# Alzheimer Disease

Evaluate cognitive impairment clinically, establish or exclude Alzheimer pathology with validated amyloid and tau biomarkers when results will alter management, treat symptoms selectively, and refer eligible early-stage patients for anti-amyloid treatment assessment with MRI-based ARIA surveillance.

**Clinical question:** How should physicians confirm Alzheimer disease pathology and select patients for symptomatic or anti-amyloid treatment?

Updated: 2026-08-21T02:00:39.939002+00:00

## What matters in practice
- Do not equate cognitive symptoms with Alzheimer disease: establish whether amyloid and tau pathology is present when etiologic confirmation will change diagnostic confidence or treatment eligibility. [1][8]
- Low CSF Aβ42 with elevated total tau or phosphorylated tau, particularly an elevated tau:Aβ42 ratio, supports Alzheimer disease pathology; amyloid PET provides an alternative amyloid assessment. [8][9]
- Plasma phosphorylated tau—especially p-tau217—has promising discriminatory performance for Alzheimer pathology, whereas neurofilament light is a nonspecific axonal-injury marker and should not establish an Alzheimer diagnosis alone. [5][9][17]
- Donepezil, rivastigmine, galantamine, and memantine are approved symptomatic therapies; their benefits are modest and do not target underlying pathology. [1]
- Lecanemab and donanemab are FDA-approved anti-amyloid antibodies for early Alzheimer disease, but amyloid-related imaging abnormalities require treatment-pathway MRI surveillance and informed risk discussion. [3][11][15]
- APOE ε4 status materially changes ARIA-E risk estimates reported for anti-amyloid antibodies and should inform counseling before treatment selection. [19]

## Separate a clinical cognitive syndrome from Alzheimer pathology

Use clinical phenotype to identify cognitive impairment, then pursue biologic confirmation only when it changes management.

Alzheimer disease is a progressive neurodegenerative disorder characterized by amyloid-beta plaques and neurofibrillary tau tangles; these brain changes may precede symptoms by 20 years or more. [1][2] In a patient with objective cognitive and functional decline, the first management decision is whether an Alzheimer etiology is sufficiently likely that confirmation would affect prognosis, medication selection, or eligibility for anti-amyloid treatment.

A biomarker result is most actionable in mild cognitive impairment or early dementia with an Alzheimer-like phenotype, atypical presentations with competing etiologies, or cognitive impairment after traumatic brain injury or contact-sport exposure where Alzheimer copathology would alter use of Alzheimer-directed therapy. [9][16] Do not use an isolated nonspecific neurodegeneration marker to label Alzheimer disease: plasma neurofilament light reflects axonal injury across several neurodegenerative disorders and has limited differential diagnostic specificity. [5]

Amyloid-negative testing should redirect the etiologic workup rather than trigger anti-amyloid treatment. In particular, chronic traumatic encephalopathy cannot currently be diagnosed with sufficient sensitivity or specificity by tau PET, and FDG-PET has no clear established clinical utility for CTE; amyloid PET or fluid biomarkers can instead identify coexisting Alzheimer pathology. [9]
- Pursue etiologic biomarkers when the result will change the diagnostic label, prognosis, counseling, or treatment pathway. [9][16]
- Treat a positive Alzheimer biomarker as evidence of pathology, then interpret it alongside the clinical syndrome and functional stage. [1][2]
- Avoid inferring CTE from flortaucipir PET; current tau ligands have not shown satisfactory sensitivity or specificity for CTE tau. [9]

*Biomarker interpretation for suspected Alzheimer disease. [5][8][9][17]*

| Test | Actionable interpretation | Next clinical action |
| --- | --- | --- |
| CSF Aβ42 with total tau and p-tau | Low CSF Aβ42 plus elevated total tau or p-tau supports Alzheimer pathology; tau:Aβ42 ratio is commonly used and may be a robust single biomarker combination. [8] | Use concordant amyloid and tau findings to support an Alzheimer etiology and determine whether the patient should enter an Alzheimer-specific treatment pathway. [8] |
| Amyloid PET | Demonstrates significant cerebral amyloid plaque burden and can support or exclude Alzheimer pathology when CSF testing is not feasible or desired. [9] | Use a positive result to support Alzheimer disease biology; pursue alternate causes of cognitive impairment when amyloid burden is not demonstrated. [9] |
| Plasma p-tau217 or p-tau181 | p-tau217 has particularly strong reported sensitivity and specificity for Alzheimer pathology; CSF p-tau217 outperforms p-tau181 for differential diagnosis of Alzheimer disease and amyloid-PET-positive disease. [9][17] | Use as a less invasive biologic assessment within a validated local pathway; confirm or adjudicate clinically consequential discordant results with established CSF or PET testing. [5][9][17] |
| Plasma neurofilament light | Reflects axonal degeneration and injury but is elevated in several neurodegenerative disorders. [5] | Do not use alone to diagnose Alzheimer disease; interpret as a nonspecific injury or severity marker. [5] |
| FDG-PET or tau PET in suspected CTE | FDG-PET findings are nonspecific, and available tau PET ligands do not adequately identify CTE tau. [9] | Do not use either modality to confirm CTE; assess for Alzheimer copathology with amyloid or fluid biomarkers when clinically relevant. [9] |

## Select anti-amyloid therapy only within an early Alzheimer pathway

Anti-amyloid antibodies require biologically supported Alzheimer disease and explicit risk-benefit counseling.

