Dementia¶

Chapter 31 | Part 2: Cardinal Manifestations and Presentation of Diseases

KEY CLINICAL POINTS¶

Dementia is an acquired deterioration in cognitive abilities impairing daily activities, affecting >6 million Americans with annual healthcare costs exceeding $300 billion
Alzheimer's disease is the most common cause (>50% of cases), followed by vascular dementia, with mixed pathology common in older individuals
Potentially reversible causes include depression, normal pressure hydrocephalus, alcohol dependence, medication side effects, and metabolic disorders
Diagnosis requires comprehensive history, neurologic examination, cognitive testing, neuroimaging, and increasingly molecular biomarkers (CSF, blood, PET)
Novel anti-A β monoclonal antibodies (lecanemab, donanemab) represent first disease-modifying therapies for early-stage Alzheimer's disease

1. DEFINITION & OVERVIEW¶

Dementia is defined as an acquired deterioration in cognitive abilities that impairs the successful performance of activities of daily living. Episodic memory (the ability to recall events specific in time and place) is the cognitive function most commonly lost. Beyond memory, dementia may erode other mental faculties including language, visuospatial function, praxis, calculation, judgment, and problem-solving abilities. Neuropsychiatric and social deficits also arise, manifesting as depression, apathy, anxiety, hallucinations, delusions, agitation, insomnia, sleep disturbances, compulsions, or disinhibition.

1.1 Clinical Course Patterns¶

The clinical course varies by etiology: - Slowly progressive: Alzheimer's disease (AD) - Static: Anoxic encephalopathy - Fluctuating (day to day or minute to minute): Dementia with Lewy bodies (DLB) Most patients with AD begin with episodic memory impairment, but in other dementias such as frontotemporal dementia (FTD), memory loss is not typically a presenting feature.

1.2 Prodromal Stages¶

Mild Cognitive Impairment (MCI): Prodromal clinical stage where individuals experience cognitive decline but remain independent in most daily activities. Can be subcategorized (e.g., amnestic MCI, dysexecutive MCI). Mild Behavioral Impairment (MBI): Emergence of sustained and impactful neuropsychiatric symptoms in older adults (apathy, emotional dysregulation, impulse control issues, social inappropriateness, hallucinations, or delusions). Like MCI, MBI can reflect a neuropsychiatric prodrome to neurodegenerative dementia. Preclinical Stage: Brain pathology present but clinical symptoms not yet manifest; increasingly recognized for AD and other dementing illnesses.

1.3 Benign Forgetfulness vs. Pathological Memory Loss¶

Subtle cumulative decline in episodic memory is a common part of aging (benign forgetfulness of the elderly). At age 85, the average person can learn and recall approximately one-half of the items they could at age 18. Subjective cognitive decline refers to individuals who experience a subjective decline from their cognitive baseline but perform within normal limits for their age and educational attainment on formal neuropsychological testing.

2. EPIDEMIOLOGY¶

Dementia affects over 6 million people in the United States with total annual healthcare costs exceeding $300 billion. The single strongest risk factor for dementia is increasing age.

2.1 Prevalence by Age¶

10% of persons age >70 years have clinically identifiable memory loss
20-40% of individuals age >85 years have clinically identifiable memory loss
Prevalence of disabling memory loss increases with each decade over age 50
Whether dementia is an inevitable consequence of normal human aging remains controversial

2.2 Modifiable Risk Factors¶

Based on large-scale epidemiologic studies, modifiable risk factors include: - Low education - Hearing loss - Social isolation - Traumatic brain injury - Hypertension - Diabetes mellitus - Obesity - Heavy alcohol use - Smoking - Depression - Physical inactivity - Air pollution exposure Improved management of mid-life cardiovascular risk factors has been credited with a decreasing incidence of dementia noted in North America and western European countries.

2.3 Global Considerations¶

Vascular dementia is more common in Asian countries due to higher prevalence of intracranial atherosclerosis
Rates of vascular dementia are rising in developing countries as vascular risk factors become more widespread
CNS infections (HIV, syphilis, cysticercosis, tuberculosis) are major contributors to dementia in the developing world
SARS-CoV-2 infection may have lasting effects on cognition in some individuals

3. ETIOLOGY & PATHOPHYSIOLOGY¶

Dementia syndromes result from disruption of specific large-scale neuronal networks by initially focal brain lesions, including neurodegenerative changes and vascular injury. The location and severity of synaptic and neuronal loss combine to produce the clinical features. Behavior, mood, and attention are modulated by ascending noradrenergic, serotonergic, and dopaminergic pathways, whereas cholinergic signaling is critical for attention and memory functions.

