Understanding terms in medicine and diagnosis

A subject-grouped glossary for appointments, trial listings, and treatment pages - dementia types, FDA phases, tests, and the pathways medicines act on.

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Diagnosis and staging

Words clinicians use when evaluating memory and thinking changes.

Source: NIA · How Alzheimer’s disease is diagnosed

Dementia: A syndrome - a group of symptoms - involving decline in memory, thinking, language, or daily function severe enough to interfere with everyday life. Dementia is not one disease and not a normal part of aging.
Mild cognitive impairment (MCI): Noticeable cognitive changes that are more than typical aging but not severe enough to substantially disrupt daily independence. MCI may or may not progress to dementia.
Syndrome vs disease: A syndrome names the pattern of symptoms (dementia). A disease names a specific cause when known (for example Alzheimer’s disease or Lewy body dementia).
Differential diagnosis: The process of sorting among possible causes of symptoms - including medicines, depression, sleep apnea, thyroid problems, vitamin deficiency, stroke, and neurodegenerative diseases.
Cognitive testing: Structured tasks that check memory, attention, language, and problem-solving. Results support clinical judgment; they are not a full IQ score and are interpreted with education, language, and hearing/vision in mind.
Early / Middle / Late stage (Mild / Moderate / Severe): Practical care stages based on how much help someone needs. Timing varies widely. Early often means more independence; middle often means more daily support; late often means around-the-clock care and comfort-focused goals.
Activities of daily living (ADLs): Basic self-care tasks such as bathing, dressing, eating, and toileting. Loss of ADLs is a key marker of dementia severity.
Instrumental activities of daily living (IADLs): More complex tasks such as managing money, medications, cooking, and transportation. These often decline earlier than basic ADLs.

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Types of dementia and related conditions

Common causes and related conditions described in this atlas. Primary type descriptions follow the Dementia Society of America overview.

Source: Dementia Society of America · Dementia Help

Alzheimer's disease (AD): A progressive condition that typically begins slowly, destroying short-term memory and other mental functions over time. The most common cause of dementia. Care note: FDA-approved disease-modifying treatments (lecanemab, donanemab) target amyloid in early stages. Cholinesterase inhibitors address symptoms.
Vascular dementia: Cognitive decline resulting from reduced blood flow to the brain, often from multiple small strokes (multi-infarct dementia). Symptoms depend on which brain areas are affected. Care note: No FDA-approved cognitive treatment. Management focuses on stroke prevention, blood pressure, diabetes control, and related vascular care.
Lewy body dementia (LBD): A progressive condition that may include visual hallucinations, decline in reasoning and mobility (tremors, falls), and fluctuating alertness. Caused by microscopic protein deposits in the brain. Care note: Care is tailored to cognition, movement, sleep, and hallucinations. Antipsychotics can trigger severe reactions in LBD.
Frontotemporal degeneration (FTD): A group of disorders caused by nerve-cell loss in the frontal and temporal lobes, which shrink over time. Affects executive function, decision-making, behavior, and language. Care note: No FDA-approved cognitive treatment. Management addresses specific symptoms, behavior, and speech/language support.
Traumatic brain injury (TBI): Cognitive disruption from a violent blow or jolt to the head, including concussions. Effects depend on injury severity and location. Care note: Treatment focuses on rehabilitation, managing symptoms, and preventing further injury.
Wernicke-Korsakoff syndrome (WKS): A neurological disorder caused by severe thiamin (vitamin B1) deficiency, often associated with chronic alcohol misuse. Affects memory, coordination, and vision. Care note: Treatment involves thiamin replacement and addressing underlying causes. Some damage may be permanent.
Creutzfeldt-Jakob disease (CJD): A rare, rapidly degenerative brain disorder caused by abnormal prion proteins. Symptoms progress quickly and include memory problems, behavior changes, and movement difficulties. Care note: No treatment can slow or stop CJD. Care focuses on comfort and managing symptoms.
Huntington's disease: A rare inherited condition causing progressive breakdown of nerve cells in the brain. Affects movement, cognition, and psychiatric function. Care note: No cure exists. Treatment addresses movement symptoms, psychiatric symptoms, and supportive care.
Multiple sclerosis (MS) - cognitive involvement: MS is an immune-mediated condition affecting nerve coverings. Some people with MS experience cognitive changes including memory, attention, and processing speed difficulties. Care note: MS disease-modifying therapies may help. Cognitive rehabilitation and compensatory strategies are also used.
AIDS dementia complex: Cognitive and motor decline that can occur in late-stage AIDS, caused by HIV affecting the brain. Effective HIV treatment has made this less common. Care note: Antiretroviral therapy is the primary treatment. Early HIV treatment helps prevent this complication.
Chronic traumatic encephalopathy (CTE): A neurodegenerative condition associated with repeated head impacts, often seen in contact sports. Currently can only be definitively diagnosed after death. Care note: No specific treatment exists. Prevention through reducing head impacts is key. Symptom management is individualized.
Mild cognitive impairment (MCI): Cognitive changes noticeable to the person and others but not severe enough to interfere significantly with daily life. MCI may or may not progress to dementia. Care note: Some anti-amyloid treatments are approved for MCI due to Alzheimer's with confirmed amyloid. Monitoring and lifestyle factors matter.
Mixed dementia: When more than one type of dementia occurs together, most commonly Alzheimer's disease with vascular dementia or Lewy body dementia. Care note: Treatment addresses each contributing condition. Diagnosis can be complex.
Parkinson's disease dementia (PDD): Cognitive decline that develops in some people with Parkinson's disease, typically years after motor symptoms begin. Related to but distinct from Lewy body dementia. Care note: Rivastigmine has FDA indication for PDD. Care coordinates cognitive and motor symptom management.

