What is the best course of action for a 60-year-old male with progressive muscle wasting, global weakness, pain, and insensitivity to touch, taking quetiapine (quetiapine)?

Immediate Hospitalization with ICU-Level Monitoring Required

This patient requires immediate hospital admission with ICU-level monitoring for suspected acute neuromuscular disorder, most likely Guillain-Barré syndrome, myasthenia gravis, or drug-induced myopathy. The combination of progressive weakness, sensory loss, inability to ambulate, and 60-pound weight loss over 4 months represents a medical emergency requiring urgent diagnostic workup and potential respiratory support 1, 2.

Critical Initial Actions

Assess for Life-Threatening Complications

• Measure respiratory function immediately: Obtain negative inspiratory force (NIF) and vital capacity (VC) at bedside, as respiratory failure can develop rapidly in neuromuscular disorders 3, 2
• Evaluate for bulbar symptoms: Check for dysphagia, dysarthria, and facial weakness, which indicate impending respiratory compromise 3, 2
• Monitor autonomic instability: Blood pressure fluctuations and heart rate abnormalities suggest Guillain-Barré syndrome 1
• Ensure ICU capability: Patient needs location where emergent intubation and mechanical ventilation are immediately available 4

Immediate Diagnostic Testing

• Creatine kinase (CK) and aldolase: Elevated levels suggest myositis or rhabdomyolysis, which can be life-threatening 2
• Troponin and ECG: Myocardial involvement can occur with inflammatory myopathies and is potentially fatal 2
• Complete metabolic panel: Assess for electrolyte abnormalities and renal function 2
• Inflammatory markers (ESR, CRP): Elevated in inflammatory myopathies 1

Differential Diagnosis and Workup

Most Likely: Guillain-Barré Syndrome

Clinical features strongly suggest GBS: Progressive ascending weakness, global sensory loss requiring significant pressure to elicit sensation, and preserved pulses 1, 4.

Required diagnostic studies 4, 1:

• Lumbar puncture: Elevated protein with normal white blood cell count is characteristic
• MRI of spine with contrast: Rule out compressive lesions and evaluate for nerve root enhancement
• Nerve conduction studies/EMG: Demonstrates acute polyneuropathy
• Antiganglioside antibody testing: For GBS variants

Immediate treatment if GBS confirmed 4:

• IVIG 0.4 g/kg/day for 5 days (total 2 g/kg) OR plasmapheresis for 5 days
• Methylprednisolone 1-2 mg/kg/day IV (though steroids not typically recommended for idiopathic GBS, a trial is reasonable for immune-related forms)
• Daily neurological assessments and pulmonary function monitoring

Alternative: Myasthenia Gravis

Consider if fluctuating weakness or ocular symptoms present 1, 3.

Diagnostic testing 1, 3:

• Acetylcholine receptor (AChR) and anti-MuSK antibodies
• Electrodiagnostic studies with repetitive nerve stimulation
• Bedside Tensilon test or ice pack test with neurology input

Treatment if MG confirmed 3:

• Pyridostigmine starting at 30 mg orally three times daily, gradually increase to maximum 120 mg four times daily
• Prednisone 1-1.5 mg/kg daily for moderate-severe symptoms
• IVIG 2 g/kg over 5 days or plasmapheresis for severe cases
• Avoid medications that worsen MG: β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, macrolides 4, 3

Alternative: Drug-Induced Myopathy from Quetiapine

Quetiapine has been associated with muscle weakness in case reports 5. The 48-year-old patient on quetiapine 400mg twice daily who presented with progressive myalgia and muscle weakness represents a similar clinical scenario 5.

If myopathy suspected 2:

• Check CK, aldolase, and inflammatory markers
• EMG/nerve conduction studies to evaluate for myositis
• Consider discontinuing quetiapine temporarily while evaluating
• MRI of affected muscles if inflammatory myositis suspected

Critical Medication Review

Quetiapine Considerations

• Do not abruptly discontinue: Risk of withdrawal symptoms and psychosis recurrence
• Quetiapine can cause muscle weakness as documented in case reports 5
• Quetiapine does NOT worsen myasthenia gravis: It is not listed among contraindicated medications (β-blockers, fluoroquinolones, aminoglycosides, macrolides) 4, 3
• Consider dose reduction if myopathy confirmed and psychiatric stability allows

Urgent Neurology Consultation

Neurologist involvement is mandatory for all grades of suspected neuromuscular weakness given potential for rapid deterioration 4, 2. Do not delay specialist referral, particularly with this severity of presentation 2.

Common Pitfalls to Avoid

• Do not overlook myocardial involvement: Failure to check troponin and ECG can miss life-threatening cardiac complications 2
• Do not delay respiratory monitoring: Neuromuscular disease patients can deteriorate very suddenly 3
• Do not use non-invasive ventilation if bulbar dysfunction present: This makes NIV failure more likely and may be impossible 3
• Do not wait for complete diagnostic workup before initiating treatment: If respiratory compromise develops, intubation should not be delayed 3

Weight Loss Investigation

The 60-pound weight loss over 4 months requires parallel investigation for malignancy, as weakness may represent a paraneoplastic syndrome 1. However, this workup should not delay treatment of the acute neuromuscular emergency.