Molecular Basis for Degenerative Dementia¶

Dementia	Molecular Basis	Causal Genes (Chromosome)	Susceptibility Genes	Pathologic Findings
AD	Ab/tau	APP (21), PS-1 (14), PS-2 (1) (<2% carry mutations, most often PS-1)	Apo e4 (19)	Amyloid plaques, neurofibrillary tangles, neuropil threads
DLB	a-Synuclein	Very rare SNCA (4)	Unknown	a-Synuclein neuronal inclusions (Lewy bodies)
LATE	TDP-43	None identified	TMEM106B, GRN	TDP-43 neuronal inclusion bodies and neurites in neurons and glia, ± hippocampal sclerosis
FTD (tau)	Tau	MAPT exon and intron mutations (17) (~10% familial)	H1 MAPT haplotype	Tau neuronal and glial inclusions varying in morphology and distribution
FTD (TDP-43)	TDP-43	GRN (10% familial), C9ORF72 (20-30% familial), rare VCP, very rare TARDBP, TBK1, TIA1	-	TDP-43 neuronal and glial inclusions varying in morphology and distribution
FTD (FUS)	FUS	Very rare FUS	-	FUS neuronal and glial inclusions varying in morphology and distribution
CJD	PrPSc	PRNP (20) (up to 15% carry dominant mutations)	Codon 129 homozygosity for Met or Val	PrPSc deposition, panlaminar spongiosis

3.1 Functional Anatomy of Major Dementias¶

Alzheimer's Disease: Typically begins in entorhinal region of medial temporal lobe → spreads to hippocampus and other limbic structures → moves through basal temporal areas → then into lateral and posterior temporal and parietal neocortex → eventually causing more widespread degeneration. Presents with episodic memory loss accompanied later by aphasia, executive dysfunction, or navigational problems. Vascular Dementia: Associated with focal damage in variable patchwork of cortical and subcortical regions or white matter tracts that disconnects nodes within distributed networks. Frontal/Subcortical Dementias (FTD, HD): Less likely to begin with memory problems; more likely to present with difficulties with judgment, mood, executive control, movement, and behavior.

3.2 Frontal-Striatal Pathways¶

Lesions of frontal-striatal pathways produce specific and predictable effects on behavior: - Dorsolateral Prefrontal Cortex → Central caudate nucleus - Lesions cause: Executive dysfunction, poor organization and planning, decreased cognitive flexibility, impaired working memory - Lateral Orbital Frontal Cortex → Ventromedial caudate - Lesions cause: Impulsiveness, distractibility, disinhibition - Anterior Cingulate Cortex/Medial Prefrontal Cortex → Nucleus accumbens - Lesions cause: Apathy, poverty of speech, emotional blunting, akinetic mutism All corticostriatal systems include topographically organized projections through globus pallidus and thalamus; damage to these nodes can reproduce the clinical syndrome associated with corresponding cortical or striatal injuries.

3.3 Molecular Basis of Degenerative Dementias¶

The major degenerative dementias are associated with abnormal aggregation of specific proteins: - Alzheimer's disease: A β and tau - Dementia with Lewy bodies: α -synuclein - LATE: TDP-43 - Frontotemporal dementia: Tau, TDP-43, or FET family proteins (FUS, EWS, TAF15) - Huntington's disease: Huntingtin - Creutzfeldt-Jakob disease: Misfolded prion protein (PrPSc)

4. CLINICAL FEATURES¶

Clinical presentation varies significantly based on the underlying etiology. The initial symptoms, neuropsychological profile, neuropsychiatric features, neurologic findings, and imaging characteristics help differentiate between major dementia syndromes.

