HOUSTON — “Silent seizures” deep within the brain may hold a clue as to what causes memory loss in patients with Alzheimer’s disease, and may help one day lead to new treatments for the 5 million Americans who suffer from this debilitating disease.
Researchers at Baylor College of Medicine had observed abnormal, episodic electrical activity in the brains of mice in a previous study, but noticed the rodents did not show any observable convulsions. Scientists speculated that these so-called “silent seizures” may produce memory problems in the mice and wondered if this type of activity could lead to similar issues in people with Alzheimer’s.
“My colleagues and I have been interested for years in determining whether ‘silent seizures’ are present in the hippocampus of patients with Alzheimer’s disease,” explains Dr. Jeffrey Noebels, a professor at the university and one of the senior study authors, in a media release.
The team tested two patients with Alzheimer’s who did not have a history of epilepsy or obvious seizures. Neither of them had any of the genes associated with either epilepsy or Alzheimer’s.
Fine wires passing through a natural opening in the skull allowed researchers to study the electrical activity deep in the brain over the course of several days. At the same time, normal EEG readings were taken on the scalp.
Both patients tested had definite silent seizures deep in their brains, but the EEG recordings taken on their scalps were normal. This showed that EEG tests do not capture the deep-brain activity occurring in Alzheimer’s patients.
When there is a history of Alzheimer’s in families, it is not unusual to see convulsive seizures. For most patients who develop the disease, however, there is no family history and no observable seizures. EEG testing is not helpful for the majority of Alzheimer’s patients because it cannot detect the deep-brain activity.
Researchers were also particularly interested in a finding that showed silent seizures were still occurring when the patients were asleep.
“What was fascinating was that this activity was present at night when the patients were sleeping, a time thought to be critical for the consolidation of recent memories, a trait that is most impaired in early Alzheimer’s disease,” says Noebels.
Noebels and his colleagues believe the results show a probable link between silent seizures and the memory loss and regression that occurs with Alzheimer’s disease.
“We need to determine whether this finding is common in Alzheimer’s disease, present in other types of progressive degenerative neurocognitive diseases and when in the course of the disease it occurs,” says co-author Dr. Andrew Cole, director of Massachusetts General Hospital Epilepsy Service and professor of neurology at Harvard Medical School.
Adds Dr. Alicia Goldman, an associate professor at the university and another co-author of the study: “From a physician’s perspective, I think this work opened my eyes to the need to look deeper into our patients’ condition in order to improve the quality of their lives as well as that of their caregivers.”
Goldman and the other researchers say more research into these links could potentially have a major impact on how Alzheimer’s disease is treated in the future.
The study’s findings were published online in the journal Nature Medicine.