Alzheimer's disease is a neurodegenerative condition, characterised in part by the presence of amyloid plaques (amyloid is a general term for protein fragments that the body produces normally) between the neurons of the brain. These plaques are largely formed from fragments of a protein called Beta amyloid. Beta amyloid is 'snipped' from a larger molecule called amyloid precursor protein (APP), with the help of a protein called presenilin. In a healthy brain Beta amyloid particles are broken down and eliminated. However, in Alzheimer's disease, they accumulate.

Approximately one third of people with Alzheimer's disease also experience seizures; and studies have shown that in some forms of the condition, sufferers can be up to 80 times more likely to have seizures than those without it. The reason for this increased seizure susceptibility has never been established, but an international team of researchers has now found some clues.

In a recent study they bred animal models to carry mutant copies of both a human amyloid precursor protein and presenilin gene. These subjects would develop Beta amyloid plaques. When Alzheimer's disease became apparent in these models, the scientists carried out two sets of video-EEG (electroencephalogram) recordings on both them and a group of 'normal' counterparts, to assess the prevalence of unprovoked seizures.

During the two recording sessions, 65% of the Alzheimer's disease group experienced at least one seizure. Of these, 46% had multiple seizures and 38% had a generalised seizure. Seizures were not seen in any of the 'normal' models.

These findings suggest that Beta amyloid protein plays a significant role in the development of epilepsy in Alzheimer's disease. With more research into the precise mechanisms involved, treatments to prevent epilepsy in Alzheimer's disease could be developed.

Interestingly, many Alzheimer's disease treatments lower people's seizure threshold, whilst some epilepsy medications cause cognitive problems. Usually this manifests itself as a lack of concentration / alertness, but at least one anticonvulsant has been seen to reduce fluency of speech. The discovery of a link between Alzheimer's disease and epilepsy might pave the way for drugs that treat both conditions to be developed.

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