AEDs & Memory Recall
Epilepsy and its treatment have been shown to impair cognitive and behavioural functions. The impact on the former by epilepsy associated seizures, brain damage, and use of anti-seizure medications can result in memory deficits, attention problems, and reading and writing difficulties.
Of the 125,000 new cases of epilepsy which develop each year in the USA, up to 50% are in children and adolescents, at a time when learning capabilities are developing. Developmental disabilities may result from complex interactions of genetic, toxicological, pharmacological and social factors.
Among these various causes, pharmacological exposure to drugs deserves special scrutiny because it is readily preventable. This research demonstrates the consequences of anti-seizure medication (AED) therapy that may contribute to transient cognitive disabilities (impairments of attention, memory, learning and/or social behaviour).
Previous studies show that AEDs may themselves cause changes in mental functions. They may be often mixed with neurocognitive behaviour, depending on the drug used. Also, there may be temporary cognitive deterioration. The researchers in a new study assert that clinical experience must be used to identify the subgroup of children who remain at risk for significant and clinically relevant cognitive and behavioural adverse effects of AEDs.
In testing the effects of AEDs on the cognitive functions of the child with epilepsy, they relied on 3 established postulates:
- Connections between neurons increase in efficacy in proportion to the degree of correlation between pre- and post-synaptic activity.
- Groups of neurons, which tend to fire together, form a cell-assembly whose activity can persist after the triggering event and serves to represent it.
- Thinking is the sequential activation of sets of cell-assemblies. Consequently, learning can be defined as the process by which an organism benefits from experience, so that its future behaviour differs from that of a comparable organism lacking this experience.
In children with epilepsy, that experience may be the use of AEDs. Accordingly, a research effort from Brazil has focussed on problems in recalling information, believing there are a subset of difficulties in learning and memory deficits probably resulting from AED in infancy. Ingrid Dragan Taricano (PhD) and Rosemary D Silva Amorim from the Faculdade de Biomedicina, Universidade de Santo Amaro (São Paulo, Brazil) presented their study
Possible Interferences of Chronic Anticonvulsant Therapy on Memory Performance at the American Physiological Society's (APS) annual meeting, part of the
Experimental Biology 2002 conference, in New Orleans in April.
In the small study, 4 (8-year old) children were distributed in 2 groups, each of 1 boy and 1 girl. The first group was "healthy" children who were not using any medications. The second group was 2 children currently using AEDs (phenobarbital and valproic acid). The children participated in repeated tests using 48 blocks in different geometric shapes, different colours, different sizes and different thicknesses, and a card illustrating 8 images of these different pieces arranged in 2 parallel rows which was shown to the children at 30 minute intervals. The children were distracted with other activities between the showings. During a 5th session, the children were asked to use the blocks to reproduce the pattern shown on the card, which was not shown. This last step was repeated 24 hours later.
Phenobarbital and valproic acid may be used alone or with other anti-seizure medication to control seizures. They may cause some degrees of sedation, so learning may be affected once that concentration is disturbed. In people with epilepsy, cognitive functions can be affected by several factors, individually or in combination. Alteration of cognition might reflect a chronic adverse effect, but the negative effects of these drugs are only one of several factors that may influence cognition.
In general, the cognitive effects of most antiepileptic drugs are modest and offset by their benefit in controlling seizures. Nonetheless, the cognitive effects may be clinically significant when treating specific patient populations, such as children and seniors. Results from this small research sample show a deterioration of the recall of information in chronically treated children.
The findings suggest that proper cognitive development of adolescents with epilepsy demands a co-operative effort between prescribing physicians and educators. Such partnerships help to diminish cognitive impairment among young people with this disorder.
Source
The American Physiological Society
http://www.the-aps.org