Clinical Differentiation of the Major Dementias¶

Disease	First Symptom	Mental Status	Neuropsychiatr y	Neurology	Imaging
AD	Memory loss	Episodic memory loss; executive, language, visuospatial variably affected	Irritability, anxiety, depression	Initially normal	Entorhinal cortex and hippocampal atrophy; posterio r-predominant cortical atrophy
Vascular	Often sudden; apathy, falls, focal weakness	Frontal/executiv e, cognitive slowing; can spare memory	Apathy, delusions, anxiety	Usually motor slowing, spasticity; can be normal	Cortical and/or subcortical infarctions, confluent white matter disease
DLB	Visual hallucinations, RBD, delirium, Capgras, parkinsonism	Drawing and frontal/executive; spares memory; delirium-prone	Visual hallucinations, depression, sleep disorder, delusions	Parkinsonism	Posterior parietal atrophy; hippocampi larger than AD
LATE	Memory loss	Episodic memory loss, mild semantic deficits	None described	Normal	Medial temporal and hippocampal atrophy, anterior predominant

Disease	First Symptom	Mental Status	Neuropsychiatr y	Neurology	Imaging
FTD	Apathy, poor judgment, speec h/language, hyperorality	Frontal/executiv e and/or language; spares drawing	Apathy, disinhibition, overeating, compulsivity	May have vertical gaze palsy, axial rigidity, dystonia, alien hand, or MND	Frontal, insular, and/or temporal atrophy; usually spares posterior parietal
CJD	Dementia, mood, anxiety, movement disorders	Variable: frontal/executive, focal cortical, memory	Depression, anxiety, psychosis in some	Myoclonus, rigidity, parkinsonism	Cortical ribboning and basal ganglia or thalamus hyperintensity on diffusion/FLAIR MRI

4.1 Alzheimer's Disease¶

First Symptom: Memory loss (75% of patients begin with memory symptoms) Other Early Symptoms: Anxiety, depression, difficulty managing money, driving, shopping, following instructions, finding words, navigating Mental Status: Episodic memory loss; executive, language, and visuospatial functions variably affected Neuropsychiatry: Early stages - mild depressive features, social withdrawal, irritability, anxiety; patients often maintain core social graces into middle/late stages; later - delusions, agitation, sleep disturbance Neurology: Initially normal; motor systems typically spared until later course Imaging: Entorhinal cortex and hippocampal atrophy; posterior-predominant cortical atrophy

4.2 Vascular Dementia¶

First Symptom: Often (but not always) sudden; variable; apathy, falls, focal weakness Mental Status: Frontal/executive dysfunction, cognitive slowing; can spare memory Neuropsychiatry: Apathy, delusions, anxiety, depression, disinhibition Neurology: Usually motor slowing, spasticity; can be normal Imaging: Cortical and/or subcortical infarctions, confluent white matter disease Risk Factors: Hypertension, atrial fibrillation, peripheral vascular disease, smoking, diabetes

4.3 Dementia with Lewy Bodies¶

First Symptom: Visual hallucinations, REM sleep behavior disorder (RBD), delirium, Capgras syndrome, parkinsonism Mental Status: Impaired drawing and frontal/executive function; spares memory; delirium-prone; dramatic fluctuations in cognition and arousal Neuropsychiatry: Visual hallucinations, depression, sleep disorder, delusions, Capgras syndrome (delusion that familiar person replaced by impostor), excessive daytime sleepiness Neurology: Parkinsonism (resting tremor, cogwheel rigidity, bradykinesia, festinating gait); lower brainstem symptoms (RBD, GI/autonomic problems) may precede parkinsonism/dementia by years or decades Imaging: Posterior parietal atrophy; hippocampi larger than in AD

First Symptom: Memory loss Mental Status: Episodic memory loss, mild semantic deficits; sparing of other cognitive domains; relatively slow progression Neuropsychiatry: None described Neurology: Normal Imaging: Medial temporal and hippocampal atrophy, anterior predominant Epidemiology: Common after age 70; found in ~20% of individuals with dementia who die at age <70 versus >50% who die at age >90

4.5 Frontotemporal Dementia¶

First Symptom: Apathy, poor judgment/insight, speech/language difficulties, hyperorality Suggestive Features: Personality change, disinhibition, weight gain, compulsive eating, prominent apathy, compulsivity, loss of empathy, progressive loss of speech fluency or single-word comprehension with relative sparing of memory and visuospatial abilities Mental Status: Frontal/executive and/or language deficits; spares drawing Neuropsychiatry: Apathy, disinhibition, overeating, compulsivity, dramatic personality changes early Neurology: May have vertical gaze palsy, axial rigidity, dystonia, alien hand, or motor neuron disease Imaging: Frontal, insular, and/or temporal atrophy; usually spares posterior parietal lobe

