According to study results published in Neurology, a comprehensive profile of witness-observable manifestations of transient loss of consciousness (TLOC) can play an important role in differentiating between the 3 most common causes of TLOC: epilepsy, syncope, and psychogenic nonepileptic seizures (PNES).

In a retrospective study conducted in patients from 3 UK medical centers, investigators sought to examine to what extent the 31-item Paroxysmal Event Observer (PEO) Questionnaire can improve the diagnostic differentiation that is attainable with the use of information provided by patients. A total of 300 individuals , 100 of whom were assigned to  each group (epilepsy, syncope, and PNES) completed an 86-item Paroxysmal Event Profile (PEP). The PEP captured TLOC-related symptoms and provided data for the analysis. All PEP respondents, who were age >16, also provided clinical and demographic personal information (ie, age, gender, medical history).

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Of the 300 patients with TLOC who returned PEPs, 249 also completed PEO questionnaires (86 with epilepsy, 84 with syncope, and 79 with PNES). Witnesses in the syncope group reported observing significantly fewer event manifestations overall compared with witnesses in the epilepsy or PNES groups (P <.0001 for both PNES vs syncope and epilepsy vs syncope).

Syncope was also associated with a significantly smaller range of manifestations, as demonstrated by the greater percentage of never replies in the syncope group (59.4%) compared with the epilepsy (32.5%) and PNES (31.2%) groups (P <.0001 for both epilepsy vs syncope or PNES vs syncope). PEO profiles in patients with epilepsy or PNES implied similar levels of heterogeneity of witness-observable event manifestations in these groups.

The use of observer-reported factors alone was able to distinguish better between syncope and epilepsy than the use of patient-reported factors (accuracy: 96% vs 85%, respectively; P =.0004). Moreover, observer-reported data improved accuracy over differentiation according to patient-reported data alone: from 90% to 100% between syncope and epilepsy (P =.005); 76% to 83% between epilepsy and PNES (P =.006) and 93% to 95% between syncope and PNES (P =.098).

The investigators concluded that the results of this study demonstrate that information from observers can make an important contribution to the differentiation between epilepsy and PNES or syncope, but is less valuable for distinguishing between syncope and PNES. Thus, the use of data beyond that obtained from TLOC manifestations are particularly important for distinguishing epilepsy from syncope.


Chen M, Jamnadas-Khoda J, Broadhurst M, et al. Value of witness observations in the differential diagnosis of transient loss of consciousness. Neurology. 2019;92(9):e895-e904