Though the diagnosis of seizures and epilepsy can be straightforward, it can also be one of the greatest clinical challenges. An adequate diagnosis requires differentiation between seizures and other causes of transient neurological disturbance and collapse; differentiation between acute symptomatic and unprovoked truly epileptic seizures; and, in people with epilepsy, classification of the disorder and identification of the cause so as to optimise treatment.
The symptoms of epileptic seizures are varied and there are many imitators, ranging from convulsive syncope through to psychogenic events. The phenomenon most commonly mistaken for a convulsive seizure is syncope. Classical teaching is that collapse in syncope is flaccid and that no motor activity occurs.3 Commonly occurring motor and ocular phenomena are not widely recognised. Lempert et al induced syncope in 42 healthy volunteers, 90% of whom experienced myoclonus, usually multifocal.4 Additional features such as head turning, oral movements, or attempts to sit up occurred in 80%. These motor phenomena are often taken to indicate that a seizure has occurred. Similar convulsive episodes seen immediately after concussive head injury may also be mistaken for epileptic phenomena.5
Neurogenic syncope is provoked and involves brief loss of consciousness and rapid recovery. A detailed history will usually be all that is required by an experienced clinician to differentiate this from seizures. Unfortunately, in inexpert hands inappropriate investigation often takes precedence. Fainting is probably the single commonest reason for requesting an electroencephalogram, which in 20% of the population will reveal non specific abnormalities open to misinterpretation.6 Given that most requests emanate from non-specialist settings and most electroencephalograms are reported by neurophysiologists without great experience of epilepsy and its management, there is considerable potential for misdiagnosing faints as seizures.