4.6 Creutzfeldt-Jakob Disease¶

First Symptom: Dementia, mood changes, anxiety, movement disorders Mental Status: Variable - frontal/executive, focal cortical, memory deficits Neuropsychiatry: Depression, anxiety, psychosis in some Neurology: Myoclonus (often startle-sensitive), rigidity, parkinsonism, akinetic-mute state Imaging: Cortical ribboning and basal ganglia or thalamus hyperintensity on diffusion/FLAIR MRI Progression: Rapid - classic cause of rapidly progressive dementia (RPD)

4.7 Other Clinical Syndromes¶

Corticobasal Syndrome (CBS): Asymmetric akinesia and rigidity, dystonia, myoclonus, alien limb phenomena, pyramidal signs, prefrontal deficits (nonfluent aphasia ± motor speech impairment, executive dysfunction, apraxia, behavioral disorder) Progressive Supranuclear Palsy (PSP): Unexplained falls, axial rigidity, dysphagia, vertical gaze deficits Primary Progressive Aphasia: Deficits in naming, word retrieval, motor speech, grammar, comprehension (lesions in dominant hemisphere speech/language networks) Chronic Traumatic Encephalopathy (CTE): Changes in cognition, mood, behavior, or motor function in individuals with high exposure to repetitive head impacts (professional athletes in collision/fighting sports, military veterans exposed to multiple blasts)

5. DIFFERENTIAL DIAGNOSIS¶

The causes of dementia are numerous and the frequency of each condition depends on age group, access to medical care, country of origin, and possibly racial/ethnic background. The differential can be organized by reversibility and by category.

Differential Diagnosis of Dementia¶

Category	Causes
Most Common	Alzheimer's disease, Vascular dementia (multi-infarct, diffuse white matter disease/Binswanger's), PDD/LBD spectrum, Alcoholism, Drug/medication intoxication, LATE
Vitamin Deficiencies*	Thiamine (B1): Wernicke's encephalopathy, B12 (subacute combined degeneration), Nicotinic acid (pellagra)
Endocrine/Organ Failure*	Hypothyroidism, Adrenal insufficiency/Cushing's syndrome, Hypo/hyperparathyroidism, Renal failure, Liver failure, Pulmonary failure
Chronic Infections	HIV, Neurosyphilis, Papovavirus (JC virus/PML), TB/fungal/protozoal, Whipple's disease*
Head Trauma	Chronic traumatic encephalopathy, Chronic subdural hematoma, Postanoxia, Postencephalitis, Normal-pressure hydrocephalus, Intracranial hypotension
Neoplastic	Primary brain tumor, Metastatic brain tumor, Paraneoplastic/autoimmune limbic encephalitis*
Toxic Disorders*	Drug/medication/narcotic poisoning, Heavy metal intoxication, Organic toxins
Psychiatric*	Depression (pseudodementia), Schizophrenia, Conversion disorder
Degenerative Disorders	Huntington's disease, Multisystem atrophy, Hereditary ataxias, FTD spectrum, Multiple sclerosis, Adult Down syndrome with AD, ALS-parkinsonism-dementia complex of Guam, Prion diseases (CJD, Gerstmann-Sträussler-Scheinker)
Miscellaneous	Sarcoidosis, Vasculitis, CADASIL, Acute intermittent porphyria, Recurrent nonconvulsive seizures
Pediatric/Adolescent	Pantothenate kinase-associated neurodegeneration, Subacute sclerosing panencephalitis, Metabolic disorders (Wilson's, Leigh's, leukodystrophies, lipid storage diseases, mitochondrial mutations)

5.1 Most Common Causes¶

Alzheimer's disease (>50% in Western countries)
Vascular dementia (second most common overall; more common in Asian countries, elderly, populations with limited healthcare access)
PDD/DLB spectrum
Drug/medication intoxication
Alcoholism
Limbic-predominant age-related TDP-43 encephalopathy (LATE)

Early-Onset Dementia (age <65): AD and FTD are most common neurodegenerative causes Late-Onset Dementia (age >65): AD, DLB, and vascular dementia are most common Mixed Pathology: Most late-onset dementia is associated with multiple pathological entities; common for individuals to show 3-4 different pathologies at autopsy Community-Based Autopsy Data (mean age at death 89.7 years, amnestic dementia): - 39% attributable risk: AD neuropathology - 25%: Cerebrovascular disease - 17%: LATE - 12%: Lewy body disease