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FDA status and clinical trial phases

How experimental treatments move from lab ideas toward possible approval - and what labels on this site mean.

Source: FDA · The drug development process

Clinical trial: A research study in people that tests whether an intervention is safe and whether it helps a defined outcome. Participation is voluntary and has eligibility rules, risks, and monitoring.
Phase 1: First studies in people, usually small. Focus is safety, dosing, and how the body handles the drug - not proving it treats dementia.
Phase 2: Larger studies that explore whether the treatment shows a signal of benefit and continue to check safety. Results guide whether Phase 3 is worth running.
Phase 3: Large trials meant to confirm benefit and better characterize risks, often against placebo or standard care. Successful Phase 3 programs are typically required for FDA approval.
Phase 4 / post-marketing: Studies after approval that watch longer-term safety, rare side effects, or how a medicine is used in broader practice.
Observational study: Researchers follow people without assigning a study drug. Useful for patterns and risk factors, but weaker for proving that a treatment caused an outcome.
Placebo-controlled / randomized: Participants are assigned by chance to the study treatment or a comparison (often placebo). Randomization reduces bias when comparing groups.
Primary endpoint: The main outcome the trial is designed to measure (for example a cognition or function score). Secondary endpoints are additional outcomes that help interpret the result.
FDA-approved: The FDA has authorized marketing for a specific use described in the product label. Approval for one disease or stage does not automatically apply to another.
Accelerated approval: An FDA pathway that can approve a drug based on an earlier marker of benefit while confirmatory trials continue. Those confirmations can succeed or lead to withdrawal.
Traditional / full approval: Approval based on clinical outcomes that show meaningful benefit, not only a biomarker change.
Off-label use: A clinician may prescribe an approved drug for a use not listed on the FDA label when they judge it appropriate. That is different from saying the FDA approved that use.
Investigational: Not FDA-approved for the dementia use being discussed. Access is usually limited to clinical trials or special programs.
Withdrawn / discontinued: A product was removed from the market or an indication was withdrawn. It may still appear in historical discussions but is not a current U.S. treatment option.

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Tests and biomarkers

Tools used to support diagnosis or to select people for certain treatments and trials.

Source: NIA · How Alzheimer’s disease is diagnosed

Biomarker: A measurable biological signal (in blood, spinal fluid, or imaging) that relates to a disease process. Biomarkers can support diagnosis or trial eligibility; they are not the whole clinical picture.
Amyloid: A protein that can form plaques in the brain in Alzheimer’s disease. Anti-amyloid antibodies aim to clear or reduce amyloid plaques.
Tau: A protein that can form tangles inside neurons in Alzheimer’s disease. Some trials and imaging methods track tau burden.
MRI (magnetic resonance imaging): A brain scan used to look for stroke, tumors, atrophy patterns, or treatment-related swelling/bleeding. Required monitoring for some anti-amyloid drugs.
CT (computed tomography): A faster X-ray-based brain scan sometimes used to rule out other causes of symptoms when MRI is not available or appropriate.
PET (positron emission tomography): A nuclear medicine scan that can show amyloid or tau patterns, or how the brain uses glucose. Often used in specialist evaluation or trials.
CSF (cerebrospinal fluid) tests: Fluid sampled by lumbar puncture (spinal tap) that can measure Alzheimer’s-related proteins. Used in specialist settings.
Blood-based biomarker tests: Emerging blood tests that estimate Alzheimer’s-related biology. Availability and how results are used are still evolving; ask what a specific test can and cannot tell you.
ARIA (amyloid-related imaging abnormalities): Brain swelling (ARIA-E) or small bleeds (ARIA-H) seen on MRI with some anti-amyloid antibody treatments. Can be symptom-free or serious; monitoring is part of labeled care.

