NEURODEGENERATIVE

Alzheimer pattern review / structural MRI / cognitive-region atlas / clinical orientation layer

3T T1structural acquisition 1.0 mmisotropic voxel grid 0.7 mmcortical surface precision FLAIRwhite-matter comparator ADNIatrophy reference cohort OASISage-normal baseline HCPconnectome atlas context QC 94%motion-corrected slice stack
[ Alzheimer MRI Review ]
Hippocampal Volumeleft/right asymmetry reviewed / memory-circuit vulnerability / percentile modelP12 / asym 7.8%
Ventricular Indexenlargement proxy / central CSF expansion / structural atrophy signal1.42x / CSF +18%
Cortical Thicknesstemporal-parietal thinning / AD-pattern support / longitudinal comparator-8.6% / AD pattern
HIPPOCAMPAL focus / Alzheimer structural review demonstration data only / not diagnostic output
[ Alzheimer Data Panel ]

STRUCTURAL
DISEASE MARKERS

Orientation values combine MRI-visible structural markers with common Alzheimer research measures. Percentiles and scores are demonstration values for the interface.

2.4medial temporal atrophy
0.5clinical dementia rating
24MMSE cognitive screen
+31%tau / amyloid risk proxy
7.8%hippocampal asymmetry
0.62memory-network coherence
-6.4%parietal association loss
+18%CSF expansion index
[ Review Log ]
[ 01 / Pathology ]

WHAT THE DISEASE
DOES TO TISSUE

Alzheimer's disease is a progressive neurodegenerative process — molecular first, structural second, symptomatic last.

Alzheimer's disease begins as a molecular problem and only later becomes something a scanner can see. Two proteins define it. Amyloid-beta, a fragment cleaved from a normal membrane protein, stops being cleared efficiently and aggregates into plaques in the space between neurons. Tau, a protein that normally stabilizes the internal transport scaffolding inside an axon, becomes abnormally phosphorylated, detaches, and twists into neurofibrillary tangles inside the cell.

Amyloid accumulation can begin fifteen to twenty years before the first memory complaint. Tau spread tracks much more closely with actual symptoms — where tangles go, function is lost. That gap between the two is why a person can carry substantial plaque burden and still test cognitively normal.

Downstream of both comes the damage that MRI eventually registers: synapses are lost first, then dendrites retract, then whole neurons die. Microglia — the brain's resident immune cells — mount a chronic inflammatory response that helps early and injures late. Volume disappears. The cortical ribbon thins. The ventricles, which are simply fluid-filled spaces, expand to fill the void left behind. Ventricular enlargement is not the disease; it is the shadow the disease casts.

Preclinical phase before symptoms15–20 YR
Share of all dementia cases60–70%
Hippocampal loss / year in AD3–5%
Normal aging comparison0.5–1%
Cases worldwide (2023 est.)55M+
Risk doubling interval after 65~5 YR

Amyloid Plaques

Extracellular deposits of misfolded amyloid-beta 42. Accumulate earliest, plateau before symptoms, and correlate poorly with day-to-day severity.

detected: PET / CSF Aβ42:40

Tau Tangles

Intracellular twisted filaments of hyperphosphorylated tau. Spread in a stereotyped anatomical order and track tightly with cognitive decline.

detected: tau PET / p-tau217

Synaptic Loss

The strongest single correlate of cognitive impairment. Connections fail before cells die, which is why function drops ahead of visible volume loss.

proxy: FDG hypometabolism

Neuroinflammation

Chronically activated microglia and astrocytes. Initially clears debris; sustained, it accelerates synaptic pruning and neuronal injury.

marker: GFAP / TSPO

Atrophy

Net tissue loss measured as reduced volume and cortical thinning. The structural endpoint — and the part this MRI console is built to read.

measured: T1 volumetry

Vascular Burden

White-matter hyperintensities and small-vessel disease frequently co-occur, lowering the damage threshold at which symptoms appear.

measured: FLAIR / Fazekas
[ 02 / Anatomy ]

THE ROUTE
THROUGH THE BRAIN

Tau pathology does not appear randomly. It follows connected circuits in a repeatable order — the basis of Braak staging.