5.3 Rapidly Progressive Dementia (RPD)¶

Definition: Progression from initial symptom onset to dementia within one year or less (excludes toxic/metabolic confusional states) Classic Cause: Creutzfeldt-Jakob disease (especially with myoclonus) More Common Causes: AD or other neurodegenerative disorder, autoimmune encephalitis Autoimmune Etiologies: - LGI1 antibodies: Faciobrachial dystonic seizures - Caspr2 antibodies: Insomnia, ataxia, myotonia - NMDA receptor antibodies: Psychosis, insomnia, dyskinesias - AMPA receptor antibodies: Limbic encephalitis with relapses

5.4 Predictors of Progression from MCI to AD Dementia¶

Prominent memory deficit
Family history of dementia
Presence of apolipoprotein ε 4 (Apo ε 4) allele
Small hippocampal volumes on brain imaging
Positive AD biofluid or imaging biomarkers

6. INVESTIGATIONS & DIAGNOSIS¶

Three major issues should be kept at the forefront: (1) What is the clinical diagnosis? (2) What component of the dementia syndrome is treatable or reversible? (3) Can the physician help to alleviate the burden on caregivers?

Evaluation of the Patient with Dementia¶

Routine Evaluation	Optional Focused Tests	Occasionally Helpful Tests
History	Psychometric testing	EEG
Physical examination	HIV, RPR, or VDRL	Parathyroid function
Thyroid function (TSH)	Lumbar puncture	Adrenal function
Vitamin B12	PET (FDG, amyloid, tau)	Urine heavy metals
Complete blood count	Chest x-ray	RBC sedimentation rate
Complete metabolic panel	Urine toxin screen	Lab screen for autoantibodies
CT/MRI	Apolipoprotein E	Angiogram
-	Blood-based AD biomarkers	Brain biopsy

6.1 History Taking¶

Key Elements: - Onset, duration, and tempo of progression - Acute/subacute onset → consider delirium, intoxication, infection, metabolic derangement - Slowly progressive memory loss over years → likely AD and/or LATE Historical Clues by Diagnosis: - Personality change, disinhibition, weight gain, compulsive eating → FTD - Early visual hallucinations, parkinsonism, RBD, Capgras syndrome, delirium-prone → DLB - Stepwise progression with vascular risk factors → Vascular dementia - Rapid progression with myoclonus → CJD - Recurrent head trauma → Chronic subdural hematoma, CTE, intracranial hypotension, NPH - Subacute amnesia/psychosis with mesial temporal MRI changes → Autoimmune encephalitis - High-risk sexual behaviors or IV drug use → HIV, syphilis - Alcohol abuse → Thiamine deficiency - Pernicious anemia, veganism, bowel irradiation, gastric surgery, chronic H2-blocker use → B12 deficiency - Battery/chemical factory work → Heavy metal intoxication - Autosomal dominant family history → HD, familial AD/FTD/DLB/prion disorders

6.2 Physical and Neurologic Examination¶

Key Findings by Diagnosis: - AD: Motor systems typically spared until later - FTD: Axial rigidity, supranuclear gaze palsy, or motor neuron disease (ALS-like) - DLB: New parkinsonian syndrome (resting tremor, cogwheel rigidity, bradykinesia, festinating gait) - CBS: Asymmetric akinesia/rigidity, dystonia, myoclonus, alien limb, pyramidal signs, nonfluent aphasia - PSP: Unexplained falls, axial rigidity, dysphagia, vertical gaze deficits - CJD: Diffuse rigidity, akinetic-mute state, prominent startle-sensitive myoclonus - Vascular: Hemiparesis or other focal deficits - B12 deficiency: Myelopathy with peripheral neuropathy - Hypothyroidism: Dry cool skin, hair loss, bradycardia Important Non-Neurologic Findings: - Peripheral neuropathy → Vitamin deficiency, heavy metal intoxication, thyroid dysfunction, Lyme disease, vasculitis - Hearing/visual impairment in elderly → May produce confusion misinterpreted as dementia - Profound bilateral sensorineural hearing loss in younger patient with short stature or myopathy → Mitochondrial disorder

