senile plaque

n. Senile plaques, also known as amyloid or neuritic plaques, are concentrations of amyloid protein and dead nerve cells in the brain. This buildup interrupts the communication between neurons and healthy brain cells, disrupting the brain's proper functioning.

Senile plaques develop naturally with increasing age, but persons with Alzheimer's disease develop significantly more senile plaques. These plaques often collect in areas of the brain responsible for memory and learning, partially explaining the memory loss evident among persons with Alzheimer's disease. Because of the correlation between age and increasing numbers of plaques, it is possible to develop a threshold of Alzheimer's disease likelihood. The presence of even a few plaques in a middle-aged adult may strongly suggest the presence of Alzheimer's disease. Conversely, many more plaques must exist in the brain of an elderly person to justify the diagnosis of Alzheimer's disease. – TJM