The reason Alzheimer's presents as a memory disorder first is purely anatomical. The pathology starts in the entorhinal cortex — the gateway that funnels sensory and associative information into the hippocampus — and then invades the hippocampus itself. That circuit is where new episodic memories are formed. Damage it, and the ability to lay down new memories fails long before older memories, language, or personality are touched.

From there the process moves outward along connected networks: lateral temporal cortex, posterior cingulate and precuneus, parietal association cortex, and finally frontal and primary sensory areas. Primary motor and visual cortex are spared until very late, which is why walking and seeing typically persist while orientation and judgment collapse.

RegionBraak stageFunction it carriesWhat loss looks like clinicallyMRI signature
Entorhinal cortexI–IIGateway between neocortex and hippocampusSubtle lapses; often still called "normal aging"thinning −10 to −14%
HippocampusII–IIIEncoding and consolidation of new episodic memoryRepeating questions, misplacing objects, losing recent eventsvolume < 15th pct
AmygdalaIIIEmotional salience and memory taggingFlattened affect, anxiety, changed emotional responsevolume −8 to −12%
Posterior cingulateIII–IVDefault-mode hub; self-referential processingDisorientation in familiar placesFDG −14 to −20%
Lateral temporalIVSemantic memory, word retrievalWord-finding failure, naming errorsthinning −6 to −10%
Parietal associationVSpatial reasoning, visuospatial integrationGetting lost driving; trouble dressing or using toolsthinning −5 to −9%
Frontal cortexV–VIExecutive control, judgment, inhibitionPoor decisions, apathy, personality changelate thinning
Primary sensorimotorVIMovement and primary sensationSpared until the final phaseminimal change
[ 03 / Trajectory ]

CLINICAL
STAGE PROGRESSION

Ranges are population estimates. Individual trajectories vary widely with age, reserve, comorbidity, and co-pathology.

Stage 01 / CDR 0

Preclinical

Biomarkers are positive; cognition is normal. Detectable only by PET, CSF, or blood assay. No structural MRI finding is reliable yet.

duration 10–20 years
Stage 02 / CDR 0.5

MCI

Measurable memory decline that does not yet compromise independence. Medial temporal atrophy becomes visible. Roughly 10–15% convert to dementia per year.

duration 2–7 years
Stage 03 / CDR 1

Mild Dementia

Diagnosis is usually made here. Recent memory clearly impaired, word-finding fails, complex tasks — finances, navigation — slip. Hippocampal loss is unmistakable.

duration 2–4 years
Stage 04 / CDR 2

Moderate

Help needed with daily activities. Disorientation to time and place, behavioral change, sleep disruption. Widespread cortical thinning and marked ventricular enlargement.

duration 2–4 years
Stage 05 / CDR 3

Severe

Full-time care required. Language reduces to few words; mobility and swallowing decline. Global atrophy with substantial total brain volume loss.

duration 1–3 years
[ 04 / Imaging ]

WHAT AN MRI
ACTUALLY MEASURES

Structural MRI cannot see amyloid or tau. It sees the tissue those proteins have already cost.

In an Alzheimer's workup, MRI does two jobs. The first is exclusion: ruling out tumor, chronic subdural hematoma, normal-pressure hydrocephalus, or extensive vascular damage that could explain the symptoms without neurodegeneration. The second is pattern support — confirming that the atrophy present matches the medial-temporal-first distribution characteristic of AD rather than the frontal pattern of FTD or the posterior-cortical pattern of a visual variant.

A volumetric T1 sequence at 1 mm isotropic resolution allows automated segmentation of the hippocampus and cortical thickness estimation across the whole surface. FLAIR is added to quantify white-matter hyperintensities. Both get compared against age- and sex-matched normative curves — an absolute hippocampal volume means nothing without a percentile.

