Abstracts

Syncopes are well known as precipitants of non-epileptic anoxic seizures, especially in infancy. By contrast, anoxic-epileptic seizures (AES) are events in which a syncope triggers an anoxic seizure followed by a true epileptic seizure. AES have been described for two decades however reports are limited to small series totalling 14 individuals. We present the largest series to date of children with this disorder.
We reviewed all 25 cases of AES presenting to The Fraser of Allander Neurosciences Unit and EEG department in Glasgow between 1972-2003 and one additional case from Fife. Clinical history, ictal EEG recordings of syncopal events (n=15) and anoxic epileptic seizures (n=3) and home videotape recordings of anoxic-epileptic seizures (n=2) were reviewed.
We identified 16 females and 10 males with a median age of 1.4 years, (range 0.5 - 10y), at presentation. In most cases the syncopal component was described as [quot]breath holding[quot], being a neurally mediated syncope with either reflex asystole, prolonged expiratory apnoea or an uncertain mechanism. In a minority of children compulsive valsalva manouvres were the trigger. All children had syncope resulting in anoxic seizures in isolation from any epileptic phenomena. 2 / 26 in addition to AES had spontaneous epileptic seizures. All interictal EEGs were normal. The anoxic seizures were brief all less than 60 seconds. The resultant epileptic seizures were predominantly [quot]clonic[quot] but in some cases including the videoed cases (available for presentation) had features of myoclonic absence. Absence, vibratory tonic and focal seizures with loss of awareness were unusual as the epileptic component. Duration of epileptic seizures was 2-40 minutes with seizures of longer than 10 minutes occuring in 9 / 26. Diazepam was used as rescue medication in 6 cases. Anti-epileptic medication used in 5 / 26 prevented development of the epileptic component but not the syncope. The syncopes and epileptic component typically remitted in pre-school years and are not associated with learning disability.
Anoxic-epileptic seizures are combination events in which syncopes trigger a spectrum of epileptic seizures in susceptible individuals. The epileptic seizure is most likely to be clonic and may have features akin to a myoclonic absence. Anoxic-epileptic seizures are uncommon but recognition is important as the common tendency to progress to a prolonged epileptic seizure can be prevented with anti-epileptic medication.