Phrenic Nerve Palsy Secondary to Parsonage–Turner Syndrome: A Diagnosis Commonly Overlooked

Neuralgic Amyotrophy (NA) or Parsonage–Turner syndrome is an idiopathic neuropathy commonly affecting the brachial plexus. Associated phrenic nerve involvement, though recognised, is thought to be very rare. We present a case series of four patients (all male, mean age 53) presenting with dyspnoea preceded by severe self-limiting upper limb and shoulder pain, with an elevated hemi-diaphragm on clinical examination and chest X-ray. Neurological examination of the upper limb at the time of presentation was normal. Diaphragmatic fluoroscopy confirmed unilateral diaphragmatic paralysis. Pulmonary function testing demonstrated characteristic reduction in forced vital capacity between supine and sitting position (mean 50%, range 42–65% predicted, mean change 23%, range 22–46%), reduced maximal inspiratory pressures (mean 61%, range 43–86% predicted), reduced sniff nasal inspiratory pressure (mean 88.25, range 66–109 cm H₂O) and preserved maximal expiratory pressure (mean 107%, range 83–130% predicted). Phrenic nerve conduction studies confirmed phrenic nerve palsy. All patients were managed conservatively. Follow-up ranged from 6 months to 3 years. Symptoms and lung function variables normalised in three patients and improved significantly in the fourth. The classic history of severe ipsilateral shoulder and upper limb neuromuscular pain should be elicited and thus NA considered in the differential for a unilateral diaphragmatic paralysis, even in the absence of neurological signs. Parsonage–Turner syndrome is likely to represent a significantly under-diagnosed aetiology of phrenic nerve palsy. Conservative management as opposed to surgical intervention is advocated as most patients demonstrate gradual resolution over time in this case series.