Predictivity of plasma prolactin levels in differentiating epilepsy from pseudoseizures: a prospective study

The predictivity of raised plasma prolactin (PRL) concentrations in differentiating seizure from syncopal attack was prospectively assessed in all patients consecutively admitted to the Clinica Neurologica of Brescia, Italy in a 12-month period who fulfilled the criteria for either a seizure or syncopal attack. Postictal plasma prolactin concentration (P1) was assessed as soon as possible after the event. Three further assessments were performed: P2 was sampled 1 h after P1, P3, and P4 were sampled in the morning for the next 2 days. Patients who had had a seizure showed significantly increased P1 concentrations, when P1 was sampled within 60 min of the attack. In seizure patients assessed > 1 h after the event, P1 was not significantly different from either P2, P3, or P4. In patients who had had a syncopal attack, PRL concentration never increased. In patients assessed < or = 60 min after the seizure, cutoff criterion of P1 exceeding by +3 SD the mean calculated on P2, P3, and P4 yielded a positive predictive value of 89% and a negative predictive value of 61%. These findings confirm that plasma prolactin concentration is highly predictive of true epilepsy but barely predictive of pseudoseizures.