Myasthenic Crisis

Myasthenic crisis is a life-threatening neurological emergency defined by acute respiratory failure or severe bulbar weakness due to myasthenia gravis (MG). It represents the most severe end of the MG spectrum, requiring immediate intensive care and mechanical ventilation.

Also Called / Synonyms

• Myasthenic crisis (MC)
• Impending myasthenic crisis (IMC), a pre-crisis state of rapid clinical decline with high risk of progression to MC ^[4]A1b
• Myasthenic exacerbation, a broader term for any acute worsening, not necessarily meeting crisis criteria

Defining the Phases: Impending vs. Manifest Crisis

In 2016, the Myasthenia Gravis Foundation of America (MGFA) introduced the term impending myasthenic crisis to identify patients with a narrow therapeutic window. According to the 2024 Chinese MG Collaborative Group Expert Consensus, IMC is defined as significant worsening of bulbar or respiratory muscle function within ≤2 weeks, meeting any of the following: MGFA type IVb; Quantitative Myasthenia Gravis (QMG) bulbar subscore ≥3; QMG respiratory subscore ≥2; or combined bulbar-respiratory subscore ≥4 ^[4]A1b. Manifest crisis (MC) is defined by the need for endotracheal intubation and mechanical ventilation for >24 hours ^[9]B2b.

Classification Systems

MG severity and crisis risk are categorized using multiple axes:

MGFA Clinical Classification (adapted from ^[2]C4)

Antibody Profile, 90% of generalized MG patients are seropositive: 84.5% anti-acetylcholine receptor (AChR), 5.9% anti-muscle-specific kinase (MuSK) ^[11]C4. Rarer targets include LRP4 ^[1]D5.

Age of Onset, Early-onset MG (<50 years) and late-onset MG (≥50 years) have distinct epidemiological and prognostic features ^[10]B2c. Very-late-onset MG (≥65 years) carries higher crisis risk ^[13]C4.

Thymic Pathology, Thymoma occurs in 20% of MG patients; thymic hyperplasia in 70% ^[1]D5. Thymoma confers a 4.8-fold increased risk of intensive care for MC (OR 4.8, 95% CI 1.19-19.43) ^[13]C4.

Clinical Significance

MC occurs in 10% to 20% of patients with MG ^[3]D5[19]C4. In a Czech nationwide registry, 6.1% of patients required intensive care for MC, with a median time from diagnosis of 5.3 months ^[13]C4. The in-hospital mortality of MC is 5.05% (14/277), and the 1-year all-cause mortality is 15.16% (42/277) ^[19]C4. Incidence of MG is rising (0.62 to 3.13 per 100,000), with a prevalence of 27.19 per 100,000 ^[10]B2c.

These definitions and classifications form the basis for every subsequent section, from pathophysiology to acute management , ensuring a consistent vocabulary across the emergency-condition template.

Pearl: Thymoma increases the risk of intensive care for MC nearly 5-fold, and the majority of crises occur within 6 months of diagnosis.

Having defined myasthenic crisis as a life-threatening escalation of MG, we now examine the pathophysiologic cascade that transforms stable neuromuscular junction dysfunction into fulminant respiratory failure.

Core Autoimmune Mechanism

The disease originates from autoantibodies targeting the neuromuscular junction . In ~85% of generalized MG patients, pathogenic IgG1 and IgG3 antibodies bind the acetylcholine receptor (AChR), impairing neuromuscular transmission by reducing available receptors ^[22]D5. A smaller subset (1-6%) harbor antibodies against MuSK (muscle-specific kinase), which disrupts agrin-LRP4-MuSK signaling and clustering of AChR at the postsynaptic membrane ^[22]D5. Both antibody types cause fluctuating weakness, but the precise molecular events that precipitate crisis involve additional systemic immune dysregulation.

Triggers and the Transition to Crisis

Crisis occurs when a superimposed trigger amplifies the baseline autoimmune attack. Common precipitants include infection, surgery (especially thymectomy ), and immune checkpoint inhibitor (ICI) therapy ^{[23]C4[25]D5[28]C4}.

• Infection: West Nile virus (WNV) can convert stable ocular MG into crisis via a post-infectious pro-inflammatory state that amplifies pre-existing autoantibody-mediated pathology, rather than through molecular mimicry ^[23]C4.
• ICI therapy: Bulbar symptoms and myasthenic crisis are frequent in ICI-induced MG; anti-AChR antibodies are found in only half of these patients, and the clinical picture often overlaps with ICI-related myositis ^[25]D5.
• Surgery: Thymectomy in patients with thymoma and concurrent Castleman’s disease carries elevated risk of postoperative crisis, mitigated by pre- and postoperative plasmapheresis ^[28]C4.

Cellular Mediators of Hypercytokinemia

Single-cell transcriptomic profiling of peripheral blood during AChR-positive crisis reveals a hypercytokinemia driven by innate immune activation ^[24]B3b. A discrete monocyte subset (FCGR3B⁺ monocytes) exhibits marked upregulation of pro-inflammatory signaling pathways during crisis, which normalizes three months later ^[24]B3b. This is accompanied by a high neutrophil-lymphocyte ratio (NLR), confirmed in 22 additional patients and correlated with MG severity scores ^[24]B3b. Concurrently, age-associated B cells show oligoclonal expansion with high autoimmune activity, while CD4⁺ and CD8⁺ T cells display persistent exhaustion ^[24]B3b. Together, these findings define a peripheral immune landscape dominated by innate activation and T-cell exhaustion, favoring sustained inflammation and antibody-driven NMJ blockade.

Neuroanatomic Localization of Weakness

The clinical phenotype of crisis, respiratory failure, dysphagia, dysphonia, reflects the topographic distribution of NMJ vulnerability. The diaphragm and intercostal muscles are highly dependent on a large safety factor of neuromuscular transmission; when AChR density is reduced, these muscles fail first. Bulbar muscles (palatal, pharyngeal, laryngeal) are also exquisitely sensitive, producing the hallmark “nasal voice” and pooling secretions that further compromise airway protection. The neuroanatomic consequence is a descending paralysis: ocular → bulbar → axial → respiratory, culminating in the need for ventilatory support.

Mechanism Cascade

Pearl: The transition from stable MG to crisis is not simply a quantitative increase in antibody titer; it is a qualitatively distinct inflammatory state driven by innate immune activation (hypercytokinemia, FCGR3B⁺ monocytes, elevated NLR). Recognizing this mechanistic shift may guide earlier use of targeted immunomodulation rather than escalation of symptomatic therapy alone.

The clinical burden of myasthenic crisis reflects its underlying autoimmune pathophysiology, with rising incidence and prevalence globally. Myasthenic crisis occurs in 10% to 20% of patients with myasthenia gravis (MG) over their lifetime ^[42]B3b.

Incidence and Prevalence

Incidence of MG itself ranges from 0.3 to 6.1 per 100,000 person‑years across populations, and prevalence from 2.2 to 58.6 per 100,000 ^[40]B2a. For crisis, population‑based estimates are limited. In the US, hospitalization rates for MG crisis rose by 6.8% annually from 2010-2019, outpacing non‑crisis admissions (4.4% per year) ^[34]B2c. In Taiwan, the incidence of first crisis among incident MG patients was 4.7% within the first year, with 96.2% of those events occurring within 3 months of diagnosis ^[33]B2c.

