Diagnostic criteria to aid the differential diagnosis of patients presenting with transient loss of consciousness: A systematic review
Introduction from Dr Markus Reuber, editor-in-chief of Seizure
Transient loss of consciousness (TLOC), the unprovoked disruption of consciousness with spontaneous recovery, is one of the commonest neurological reasons why patients attend emergency departments (1). Over 90% of presentations are due to epileptic seizures (ES), syncope, or psychogenic non-epileptic seizures (PNES) (2).The accurate and rapid distinction between these different causes of TLOC is key to patients accessing appropriate diagnostic and treatment pathways. Unfortunately, most initial assessments are carried out by generalists such as doctors working in emergency departments or primary care, and initial post-event investigations have low sensitivity and limited specificity. Not surprisingly, misdiagnosis rates for the causes of TLOC of 20-30% have been reported (2).
In my editor’s choice article from the current volume of Seizure, Alistair Wardrope et al. explore whether simple decision rules – for instance based on demographic, clinical or semiological features – could predict the most likely cause of TLOC and enable non-experts to investigate and treat patients with this presentation more effectively (3). Following a systematic literature search, 16 publications met the inclusion and exclusion criteria for this review. Only two of these studies compared all three common causes of TLOC, the others aimed to differentiate between epilepsy and PNES. Although all of these studies reported that combinations of different criteria can support the differential diagnosis to some extent, no individual criterion differentiated between the diagnoses with high sensitivity and specificity. What is more, none of the diagnostic questionnaires investigated have been validated prospectively against gold-standard diagnostic criteria.
While more and more clinical decision-making processes are driven by evidence-based scores or flow charts, the highly important diagnostic distinction between the common causes of TLOC will still need to be made on the basis of informal judgements of clinicians who will come to a more or less well-educated view about which facts to weigh more or less heavily as they consider discharging their patient, referring them to a neurologist or cardiologist. It is astonishing how little we know about some of the most basic questions in clinical epileptology.
(1) Dickson JM, Taylor LH, Shewan J, Baldwin T, Grunewald RA, Reuber M. Cross-sectional study of the prehospital management of adult patients with a suspected seizure (EPIC1). BMJ Open 2016;6:e010573.
(2) Malmgren K, Reuber M, Appleton, R. Differential diagnosis of epilepsy. In: Shorvon S, ed. Oxford Textbook of epilepsy and epileptic seizures. Oxford: Oxford University Press; 2012:81-94.
(3) Wardrope A, Newberry E, Reuber M. Diagnostic criteria to aid the differential diagnosis of patients presenting with transient loss of consciousness: a systematic review. Seizure 2018