First let’s define a key word:
Hippocampus: The brain structure responsible for memory development. The hippocampus is a key part of the brain affected by Alzheimer’s disease, and also a common source of seizures in people with epilepsy.
New research from Massachusetts General Hospital suggests a potential new connection between the devastating memory loss associated with Alzheimer’s disease (AD) and “silent” seizures in the memory center of the brain.
The small study enrolled two female patients in their 60s with early AD and no known history of seizures. Because electrodes placed on the scalp are often unable to detect seizure activity deep in the brain, researchers surgically implanted electrodes on both sides of the brain through the foramen ovale (FO), a narrow opening at the base of the skull, in addition to scalp EEG. Each patient’s brain activity was monitored for 24 to 72 hours.
The FO electrodes recorded evidence of seizures in the hippocampuses of both patients, while the scalp EEG readings did not detect any abnormal electrical activity. Most notably, these seizures primarily occurred when patients were asleep, a critical time for memory consolidation.
“While it is not surprising to find dysfunction in brain networks in Alzheimer’s disease, our novel finding that networks involved in memory function can become silently epileptic could lead to opportunities to target that dysfunction with new or existing drugs to reduce symptoms or potentially alter the course of the disease,” says Andrew Cole, MD, Director of the Mass General Epilepsy Service and senior author of the Nature Medicine paper.
One patient received anti-seizure medicine as a treatment following the scan, which seemed to cut down on AD-linked symptoms such as confusion and repeating the same question. The other patient started on the medication but it had to be discontinued due to adverse effects on her mood.
A recent study led by Alice Lam, MD, PhD, also of the MGH Epilepsy Service and lead author of the current study, demonstrated a novel tool for detecting hippocampal seizures not detectible by scalp EEGs in patients with epilepsy. Cole and his team are working to refine this tool and apply it to AD.
Due to the small size of the study, further research is also needed to validate the results with a broader population.