Demographic Patterns

Crisis affects all ages but shows a bimodal distribution: young women and older men ^[30]B2c. Among US hospitalizations, black women had the highest annual incidence of MG admission (0.01 per 1,000), followed by white women, white men, and black men (0.009, 0.008, 0.007 per 1,000) ^[30]B2c. Older age is a major risk factor: among Medicare beneficiaries ≥65 years, in‑hospital mortality for crisis admissions averaged 5.0% versus 1.8% for all adults ^[34]B2c. Hispanic and African American patients with MG have higher cumulative incidence of exacerbations over time ^[36]B2c.

Temporal Trends

MG incidence is increasing in multiple regions. In the Czech Republic, incidence rose from 0.62 to 3.13 per 100,000 between 2015 and 2017 ^[10]B2c. In Germany, prevalence in 2019 was estimated at 39.3 per 100,000 and incidence at 4.6 per 100,000 ^[31]B2c. Taiwan’s prevalence increased from 19 to 24 per 100,000 from 2013-2019 ^[33]B2c. These trends are partly attributed to an aging population, improved diagnostics, and increasing awareness ^[38]D5.

Risk Factors for Myasthenic Crisis

Multiple factors predispose to crisis, as summarized in the table below.

Infection is the most common trigger, accounting for 67% of crises in some series ^{[38]D5[42]B3b}. Seasonality is not well‑established, but respiratory infections peak in winter, likely contributing to seasonal variation. The risk of crisis is highest within the first 6 months after MG diagnosis (median 5.3 months in one study) ^[13]C4. Vaccination against influenza and pneumococcus is recommended because infection prevention is critical; there is no evidence that standard vaccines trigger crisis, though live vaccines are generally avoided in patients on immunosuppression ^[38]D5.

Pearl: Infection is the most common trigger, and diabetes, hypomagnesemia, and cautionary drugs markedly increase risk.

The transition from stable myasthenia gravis to crisis is often heralded by a recognizable constellation of symptoms, though the pace and pattern vary with the trigger. The median age at crisis is 72 years, and the initial presentation may be ocular, bulbar, or respiratory from the outset ^[51]C4.

Presenting Symptoms

• Ocular symptoms (ptosis, diplopia) are the most common first manifestation overall, but during crisis they are often overshadowed by bulbar and respiratory complaints ^{[22]D5[61]B2a}.
• Bulbar weakness dominates: dysphagia, dysphonia, nasal regurgitation, and inability to manage secretions. In one series, 4 of 5 patients with de novo MG presented with dysphagia as the primary symptom, and one was already in crisis ^[47]C4. Bilateral vocal fold paralysis can be the leading sign, easily mistaken for airway obstruction ^[48]C4.
• Respiratory difficulty may develop insidiously as orthopnea, tachypnea, or use of accessory muscles, or abruptly with paradoxical breathing and respiratory arrest.
• Autonomic symptoms are uncommon but serious: chest pain or hemodynamic instability should raise suspicion for takotsubo cardiomyopathy, which occurs in 0.5-1% of crises and carries 17.5% mortality ^[49]C4[60]C4.
• Non‑motor symptoms such as dysgeusia (altered taste) can precede crisis and may predict relapse in thymoma‑associated MG ^[50]C4.

Neurological Examination Findings

• Motor system: Fluctuating, fatigable weakness in ocular, bulbar, and proximal limb muscles. Key findings include ptosis fatigable on sustained upgaze, impaired adduction or elevation of the eyes, weak palatal elevation, poor cough, and tongue weakness. Neck flexor and respiratory muscle strength should be assessed quantitatively.
• Sensory examination is normal; reflexes are normal or brisk but not depressed.
• Specific bedside maneuvers:
• Single breath count (normal > 20; < 15 indicates severe respiratory compromise).
• Ice pack test: improvement of ptosis after 2 minutes of ice application supports MG.
• Forced vital capacity (FVC) measurement: a decline to < 20 mL/kg is a widely used threshold for imminent respiratory failure, though not validated in crisis-specific trials ^[51]C4.
• Examination in ICI‑induced MG: may reveal concurrent myositis (proximal weakness, elevated creatine kinase to a mean of 4,799 IU/L) and myocarditis , requiring cardiac monitoring ^{[52]B2b[25]D5}.

Phenotypic Variants

Red Flags Requiring Immediate Action

• Respiratory distress: tachypnea, accessory muscle use, paradoxical breathing, inability to complete sentences, single breath count < 20.
• Severe bulbar weakness: drooling, inability to swallow secretions, cough ineffective, dysphonia.
• Rapidly progressive weakness over hours to days.
• Autonomic instability: hypotension, arrhythmia, chest pain → suspect takotsubo cardiomyopathy ^[49]C4[60]C4.
• New dysgeusia in a known MG patient with thymoma may herald crisis ^[50]C4.

Atypical Presentations

• Isolated dysphagia can be the sole presenting symptom of MG, leading to delayed diagnosis until crisis ^[47]C4.
• Bilateral vocal fold paralysis as first manifestation mimics acute airway obstruction and requires urgent laryngoscopy ^[48]C4.
• Dysgeusia as a non‑motor symptom may precede other signs by weeks ^[50]C4.
• ICI‑induced MG often presents with overlapping myositis/myocarditis, so elevated CK or troponin should not be dismissed as non‑specific ^{[52]B2b[25]D5}.

Pearl: In an elderly patient with new-onset bulbar weakness and respiratory difficulty, always consider myasthenic crisis even if no prior MG diagnosis, half of takotsubo‑associated crises occur in undiagnosed MG ^[49]C4.

The clinical presentation of fluctuating, fatigable weakness in ocular, bulbar, or limb muscles directs the workup toward confirming neuromuscular junction dysfunction. The diagnosis rests on serological detection of pathogenic antibodies, electrophysiological evidence of impaired transmission, and exclusion of mimics.

Serological Testing

• Acetylcholine receptor (AChR) antibodies - Found in nearly 90% of patients with generalized MG and in nearly 50% of those with isolated ocular MG ^[64]D5. Their presence confirms the diagnosis.
• Muscle-specific kinase (MuSK) antibodies - Identified in a smaller subset, often with prominent bulbar and respiratory involvement. Testing is indicated when AChR antibodies are negative ^[22]D5.
• LRP4 antibodies - Detected in approximately 20% of double-seronegative patients (negative for both AChR and MuSK) ^[59]C4.
• Seronegative MG - Up to 10-15% of MG patients have no detectable antibodies ^[62]B2b. In these patients, electrophysiological testing becomes critical.

Electrophysiological Testing

• Repetitive nerve stimulation (RNS) - A decremental response of >10% in a distal or proximal muscle supports the diagnosis. In double-seronegative MG, RNS is positive in 57.7% of cases ^[59]C4.
• Single-fiber electromyography (SFEMG) - This is the most sensitive electrodiagnostic test, particularly useful in ocular MG or when RNS is equivocal ^[64]D5. It demonstrates increased jitter and blocking, reflecting impaired neuromuscular transmission. In experienced hands, SFEMG can detect abnormalities in the majority of patients with MG, though exact sensitivity numbers are not reported in the available literature.

