[Diaphragmatic Paralysis in Parsonage-Turner syndrome: beyond brachial neuralgia]

Objective: To describe a case of bilateral diaphragmatic paralysis secondary to Parsonage–Turner syndrome, emphasizing its uncommon clinical presentation, the multidisciplinary diagnostic approach, and the therapeutic strategies implemented. Case report: A 63-year-old male, former smoker with hypertension and type 2 diabetes, presented with sudden and intense pain in both upper limbs followed by proximal paresis. Within 24 hours, he developed hypercapnic respiratory failure requiring invasive mechanical ventilation. Chest computed tomography revealed elevation of both hemidiaphragms, and diaphragmatic ultrasound confirmed bilateral dysfunction. Neurophysiological studies demonstrated a sensory–motor neuropathy without associated structural abnormalities. After excluding other causes, a diagnosis of bilateral diaphragmatic paralysis secondary to Parsonage–Turner syndrome was established. Non-invasive positive pressure ventilation was initiated, leading to clinical improvement and no hospital readmissions. At one-year follow-up, the patient remains clinically stable with good tolerance to nocturnal ventilatory support. Conclusion: This case highlights the importance of considering Parsonage–Turner syndrome in the differential diagnosis of diaphragmatic dysfunction, particularly in patients with recent viral infections and neuromuscular symptoms. The combined use of functional assessments such as maximal transdiaphragmatic pressure (PdiMax) measurement and diaphragmatic ultrasound enables objective characterization of diaphragmatic function and represents a high-value diagnostic approach to guide ventilatory management and respiratory rehabilitation.