rate; urinary retention; dry mouth	-	ROUTINE	ROUTINE	ROUTINE
Acetaminophen	PO	Headache (IVIG-related or general)	650-1000 mg :: PO :: q6h :: 650-1000 mg PO q6h; max 4g/day	Severe liver disease	LFTs if prolonged	STAT	ROUTINE	ROUTINE	STAT
Ondansetron	IV	Nausea (IVIG-related)	4 mg :: IV :: q6h :: 4 mg IV/PO q6h PRN	QT prolongation	QTc monitoring	-	ROUTINE	-	ROUTINE
Diphenhydramine	IV	IVIG premedication	25-50 mg :: IV :: - :: 25-50 mg IV/PO 30 min before IVIG infusion	Angle-closure glaucoma; avoid in elderly (anticholinergic)	Sedation	-	ROUTINE	-	ROUTINE
Enoxaparin	SC	DVT prophylaxis	40 mg :: SC :: daily :: 40 mg SC daily	Active bleeding, CrCl <30 (use UFH)	Platelets q3 days	-	ROUTINE	-	ROUTINE
Pneumatic compression devices	-	DVT prophylaxis	N/A :: - :: continuous :: Apply bilaterally on admission	Acute DVT	Skin checks	STAT	STAT	-	STAT
Pantoprazole	IV	GI prophylaxis (if on steroids)	40 mg :: IV :: daily :: 40 mg IV/PO daily	Prolonged use risks (C. diff, osteoporosis)	GI symptoms	-	ROUTINE	ROUTINE	ROUTINE
Insulin sliding scale	-	Steroid-induced hyperglycemia	140-180 mg :: - :: - :: Per institutional protocol; target glucose 140-180 mg/dL	Hypoglycemia	Blood glucose q6h or more frequent	-	ROUTINE	-	ROUTINE

3C. Second-line/Refractory

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
IV methylprednisolone (CPT 96365)	IV	-	1000 mg :: IV :: daily :: 1000 mg IV daily x 3-5 days. CAUTION: steroids can transiently worsen MG in first 5-10 days — only initiate in monitored setting with respiratory support available. Some centers use slow oral prednisone uptitration instead	Uncontrolled diabetes (relative), active infection (relative)	FVC/NIF closely; glucose q6h; BP; GI prophylaxis	-	URGENT	-	URGENT
Prednisone (oral uptitration)	PO	-	10-20 mg :: PO :: daily :: Start 10-20 mg PO daily; increase by 10 mg every 3-5 days to target 1 mg/kg/day (max 60-80 mg); maintain for 4-8 weeks, then slow taper over months	Active infection, uncontrolled DM (relative)	Glucose, BP, weight, bone density, mood; GI prophylaxis; PJP prophylaxis if prolonged high-dose	-	ROUTINE	ROUTINE	-
Second course IVIG or PLEX	-	-	N/A :: - :: per protocol :: Repeat standard dosing if inadequate response to first course; wait 2-4 weeks between courses	Same as initial	Same as initial	-	URGENT	-	URGENT
Eculizumab	IV	-	900 mg :: IV :: - :: 900 mg IV q1 week x 4 weeks, then 1200 mg IV q2 weeks; for AChR-positive refractory generalized MG	Unresolved Neisseria meningitidis infection; must vaccinate ≥2 weeks before starting	Meningococcal infection; complement levels; CBC	-	EXT	ROUTINE	-
Efgartigimod (Vyvgart)	IV	-	10 mg/kg :: IV :: - :: 10 mg/kg IV weekly x 4 weeks per cycle; repeat cycles based on clinical response; for AChR-positive generalized MG	Active infection, IgG <2 g/L	IgG levels (target reduction); infection signs; CBC	-	EXT	ROUTINE	-
Rituximab	IV	-	375 mg/m2 :: IV :: - :: 375 mg/m2 IV weekly x 4 weeks OR 1000 mg IV x 2 doses 2 weeks apart; especially effective in MuSK-positive MG	Active infection, hepatitis B (reactivation risk — screen first)	CD20 count, immunoglobulins q3 months; hepatitis B screening; PML risk (rare)	-	EXT	ROUTINE	-

