Are “Silent Seizures” Secretly Causing Alzheimer’s?
Roughly ten years ago, scientists noticed seizure-like brain patterns in mice and speculated that these “silent seizures”—which cause no visible outward symptoms but look the same as a regular seizure in terms of brain patterns—could be contributing to memory issues. Now they’ve tested that theory on humans with some interesting results.
Massachusetts General Hospital researchers recently published an article in Nature Medicine about two female Alzheimer’s patients in their 60s that they’d identified as having had seizure-like activity in the hippocampus of the brain, despite having no history of seizures.
The two women, who have experienced confusion and memory loss, had electrodes placed next to their hippocampi through the foramen ovale, which are natural holes in the base of the skull. This allowed researchers to measure the strange hippocampal activity not detectable by the traditional methods of looking at the brain, such as an EEG.
The hippocampus is highly involved in the processing of memories and is known to be one of the areas of the brain highly affected by Alzheimer’s disease. On top of that, the seizures in that area of the brain tended to happen while the patients were sleeping, when they were even more likely to interfere with the processing and storage of memories. Researchers believe the location and timing of the seizures may contribute to the symptoms of confusion and forgetfulness in Alzheimer’s patients.
In one of the women studied, anti-seizure medication was administered after she experienced three silent seizures in less than a 12-hour period while sleeping. The medication appeared to work for her, after which she was only reported to have episodes of confusion after missing several doses in a row. The other patient was also given anti-seizure medication but had to discontinue use due to adverse side effects.
Researchers hope to develop less invasive ways to study these seizures in the hippocampus so that larger research projects can be undertaken with less risk to the patients. If more (and larger) studies prove that silent seizures are indeed causing Alzheimer’s disease, and perhaps other dementias as well, it will offer a new target for researchers to work on. If they can find a way to stop the seizures for most Alzheimer’s patients, they may be able to prevent or effectively treat innumerable cases of Alzheimer’s.
Andrew Cole, MD, director of the MGH Epilepsy Service and senior author of the Nature Medicine paper, says that “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.”
“This is a critical step toward a better understanding of network dysfunction in the disease” he continued, “and opens the window to novel therapeutic approaches for this common condition.”
Future studies will investigate how common these silent seizures are in Alzheimer’s patients and patients with other neurodegenerative disorders, as well as whether they have an impact on the course of the disease and how they respond to treatment.