According to a study in PLOS Computational Biology, different characteristics of brain tissue that surround the origin site of seizure’s may determine which of two major patterns of brain activity are seen before an epileptic seizure begin.
At the start of an epileptic seizure, the brain’s electrical activity follows either a “high amplitude slow” pattern or a “low amplitude fast” pattern. After surgical treatment, patients who have seizures that come after the high amplitude slow pattern are more likely to experience continuing seizures. However, the mechanisms that underlie these differing onset patterns are not clear.
To understand the onset of the patterns, a team of researchers from Newcastle University, U.K. used a previously made computer model that simulated brain activity at the onset of a seizure. The output of the model suggested that the initial seizure may be determined by characteristics of the neighbouring “healthy” brain tissue and not by brain tissue at the spot where the seizure originates.
The simulation suggested that the high amplitude slow pattern happens when the surrounding tissue of the brain is characterized by higher excitability; meaning that the brain cell strongly responds to stimulation and reacts immediately to seizure initiation. In the meantime, the low amplitude fast pattern occurs when surrounding brain tissue has lower excitability. Consequently, seizure activity penetrates them slowly.
The study shows why different treatment outcomes are associated with the different onset patterns. Surgically removing seizure-stimulating brain tissue may be enough to stop seizure activity in neighbouring low-excitability tissue. High-excitability tissue, however, may still be triggered by alternative trigger spots after surgery.