3D. Disease-Modifying or Chronic Therapies

Treatment	Route	Indication	Dosing	Pre-Treatment Requirements	Contraindications	Monitoring	ED	HOSP	OPD	ICU
Azathioprine	PO	-	50 mg :: PO :: daily :: Start 50 mg PO daily; increase by 50 mg every 1-2 weeks to target 2-3 mg/kg/day; onset of effect 6-12 months	-	TPMT deficiency; pregnancy; concurrent allopurinol (dose reduce by 75%)	CBC weekly x 4 weeks, then biweekly x 2 months, then monthly; LFTs monthly x 3, then q3 months	-	ROUTINE	ROUTINE	-
Mycophenolate mofetil	PO	-	500 mg :: PO :: BID :: Start 500 mg PO BID; increase to 1000 mg PO BID after 2 weeks; max 1500 mg BID; onset 6-12 months	-	Pregnancy (Category D), breastfeeding	CBC q1 week x 1 month, then biweekly x 2 months, then monthly; LFTs q3 months	-	ROUTINE	ROUTINE	-
Tacrolimus	PO	-	3 mg :: PO :: daily :: 3 mg PO daily in 2 divided doses; target trough 5-10 ng/mL; onset 3-6 months	-	Renal failure, uncontrolled hypertension	Trough level q1 week initially, then monthly; Cr, K+, glucose, BP; drug interactions (CYP3A4)	-	-	ROUTINE	-
Cyclosporine	PO	-	2-3 mg/kg :: PO :: - :: Start 2-3 mg/kg/day PO in 2 divided doses; target trough 100-200 ng/mL; onset 3-6 months	-	Renal failure, uncontrolled HTN, malignancy	Trough levels, Cr, BP, Mg, lipids monthly	-	-	ROUTINE	-

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⚠️ MEDICATIONS TO AVOID IN MYASTHENIA GRAVIS

Drug Category	Specific Agents	Risk
Aminoglycosides	Gentamicin, tobramycin, amikacin, streptomycin	NMJ blockade; can precipitate crisis
Fluoroquinolones	Ciprofloxacin, levofloxacin, moxifloxacin	NMJ blockade; FDA black box warning for MG
Macrolides	Azithromycin, erythromycin, clarithromycin	NMJ blockade (less than aminoglycosides but still risky)
Beta-blockers	Propranolol, metoprolol, atenolol (all)	Worsen NMJ transmission; can precipitate crisis
Calcium channel blockers	Verapamil (worst); diltiazem	Impair NMJ transmission
Magnesium (IV)	Magnesium sulfate	Directly blocks NMJ; can precipitate respiratory failure. Do NOT give IV Mg in MG unless life-threatening hypomagnesemia with close monitoring
Telithromycin	Ketek	Severe exacerbation; contraindicated
D-Penicillamine	Cuprimine	Can induce autoimmune MG
Neuromuscular blockers	Succinylcholine (unpredictable), non-depolarizing agents (prolonged effect at standard doses)	Use reduced doses of non-depolarizing agents if intubation required
Botulinum toxin	Botox, Dysport	Systemic weakness risk
Statins	All (rare)	Reported to unmask or worsen MG (rare; benefit usually outweighs risk)
Immune checkpoint inhibitors	Nivolumab, pembrolizumab, ipilimumab	Can trigger or exacerbate MG (potentially fatal); oncology must coordinate with neurology
Quinine/Quinidine	Antimalarials, antiarrhythmics	NMJ blockade
Phenytoin	Dilantin	Can worsen MG (mechanism unclear)
Lithium	Mood stabilizer	May worsen NMJ transmission