Imaging

• Chest computed tomography (CT) or magnetic resonance imaging (MRI) - Essential for detecting thymoma, which is present in 10-15% of MG patients. Thymoma is a risk factor for myasthenic crisis (OR 4.8, 95% CI 1.19-19.43) ^[13]C4. Imaging should be performed in all patients at diagnosis.

Other Tests

• Ice pack test - Placing ice over a ptotic eyelid for 2 minutes can transiently improve ptosis in ocular MG. This test is simple and specific.
• Edrophonium (Tensilon) test - Rarely used now due to risk of bradycardia and availability of serology; however, a positive response (improvement in weakness) supports the diagnosis.

Diagnostic Algorithm

Differential Diagnosis

The following conditions can mimic myasthenic crisis and must be considered:

Pearl: In a patient with a known MG diagnosis presenting with respiratory distress, do not delay treatment for serological confirmation, rely on clinical history and prior antibody status. In seronegative patients, SFEMG is the most sensitive test and can clinch the diagnosis when clinical suspicion is high.

Once the diagnosis is established, severity must be classified using a structured system to anchor treatment decisions and prognosis. The Myasthenia Gravis Foundation of America (MGFA) clinical classification remains the universal staging tool, grading weakness from Class I (ocular only) through Class V (intubation) ^{[10]B2c[11]C4[53]B2b}. Most patients with generalized disease fall into Class II (mild) or III (moderate); late-onset MG (≥50 years) more often presents as Class IIb (predominantly bulbar) ^[10]B2c. The MGFA post-intervention status (MGFA-PIS) then captures longitudinal outcomes, from complete stable remission to unchanged or worse ^[9]B2b[11]C4.

Refractory Disease

Refractory MG carries a substantially worse prognosis and requires early identification. By one commonly used definition, patients fail to lower prednisolone below 20 mg/day, need regular intravenous immunoglobulin or plasmapheresis, or maintain a Myasthenia Gravis Activities of Daily Living (MG-ADL) score ≥6 after ≥12 months of corticosteroids plus at least one oral immunosuppressant ^[53]B2b. An alternative nationwide cohort definition required plasma exchange or IVIG at least three times per year after ≥2 immunosuppressants ^[68]B2b. In a Czech registry, 5.0% of patients were refractory, with a higher proportion of MGFA Class IIb (45.3% vs 33.6%) and IIIb (14.1% vs 4.6%) compared to non-refractory patients, and significantly lower forced vital capacity (FVC 70.1% vs 74.0% predicted) ^[10]B2c. The adjusted hazard ratio for mortality in refractory MG is 2.49 (95% CI 1.26-4.94) and for myasthenic crisis 3.14 (95% CI 2.25-4.38) compared to non-refractory MG ^[68]B2b.

Predictive Models for Crisis and Exacerbation

Early features also predict refractory disease: failure to achieve a lowest effective prednisolone dose ≤20 mg/day plus initiation of an oral immunosuppressant during the first year after diagnosis conferred an 18.7-fold higher risk of refractory MG) ^[53]B2b.

Weaning Risk Stratification

In myasthenic crisis requiring invasive ventilation, 91% of patients undergo intermediate (2-6 days) or prolonged (≥7 days) weaning by the WEAN Safe classification ^[74]B2b. Independent predictors of prolonged weaning are thymoma (OR 3.02, 95% CI 1.01-9.07) and absence of MG-specific immunosuppressive treatment at ICU admission (OR 3.70, 95% CI 1.22-11.23) ^[74]B2b. Age itself is not a predictor, but very-late-onset (≥65 years) patients have more comorbidities and similar outcomes ^[74]B2b.

Long-Term Mortality Risk

In a nationwide Korean cohort, the all-cause mortality rate in MG was 144.40 per 10,000 person-years vs 92.60 in matched controls (adjusted HR 1.41, 95% CI 1.34-1.49) ^[32]B2c. Risk factors include older age, male sex, high comorbidity burden, high-dose corticosteroid use (≥15 mg/day), thymoma, and history of myasthenic crisis. Thymectomy is associated with reduced mortality ^[32]B2c. Non-thymomatous MG follows a more benign course than thymomatous MG, with lower postoperative crisis rates (5.6% vs 13.4%) and long-term mortality (1.4% vs 9.9%) ^[9]B2b.

These stratification tools directly inform treatment thresholds, guiding the intensity of acute therapy (Section 7) and long-term immunotherapy decisions.

Pearl: Use the Kanai score (vital capacity <80%, disease duration <3 months, bulbar symptoms) to identify patients at high risk for postoperative crisis before thymectomy, a score ≥4 points warrants preoperative optimization and planned ICU admission ^[43]B3b.

Once a myasthenic crisis is recognized and severity classified (Section 6), management proceeds simultaneously along three axes: airway/respiratory support, rapid immunomodulation to abort the attack, and identification/removal of the trigger. The goal is to halt disease activity within hours to days, prevent progression to respiratory failure, and facilitate weaning from ventilatory support.

Step 1: Triage and Respiratory Support

All patients with impending or manifest crisis require immediate admission to a neurological intensive care unit (ICU) or high-dependency unit ^{[78]D5 [79]D5}. Forced vital capacity (FVC) < 20 mL/kg, maximal inspiratory pressure < 30 cmH₂O, or maximal expiratory pressure < 40 cmH₂O signal impending respiratory failure and warrant proactive noninvasive ventilation (NIV) ^[79]D5. Bilevel positive airway pressure (BiPAP) is the preferred first-line ventilatory strategy in myasthenic crisis because it reduces the need for intubation and avoids the complications of invasive mechanical ventilation ^[79]D5 (Evidence: 5). However, if bulbar weakness is severe (inability to manage secretions, weak cough), or if NIV fails to maintain oxygenation or ventilation, early intubation is mandatory ^[79]D5.

Step 2: Rescue Immunomodulation, Plasma Exchange or IVIG

Two established therapies rapidly remove or neutralize pathogenic autoantibodies. Therapeutic plasma exchange (PLEX) is often favored in the acute setting because it rapidly removes circulating anti-AChR antibodies and other immune mediators; a typical course is 5 to 7 exchanges of 1.0-1.5 plasma volumes every other day ^{[78]D5 [80]D5} (Evidence: 5). Intravenous immunoglobulin (IVIG) is administered as 0.4 g/kg/day for 5 days ^{[78]D5 [81]B2b} (Evidence: 2b). A 12-year neuro-ICU case series reported that over 90% of patients received prednisolone and/or IVIG, and intubation was required in 63% ^[81]B2b. No high-quality randomized trial directly compares PLEX to IVIG in crisis; the choice often depends on institutional preference, vascular access, and hemodynamic stability ^{[78]D5 [80]D5}. Both modalities are considered first-line rescue therapy ^[82]D5.

