A 34-year-old man was admitted to our hospital's department of neurology because he had experienced a cryptogenic stroke followed by a transient ischaemic attack. The patient suffered from congenital hydrocephalus which was treated by ventriculoatrial shunt at 8 months of age. Twelve months later, because of recurrent infections, the catheter was partially removed and the distal segment was left in place. At admission, the transoesophageal echocardiogram showed severe pulmonary hypertension (80 mm Hg confirmed by invasive measurement). The distal tip of the catheter had migrated into the left atrium through a patent foramen ovale inducing a massive right-to-left shunt. We surgically removed the catheter and closed the interatrial defect. At 1 and 6 months follow-up the patient was asymptomatic with a reduced pulmonary hypertension (50 mm Hg). Since there was no other clinical finding responsible for the recurrent thromboembolic events, both at the pulmonary and cerebral level, the catheter was removed to prevent further complications.