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4. OTHER RECOMMENDATIONS

4A. Referrals & Consults

Recommendation	ED	HOSP	OPD	ICU	Indication
Neurology consultation (neuromuscular specialist if available)	STAT	STAT	-	STAT	All myasthenic crisis; treatment decisions; medication management
Pulmonology / Critical care	URGENT	URGENT	-	STAT	Declining respiratory function; ventilator management
Thoracic surgery	-	ROUTINE	ROUTINE	-	Thymoma evaluation; thymectomy planning (if not previously done)
Respiratory therapy	STAT	STAT	-	STAT	Bedside FVC/NIF monitoring; pulmonary toilet
Speech-language pathology (SLP)	URGENT	STAT	ROUTINE	URGENT	Dysphagia evaluation; aspiration prevention (bulbar weakness common in crisis)
Physical therapy (PT)	-	URGENT	ROUTINE	ROUTINE	Prevent deconditioning; safe mobilization; fall prevention
Occupational therapy (OT)	-	URGENT	ROUTINE	ROUTINE	ADL assessment; energy conservation techniques; adaptive equipment
Pharmacy (clinical pharmacist)	STAT	STAT	-	STAT	Medication reconciliation — review ALL medications for MG-unsafe drugs
Social work	-	ROUTINE	ROUTINE	-	Discharge planning; support resources; insurance for IVIG/PLEX
Palliative care	-	ROUTINE	-	ROUTINE	Goals of care discussion for refractory or elderly patients
Infectious disease	-	ROUTINE	-	-	If infection trigger unclear or complex; immunosuppressed patient management
Endocrinology	-	ROUTINE	ROUTINE	-	If concurrent thyroid disease; steroid-induced diabetes management

4B. Patient Instructions

Recommendation	ED	HOSP	OPD
Call 911 / Return to ED if: increasing difficulty breathing, trouble swallowing, choking on food or saliva, unable to hold head up, rapidly worsening weakness	STAT	STAT	ROUTINE
Carry MG crisis card / MedicAlert bracelet at all times	-	ROUTINE	ROUTINE
Bring complete medication list to every medical visit; alert ALL providers about MG diagnosis	-	ROUTINE	ROUTINE
NEVER take antibiotics, pain medications, or new prescriptions without checking with neurology	-	ROUTINE	ROUTINE
Take pyridostigmine 30-60 minutes before meals for best swallowing function	-	ROUTINE	ROUTINE
Avoid extreme heat (worsens weakness), overexertion, and sleep deprivation	-	ROUTINE	ROUTINE
Report any new medication prescribed by other providers to your neurologist	-	ROUTINE	ROUTINE
Infection prevention: hand hygiene, avoid sick contacts, up-to-date vaccinations (inactivated only if immunosuppressed; NO live vaccines)	-	ROUTINE	ROUTINE
Follow-up with neurology 1-2 weeks post-discharge; sooner if symptoms worsen	-	ROUTINE	ROUTINE

4C. Lifestyle & Prevention

Recommendation	ED	HOSP	OPD
Infection avoidance (number one trigger for crisis)	-	ROUTINE	ROUTINE
Influenza vaccination annually (inactivated)	-	-	ROUTINE
Pneumococcal vaccination	-	-	ROUTINE
COVID-19 vaccination (inactivated/mRNA; coordinate timing with immunosuppression cycle)	-	-	ROUTINE
NO live vaccines if on immunosuppression (MMR, varicella, live zoster, yellow fever)	-	ROUTINE	ROUTINE
Adequate sleep (fatigue worsens MG)	-	ROUTINE	ROUTINE
Stress management (emotional stress triggers exacerbation)	-	ROUTINE	ROUTINE
Moderate exercise as tolerated; avoid overexertion; rest periods during activity	-	ROUTINE	ROUTINE
Heat avoidance (hot weather, hot tubs, saunas worsen NMJ transmission)	-	ROUTINE	ROUTINE
Smoking cessation	-	ROUTINE	ROUTINE
Alcohol limitation (alcohol worsens weakness)	-	ROUTINE	ROUTINE
Eye protection (sunglasses, patching for diplopia; artificial tears for incomplete lid closure)	-	ROUTINE	ROUTINE