Step 3: Escalation for Refractory Crisis, Newer Targeted Agents

For patients who fail to improve after a full course of PLEX or IVIG, or who have refractory disease, complement inhibitors and FcRn antagonists offer rapid rescue. Eculizumab, a terminal complement C5 inhibitor approved for refractory generalized MG (AChR antibody-positive), has been used as rescue therapy in crisis with dramatic responses: within 48 hours of administration, Quantitative Myasthenia Gravis (QMG) scores improved from 28.2±4.8 to 15.0±4.1, and MG-ADL scores decreased from 16.8±2.8 to 6.0±4.3 in a retrospective case series ^[20]C4 (Evidence: 4). Individual case reports describe extubation within 17 hours and nasogastric tube removal within 48 hours ^{[20]C4 [86]C4} (Evidence: 4). Efgartigimod, a neonatal Fc receptor antagonist (10 mg/kg IV weekly for 4 weeks), has also shown rapid action: in a prospective case series of 10 patients with MC, all were weaned from ventilation after a mean of 10.44±4.30 days, and MG-ADL scores dropped from 15.6±4.4 to 3.4±2.2 after one cycle ^[77]C4 (Evidence: 4). A separate case series of 3 patients reported extubation at 7 days after the first efgartigimod infusion ^[87]C4 (Evidence: 4). Both agents are well tolerated and do not require central venous access.

Cyclophosphamide (30-50 mg/kg monthly IV) has been used as induction therapy in refractory MG, with clinical improvement in 75% of patients and median progression-free survival of 9 months, but it is not a first-line acute rescue therapy ^[91]B2b (Evidence: 2b).

Step 4: Corticosteroids and Trigger Management

High-dose corticosteroids (e.g., prednisone 1 mg/kg/day) are often started concurrently with PLEX/IVIG, but they should be initiated after the acute immunotherapy has begun because early high-dose steroids can transiently worsen weakness ^{[78]D5 [81]B2b}. In the acute phase, the primary goal is to avoid exacerbating agents, do not use non-depolarizing neuromuscular blockers, beta-blockers, aminoglycosides, macrolides (except azithromycin ), or certain antiarrhythmics (e.g., procainamide, quinidine) ^{[78]D5 [88]C4 [79]D5}. Azithromycin appears safe in MG patients with COVID-19 ^[88]C4.

Monitoring and Transition

Frequent assessment of respiratory parameters (FVC, negative inspiratory force, oxygen saturation, and arterial blood gases) is essential. Once the patient is hemodynamically stable and weaning from ventilatory support has begun, transition to the chronic management program (Section 8) should be arranged, including optimization of long-term immunotherapy and thymectomy evaluation.

Controversies and Guideline Disagreement

Pearl: In myasthenic crisis, initiate BiPAP early for impending respiratory failure and start PLEX or IVIG immediately; if no response within 48-72 hours, consider eculizumab or efgartigimod as rescue therapy, as they have shown rapid clinical improvement even in refractory cases ^[20]C4[77]C4.

Figure 1: Acute management algorithm for myasthenic crisis (adapted from ^{[78]D5[79]D5[20]C4}).

Once the acute crisis resolves, the focus shifts to a chronic immunosuppressive strategy designed to prevent recurrence and achieve sustained remission. The evidence ladder for long-term therapy is built largely on observational studies and expert consensus, with only a few drugs tested in randomized trials. The following steps outline a rational escalation approach, integrating the limited but actionable data from the myasthenic crisis literature.

Step 1: Initiate or Optimize Oral Immunosuppression

For all patients who survive a myasthenic crisis, long-term immunotherapy is indicated. Corticosteroids ( prednisone ) remain the backbone. The goal is to titrate to the lowest effective dose, often combined with a steroid-sparing agent. Azathioprine is the most studied baseline immunosuppressant, supported by decades of observational data ^[93]D5. Alternatives include mycophenolate mofetil, cyclosporine A, tacrolimus , and methotrexate , all used off-label in most Western countries ^[93]D5. The choice depends on tolerability, comorbidities, and speed of onset. Azathioprine requires several months to achieve full effect, so corticosteroids are used in the interim.

Step 2: Second-Line Agents for Refractory Disease

When disease remains active despite adequate doses of corticosteroids and azathioprine (or an alternative first-line agent), escalation to combination therapy is warranted. Drug combinations, such as corticosteroids plus cyclosporine A, can provide more rapid control ^[93]D5. All such regimens require supervision by an experienced neuroimmunological center because of potentially serious adverse reactions ^[93]D5. Serial measurement of anti-acetylcholine receptor antibodies, when elevated, can guide tapering and monotherapy reduction ^[93]D5.

Step 3: Biologic Therapies for Refractory Myasthenic Crisis

A subset of patients remain resistant to conventional immunotherapy. Two biologic options have emerged from the available evidence:

• Eculizumab (complement C5 inhibitor) has shown rapid and sustained benefits in refractory acetylcholine receptor antibody-positive (AChR-Ab+) late-onset generalized myasthenia gravis (LOMG). In a retrospective study of 31 patients with refractory LOMG, eculizumab reduced the Myasthenia Gravis Activities of Daily Living (MG-ADL) score by 2.976 points at Month 1 and 5.430 points at Month 12 (both P<0.001). The cumulative minimal symptom expression (MSE) rate reached 22.58% at Month 1 and 72.24% at Month 12, and the mean prednisone dose decreased by 7.574 mg/day (P<0.001) ^[72]B2b. In a case report series, eculizumab enabled ventilator discontinuation within 2 days in a patient with refractory myasthenic crisis ^[86]C4. These findings, while not from randomized trials, position eculizumab as a promising rescue therapy for refractory cases.

• Granulocyte macrophage colony-stimulating factor (GM-CSF, sargramostim) was associated with clinical improvement, expansion of Foxp3+ regulatory T cells, and enhanced Treg suppressive function in a single patient with prolonged myasthenic crisis refractory to conventional therapy ^[92]C4. Definitive conclusions cannot be drawn, but the correlation with animal models suggests further clinical trials are warranted ^[92]C4.

Step 4: Thymectomy

In nonthymoma patients with generalized myasthenia gravis, including older children and adults up to the fifth decade, complete transsternal thymectomy is recommended based on available open trials and expert opinion, preferentially during the first year of disease ^[93]D5. Endoscopic surgery may also be effective ^[93]D5. Before surgery, pretreatment with immunosuppressive medication or plasmapheresis is usually recommended to reduce perioperative morbidity and mortality, which is now near zero in experienced centers ^[93]D5. Thymoma patients require thymomectomy and sometimes postsurgical chemotherapy and radiation treatment ^[93]D5.

Controversies and Guideline Disagreement

Pearl: After stabilizing a myasthenic crisis, initiate chronic immunosuppression early with corticosteroids plus a steroid-sparing agent (azathioprine or mycophenolate); for refractory AChR-Ab+ disease, eculizumab can provide rapid symptom improvement and allow corticosteroid reduction, though its use in the acute crisis setting remains off-label and based on limited evidence ^{[72]B2b[86]C4}.

The evidence ladder for long-term management , built on decades of clinical experience, rests on a foundation of landmark trials that sequentially shifted the standard of care for both maintenance therapy and crisis management. Understanding this evolution - from the empiric use of acetylcholinesterase inhibitors to the rise of targeted biologics - clarifies why current protocols are structured as they are.

