SYMPTOMS OF TRANSIENT EPILEPTIC AMNESIA SERIES

4, 6, 8 ALF is the excessively rapid loss of memory, over extended intervals, of information that appears to have been acquired and stored normally over standard testing intervals of around half an hour. The syndrome is of particular neuropsychological interest as the amnestic seizures are frequently accompanied by a distinctive group of persistent interictal memory complaints: accelerated long-term forgetting (ALF), autobiographical amnesia (AbA) and topographical amnesia (TopA). 4 Since then, further reports have defined an epilepsy syndrome characterized by recurrent brief attacks of transient amnesia, often occurring on waking, with onset typically in middle age. The suggestion was supported by case reports over the following century, preceding the definition of TEA. Hughlings-Jackson 3 was probably the first author to raise the possibility that transient amnesia could be the sole or most prominent manifestation of an epileptic seizure, in his description of his physician–patient, Dr Z. 1, 2 Their superficial resemblance to the attacks occurring in ‘transient global amnesia’ (TGA) warranted a related but contrasting term. The term ‘transient epileptic amnesia’ (TEA) was coined in 1990 to highlight the existence of a distinctive form of epilepsy causing transient amnesic attacks. Its aetiology, the monthly occurrence of seizures in some patients and the mechanisms and interrelationships of the interictal features-amnestic and affective-all warrant further study. It is an important, treatable cause of memory loss in older people, often mistaken for dementia, cerebrovascular disease and functional amnesia. We conclude that transient epileptic amnesia is a distinctive syndrome of late-onset limbic epilepsy of unknown cause, typically occurring in late middle age. Review of the literature cases revealed broadly consistent features except that topographical amnesia, olfactory hallucinations and emotionality have been reported rarely to date by other researchers. Neuropsychological testing and comparison to two age and IQ-matched control groups ( n = 24 and 22) revealed consistent findings across the two cohorts, namely elevated mean IQ, preserved executive function, mild impairment at the group level on standard measures of memory, with additional evidence for accelerated long-term forgetting and autobiographical amnesia, particularly affecting episodic recollection.

SYMPTOMS OF TRANSIENT EPILEPTIC AMNESIA SERIES

Some clinical features were detected more commonly in the second series than the first, probably as a result of heightened awareness. Seizures ceased with anticonvulsant treatment in 93% of cases. Epileptiform changes were present in 35% of cases, while suspected causative magnetic resonance imaging abnormalities were detected in only 5%. The majority of patients describe at least one of the atypical forms of memory disturbance mentioned above easily provoked tearfulness is a common accompanying feature. Amnesia is the only manifestation of epilepsy in 24% of patients olfactory hallucinations occur in 43%, motor automatisms in 41%, brief unresponsiveness in 39%. Findings in our two cohorts are substantially consistent: The onset of transient epileptic amnesia occurs at an average age of 62 years, giving rise to amnestic episodes at a frequency of around 1/month, typically lasting 15–30 min and often occurring on waking. We describe the clinical and neuropsychological features in 65 consecutive cases of transient epileptic amnesia referred to our study, comparing these to our previous cohort of 50 patients and to those reported in 102 literature cases described since our 2008 review. However, this highly treatment-responsive condition remains under-recognized and undertreated. Subsequent descriptions have highlighted its association with ‘atypical’ forms of memory disturbance including accelerated long-term forgetting, disproportionate autobiographical amnesia and topographical amnesia.

The term transient epileptic amnesia was coined in 1990 to describe a form of epilepsy causing predominantly amnestic seizures which could be confused with episodes of Transient Global Amnesia.

Symptoms of transient epileptic amnesia