Development of syndrome of inappropriate antidiuretic hormone secretion (SIADH) after Onyx embolisation of a cavernous carotid fistula.

Patients with cavernous carotid fistulas (CCFs) can present with pituitary hypoperfusion and hypopituitarism; however, there are no previous reports of pituitary or hormonal abnormalities developing after CCF embolisation in an asymptomatic patient. We describe a patient with no hormonal abnormalities who developed syndrome of inappropriate antidiuretic hormone (SIADH) secretion after CCF embolisation. The patient had bilateral indirect CCFs, which were completely embolised via a transvenous approach, and was neurologically stable postoperatively and discharged. In the subsequent 2 weeks the patient was readmitted twice for acute hyponatraemia and a tonic-clonic seizure. Laboratory studies revealed severe SIADH. Clinical status and sodium levels improved after treatment. One year later the patient was weaned off all medications and remained neurologically stable. SIADH may be a delayed phenomenon after CCF embolisation. Given the proximity of embolised vessels to the pituitary's vascular supply, CCF treatment may result in flow disturbance, ischaemia and hormonal abnormalities.