Lecanemab and donanemab are FDA-approved anti-amyloid immunotherapies for Alzheimer disease. [15] Their use belongs in an early-disease, biomarker-guided pathway rather than empiric treatment of nonspecific cognitive decline, because amyloid-directed therapy addresses amyloid pathology and carries clinically important ARIA risk. [1][11]

For donanemab, FDA-reported trial outcomes showed less decline than placebo at week 76 on the Integrated Alzheimer’s Disease Rating Scale (difference 2.92), ADAS-Cog13 (difference -1.33), instrumental activities of daily living (difference 1.70), and CDR-Sum of Boxes (difference -0.70). [3] Across anti-beta-amyloid trials, reported slowing on composite measures has ranged approximately 25% to 40%, depending on the measure used. [24] Present these outcomes as slowing of decline rather than recovery or cure.

Before treatment selection, discuss ARIA and establish an MRI monitoring plan. Lecanemab and donanemab have reported ARIA in about 21% of treated patients in a treatment-pathway review; when ARIA is detected, MRI every 30 days until resolution was proposed. [11] APOE ε4 genotype identifies substantially different ARIA-E risks: reported rates for lecanemab were 5.4% in noncarriers, 10.9% in heterozygotes, and 32.6% in homozygotes; corresponding reported donanemab rates were 15.7%, 22.8%, and 40.6%. [19]
- Confirm Alzheimer amyloid pathology before considering an amyloid-directed antibody. [1][9][15]
- Counsel that treatment slows measured clinical decline; it has not been shown to stop or reverse disease progression. [3][4][24]
- Use APOE ε4-informed counseling because ARIA-E risk is higher in carriers, especially homozygotes. [19]
- If ARIA is identified, obtain serial MRI about every 30 days until it resolves. [11]

### Treatment claims to avoid

Do not characterize approved Alzheimer medicines, anti-amyloid antibodies, or supplements as curative. FDA states that no treatment has been shown to stop or reverse Alzheimer disease progression, and products marketed as unapproved Alzheimer cures create avoidable harm and confusion. [4]

*Anti-amyloid treatment counseling priorities. [3][11][19][24]*

| Decision domain | Evidence relevant to counseling | Practical implication |
| --- | --- | --- |
| Expected benefit | Donanemab reduced clinical decline versus placebo on iADRS and CDR-SB at week 76; anti-beta-amyloid trials have reported 25% to 40% slowing on composite scores. [3][24] | Frame expected benefit as a modest slowing of decline, not cognitive restoration. [3][24] |
| ARIA | ARIA has been reported in about 21% with lecanemab and donanemab in a clinical-pathway review. [11] | Discuss ARIA before treatment and ensure MRI capacity for surveillance and follow-up. [11] |
| APOE ε4 genotype | Reported ARIA-E rates rise from 5.4% to 32.6% across lecanemab noncarrier to homozygote groups and from 15.7% to 40.6% for donanemab. [19] | Use genotype-informed shared decision-making, with particular caution in ε4 homozygotes. [19] |
| Detected ARIA | MRI every 30 days until ARIA resolves has been recommended in a treatment-pathway review. [11] | Coordinate repeat MRI and treatment decisions through the anti-amyloid treatment program. [11] |

## Use cognitive enhancers for symptomatic benefit, not pathology clearance

Select symptomatic therapy independently of whether anti-amyloid therapy is pursued.

FDA-recognized symptomatic Alzheimer therapies are the cholinesterase inhibitors donepezil, rivastigmine, and galantamine, plus the N-methyl-D-aspartate receptor antagonist memantine. [1] These agents do not target the underlying amyloid or tau pathology, and expected benefit is modest and transitory. [1] They may remain clinically useful for symptomatic management while biomarker evaluation or anti-amyloid eligibility assessment proceeds.

Cholinesterase inhibitor adverse effects reflect enhanced muscarinic tone; nausea and vomiting have been reported in approximately one in four to one in seven treated patients. [12] Reassess tolerability after initiation or escalation and distinguish medication-related gastrointestinal symptoms from intercurrent illness before discontinuing a potentially beneficial agent.