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Pathways and treatment classes

How common dementia medicines and research approaches are thought to work - in plain language.

Source: Alzheimer’s Association · Medications for memory

Cholinesterase inhibitor: Medicines such as donepezil, rivastigmine, and galantamine that slow the breakdown of acetylcholine, a chemical involved in memory and attention. They treat symptoms; they do not stop the underlying disease.
Acetylcholine: A neurotransmitter important for learning and memory. Levels can fall in Alzheimer’s disease, which is why cholinesterase inhibitors are used.
NMDA receptor antagonist (memantine): Memantine moderates glutamate signaling through NMDA receptors. Used for moderate-to-severe Alzheimer’s symptoms; often combined with a cholinesterase inhibitor.
Glutamate: An excitatory brain chemical. Excess activity can be harmful to neurons; memantine is intended to dampen harmful overstimulation without shutting signaling off entirely.
Anti-amyloid monoclonal antibody: Lab-made antibodies (for example lecanemab or donanemab) designed to bind amyloid and help clear plaques. Used in early Alzheimer’s with confirmed amyloid; require MRI monitoring for ARIA.
Monoclonal antibody: A biologic drug engineered to recognize a specific target. In dementia care, several target amyloid; others are investigational.
Disease-modifying vs symptomatic: Disease-modifying approaches aim to change the underlying biology (for example clearing amyloid). Symptomatic treatments aim to ease thinking, behavior, or function without necessarily changing long-term disease course.
Fixed-dose combination: Two (or more) medicines in one pill or capsule at set doses - for example Namzaric (memantine + donepezil) or Auvelity (dextromethorphan + bupropion).
Antipsychotic: Medicines sometimes used short-term for severe agitation or psychosis when safety is at risk. They carry important warnings in dementia, especially related to stroke and death risk in older adults with dementia-related psychosis.
Muscarinic agonist / antagonist (for example KarXT): Drugs that tune acetylcholine receptors of the muscarinic type. Cobenfy (xanomeline + trospium) is approved for schizophrenia; Alzheimer’s psychosis and agitation uses remain investigational.
GLP-1 agonist (for example semaglutide): A class used for diabetes and weight management. Large Alzheimer’s trials (such as EVOKE) are testing whether these medicines affect cognition; that use is not an FDA dementia indication.
Brainshuttle / enhanced brain delivery: Engineering approaches meant to help antibodies cross into the brain more efficiently. Trontinemab is an example in late-stage Alzheimer’s research.

Subject

Reading study claims

Terms that help sort a news headline from decision-ready evidence.

Source: NIA · Clinical trials and older adults

Efficacy vs effectiveness: Efficacy is benefit under ideal trial conditions. Effectiveness is how well something works in everyday care, with broader patients and real-world adherence.
Statistically significant: A result is unlikely to be due to chance alone under the study’s statistical rules. It does not automatically mean the change is large enough to matter in daily life.
Clinically meaningful: A change big enough that patients, families, or clinicians would notice or value it - a higher bar than statistical significance alone.
Surrogate endpoint: A stand-in measure (such as plaque reduction on a scan) used instead of direct clinical outcomes. Surrogates can be useful but may not guarantee better thinking or function.
Open-label extension: After a blinded trial, participants may receive the active treatment knowingly. Useful for longer safety follow-up; weaker for proving benefit because there is no blinded comparison.
Conflict of interest / funding: Who paid for the study and whether authors have financial ties. Conflicts do not invalidate results, but they are worth noting when weighing a claim.

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Approved options, combinations, investigational programs, and lifestyle evidence.

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Clinical trials section

Recruiting and landmark trials with locations from ClinicalTrials.gov.