The Era of Acetylcholinesterase Inhibitors and Thymectomy

Before the 1970s, treatment of myasthenic crisis relied almost entirely on continuous intravenous pyridostigmine or neostigmine . A systematic review of eight observational studies found that while these agents could improve outcome measures when plasmapheresis or IVIG were unavailable, they carried risks of cardiac arrhythmia and pneumonia, though not statistically different from those of plasmapheresis ^[99]B2a. Thymectomy emerged as a mainstay after the landmark observation that removal of the thymus improved long-term outcomes, but it also introduced the risk of postoperative myasthenic crisis (POMC). Meta-analyses of over 25 studies confirmed that preoperative bulbar symptoms, a history of crisis, and disease severity (Osserman stage IIA-IV) are independent predictors of POMC, with odds ratios ranging from 3.8 to 10.0 ^{[6]A1a[101]B3a[103]B2b}. The use of sugammadex for neuromuscular blockade reversal, introduced in the 2010s, was associated with a reduction in POMC from 8.7% to 4.3% (OR 0.48, 95% CI 0.25-0.91) in a Japanese nationwide database analysis ^[102]B2b.

The Shift to Immunomodulation: Plasma Exchange and IVIG

The 1990s brought a pivotal change. The randomized trial by Gajdos et al. (1997) compared three sessions of plasma exchange with IVIG at 0.4 g/kg/day for either 3 or 5 days in 87 patients with MG exacerbation. The median improvement in the myasthenic muscular score was similar between groups: +18 in the PE group and +15.5 in the IVIG group (p = 0.65). Tolerance favored IVIG, with only 1 side effect versus 8 in the PE group (p = 0.01) ^[94]A1b. This trial established IVIG as a first-line alternative to PE, though the small sample size precluded a definitive superiority claim. Subsequent work investigated whether IVIG could prevent crisis after surgery. A double-blind, randomized trial of 47 well-controlled patients found that preoperative IVIG 0.4 g/kg/day × 5 days did not reduce the incidence of postoperative crisis compared with placebo (1 patient in each arm) ^[95]A1b. This provided Class I evidence that prophylactic IVIG is unnecessary in stable patients.

The Arrival of Targeted Biologics

The 2020s introduced a new treatment paradigm. The neonatal Fc receptor (FcRn) antagonist efgartigimod was shown in the phase 3 ADAPT trial to produce rapid, clinically meaningful improvements in MG-ADL scores in anti-AChR antibody-positive patients, with a favorable safety profile ^[97]D5. For the specific setting of impending myasthenic crisis, a randomized open-label study of 38 patients compared efgartigimod (10 mg/kg weekly × 4) with IVIG (0.4 g/kg/day × 5). Remission rates were similar (90.48% vs 94.12%, p = 1.000), but the median time to remission was significantly shorter with efgartigimod: 8 days (95% CI 5.75-10.67) versus 12 days (95% CI 9.92-13.20) (p = 0.009) ^[4]A1b. A multicenter real-world study of 61 patients with acute exacerbations confirmed that 81.9% achieved a meaningful improvement at week 1 (after a single dose), and 98.1% at week 4 ^[18]C4. Even in the extreme elderly (≥80 years), efgartigimod reduced MG-ADL scores by 52.2% at week 4, with a 91.7% clinical meaningful improvement rate ^[104]B2b.

Complement inhibition entered the crisis arena through case reports. A 32-year-old woman with thymomatous AChR-antibody-positive generalized MG who failed TPE and high-dose prednisone during a postpartum crisis was treated with eculizumab after prophylactic meningococcal vaccination. She was extubated 6 days after the first dose ^[98]C4. A systematic review accompanying that case identified 19 additional patients treated with eculizumab for crisis, supporting its role when conventional therapies fail.

Most recently, the phase 3 Vivacity-MG3 trial of nipocalimab (30 mg/kg loading then 15 mg/kg every 2 weeks) added to standard therapy in 153 antibody-positive patients demonstrated a least-squares mean MG-ADL reduction of -4.70 versus -3.25 for placebo (difference -1.45, 95% CI -2.38 to -0.52; p = 0.0024) over 6 months ^[96]A1b. Serious adverse events were similar (9% vs 14%), though three fatal outcomes occurred (one myasthenic crisis in the nipocalimab group).

What Was Abandoned and Why

Early reliance on high-dose azathioprine as a first-line agent waned after a 12-year survey of 104 patients reported adverse reactions in 35%, including hematologic (18%), gastrointestinal (13%), and infectious complications (13%), with temporary discontinuation needed in 11% ^[100]C4. The overlapping toxicity of prednisone and azathioprine led to the adoption of mycophenolate mofetil and tacrolimus as preferred steroid-sparing agents in many centers ^[44]A1c. The use of pyridostigmine during crisis itself is now discouraged by most guidelines because it can worsen airway secretions; the systematic review noted that only a small proportion of patients received AChE inhibitors at the start of crisis, and those who did had a numerically higher rate of pneumonia ^[99]B2a.

Controversies and Guideline Disagreement

Pearl: The evolution from acetylcholinesterase inhibitors to IVIG/PE and now to FcRn antagonists reflects a consistent drive toward faster, safer, and more targeted therapy - the median time to remission with efgartigimod (8 days) is one-third shorter than with IVIG (12 days) ^[4]A1b, a difference that matters in the narrow window of crisis.

Building on the historical evolution of immunosuppression, the post-crisis immunotherapy program is now stratified by antibody profile, trigger factors, and comorbidity burden. The goal is to achieve rapid, sustained disease control while minimizing treatment-related toxicity, a balance that requires explicit sequencing rules, safety monitoring protocols, and de-escalation thresholds.

Step 1: Selecting the Maintenance Immunotherapy After Crisis Resolution

For patients with anti-acetylcholine receptor antibody-positive generalized MG, the first-line acute therapies (IVIG or PLEX) are followed by a bridging plan to long-term immunotherapy. The 2016 International Consensus Guidance from the Myasthenia Gravis Foundation of America notes that expert experience favors PLEX for faster onset, but IVIG offers a more favorable safety profile ^[20]C4. However, new evidence supports early use of targeted biologics in selected patients. The extended preoperative immunotherapy duration exceeding 14 days reduced the risk of postoperative acute exacerbation in thymoma-associated MG (HR 0.419, P < 0.001) ^[105]B2b. This suggests that in patients awaiting thymectomy, a minimum 2-week preoperative immunotherapy course (e.g., IVIG, PLEX, or a biologic) is protective.

For patients with refractory crisis or poor response to IVIG/PLEX, complement C5 inhibitors offer a rapid-acting alternative. In a retrospective case series, eculizumab 900 mg IV (single dose) led to ventilator weaning within 17 hours and nasogastric tube removal within 48 hours in 3 of 4 impending crisis episodes ^[20]C4. Ravulizumab, a long-acting C5 inhibitor, has also shown efficacy in thymoma-associated MG crisis, with two of three patients achieving rapid extubation ^[107]C4. The FcRn inhibitor efgartigimod (10 mg/kg weekly × 4 doses) produced a 52.2% reduction in MG-ADL scores at week 4 in elderly patients (≥80 years), with a mean time to clinically meaningful improvement of 1.3 weeks ^[104]B2b.

