What is the recommended treatment approach for myopathy (muscle disease) following COVID-19 infection?

Post-COVID-19 Myopathy: Treatment Approach

For skeletal muscle myopathy following COVID-19 infection, initiate a structured rehabilitation program centered on gradual recumbent exercise (starting 5-10 minutes daily), combined with nutritional optimization and physical therapy, while screening for critical illness myopathy in patients with prior ICU admission. 1, 2

Distinguish Myopathy from Myocarditis

Before addressing skeletal muscle myopathy, exclude cardiac myocardial involvement, as this fundamentally changes management:

• Obtain ECG, cardiac troponin (cTn), and echocardiogram if patients report chest pain, palpitations, dyspnea, or had severe COVID-19 requiring hospitalization 1, 3
• If cardiac involvement is confirmed, mandate complete exercise abstinence for 3-6 months 1, 4
• The guidelines provided focus heavily on myocarditis because it carries mortality risk; skeletal myopathy does not but severely impacts quality of life 5, 2

Initial Assessment of Skeletal Muscle Myopathy

Perform comprehensive neuromuscular evaluation to characterize the type and severity of muscle involvement:

• Check creatine kinase (CK) levels as a biomarker of muscle damage 2
• Consider electromyography (EMG) and nerve conduction studies, particularly for patients with ICU stays, to diagnose critical illness myopathy 6
• Assess functional capacity with six-minute walk test and measure calf circumference for anthropometric tracking 2
• Screen for malnutrition, as it contributes significantly to muscle damage and poor prognosis 2

Rehabilitation Protocol

Begin structured, low-intensity exercise with gradual progression, adapting the approach used for post-acute sequelae of COVID-19 (PASC):

Exercise Prescription

• Start with recumbent or semi-recumbent exercise (rowing, swimming, cycling) for 5-10 minutes daily 1, 3
• Progress duration gradually as functional capacity improves, avoiding post-exertional malaise 1
• Transition to upright exercise only after orthostatic tolerance improves 1
• Critical caveat: This graduated approach differs from cardiac myocarditis, where exercise is completely prohibited for 3-6 months 1, 4

Respiratory Muscle Training

• Implement pressure threshold loading techniques if respiratory muscle weakness is present 1
• Use Test of Incremental Respiratory Endurance (TIRE) to assess respiratory muscle strength, endurance, and fatiguability 1
• Incorporate diaphragmatic breathing exercises as adjunct therapy 1

Physical Therapy

• Provide neuromuscular electrical stimulation for ICU-acquired weakness to restore muscle condition 2, 7
• Include strength training as tolerated, with careful monitoring for post-exertional symptoms 5
• Implement home-based rehabilitation programs for mild-to-moderate cases 7

Nutritional Management

Optimize nutritional status aggressively, as malnutrition directly contributes to muscle damage and disease severity:

• Provide adequate protein intake to support muscle recovery 2
• Consider nutraceutical therapy as part of comprehensive management 5
• Address gut microbiome dysregulation, which may contribute to persistent symptoms 5

Pharmacological Considerations

Avoid routine corticosteroids for skeletal myopathy, as their use is reserved for specific cardiac or inflammatory conditions:

• Corticosteroids are indicated only for COVID-19 myocarditis with hemodynamic compromise or multisystem inflammatory syndrome in adults (MIS-A) 1
• Do not use NSAIDs unless there is documented pericardial involvement, as they increase inflammation and mortality risk in myocarditis 3, 4
• Consider low-dose colchicine only if persistent chest pain has an inflammatory component 3

Addressing Underlying Mechanisms

Target the pathophysiological drivers of post-COVID myopathy:

• Manage persistent inflammatory response with monitoring of CRP, ferritin, D-dimer, and IL-6 every 3 months until normalization 3, 5
• Address neurological damage if polyneuropathy, Guillain-Barré syndrome, or dysautonomia is present 8
• Discontinue or adjust myotoxic medications (e.g., statins, dexamethasone) if they contributed to muscle injury 8, 2

Follow-Up and Monitoring

Establish systematic surveillance to track recovery and identify complications:

• Reassess functional capacity with six-minute walk test at regular intervals 2
• Monitor CK levels and repeat EMG if weakness persists or worsens 6
• Screen for development of chronic complications, as 21% of myocarditis patients develop dilated cardiomyopathy during long-term follow-up (though this applies to cardiac, not skeletal myopathy) 4
• Coordinate multidisciplinary care with neurology, physical medicine and rehabilitation, and nutrition specialists 3

Special Populations

For ICU survivors with critical illness myopathy, the approach requires more intensive intervention:

• Prioritize early mobilization and neuromuscular electrical stimulation 2, 6
• Plan for extended rehabilitation in dedicated facilities, as motor recovery may take months 6
• Recognize that critical illness myopathy shows low-amplitude compound muscle action potentials on nerve conduction studies and myopathic changes on EMG, more pronounced in lower limbs 6

Common Pitfalls to Avoid

• Do not confuse skeletal myopathy with myocarditis: The former allows graduated exercise; the latter requires complete abstinence 1, 4
• Do not use empiric corticosteroids for skeletal muscle pain without documented inflammatory myocarditis or severe infiltrates on biopsy 1
• Do not overlook malnutrition, as it is a key modifiable factor affecting both disease severity and muscle recovery 2
• Do not prescribe aggressive exercise initially, as post-exertional malaise is common in PASC and can worsen symptoms 1