The single most important caveat: atrophy is a lagging indicator. By the time the hippocampus is visibly small, the underlying process has been running for a decade or more. That is precisely why blood-based p-tau217 assays have become such a significant development — they move detection back toward the beginning of the curve.

Structural T1 acquisition3T / 1.0mm
Cortical surface precision0.7mm
White-matter comparatorFLAIR
Scheltens MTA scale range0–4
MTA threshold, age > 75≥ 2
Fazekas WMH grading0–3
Evans index cutoff> 0.30
Typical follow-up interval12 MO
MeasureSequenceWhat it quantifiesTypical AD finding
Hippocampal volumeT1 volumetricAbsolute volume normalized to intracranial volume, expressed as a percentile< 15th percentile
MTA scoreCoronal T1Visual rating of medial temporal atrophy — choroid fissure, temporal horn, hippocampal heightgrade 2–4
Cortical thicknessT1 surface modelRibbon thickness across temporal, parietal, and cingulate regions−6 to −12%
Ventricular indexT1 / axialEvans ratio: frontal horn width against maximal inner skull width1.3–1.6× normal
Hippocampal asymmetryT1 volumetricLeft-versus-right difference; often left-predominant early in AD5–10%
WMH burdenFLAIRPeriventricular and deep white-matter signal change from small-vessel diseaseFazekas 1–3
MicrobleedsSWI / GRELobar hemosiderin deposits suggesting cerebral amyloid angiopathyscreening required
Whole-brain changeSerial T1Annualized atrophy rate between registered timepoints1–2% / year
[ 05 / Biomarkers ]

THE A / T / N
FRAMEWORK

Modern diagnosis is biological, not purely clinical: amyloid status, tau status, and neurodegeneration are scored independently.

The A/T/N scheme separates three questions that used to be collapsed into one. A asks whether amyloid is present. T asks whether pathological tau is present. N asks how much neurodegeneration has already occurred. A person can be A+ T− N− and be biologically on the Alzheimer's continuum while cognitively intact; a person can be A− T− N+ and have neurodegeneration from an entirely different cause. Structural MRI — the layer this console models — contributes only to N.

AxisModalityMarkerInterpretation
A — AmyloidPETAmyloid tracer retention (centiloid scale)Positive typically > 20–30 centiloids
A — AmyloidCSFAβ42 / Aβ40 ratioReduced ratio indicates cortical deposition
A — AmyloidBloodPlasma Aβ42/40Screening-grade; modest effect size
T — TauBloodPlasma p-tau217Highest-performing blood marker to date
T — TauPETTau tracer binding by Braak regionDistribution tracks symptom severity
N — NeurodegenerationMRIHippocampal volume, cortical thicknessStructural loss; lagging but specific
N — NeurodegenerationFDG-PETTemporoparietal hypometabolismSynaptic dysfunction ahead of atrophy
N — NeurodegenerationBloodNeurofilament light (NfL)Non-specific axonal injury signal
[ 06 / Risk ]

RISK
ARCHITECTURE

Roughly 40–45% of dementia cases worldwide are attributable to modifiable factors — a population estimate, not an individual guarantee.

Age is the dominant risk factor, and it is not modifiable: incidence roughly doubles every five years after 65. Genetics contribute on two levels. Rare autosomal-dominant mutations in APP, PSEN1, or PSEN2 cause early-onset disease with near-complete penetrance but account for well under 1% of cases. The common variant is APOE ε4, which shifts risk substantially without determining outcome — many ε4 carriers never develop dementia, and many people with Alzheimer's carry no ε4 allele at all.

Agenon-modifiable

Incidence doubles roughly every five years past 65. The single strongest predictor by a wide margin.

APOE ε4non-modifiable

One copy raises risk ~2–3×; two copies substantially more, with earlier onset. Not deterministic.

Hearing Lossmodifiable

Untreated midlife hearing loss is the largest single modifiable contributor. Aids may attenuate risk.

Vascular Healthmodifiable

Hypertension, diabetes, obesity, and smoking damage small vessels and lower the symptom threshold.

