Bilateral Isolated Phrenic Neuropathy: a Rare Cause of Dyspnoea

Bilateral diaphragm paralysis due to bilateral isolated phrenic neuropathy (BIPN) is a very rare cause of unexplained respiratory failure. We present a 65-year-old patient with no relevant previous medical history who presented in the Pulmonology Clinic with mMRC1 dyspnoea and orthopnoea. After the medical work-up, diaphragmatic paresis was diagnosed. Inspiratory muscle training resulted in mild symptomatic improvement and treatment with noninvasive mechanical ventilation (NIV) was initiated. This condition is generally chronic and has a poorer prognosis, compared to other cases of phrenic nerve involvement. In this case, NIV restored near-normal daily function. LEARNING POINTS: Besides being a rare cause of dyspnoea, diaphragmatic dysfunction should be considered in the medical evaluation. Noninvasive mechanical ventilation is the mainstay of treatment for symptomatic patients. Neurologic and electrodiagnostic evaluation is essential, since the differential diagnosis of phrenic nerve dysfunction may imply different treatment strategies.