Step 2: Safety Monitoring Protocols for Biologics

All complement inhibitors require meningococcal vaccination at least 2 weeks before initiation, or prophylactic antibiotics (e.g., penicillin) if urgent dosing is needed. Patients should be monitored for Neisseria meningitidis infection, a boxed warning for eculizumab ^[20]C4. In the case series, no infections occurred during short-term follow-up ^[20]C4. For efgartigimod, baseline IgG levels should be checked; the mean reduction in IgG was 58.0% after one cycle ^[104]B2b. In patients with baseline IgG < 6 g/L, individualized dosing may be needed, one patient with IgG 4.24 g/L achieved a 59% reduction without serious infection, but continued administration beyond the second infusion did not further improve IgG clearance ^[104]B2b. Routine IgG monitoring every 4 weeks during the first cycle is prudent.

For PLEX, a less recognized phenomenon is antibody overshoot, a rise in AChR antibody titer to a median of 1292% of baseline following 3-12 sessions, associated with clinical deterioration in 4 of 5 patients ^[109]C4. Clinicians should watch for worsening symptoms 4-6 weeks after PLEX and consider re-treatment or escalation to a biologic if overshoot occurs.

Step 3: De-escalation and Steroid-Sparing Strategies

Once the patient is stable, the goal is to taper corticosteroids to the lowest effective dose while maintaining disease control. Post-thymectomy, the combination of prednisone plus tacrolimus (Pred + TAC) was associated with sustained clinical response in both non-thymomatous (HR 0.40, P = 0.026) and thymomatous MG (HR 0.35, P = 0.030) compared to prednisone alone ^[9]B2b. Pred + mycophenolate mofetil (MMF) also showed benefit (HR 0.21, P = 0.020) in non-thymomatous cases ^[9]B2b.

For patients unable to tolerate oral immunosuppressants, chronic low-dose IVIg (0.4 g/kg/month) is a steroid-sparing option. In a retrospective study of 109 patients, mean prednisone dose decreased from 33.1 mg/day at baseline to 7.2 mg/day after 36 months, with the greatest effect within 6 months (33.1 to 17.9 mg/day) ^[110]B2b. 92.5% of patients remained stable over 3 years ^[110]B2b.

Special Population: Immune Checkpoint Inhibitor-Triggered MG

Checkpoint inhibitors (e.g., nivolumab , pembrolizumab , ipilimumab ) can trigger de novo or exacerbate pre-existing MG, often with severe crisis. Steroids are first-line; eculizumab has been used successfully in PD-1 inhibitor-induced MG with rapid improvement ^{[106]C4[112]C4[113]C4}. Combination CTLA-4/PD-1 blockade carries a higher risk of fatal outcomes ^[113]C4. These patients require urgent cessation of the checkpoint inhibitor and multidisciplinary oncology-neurology co- management .

Pearl: After crisis, choose the maintenance immunotherapy based on antibody status and thymoma; for AChR-positive refractory cases, complement inhibitors (eculizumab/ravulizumab) provide rapid, sustained control, while efgartigimod offers a steroid-sparing option with a favorable safety profile in elderly patients ^{[20]C4[104]B2b[107]C4}.

Controversies and Guideline Disagreement

Once the acute immunomodulatory phase has stabilized the patient, the clinical focus transitions to restoring function, managing residual symptoms, and preventing secondary complications. This phase requires a structured, multidisciplinary approach integrating respiratory weaning, dysphagia management , early mobilization, and prophylaxis against hospital-acquired events.

Respiratory Monitoring and Weaning

Serial measurements of forced vital capacity (FVC) and negative inspiratory force (NIF) guide extubation readiness. In the case series by Ramos-Fransi et al., median time to weaning from mechanical ventilation was 12 days (range 3-176 days) ^[118]B2b. Alarm thresholds used during early mobilization include:

• Tidal volume < 180 mL
• SpO₂ < 90%
• Respiratory rate ≥ 30 breaths/min ^[115]C4

Table 1. Intubation and Extubation Thresholds

Note: Thresholds are derived from general ICU practice and the monitoring parameters reported in Okamoto et al. ^[115]C4.

Autonomic Complications

Autonomic instability, including cardiac arrhythmias, blood pressure lability, ileus, and urinary retention, can occur during critical illness and should be monitored with continuous telemetry and daily abdominal examination. A multidisciplinary team including a neurointensivist and pharmacist is recommended ^[116]D5.

DVT/PE Prophylaxis

Standard pharmacologic prophylaxis with low molecular weight heparin (e.g., enoxaparin 40 mg subcutaneously once daily) or unfractionated heparin 5000 U subcutaneously three times daily is indicated unless contraindicated by bleeding risk. Sequential compression devices should be added when pharmacologic prophylaxis is delayed.

Pain Management

Pain in myasthenic crisis is typically musculoskeletal (from prolonged immobility) or neuropathic (from critical illness polyneuropathy). First-line agents include acetaminophen 650 mg every 6 hours and gabapentin 300 mg three times daily (titrated). Avoid fluoroquinolones ( levofloxacin , ciprofloxacin , moxifloxacin ) because they can precipitate acute exacerbation; in FDA postmarketing reports, 30% of fluoroquinolone-associated exacerbations required ventilatory support and 5% were fatal ^[123]C4. Also avoid magnesium-containing medications and certain antibiotics that impair neuromuscular transmission.

Rehabilitation

Early rehabilitation should be initiated as soon as the patient is hemodynamically stable, but with careful monitoring for overwork weakness. In a nationwide Japanese database study, high-intensity rehabilitation was associated with delayed recovery in activities of daily living (HR 0.69; 95% CI 0.48-0.99) ^[114]B2b. Therefore, a moderate, stepwise approach is recommended:

• Start: Range-of-motion exercises and assisted sitting (day 3-5 in ICU) ^[115]C4
• Progress: Standing and gait training once respiratory status is stable (tidal volume ≥ 500 mL, SpO₂ ≥ 92%)
• Monitor: Grip strength and leg elevation duration before each session; reduce workload if Borg Scale ≥ 16 or heart rate exceeds 70% of heart rate reserve ^[115]C4
• Advance: Resistance training and endurance exercise (e.g., lower-limb ergometer) after weaning from ventilation, targeting 60-90 min/day ^[115]C4

Hospital-Acquired Complications

Aspiration pneumonia is the most common preventable complication. In a scoping review, 75% of patients with silent aspiration developed aspiration pneumonia ^[8]D5. All patients should undergo instrumental swallowing assessment (FEES or VFSS) before oral feeding is resumed. Pressure injuries are prevented with regular turning (every 2 hours) and specialized mattresses. Catheter-associated urinary tract infections are minimized by removing indwelling catheters as soon as possible.

Table 2. Common Hospital-Acquired Complications

Pearl: Early rehabilitation after myasthenic crisis should be moderate in intensity, high-intensity therapy may paradoxically delay functional recovery ^[114]B2b; always monitor grip strength and leg elevation duration before each session to detect overwork weakness ^[115]C4.

Building on the rehabilitation foundation, the ICU phase of myasthenic crisis is marked by a constellation of complications that determine outcome. Prevention and early detection are as critical as immunomodulation itself.

