Posterior reversible encephalopathy syndrome during intravenous immunoglobulin therapy in Guillain-Barré syndrome

A 63-year-old woman was diagnosed with Guillain-Barré syndrome (GBS), and intravenous immunoglobulin (IVIg) therapy was initiated. On the second day of IVIg therapy, she became less alert (JCS III-200) and had hyponatremia. Brain MRI showed vasogenic edema in bilateral occipital lobes, which disappeared afterwards. Her clinical course and MRI findings were consistent with those of posterior reversible encephalopathy syndrome (PRES). As a result of considering the timing of the onset of GBS and PRES and the degree of hyponatremia and hypertension in some documented patients, the cause of PRES onset in this case is considered to be IVIg therapy itself and IVIg therapy-induced hyponatremia.