6.3 Cognitive and Neuropsychiatric Examination¶

Brief Screening Tools: - Mini-Mental State Examination (MMSE): 30-point test - Montreal Cognitive Assessment (MOCA) MMSE Components (each correct answer = 1 point): - Orientation: Season/date/month/year/floor/hospital/town/state/country - Registration: Name and restate three objects - Recall: Remember same three objects after 5 minutes - Language: Name pencil and watch; repeat "no ifs, ands, or buts"; follow three-step command; obey written command; write sentence; copy design Limitations: Not highly sensitive to early-stage dementia; does not reliably discriminate between dementia syndromes; may be normal in MCI and some clinically apparent AD Neuropsychological Testing Domains: - Working and episodic memory - Executive function - Language - Visuospatial and perceptual abilities

6.4 Cognitive Profiles by Dementia Type¶

AD: Early deficits in episodic memory, category generation ("Name as many animals as you can in 1 minute"), visuoconstructive ability; verbal/visual episodic memory deficits usually first detected LATE: Prominent episodic memory deficits; sparing of other cognitive domains; relatively slow progression PDD/DLB: More severe deficits in executive and visuospatial function; better on episodic memory tasks than AD Vascular: Mixture of executive and visuospatial deficits with prominent psychomotor slowing Delirium: Most prominent deficits in attention, working memory, and executive function; assessment of other domains challenging FTD: Earliest deficits in executive control or language (speech or naming); some patients lack these findings despite profound social-emotional deficits

6.5 Laboratory Testing¶

American Academy of Neurology Recommendations (Routine): - Complete blood count - Electrolytes, glucose - Renal function - Liver function - Thyroid function (TSH) - Vitamin B12 level - Structural neuroimaging (MRI or CT)

6.6 Neuroimaging¶

MRI/CT Indications: - Rule out primary/metastatic neoplasms - Locate areas of infarction or inflammation - Detect subdural hematomas - Suggest NPH or diffuse white matter disease - Establish regional pattern of atrophy MRI Patterns by Diagnosis: - AD: Hippocampal atrophy + posterior-predominant cortical atrophy - LATE: Marked hippocampal and medial temporal lobe atrophy - FTD: Focal frontal, insular, and/or anterior temporal atrophy - DLB: Less prominent atrophy; greater amygdala than hippocampal involvement - CJD: Restricted diffusion within cortical ribbon and/or basal ganglia on DWI - Vascular: Extensive multifocal white matter abnormalities - NPH: Communicating hydrocephalus with vertex effacement, gaping Sylvian fissures despite minimal cortical atrophy

6.7 FDG-PET Patterns¶

AD: Temporal-parietal hypometabolism, often with early and prominent posterior cingulate cortex and precuneus involvement
FTD: Frontal and anterior temporal hypometabolism
DLB: Occipital cortex and precuneus hypometabolism with sparing of posterior cingulate ("cingulate island sign")
LATE: Severe medial temporal hypometabolism with sparing of association cortices

6.8 Amyloid and Tau PET Imaging¶

FDA-Approved Amyloid PET Ligands: - 18F-florbetapir - 18F-florbetaben - 18F-flutametamol FDA-Approved Tau PET Ligand: - 18F-flortaucipir Amyloid PET: - Binds to diffuse and neuritic amyloid plaques and vascular amyloid deposits (cerebral amyloid angiopathy) - ~25% of cognitively normal individuals at age 70 are positive - Main clinical value: Exclude AD in patients with negative scans - In older amnestic patients with hippocampal atrophy, negative amyloid PET suggests LATE - Useful for identifying candidates for anti-A β monoclonal antibodies Tau PET: - Binds to paired helical filaments of tau (neurofibrillary tangles) in AD - Does not reliably detect tau deposits in non-AD conditions - More tightly linked to cognitive state than amyloid - More useful for "ruling in" AD and disease staging Combined Utility: Patients positive on both modalities show most rapid decline

6.9 CSF Biomarkers¶

Indications: When CNS infection/inflammation is possible, or to assess AD molecular biomarkers in lieu of PET AD CSF Pattern: - Low A β 42 (or low A β 42/A β 40 ratio) - Mild to moderately elevated total tau - Elevated phosphorylated tau (p-Tau181 or p-Tau217) Performance: Novel fully automated CSF A β and tau assays perform comparably to amyloid PET; A β 42/A β 40 or p-Tau181/A β 42 ratios show higher concordance with amyloid PET and neuropathology than any single CSF biomarker

6.10 Blood-Based Biomarkers¶

Emerging plasma biomarkers: - Plasma A β 42/A β 40 - p-Tau181 - p-Tau217 Measured with mass spectrometry or highly sensitive immunoassays; evolving rapidly and likely to be approved for clinical use in near future, greatly enhancing scalability and cost-effectiveness of biomarker testing