Respiratory Monitoring

Serial bedside spirometry remains the cornerstone of respiratory surveillance. Forced vital capacity (FVC) and negative inspiratory force (NIF) are measured every 4-6 hours; a declining trend prompts escalation to noninvasive ventilation or intubation ^[51]C4. In the German multicenter cohort of 250 crises, the median duration of mechanical ventilation was 12 days; prolonged ventilation (>15 days) was associated with age, late-onset MG, multiple comorbidities, pneumonia (OR 3.13, p=0.0001), and resuscitation (OR 9.15, p=0.0008) ^[51]C4. Weaning failure occurred in 64.2% of episodes, and extubation failure in 43.0% after the first attempt ^[37]B3b. Independent predictors of weaning failure included older age, ≥3 comorbidities, late-onset MG, atelectasis, pneumonia, and sepsis ^[37]B3b. In a French expert center, 91% of patients experienced intermediate or prolonged weaning per the WEAN Safe classification, yet extubation failure was only 5%, reflecting a cautious, stepwise approach with repeated spontaneous breathing trials ^[74]B2b.

Autonomic Complications

Autonomic instability is underrecognized. Takotsubo cardiomyopathy (stress-induced cardiomyopathy) has been reported in MG exacerbation, often with myasthenic crisis as the trigger (37.5% of cases in a systematic review of 40 cases) ^[60]C4. It presents with ECG abnormalities, troponin elevation, and transient left ventricular dysfunction, but chest pain is absent in 82.5% of cases ^[60]C4. Mortality in these patients was 17.5% ^[60]C4. Ileus and urinary retention may occur from anticholinergic overload or from the crisis itself; monitoring of bladder scans and bowel sounds is warranted.

DVT/PE Prophylaxis

Prolonged immobility and central venous access increase thromboembolic risk. All patients should receive pharmacologic prophylaxis with low molecular weight heparin or unfractionated heparin, in accordance with general ICU guidelines ^[51]C4. No specific MG crisis data exist, but the high rate of sepsis and multiorgan failure (the main cause of death) underscores the importance of minimizing additional complications ^[51]C4.

Pain Management

Pain is often overlooked. Sources include oropharyngeal ulceration from endotracheal tubes, pressure points, and musculoskeletal strain from positioning. Acetaminophen (1 g every 6 hours) is first-line; opioids should be used cautiously due to respiratory depression risk. Avoid neuromuscular blocking agents and non-depolarizing muscle relaxants entirely.

Rehabilitation

Early mobilization, as soon as hemodynamic and respiratory stability permit, reduces ICU-acquired weakness. Passive range-of-motion exercises, followed by active-assisted therapy, are initiated in the ICU. Speech therapy for dysphagia and respiratory muscle training are integral to weaning success.

Hospital-Acquired Complications

Pneumonia is the most frequent infection, occurring in 69.6% of deceased patients in one necropsy series ^[39]B3b. Ventilator-associated pneumonia before the first weaning attempt occurred in 15% of patients in a French cohort ^[74]B2b. Urinary tract infections (17.7%) and bloodstream infections (16.5%) are also common ^[39]B3b. Prevention bundles include oral care, head -of-bed elevation, and daily sedation interruption. Pressure injury prophylaxis with specialized mattresses and regular repositioning is mandatory. The table below summarizes key complications, their frequency, prevention, and management.

Controversies and Guideline Disagreement

Pearl: The most critical intervention to prevent complications is early, aggressive immunomodulation - the single strongest predictor of short weaning duration is the presence of MG-specific immunosuppressive therapy at ICU admission ^[74]B2b.

Complications such as sepsis and multiorgan failure drive the mortality of myasthenic crisis, but the trajectory after the acute phase is equally determined by baseline disease characteristics and the choice of rescue therapy. Understanding the natural history, both untreated and with modern immunomodulation, grounds prognostication and shared decision-making.

Survival and Functional Outcomes

In-hospital mortality has fallen substantially with protocol-driven care. Contemporary series report rates of 5.05% (14/277) in a prospective Chinese cohort ^[19]C4 and 12% in a German multicenter analysis of 250 mechanically ventilated patients ^[51]C4. A smaller prospective study found 2.63% (2/76) mortality ^[41]B2b. All-cause mortality at one year post-crisis reaches 15.16% (42/277), with septic shock (35.7%) and multiple organ failure (21.4%) as leading causes ^[19]C4. Among survivors, 20.5% still require mechanical ventilation at hospital discharge ^[51]C4.

Functional recovery is often substantial. MG-ADL scores improve from a mean of 21.3 at crisis onset to 5.5 at 6 months and 2.8 at 1 year ^[19]C4. By one year, 79.76% (197/247) of patients achieve a favorable post-intervention status ^[19]C4. The median duration of mechanical ventilation is 12 days (IQR not reported) ^[51]C4 to 17.1 days ^[41]B2b.

Predictors of Poor Prognosis

Several factors independently predict prolonged ventilation, higher mortality, and worse long-term outcomes:

• In-hospital mortality: >3 comorbidities, acute respiratory distress syndrome, resuscitation ^[51]C4; older age at crisis (OR 1.03), thymoma (OR 1.84), Charlson Comorbidity Index ≥3 (OR 2.68), prolonged ICU stay (OR 1.03) ^[19]C4
• Long-term mortality: history of myasthenic crisis within 2 years of diagnosis (HR 2.33, 95% CI 1.87-2.89) ^[35]B2c
• Recurrent crisis: prior crisis (HR 5.75, 95% CI 4.15-7.96) ^[35]B2c

Long-Term Trajectory After Crisis

Even after achieving minimal symptom expression (MSE), the risk of exacerbation persists. The median time to exacerbation post-MSE is 35.1 months (25th-75th percentile: 12.7-63.9 months) ^[70]B2b. A validated nomogram incorporating five factors, shorter disease duration to MSE, smaller AChR-ab reduction (ΔAChR-ab), thymoma, comorbid immune-related diseases, and history of crisis/impending crisis, predicts exacerbation risk with an AUC of 0.886 (derivation) and 0.829 (external validation) ^[70]B2b.

Thymoma-associated MG (TAMG) follows a more aggressive course: shorter time from symptom onset to crisis (17.95 vs 51.31 months), longer hospital stay (39.2 vs 33.2 days), and higher risk of postoperative crisis ^[54]B2b. Novel therapies such as efgartigimod (10 mg/kg weekly ×4) and complement inhibitors (eculizumab, ravulizumab) show promise in refractory cases, with rapid symptom improvement and steroid-sparing effects ^{[4]A1b[57]B2b[72]B2b[75]B2b[107]C4[124]B2b[127]C4}.

Pearl: A patient who survives a myasthenic crisis has a 1 in 5 chance of requiring ventilation at discharge and a 1 in 6 chance of dying within the year, but nearly 80% achieve good functional recovery by 12 months. The strongest modifiable predictor of prolonged ventilation is pneumonia; prevention and early treatment of respiratory infection is the single most impactful intervention after the crisis is controlled.

While the natural history of MG continues to improve with modern therapy, special populations present unique diagnostic and management challenges that require tailored approaches.

Pediatrics

Pediatric myasthenic crisis is rare but life-threatening. Diagnosis may be delayed because young children cannot articulate fluctuating symptoms. Presenting features include ptosis, diplopia, bulbar weakness, and respiratory distress, often triggered by infection ^[137]C4. Repetitive nerve stimulation is diagnostic; single-fiber EMG may be more sensitive ^[3]D5. Management follows adult guidelines, but doses are weight-based. IVIG and PLEX are first-line immunomodulatory therapies for crisis ^[130]D5. Thymectomy is considered in seropositive children, though timing remains debated ^[130]D5. Prognosis is generally favorable with prompt treatment, but complications such as aspiration pneumonia can occur.