Memantine is a noncompetitive antagonist at extrasynaptic NMDA receptors and has an approximately 60-hour half-life with once-daily administration described in a vascular cognitive impairment review. [20] Its FDA-recognized role is Alzheimer symptomatic treatment, whereas vascular cognitive impairment has no FDA-approved therapy; do not extrapolate an Alzheimer drug label to pure vascular cognitive impairment without recognizing that distinction. [1][20]
- Use donepezil, rivastigmine, galantamine, or memantine to target symptoms rather than to claim disease modification. [1]
- Ask specifically about nausea and vomiting after cholinesterase inhibitor initiation or dose change. [12]
- When vascular and Alzheimer pathologies coexist, identify the Alzheimer component before presenting cognitive enhancers as Alzheimer-directed treatment. [20][21]

*Role and limitation of approved symptomatic Alzheimer therapies. [1][12][20]*

| Therapy class | Agents | Clinical use and limitation |
| --- | --- | --- |
| Cholinesterase inhibitor | Donepezil, rivastigmine, galantamine. [1] | FDA-recognized symptomatic Alzheimer therapies; benefits are modest and do not target underlying pathology. Monitor for muscarinic adverse effects including nausea and vomiting. [1][12] |
| NMDA receptor antagonist | Memantine. [1] | FDA-recognized symptomatic Alzheimer therapy; it does not target underlying pathology. It is described as a noncompetitive extrasynaptic NMDA receptor antagonist. [1][20] |

## Identify mixed pathology before assigning a single-cause treatment plan

Alzheimer biomarkers clarify co-pathology but do not eliminate competing contributors to cognitive decline.

Vascular cognitive impairment and dementia has no FDA-approved treatment, whereas three cholinesterase inhibitors and memantine are FDA-approved Alzheimer symptomatic therapies and lecanemab and donanemab are FDA-approved anti-amyloid therapies for Alzheimer disease. [20] In patients with cerebrovascular disease and cognitive impairment, establish whether Alzheimer pathology is also present before assigning an Alzheimer-specific treatment rationale.

Medication review is a direct management intervention in vascular cognitive impairment: stroke best-practice guidance advises attention to drugs that may increase cognitive fluctuations or cognitive decline. [21] This is especially important when interpreting short-interval cognitive worsening, because medication effects can confound estimation of neurodegenerative progression.

In retired contact-sport athletes, fluid biomarkers can identify neurodegeneration and Alzheimer co-pathology, but phosphorylated tau biomarkers are not thought to be elevated in CTE without Alzheimer co-pathology. [9] A positive p-tau181 or p-tau217 result in this setting therefore supports investigation for Alzheimer biology rather than a clinical diagnosis of CTE. [9]
- Do not present an Alzheimer drug as FDA-approved treatment for pure vascular cognitive impairment. [20]
- Review medications that may worsen cognitive fluctuation or decline in vascular cognitive impairment. [21]
- In repetitive-head-impact exposure, use amyloid and p-tau biomarkers to assess Alzheimer copathology, not to confirm CTE. [9]

*Branches that change the diagnostic and treatment pathway. [9][20][21]*

| Clinical context | High-yield discriminator | Management consequence |
| --- | --- | --- |
| Cerebrovascular disease with cognitive impairment | Determine whether Alzheimer pathology is present; vascular cognitive impairment alone has no FDA-approved therapy. [20] | Address vascular and medication contributors while reserving Alzheimer-specific framing for biomarker-supported Alzheimer disease. [20][21] |
| Retired contact-sport athlete with cognitive symptoms | Amyloid PET or CSF/plasma amyloid and p-tau testing can identify Alzheimer co-pathology; tau PET does not reliably identify CTE tau. [9] | Do not diagnose CTE from PET; use confirmed Alzheimer pathology to inform access to Alzheimer-directed treatment. [9] |
| Elevated neurofilament light | NfL is a nonspecific marker of axonal degeneration and injury. [5] | Broaden rather than narrow the differential diagnosis; obtain etiology-specific biomarker evidence before initiating an Alzheimer pathway. [5] |

## Monitor progression, toxicity, and care needs on separate tracks

A treatment response assessment should not substitute for adverse-event surveillance or etiologic reassessment.

For anti-amyloid therapy, separate clinical trajectory from ARIA monitoring. Cognitive and functional scales quantify change over time, whereas MRI detects treatment-related ARIA; an ARIA finding warrants repeat MRI approximately every 30 days until resolution. [3][11] New neurologic symptoms during treatment should therefore trigger assessment for ARIA rather than being presumed to represent inevitable disease progression. [11]

Blood biomarkers may become useful longitudinal adjuncts, but their roles are not interchangeable. Longitudinal increases in plasma phosphorylated tau have been associated with brain atrophy and cognitive decline, particularly in Alzheimer disease, while NfL tracks axonal injury without Alzheimer specificity. [5] Use biomarker trends, when obtained, to complement rather than replace clinical and imaging-based evaluation.

