Phrenic Neuropathy Etiologies and Recovery Trajectories in Outpatient Rehabilitation and Neuromuscular Medicine Clinics: A Retrospective Analysis

Introduction/Aims: Phrenic Neuropathy (PhN) impairs diaphragm muscle function, causing a spectrum of breathing disability. PhN etiologies and their natural history are ill defined. This knowledge gap hinders informed prognosis and management decisions. This study aims to help fill this knowledge gap on PhN etiologies, outcomes, and recovery patterns, especially in the context of non-surgical clinical practice. Methods: This is a retrospective study from two interdisciplinary clinics, physiatry and neurology based. Patients were included if PhN was identified, and other causes of hemi-diaphragm muscle dysfunction excluded. Patients were followed serially per the discretion of the neuromuscular trained neurologist or physiatrist. Recovery was assessed using pulmonary function tests (PFTs), diaphragm muscle US thickening ratio, and patient-reported outcomes in patients presenting within two years of PhN onset. Results: We identified 151 patients with PhN. The most common etiologies included idiopathic (27%), associated with cardiothoracic procedure (24%), and intensive care unit (17%). Of these patients, 117 (77%) were evaluated within two years of PhN onset. Of patients included in outcome analyses, 69% saw improvement on serial US, 50% on serial PFTs and 79% reported symptomatic improvement at an average of 13, 16, and 17 months respectively. Conclusion: This study maps PhN etiologies and recovery. A clear majority of PhN patients show improvement in diaphragm muscle function, but on average improvements took 13-17 months depending on the assessment type. These insights are vital for developing tailored treatments and can guide physicians in prognosis and decision-making, especially if more invasive interventions are being considered.