Parsonage-turner syndrome: a pulmonologist's guide to the forgotten diaphragm

PURPOSE OF REVIEW: Parsonage-Turner syndrome (PTS), or neuralgic amyotrophy, is framed as a shoulder disorder owned by neurology, and that framing has cost pulmonologists patients. Roughly 1 in 13 develops phrenic neuropathy, and many patients referred for unexplained dyspnea, orthopnea, or rapid eye movement (REM)-predominant sleep-disordered breathing have an undiagnosed, treatable inflammatory neuropathy. This review reframes PTS for pulmonologists. RECENT FINDINGS: Three developments have reshaped practice. High-resolution neuromuscular ultrasound and MR neurography now identify the hourglass constrictions and fascicular entwinement of PTS at the bedside, including in the phrenic nerve. COVID-19 infection and SARS-CoV-2 vaccination produced a global cluster, expanding the phenotype toward bilateral and respiratory-predominant disease. Large Dutch cohort data have replaced anecdote with structure: roughly 60% of patients with phrenic involvement recover meaningfully within 2 years, while the remainder respond best to early noninvasive ventilation and, in refractory cases, diaphragmatic plication. SUMMARY: Every pulmonologist evaluating unexplained dyspnea, disproportionate orthopnea, or REM-predominant hypopneas should ask one question: was there severe shoulder or neck pain in the weeks before the breathing changed? If yes, screen with upright and supine spirometry and diaphragm ultrasound. The diagnosis is reachable in a single visit, the immunomodulation window is short, and the cost of missing it is years of avoidable disability.