Can bulbar palsy be caused by rheumatological issues?

Can Bulbar Palsy Be Caused by Rheumatological Issues?

Yes, bulbar palsy can be caused by rheumatological issues, most notably through immune-related myositis affecting bulbar muscles, which presents with dysphagia, dysarthria, and dysphonia. 1

Primary Rheumatological Mechanisms

Immune-Related Myositis

• Immune checkpoint inhibitor (ICI)-induced myositis is a recognized rheumatological cause of bulbar symptoms, occurring in approximately 1% of patients receiving cancer immunotherapy, with median onset at 4 weeks of treatment 1
• Clinical presentation includes myalgia with axial, limb-girdle, bulbar and oculomotor weakness 1
• The pathological mechanism involves rhabdomyolysis leading to elevated creatine kinase (CK), spontaneous activity on electromyography, and myogenic recruitment patterns 1
• Bulbar muscle involvement can be fatal due to both direct bulbar dysfunction and secondary myocardial inflammation 1

Diagnostic Approach for Rheumatological Bulbar Palsy

• Workup should include: CK, AST, ALT, LDH, myositis-associated antibodies, paraneoplastic antibodies, MRI, EMG, and biopsy on an individual basis 1
• Anti-acetylcholine receptor (AChR) antibodies should be tested if myasthenia gravis is suspected 1
• Over 80% of patients with immune-related myositis show fasciitis on MRI 1
• Rule out dermatomyositis if skin involvement is present 1

Management of Rheumatological Bulbar Palsy

Immediate Treatment for Life-Threatening Bulbar Symptoms

• In the presence of bulbar symptoms (dysphagia, dysarthria, dysphonia), dyspnoea, and/or myocarditis, high-dose corticosteroids (pulses then 1-2 mg/kg) and additional treatment options such as IVIG and/or plasma exchange are necessary 1
• Immunotherapy withdrawal is mandatory for grade 2 or higher symptoms 1
• Approximately 40% of patients with bulbar involvement require IVIG and/or plasma exchange in addition to corticosteroids 1

Stepwise Treatment Algorithm

• For grade 2 symptoms without bulbar involvement: initiate corticosteroids at 0.5-1 mg/kg/day prednisone 1
• For any bulbar symptoms: immediately escalate to high-dose corticosteroids (methylprednisolone 1-2 mg/kg) plus IVIG and/or plasma exchange 1
• For refractory cases, IL-6 receptor inhibitors may be considered, as well as TNF-α inhibitors if associated fasciitis is present 1

Multidisciplinary Coordination

• Early referral to a rheumatologist should be considered for grade 2 symptoms before starting corticosteroids, in cases of insufficient response, and when corticosteroid-sparing regimens are needed 1
• Oncologists should consult rheumatologists promptly when rheumatic musculoskeletal and systemic signs or symptoms are suspected 1

Differential Diagnosis Considerations

Other Autoimmune Causes

• Systemic lupus erythematosus (SLE) can cause velopharyngeal insufficiency through dysmotility of velopharyngeal structures, resulting in impaired soft palate elevation and retraction 2
• Sjögren syndrome (immune-related sicca syndrome) can present with dry mouth and, rarely, neurological manifestations, though bulbar palsy is uncommon 1
• Vasculitis, scleroderma-like reactions, and lupus have been reported with immunotherapy but remain rare causes of bulbar symptoms 1

Non-Rheumatological Mimics to Exclude

• Guillain-Barré syndrome (GBS) variants, including acute bulbar palsy plus syndrome, can present with bulbar weakness combined with cranial symptoms or ataxia 1, 3, 4
• Metastases, paraneoplastic syndromes, and unrelated rheumatic diseases should be considered as potential differential diagnoses 1
• Consecutive lacunar strokes affecting bilateral corticobulbar tracts can cause pseudobulbar palsy mimicking brainstem lesions 5

Critical Pitfalls and Caveats

Mortality Risk

• Immune-related myositis with bulbar involvement has approximately 20% mortality rate compared to less than 10% for idiopathic inflammatory myositis, primarily due to associated myocarditis 1
• Cardiac evaluation must be systematic for any patient with myositis or suspected myositis, as myocarditis is part of the myositis clinical spectrum 1

Timing and Recognition

• Median exposure to ICI therapy before myositis onset is only 4 weeks, requiring high clinical suspicion early in treatment 1
• CK levels are elevated in most patients with myositis (median 2650 IU/L), whereas CK is usually normal in patients with myalgia alone 1
• High-sensitivity troponin T can be elevated in skeletal muscle involvement without myocardial damage, whereas troponin I is specific to myocardium 1

Treatment Nuances

• Over 80% of patients with immune-related myositis experience favorable clinical outcomes within several months after ICI discontinuation and immunomodulatory treatment 1
• Improvement is often noted within days after ICI discontinuation in patients with moderate symptoms 1
• Corticosteroids should be progressively tapered when improvement is achieved 1