Utility and reliability of placebo infusion in the evaluation of patients with seizures

Placebo infusions are occasionally used to elicit psychogenic seizures. How frequently placebo infusions elicit patients’ typical events, atypical and potentially confusing events, or even epileptic seizures is not known. We report the results of placebo infusions during video EEG in 68 patients who also had events recorded without placebo. A single investigator administered a saline placebo that was represented to the patient as an activating substance. We compared the events recorded without placebo with events recorded with placebo. Twenty patients had only epileptic seizures without placebo; with placebo, two of 20 (10%) had their typical epileptic seizures and three of 20 (15%) had atypical nonepileptic events. Forty patients had only psychogenic seizures without placebo; with placebo, 33 of 40 (82%) had their typical psychogenic seizures and three of 40 (8%) had atypical events. Eight patients had both psychogenic and epileptic seizures without placebo; with placebo, four of eight had their typical psychogenic seizures. Thus, placebo infusion elicits typical psychogenic events in most patients with psychogenic seizures, but atypical events or epileptic seizures may occur in a minority and lead to incorrect diagnosis.