6.11 α -Synuclein Biomarkers¶

CSF Seed Amplification Assay: High sensitivity and specificity in clinically diagnosed PD patients; detects pathology in subset of individuals at risk for PD (anosmia or RBD) Skin Biopsy: Phosphorylated α -synuclein colocalizing with nerve fiber bundles - high sensitivity and specificity in PD and DLB

6.12 EEG¶

Not routinely used but helpful for: - CJD: Repetitive bursts of diffuse high-amplitude sharp waves ("periodic complexes") - Nonconvulsive seizure disorder: Epileptiform discharges

6.13 Brain Biopsy¶

Not advised except to diagnose: - Vasculitis - Potentially treatable neoplasms - Unusual infections when diagnosis uncertain Note: Systemic disorders with CNS manifestations (e.g., sarcoidosis) can often be confirmed through lymph node or solid organ biopsy

7. MANAGEMENT & TREATMENT¶

The major goals of dementia management are to treat reversible causes and to provide comfort and support to the patient and their caregivers.

Pharmacologic Treatment Summary¶

Drug Class	Agents	Indications	Key Points
Cholinesterase Inhibitors	Donepezil, Rivastigmine, Galantamine	AD (all), PDD (rivastigmine)	May help psychiatric symptoms in DLB
NMDA Antagonist	Memantine	Moderate-severe AD	Reduces caregiver burden; avoid in DLB
Anti-Ab Antibodies	Lecanemab, Donanemab, Aducanumab	MCI and mild dementia due to AD	Require positive amyloid biomarkers; monitor for ARIA
Atypical Antipsychotics	Quetiapine, Brexpiprazole	Agitation, aggression, psychosis	Brexpiprazole only FDA-approved for AD agitation; increased mortality risk
Antidepressants	SSRIs (escitalopram), SNRIs	Depression, anxiety	Few cognitive side effects
Anticonvulsants	Levetiracetam, Lamotrigine	Seizures	Preferred due to favorable cognitive profile

7.1 Treatment of Underlying Causes¶

Thyroid replacement for hypothyroidism
Vitamin therapy for thiamine or B12 deficiency or elevated homocysteine
Antimicrobials for opportunistic infections or antiretrovirals for HIV
Ventricular shunting for NPH
Surgical, radiation, and/or chemotherapeutic treatment for CNS neoplasms
Removal of cognition-impairing drugs or medications
Vigorous treatment of psychiatric disorders

7.2 Symptomatic Treatment of Mood Disorders¶

Antidepressants: SSRIs or SNRIs - provide anxiolytic properties with few cognitive side effects Depression Treatment: Start with low dose SSRI (e.g., escitalopram starting dose 5 mg daily, target dose 5-10 mg daily); monitor for efficacy and toxicity Note: Patients with degenerative diseases may be depressed or anxious; treatment often helps mood/anxiety symptoms even if cognition does not improve

7.3 Management of Behavioral Symptoms¶

Agitation, hallucinations, delusions, and confusion represent major causes for nursing home placement. First-Line Approach (Non-Pharmacologic): Aggressively seek modifiable environmental or metabolic factors: - Hunger - Lack of exercise - Toothache - Constipation - Urinary tract infection - Respiratory infection - Electrolyte imbalance - Drug toxicity Pharmacologic Approaches: Second-Generation Antipsychotics: - Quetiapine: Starting dose 12.5-25 mg daily - Use for agitation, aggression, psychosis - Significant risk profile including increased mortality in dementia patients Brexiprazole: - First FDA-approved drug for agitation in AD dementia (2023) - Acts on noradrenergic, serotonergic, and dopaminergic systems - Approved based on 12-week, double-blind, placebo-controlled RCT Medications to Avoid: - Higher doses of antipsychotics when patients don't respond - Anticholinergic drugs (e.g., diphenhydramine) - Sedatives (e.g., barbiturates, benzodiazepines) Note: Phenothiazines and benzodiazepines may ameliorate behavior problems but have untoward side effects (sedation, rigidity, dyskinesia, paradoxical disinhibition)

7.4 Cholinesterase Inhibitors¶

Approved for AD: - Donepezil - Rivastigmine - Galantamine Approved for PDD: - Rivastigmine Additional Benefits: Sometimes improve apathy, visual hallucinations, depression, and other psychiatric symptoms, especially in DLB, potentially obviating need for more toxic therapies

