Brain Health Glossary

Dementia is an umbrella term for conditions caused by damaged brain cells that progressively impair a person’s ability to think, reason and remember. The impairment is extensive enough to

interfere with daily life. ACETYLCHOLINE The neurotransmitter that supports normal brain and nerve function and behaviors including memory and learning. Imbalances in the level of

acetylcholine play a role in some neurological disorders, including Alzheimer’s and Parkinson’s.  ADUHELM (ADUCANUMAB) A medication that received approval on an accelerated basis by the U.S.

Food and Drug Administration in 2021 to slow cognitive decline in patients with early-stage Alzheimer’s. One of the first medications intended to treat a cause, not just the symptoms, by

clearing amyloid plaques from the brain. It has seen limited use after questions were raised about its safety and effectiveness. See also Leqembi (lecanemab).  ALZHEIMER’S DISEASE The most

common form of dementia, Alzheimer’s is progressive — it gets worse over time — and affects memory, thinking and the ability to carry out daily tasks. It is characterized by the abnormal

buildup of amyloid plaques and tau tangles in the brain, which are considered the hallmarks of Alzheimer’s. AMYLOID PLAQUES The result of large accumulations of a naturally occurring

protein, beta-amyloid, that form clusters. See also entry for tau. Alzheimer’s is believed to be caused by a buildup of plaques and tau tangles in the brain, which damage and destroy brain

cells, disrupting normal communication among cells. APHASIA A disorder resulting from damage to parts of the brain involved in language. Stroke or neurological diseases such as Alzheimer’s

or frontotemporal dementia are among possible causes. There are several types of aphasia, depending on what part of the brain is affected. For example, people with damage in the temporal

lobe — behind the ears — might speak in long but meaningless sentences and cannot understand the meaning of what others say. Those with damage to the frontal lobe — behind the forehead — may

be able to understand others but cannot say more than a few words at a time. DELIRIUM Not a form of dementia, but sometimes mistaken for that condition, delirium is one of several treatable

conditions with symptoms that resemble those of dementia, so they can be misdiagnosed. Delirium comes on quickly, while dementia usually occurs over the course of years.  DEMENTIA An

overall term used to refer to a number of conditions caused by damaged brain cells. The main types of dementia are Alzheimer’s, frontotemporal, Lewy body and vascular. “Mixed dementia”

describes having more than one of these disorders. These conditions impair a person’s ability to think, reason and remember, enough to interfere with daily life. EARLY-ONSET DEMENTIA A form

of dementia diagnosed in a person younger than 65. Like other forms of dementia, it can lead to loss of memory and personality changes.  FRONTOTEMPORAL DEMENTIA Frontotemporal dementia

(FTD), results from damaged neurons in the area of the brain behind the forehead (the frontal lobes) or behind the ears (the temporal lobes). This form of dementia, also called

frontotemporal disorders, gets worse over time and often occurs at younger ages than other dementias. FTD falls into three categories. Behavioral variant FTD, the most common form, involves

changes in personality, judgment and ability to plan. Primary progressive aphasia affects a person’s ability to use language and communicate. The rarest form, movement disturbances includes

muscle weakness or stiffness or problems with balance or walking. LEQEMBI (LECANEMAB) A medication approved by the Food and Drug Administration in July 2023 to slow cognitive decline in

patients with early-stage Alzheimer’s. One of the first medications to treat the cause, not just the symptoms, by clearing amyloid plaques from the brain. See also Aduhelm (aducanumab). 

LEWY BODY DEMENTIA An umbrella term for a group of disorders associated with the presence of abnormal protein deposits called Lewy bodies in the brain. Symptoms get worse over time and

include problems with thinking — including visual hallucinations — movement, sleep disorders and mood. Named after Friedrich Lewy, the neurologist who discovered them. Parkinson’s disease is

included in this broad category of dementia. MILD COGNITIVE IMPAIRMENT Lapses in memory or the inability to find words, problems that are noticeable to friends and seem worse in degree than

seen in other people of the same age. The symptoms of MCI are not as severe as dementia. Not everyone who has MCI will develop dementia. MIXED DEMENTIA A condition that gets worse over time

as more than one form of dementia occurs simultaneously. The most common form of mixed dementia involves both the abnormal protein buildup associated with Alzheimer’s disease and blood

vessel problems of vascular dementia.   POSTERIOR CORTICAL ATROPHY A rare form of Alzheimer’s disease that gets gradually worse and affects the part of the brain responsible for spatial

perception, complex visual processing, spelling and calculation. Those with PCA might have trouble reading a sentence, judging distances and using common tools. TAU A naturally occurring

protein that is thought to be part of the cause of Alzheimer’s disease when it becomes tangled inside nerve cells in the brain. See also entry for amyloid plaques. Alzheimer’s is believed to

be caused by a buildup of plaques and tangles in the brain that damage and destroy brain cells, disrupting normal communication among cells. VASCULAR DEMENTIA Occurs because of damage to or

blockage of blood vessels in the brain. Symptoms, which get worse over time, include changes to memory, thinking and behavior. For more on Alzheimer's and other dementias, click here.