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5. DIFFERENTIAL DIAGNOSIS

Alternative Diagnosis	Key Distinguishing Features	Tests to Differentiate
Cholinergic crisis	EXCESSIVE pyridostigmine; salivation, lacrimation, urination, diarrhea, emesis (SLUDE); miosis; fasciculations; weakness WORSENS with additional pyridostigmine	Hold pyridostigmine — if strength improves, cholinergic; if worsens, myasthenic crisis. Clinical distinction is key
Guillain-Barré syndrome	Ascending paralysis, areflexia, albuminocytologic dissociation, preceding infection, no fatigability	NCS/EMG (demyelinating neuropathy vs NMJ); LP (elevated protein); no response to pyridostigmine
Lambert-Eaton myasthenic syndrome	Proximal weakness IMPROVES with repeated use; autonomic dysfunction (dry mouth); associated with small cell lung cancer; hyporeflexia	VGCC antibodies; NCS (incremental response with high-rate repetitive stimulation — opposite of MG)
Botulism	Descending paralysis (cranial → limbs); dilated pupils; foodborne or wound exposure; autonomic dysfunction	Stool/serum botulinum toxin; NCS (incremental); clinical history
ALS	Progressive weakness without fluctuation; upper AND lower motor neuron signs; no fatigability pattern; fasciculations	NCS/EMG (denervation); no response to IVIG/PLEX; no AChR antibodies
Brainstem stroke	Acute onset; cranial nerve findings; crossed findings (ipsilateral cranial nerve + contralateral limb); no fatigability	MRI DWI (restricted diffusion); CTA
MS exacerbation	CNS symptoms (optic neuritis, sensory level, cerebellar ataxia); dissemination in space and time; no NMJ findings	MRI brain/spine; LP (oligoclonal bands); no AChR antibodies
Thyroid storm	Severe weakness, tachycardia, fever, agitation, lid lag; thyroid hormone excess	TSH (suppressed), free T4 (elevated)
Periodic paralysis (hypo/hyperkalemic)	Episodic weakness triggered by meals, exercise, rest; normal between attacks	Serum potassium during attack; genetic testing
Conversion disorder / FND	Non-physiologic weakness; Hoover sign; distractible; no fatigable pattern	Normal NCS/EMG; normal antibodies; clinical exam

6. MONITORING PARAMETERS

Parameter	ED	HOSP	OPD	ICU	Frequency	Target/Threshold	Action if Abnormal
Forced Vital Capacity (FVC)	STAT	STAT	ROUTINE	STAT	q4-6h on floor; q2-4h in ICU; q1-2h if declining	>20 mL/kg	If <20 mL/kg → intubate electively; if declining >30% → prepare for intubation
Negative Inspiratory Force (NIF)	STAT	STAT	ROUTINE	STAT	With FVC measurements	More negative than -30 cmH2O	If weaker than -30 → intubate
Single breath count	STAT	STAT	-	STAT	q4h as screening	Count to >20	If <15 → correlate with FVC; if <10 → imminent failure
Oxygen saturation	STAT	STAT	-	STAT	Continuous in ICU; q4h on floor	≥94%	LATE finding; do not rely on alone
Blood pressure	STAT	STAT	ROUTINE	STAT	q4h on floor; continuous in ICU	Stable	Autonomic dysregulation possible (less common than GBS)
Heart rate and rhythm	STAT	STAT	-	STAT	Continuous telemetry in ICU; q4h on floor	Normal sinus	Arrhythmia: cardiology consult
Neurologic exam (strength, bulbar function)	STAT	STAT	ROUTINE	STAT	q4-8h; MGFA post-intervention status at discharge	Improving or stable	If worsening → re-evaluate treatment; consider repeat IVIG/PLEX
Swallowing assessment	URGENT	STAT	ROUTINE	STAT	Daily	Safe oral intake	NPO; NG tube; modified diet
Blood glucose	-	ROUTINE	ROUTINE	ROUTINE	q6h if on steroids; BID if stable	<180 mg/dL	Insulin; reduce steroid if possible
Renal function (Cr, BUN)	-	ROUTINE	-	ROUTINE	Daily during IVIG; q48h otherwise	Stable	Hold IVIG; hydration
CBC	-	ROUTINE	ROUTINE	ROUTINE	Weekly during immunosuppression initiation; q3 months chronic	Normal	Dose adjust or hold immunosuppressant
LFTs	-	ROUTINE	ROUTINE	-	Monthly x3 for azathioprine/mycophenolate, then q3 months	Normal	Dose adjust or hold

