Revisiting the Cause of Focal Neurological Deficits and Profound Dyspnea at High Altitude-The Potential Role of Patent Foramen Ovale.

A 49-year-old man developed weakness due to acute infarction of the left precentral gyrus. Subsequent investigation revealed a large patent foramen ovale (PFO), and it was concluded that the cerebral infarction was likely caused by a paradoxical embolus in association with the PFO. In hindsight, the PFO may explain several previous transient focal neurological deficits, some of which had occurred at high altitude and had been attributed to migraine. Furthermore, the large PFO may explain several episodes of profound shortness of breath that had occurred while exercising at high altitude during his lifetime, typically above 5000 m. Arterial hypoxemia due to hypobaric hypoxia may be exacerbated in individuals with PFO and affect physical performance at high altitude.