A 64-year-old woman with schizophrenia, which was well managed by risperidone 4 mg/day, fludiazepam 0.75 mg/day, and flunitrazepam 2 mg/day in recent years, was brought to the emergency department because of an abrupt onset of an altered level of consciousness, irritability, and psychosis. Laboratory results showed hyponatremia (115 mmol/liter) and hypokalemia (2.6 mmol/liter). Otherwise, abdominal ultrasonography, brain CT, CSF analysis, and other examinations revealed no remarkable findings. The family reported that for the past few days, there had been a marked excess of water intake. With a diagnosis of polydipsia-induced hyponatremia, she was admitted for electrolyte replacement.
Upon admission, the treating physicians instantly discontinued all psychotropics. Because her condition did not improve even as her serum sodium and potassium concentrations were restored, psychiatric consultation was requested on Hospital Day 4. A diagnosis of delirium was made, and risperidone 4 mg/day was resumed. Her condition, however, gradually worsened. On Hospital Day 7, an EEG was obtained, which revealed generalized epileptiform discharges. The brain MRI showed negative findings. Consultation with a neurologist resulted in a diagnosis of NCSE; a regimen of levetiracetam 1,500 mg/day and intravenous valproic acid 1,200 mg/day was started, and risperidone was withheld. Four days after the initiation of antiepileptic agents, the patient's condition was notably improved. An EEG performed subsequently did not show any further epileptiform discharges.