Revisit goals of care as function changes. Alzheimer disease progressively affects memory, thinking, language, and eventually the ability to perform simple tasks. [3] At each follow-up, document changes in instrumental and basic activities, update caregiver capacity, and reassess whether the burden of infusion visits, MRI surveillance, and adverse-event risk remains proportionate to the patient’s goals.
- Track cognition and function separately from MRI safety surveillance during anti-amyloid treatment. [3][11]
- Interpret longitudinal p-tau and NfL changes in context; p-tau is more Alzheimer-linked, whereas NfL is nonspecific. [5]
- Use functional decline and caregiver capacity to reassess whether an intensive disease-modifying treatment pathway remains aligned with goals. [3][11]

*Follow-up targets by treatment pathway. [3][5][11][12]*

| Patient pathway | What to monitor | Action triggered by abnormality |
| --- | --- | --- |
| Anti-amyloid antibody treatment | Clinical decline measures and MRI for ARIA. [3][11] | If ARIA is detected, repeat MRI every 30 days until resolution. [11] |
| Cholinesterase inhibitor treatment | Nausea and vomiting after initiation or escalation. [12] | Reassess tolerability and the medication’s net symptomatic value. [12] |
| Biomarker follow-up | Plasma p-tau trends and NfL trends, interpreted with the clinical course. [5] | Do not use rising NfL alone to establish Alzheimer progression; reconsider competing sources of axonal injury. [5] |

## References
1. June 9, 2023 Peripheral and Central Nervous System ... — www.fda.gov — https://www.fda.gov/media/169263/download
2. FDA issues guidance regarding drug development for early Alzheimer’s disease | FDA — www.fda.gov — https://www.fda.gov/drugs/drug-alerts-and-statements/fda-issues-guidance-regarding-drug-development-early-alzheimers-disease
3. FDA approves treatment for adults with Alzheimer’s disease | FDA — www.fda.gov — https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-treatment-adults-alzheimers-disease
4. Watch Out for False Promises About So-Called Alzheimer's Cures | FDA — www.fda.gov — https://www.fda.gov/consumers/consumer-updates/watch-out-false-promises-about-so-called-alzheimers-cures
5. Blood-based high sensitivity measurements of beta-amyloid and phosphorylated tau as biomarkers of Alzheimer’s disease: a focused review on recent advances | Journal of Neurology, Neurosurgery & Psychiatry — jnnp.bmj.com — https://jnnp.bmj.com/content/92/11/1231
6. tau181 and NfL with tau- PET, Aβ-PET and cognition — jnnp.bmj.com — https://jnnp.bmj.com/content/jnnp/early/2021/07/14/jnnp-2020-325537.full.pdf
7. PET of Brain Amyloid and Tau in Mild Cognitive Impairment — www.nejm.org — https://www.nejm.org/doi/full/10.1056/NEJMoa054625
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13. a quasi-experiment and target trial emulation study — www.thelancet.com — https://www.thelancet.com/journals/lanepe/article/PIIS2666-7762(26)00019-0/fulltext
14. Recent advances in Alzheimer's disease: mechanisms ... — www.nature.com — https://www.nature.com/articles/s41392-024-01911-3
15. The evolving landscape of Alzheimer’s disease therapy: From Aβ to tau — www.cell.com — https://www.cell.com/cell/fulltext/S0092-8674(25)01368-6
16. Designing the next-generation clinical care pathway for Alzheimer’s disease | Nature Aging — www.nature.com — https://www.nature.com/articles/s43587-022-00269-x
17. Blood-based biomarkers for Alzheimer's disease — www.cell.com — https://www.cell.com/neuron/pdfExtended/S0896-6273(23)00390-2
18. Beyond Alzheimer's disease—translating biomarker ... — www.science.org — https://www.science.org/doi/pdf/10.1126/scitranslmed.adr2511
19. XPro1595 in early Alzheimer’s disease with inflammation: results from the phase 2 MINDFuL trial | npj Dementia — www.nature.com — https://www.nature.com/articles/s44400-026-00091-x
20. Vascular cognitive impairment and dementia: Prevention, treatments, mechanisms and management options for the future | Neuropsychopharmacology — www.nature.com — https://www.nature.com/articles/s41386-026-02331-3
21. Canadian Stroke Best Practice Recommendations — journals.lww.com — https://journals.lww.com/01258365-202519010-00025
22. Nurse practitioner–directed continuing education... : Journal of the American Association of Nurse Practitioners — journals.lww.com — https://journals.lww.com/10.1097/JXX.0000000000001276
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## Editorial note

Prepared from cited clinical literature using Astra's research workflow. Verify recommendations against current guidance and patient-specific factors.