A 68-year-old man developed progressive four-limb weakness and areflexia 17 days after an influenza vaccination. He was diagnosed with Guillain-Barre syndrome (GBS), and remained ventilator dependent and bed-bound for 3 months, despite plasmapheresis and immunoglobulin infusion. However, cognitive impairment, excessive daytime sleepiness, and motor disability were still present, even when he was no longer ventilator dependent. Brain computerized tomography scan and isotope cisternography was consistent with normal pressure hydrocephalus. His motor control and cognitive function recovered almost completely after insertion of a ventriculoperitoneal shunt. Although hydrocephalus is not frequently associated with GBS, our case report indicates that brain imaging is necessary in GBS patients whose cognitive functions deteriorates after disease onset.