Pregnancy

Pregnancy has an unpredictable effect on MG. Exacerbation occurs in 33.8% of pregnancies, with a 6.4% risk of myasthenic crisis during pregnancy and 8.2% postpartum ^[131]B2a. Worsening is most common in the first trimester and postpartum period ^[141]D5. Stable disease before conception is associated with fewer relapses ^[136]B2b. Transient neonatal MG occurs in 13% of newborns due to transplacental passage of antibodies ^[131]B2a. Fetal arthrogryposis multiplex congenita is a rare but serious complication ^[136]B2b.

Treatment considerations: Pyridostigmine is first-line symptomatic therapy and is generally considered safe during pregnancy ^[141]D5. Corticosteroids are used but carry an increased risk of cleft palate (first trimester) and preterm delivery ^[141]D5. Immunosuppressants with known teratogenicity (e.g., mycophenolate mofetil, cyclophosphamide ) should be avoided ^[130]D5. IVIG and PLEX are safe and effective for acute exacerbations ^{[130]D5[136]B2b}. For myasthenic crisis, PLEX is often preferred due to faster onset, but IVIG is an alternative ^[130]D5.

Delivery planning: Spontaneous vaginal delivery is encouraged when possible; caesarean section is reserved for obstetric indications ^[135]C4. Regional anesthesia (epidural) is preferred over general anesthesia due to risk of prolonged neuromuscular blockade ^[135]C4. Breastfeeding is generally safe with pyridostigmine and prednisone ; limited data exist for other immunosuppressants ^[141]D5.

Elderly

Myasthenia gravis in the elderly is increasingly recognized, with late-onset MG (LOMG, onset ≥50 years) and very-late-onset MG (VLOMG, ≥65 years) comprising a growing proportion ^{[134]B2b[104]B2b}. Elderly patients often present with ocular symptoms or bulbar weakness, which can mimic stroke, leading to diagnostic delay ^[133]C4. Myasthenic crisis occurs at similar rates as in younger patients (13%) ^[134]B2b. Comorbidities are common, including cardiovascular disease and renal impairment, which complicate management ^{[104]B2b[134]B2b}. Thymoma is less frequent, and thymectomy is not routinely recommended ^[134]B2b.

Treatment modifications: Immunosuppressants carry higher risk of infection and side effects. Efgartigimod 10 mg/kg weekly for 4 weeks has shown efficacy and safety in patients ≥80 years, with rapid improvement in acute exacerbations (MG-ADL reduction 69.8% ± 16.9% at week 4) ^[104]B2b. IVIG carries a risk of thromboembolic complications, especially in elderly patients with vascular risk factors ^[140]C4. Takotsubo cardiomyopathy has been reported in association with myasthenic crisis in elderly patients ^{[138]C4[139]C4}; close cardiac monitoring is advised.

Immunocompromised

Patients with MG on immunosuppressive therapy are at increased risk for opportunistic infections. Nocardiosis is a rare but serious infection, with risk factors including elderly men, thymoma, and steroid use ^[142]C4. Pulmonary nocardiosis can precipitate myasthenic crisis; treatment with co-trimoxazole is effective ^[142]C4. In patients with immune checkpoint inhibitor-induced MG, eculizumab has been used successfully ^[20]C4. Efgartigimod may also be considered ^[132]C4. Vaccination against encapsulated organisms (e.g., Neisseria meningitidis) is recommended before complement inhibitor therapy ^[20]C4.

Pearl: In elderly patients with myasthenic crisis, consider Takotsubo cardiomyopathy if hemodynamic instability occurs; and in immunocompromised hosts, nocardiosis should be in the differential for new pulmonary infiltrates.

Building on the considerations for pregnant patients, the same principles of proactive management apply to all individuals with MG to prevent crisis. Prevention centers on modifying risk factors, optimizing baseline therapy, and early detection of deterioration.

Primary Prevention

Avoiding precipitating events is the cornerstone. Respiratory infections are the most common identifiable trigger, occurring in 30-40% of crises ^[143]D5. Annual influenza vaccination and COVID-19 vaccination are recommended, influenza vaccine does not increase crisis risk (relative incidence 0.84, 95% CI 0.65-1.09) ^[148]C4. COVID-19 vaccination may rarely trigger new-onset MG or exacerbation, but the benefit of preventing infection outweighs this risk, especially in well-compensated patients ^[149]C4.

Optimizing maintenance immunosuppression reduces crisis likelihood. The presence of a steroid-sparing immunosuppressant (SSIS) at crisis onset predicts shorter ICU stay (HR for time to discharge 2.23, 95% CI 1.13-4.42) and shorter ventilation duration (HR for extubation 2.73, 95% CI 1.37-5.43) ^[144]B2b. When prednisone is used, doses ≥60 mg/day during ICU stay increase sepsis risk (OR 13.07, 95% CI 2.17-86.73); thus, the lowest effective dose should be targeted ^[144]B2b.

Other modifiable factors: avoid drugs that exacerbate MG (e.g., certain antibiotics , beta-blockers, magnesium), promptly treat infections, and manage emotional stress, which can trigger takotsubo syndrome in some patients ^[49]C4.

Secondary Prevention

After a myasthenic crisis, the goal is to prevent recurrence. Initiate or continue a maintenance SSIS (e.g., azathioprine , mycophenolate , tacrolimus ) and taper prednisone to <60 mg/day as feasible ^[144]B2b. Serial monitoring of MG functional status and respiratory function (e.g., forced vital capacity, single breath count) is essential. The telephonic single breath count test (SBCT) with a cutoff of ≤25 has a positive predictive value of 71% for detecting exacerbation and can triage patients for early intervention ^[147]C4.

Screening & Surveillance

Screen for MG in patients with unexplained pharyngeal dysphagia: initial AChR antibody testing; if negative, test for MuSK and LRP4 antibodies ^[47]C4. Routine instrumental swallowing evaluations (VFSS or FEES) are recommended because silent aspiration occurs in 75% of silent aspirators and leads to aspiration pneumonia ^[8]D5.

In known MG patients, surveillance for thymoma and associated autoimmune conditions is warranted. Titin antibodies should be checked in all MG patients, as their presence in AChR-positive patients predicts more severe disease, including crisis ^[146]C4. Also screen for Hashimoto's thyroiditis (present in 21% of MG patients) ^[146]C4.

Myocardial injury surveillance: troponin T elevation is an independent predictor of death (OR 8.818, p<0.001) and is associated with infection and crisis ^[145]B2b. Consider checking troponin levels in hospitalized MG patients with clinical suspicion.

Patient Education

Most crises do not occur suddenly, there is a window for prevention ^[143]D5. Patients should be taught to recognize early warning signs: worsening dysphagia, shortness of breath, declining single breath count, and increased fatigue. They should have an action plan including when to contact their neurologist, when to use rescue medications, and when to go to the emergency department. Emphasize infection prevention (hand hygiene, vaccinations) and avoidance of stress and exacerbating drugs.

Pearl: A single breath count ≤25 on telephone screening should prompt immediate ED referral, early recognition during the prodromal window can avert intubation and improve outcomes ^[147]C4.