7. DISPOSITION CRITERIA

Disposition	Criteria
Discharge home	Exacerbation resolved; FVC >60% predicted and stable; able to swallow safely; adequate oral medications; no respiratory distress; stable immunotherapy regimen; follow-up within 1-2 weeks
Admit to floor (monitored bed)	Moderate exacerbation; FVC 20-30 mL/kg; requires IVIG or PLEX; dysphagia requiring modified diet; unable to maintain medications orally
Admit to ICU	Myasthenic crisis; FVC <20 mL/kg or declining rapidly; intubated; bulbar weakness with aspiration risk; post-operative thymectomy with respiratory concerns
Transfer to higher level	Need for PLEX not available; neuromuscular specialist consultation; need for ICU with neurology expertise
Inpatient rehabilitation	Significant weakness; unable to perform ADLs independently; able to tolerate 3h/day therapy

8. EVIDENCE & REFERENCES

Recommendation	Evidence Level	Source
IVIG (2 g/kg over 2-5 days) for myasthenic crisis	Class I, Level A	Zinman et al. (2007); Gajdos et al. Cochrane (2012)
PLEX (5 exchanges) for myasthenic crisis	Class I, Level A	Cortese et al. (2011); Cochrane Review
IVIG and PLEX are equivalent for crisis	Class I, Level A	Barth et al. (2011)
PLEX preferred for MuSK-positive MG	Class IIa, Level C	Expert consensus; Evoli et al. (2003)
Hold pyridostigmine during intubation/crisis	Class IIa, Level C	Expert consensus
Avoid aminoglycosides, fluoroquinolones in MG	Class III (Harm)	FDA safety communication; multiple case reports
Avoid IV magnesium in MG	Class III (Harm)	NMJ blockade; case reports of respiratory failure
Steroids can transiently worsen MG (monitor closely when initiating)	Class IIa, Level B	Multiple observational studies
Thymectomy benefit in non-thymomatous MG	Class I, Level B	MGTX trial (Wolfe et al. NEJM 2016)
Eculizumab for refractory AChR+ generalized MG	Class I, Level A	REGAIN trial (Howard et al. Lancet Neurol 2017)
Efgartigimod for AChR+ generalized MG	Class I, Level A	ADAPT trial (Howard et al. Lancet Neurol 2021)
Rituximab for MuSK-positive MG	Class IIa, Level B	Hehir et al. (2017); Díaz-Manera et al. (2012)
20/30/40 rule for intubation	Class IIa, Level C	Wijdicks & Klein (2017)
Bedside FVC superior to ABG for monitoring	Class I, Level B	Multiple studies; ABG changes are LATE findings
Azathioprine as first-line steroid-sparing	Class I, Level B	Palace et al. (1998)
Mycophenolate as steroid-sparing	Class II, Level B	Mixed trial results but widely used

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APPENDIX: MYASTHENIC vs CHOLINERGIC CRISIS

Feature	Myasthenic Crisis	Cholinergic Crisis
Cause	Undertreated MG; infection trigger	Excessive pyridostigmine
Pupils	Normal	Miosis (constricted)
Secretions	Normal or decreased	Excessive salivation, tearing, bronchorrhea
Fasciculations	Absent	Present
GI symptoms	Absent	Diarrhea, nausea, vomiting, cramping
Response to pyridostigmine	Improves	Worsens
Treatment	IVIG/PLEX; increase immunotherapy	HOLD pyridostigmine; supportive care

APPENDIX: MGFA CLINICAL CLASSIFICATION

Class	Description
I	Ocular weakness only; may have weakness of eye closure. All other muscle strength is normal
II	Mild weakness affecting muscles other than ocular; may also have ocular weakness of any severity
IIa	Predominantly limb, axial muscles, or both; may have lesser involvement of oropharyngeal muscles
IIb	Predominantly oropharyngeal, respiratory muscles, or both; may have lesser or equal involvement of limb, axial muscles
III	Moderate weakness affecting muscles other than ocular; may also have ocular weakness of any severity
IIIa	Predominantly limb, axial muscles
IIIb	Predominantly oropharyngeal, respiratory muscles
IV	Severe weakness affecting muscles other than ocular
IVa	Predominantly limb, axial muscles
IVb	Predominantly oropharyngeal, respiratory (can include feeding tube, without intubation)
V	Intubation required to maintain airway (with or without mechanical ventilation) = MYASTHENIC CRISIS