Transient loss of consciousness: the value of the history for distinguishing seizure from syncope.

We studied 94 consecutive patients (age 15 or over) to investigate which aspects of the history and clinical findings help to distinguish seizures from syncope and related conditions. Clonic movements or automatism observed by an eyewitness classified an event as a seizure. The seizure group consisted of 41 patients and the syncope group of 53 patients. The likelihood ratio was used to calculate the predictive power of single findings and logistic regression to analyse combinations of findings. The best discriminatory finding was orientation immediately after the event according to the eyewitness and the age of the patient in the absence of an eyewitness report (P less than 0.001). We found a seizure five times more likely than syncope if the patient was disoriented after the event and three times more likely if the patient was less than 45 years of age. Nausea or sweating before the event were useful to exclude a seizure. Incontinence and trauma were not discriminative findings.