Education / Reservemodifiable

Cognitive reserve delays symptom onset for a given pathology burden — it masks damage rather than preventing it.

Physical Activitymodifiable

Regular aerobic exercise is associated with lower incidence and slower hippocampal volume loss.

Sleepmodifiable

Deep sleep drives glymphatic clearance of amyloid. Chronic disruption impairs that removal.

Social Isolationmodifiable

Late-life isolation and depression both associate with elevated incidence and faster decline.

Head Injurymodifiable

Repeated traumatic brain injury increases later-life dementia risk across several pathologies.

[ 07 / Differential ]

WHAT ELSE
LOOKS LIKE THIS

Atrophy is not self-identifying. Distribution, symptom sequence, and rate of onset separate the diagnoses.

ConditionAtrophy patternLeading symptomDistinguishing feature
Alzheimer'sMedial temporal → temporoparietalEpisodic memory lossA+ / T+ biomarkers
FrontotemporalFrontal and anterior temporalBehavior or language changeyounger onset, memory spared
Lewy bodyRelatively preserved medial temporalVisual hallucinations, fluctuationparkinsonism, REM sleep disorder
VascularInfarcts, confluent WMHExecutive slowingstepwise decline, vascular history
Normal-pressure hydrocephalusVentricles out of proportion to sulciGait disturbance firstpotentially treatable by shunt
Depression / pseudodementiaNone specificEffortful, inconsistent recallreversible with treatment
Thyroid / B12 deficiencyNone specificDiffuse cognitive slowingreversible; always screened
[ 08 / Glossary ]

TERMS USED
ON THIS CONSOLE

Every readout on the review panel above maps to one of these.

HippocampusSeahorse-shaped structure in the medial temporal lobe responsible for forming new episodic memories. Among the earliest regions damaged in Alzheimer's.
Entorhinal CortexThe interface between the hippocampus and the rest of the cortex. Tau pathology characteristically appears here first.
Posterior CingulateA central hub of the default-mode network. Shows reduced glucose metabolism very early, often before measurable atrophy.
MTA ScoreScheltens medial temporal atrophy scale, 0–4, rated visually on coronal T1. Thresholds are age-adjusted.
Evans IndexRatio of maximal frontal horn width to maximal inner skull diameter. Above 0.30 indicates ventricular enlargement.
Fazekas Grade0–3 rating of white-matter hyperintensity burden on FLAIR, reflecting small-vessel disease load.
CDRClinical Dementia Rating: 0 normal, 0.5 questionable/MCI, 1 mild, 2 moderate, 3 severe.
MMSEMini-Mental State Examination, 0–30. Below 24 commonly flags impairment, though education and language strongly affect it.
p-tau217A phosphorylated tau species measurable in blood; currently the most accurate blood-based indicator of AD pathology.
Braak StagingSix-stage neuropathological scheme describing the stereotyped anatomical spread of tau tangles.
Cognitive ReserveCapacity to sustain pathology without proportional symptoms, built through education, occupation, and engagement.
ADNI / OASISPublic longitudinal neuroimaging cohorts used as normative and comparison references in atrophy research.
[ 09 / Notice ]

ORIENTATION MODEL
NOT A DIAGNOSIS

Every numeric readout on this page is demonstration data generated for the interface.

This console is a design and visualization exercise. The scan imagery, percentiles, confidence scores, and regional correlations are illustrative — they are not derived from a patient study and carry no clinical meaning. The explanatory text reflects general published understanding of Alzheimer's disease at a summary level and is not comprehensive.

Alzheimer's diagnosis requires clinical assessment, cognitive testing, laboratory screening, imaging interpreted by a radiologist, and increasingly biomarker confirmation — integrated by a physician. If you or someone you know is experiencing memory changes, speak to a doctor. Reversible causes are common and worth excluding early, and treatment options depend heavily on how early the process is identified.

ADNIAlzheimer's Disease Neuroimaging Initiative OASISOpen Access Series of Imaging Studies NIA-AAresearch framework / A-T-N criteria LANCETcommission on dementia prevention