events that mimic an epileptic seizure
but do not involve abnormal, rhythmic discharges of cortical neurons
. They are caused by either physiological
conditions. The latter is discussed more fully in psychogenic non-epileptic seizures
Reflex anoxic seizures
are a condition of the brain where the child may become pale and limp and cease breathing, only to recover a short time later. Anoxic seizures are caused by a reflex asystole of the heart due to increased vagal responsiveness. They are non-epileptic.
A wide spectrum of phenomena may resemble epileptic seizures, which may lead to people who do not have epilepsy
being misdiagnosed. Indeed, a significant percentage of people initially diagnosed with epilepsy will later have this revised. In one study, the majority of children referred to a secondary clinic with "fits, faints and funny turns" did not have epilepsy, with syncope (fainting) as the most common alternative. In another study, 39% of children referred to a tertiary epilepsy centre did not have epilepsy, with staring episodes in mentally retarded
children as the most common alternative. In adults, the figures are similar, with one study reporting a 26% rate of misdiagnosis.
The International League Against Epilepsy (ILAE) define an epileptic seizure
as "a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain." Epileptic seizures can occur in someone who does not have epilepsy – as a consequence of head injury
, drugs, toxins, eclampsia
or febrile convulsions
, for example.
Medically, when used on its own, the term seizure implies an epileptic seizure. The lay use of this word can also include sudden attacks of illness, loss of control, spasm or stroke. Where the physician is uncertain as to the diagnosis, the medical term paroxysmal event and the lay terms spells, funny turns or attacks may be used.
The various pathophysiological causes include: