"Neurally mediated syncope" is the most common cause of syncope in all age groups, and includes various overlapping entities, such as neurocardiogenic syncope, vasovagal syncope, and vasodepressor syncope. These are distinctly different from orthostatic hypotension and seizures.
A careful history is the most important “test” to diagnose neurally mediated syncope. It is frequently preceded by a characteristic prodrome with symptoms such as nausea, dizziness, feelings of warmth or coldness, visual dimming or blurring, clammy skin, facial pallor, general weakness, decreased hearing, or fecal urgency. Symptoms last 30 seconds to several minutes prior to syncope.
Differentiating syncope from seizures:
Brief, multifocal,arrhythmic, myoclonic jerks are observed in up to 90% of patients at the time of syncope. These are caused by brainstem hypoperfusion and may be mistaken for seizures. The jerks follow the LOC (rather than immediate) and the eyes deviate upward (rather than lateral). If tongue biting occurs, it’s the tip (rather than the side, which is what occurs with seizures).