Diagnosis and Management of Phrenic Paralysis Associated Hypoxemia.

Phrenic nerve paralysis caused by herpes zoster infection is an exceptionally rare condition associated with severe respiratory complications. An even rarer phenomenon is the development of hypoxemia due to a right-to-left shunt through a patent foramen ovale (PFO), triggered by mediastinal shift and redirection of venous flow caused by right diaphragmatic elevation. We report the case of a 74-year-old woman admitted to the intensive care unit with severe hypoxemia refractory to oxygen therapy, requiring mechanical ventilation, following a recent herpes zoster infection affecting the C4 dermatome. Imaging revealed right hemidiaphragm elevation due to phrenic nerve paralysis, leading to mediastinal shift and a right-to-left shunt through a PFO without an interatrial pressure gradient. Transesophageal echocardiography confirmed a massive shunt. Emergency percutaneous PFO closure was performed, resulting in immediate improvement in oxygenation. In this article, the authors provide a framework for navigating the diagnostic reasoning and management of this rare condition. In conclusion, this case emphasizes the importance of considering phrenic nerve paralysis and PFO-related shunting in the differential diagnosis of unexplained hypoxemia, particularly in patients with recent cervical herpes zoster infections. Early screening for diaphragmatic dysfunction and transesophageal echocardiography are essential diagnostic tools, and percutaneous PFO closure offers a safe and effective solution for severe shunt-related hypoxemia.