7.5 Memantine¶

Mechanism: Acts on NMDA glutamate receptors Indication: Moderate to severe AD Primary Benefit: Decreasing caregiver burden, most likely by decreasing resistance to dressing and grooming support Combination Therapy: Memantine + cholinesterase inhibitor delayed nursing home placement in several studies for moderate to severe AD (though some studies did not support adding memantine) Caution: Use with great caution or not at all in DLB due to risk of worsening agitation and confusion

7.6 Anti-Amyloid Monoclonal Antibodies¶

Novel class of disease-modifying therapies targeting A β for MCI and mild dementia due to AD. FDA-Approved Agents: 1. Aducanumab (2021 - accelerated approval) - Administration: Monthly IV infusion - Evidence: Strong biomarker evidence of amyloid plaque lowering on PET - Clinical efficacy questionable (discordant results in two phase 3 RCTs) 2. Lecanemab (2023 - traditional approval) - Administration: Every 2 weeks IV infusion - Evidence: Phase 3 RCT showed 27% less decline over 18 months vs placebo on CDR-SB 3. Donanemab (2024 - FDA approved) - Administration: Monthly IV infusion - Evidence: Similar positive clinical results in phase 3 RCT Mechanism: Reduce amyloid plaque burden as measured by PET; modestly slow clinical decline Patient Selection: Amyloid PET useful for identifying candidates; positive AD CSF biomarkers also sufficient

Significant side effects of anti-A β monoclonal antibodies: - Infusion reactions - ARIA-E: Edema or sulcal effusions - ARIA-H: Microhemorrhages Note: Careful monitoring with serial MRI required during treatment

7.8 Anticonvulsants¶

Indication: Seizure control in dementia patients Preferred Agents: - Levetiracetam - Lamotrigine Rationale: Efficacy in animal models of AD and favorable cognitive side effect profiles Potential Cognitive Benefit: Small clinical trial found potential cognitive benefit for levetiracetam over placebo in AD patients with epileptiform activity on EEG or magnetoencephalography

8. PROGNOSIS & COMPLICATIONS¶

Prognosis varies significantly based on the underlying etiology, age at onset, and presence of comorbid conditions.

8.1 Progression and Mixed Pathology¶

Most late-onset dementia is associated with multiple pathological entities; common for individuals who suffered from dementia to show 3-4 different pathologies at autopsy. LATE Prevalence: - ~20% of individuals with dementia who die at age <70 - >50% of individuals with dementia who die at age >90 Mixed Pathology Impact: In older patients, vascular brain injury is often mixed with neurodegenerative disorders (particularly AD), making it difficult to estimate the contribution of cerebrovascular disease to the cognitive disorder.

8.2 Prognostic Biomarkers¶

Amyloid and Tau PET: Patients positive on both modalities show the most rapid decline in cognition and function Use in Cognitively Unimpaired Adults: Should currently be restricted to research studies and clinical trials testing interventions aimed at reducing risk of MCI and dementia in asymptomatic individuals positive for AD biomarkers

8.3 Complications¶

Falls and injuries
Aspiration pneumonia
Malnutrition
Pressure ulcers
Institutionalization
Caregiver burden and "burnout"
Depression in patients and caregivers

9. SPECIAL CONSIDERATIONS¶

Certain populations and scenarios require specific consideration in the evaluation and management of dementia.

9.1 Potentially Reversible Causes¶

In a study of 1000 persons attending a memory disorders clinic: - 19% had a potentially reversible cause of cognitive impairment - 23% had a potentially reversible concomitant condition that may have contributed to impairment Three Most Common Potentially Reversible Diagnoses: 1. Depression 2. Normal pressure hydrocephalus 3. Alcohol dependence Medication side effects should be considered in every patient.

9.2 Caregiver Support¶

Behavioral problems (agitation, hallucinations, delusions, confusion) represent major causes for nursing home placement and institutionalization. Physician Goals: - Help alleviate burden on caregivers - Recognize and treat depression in caregivers - Provide resources for caregiver support Functional Assessment: Knowledge of patient's functional abilities helps clinician and family organize therapeutic approach

9.3 Pediatric and Adolescent Considerations¶

Additional conditions in children/adolescents: - Pantothenate kinase-associated neurodegeneration - Subacute sclerosing panencephalitis - Metabolic disorders: - Wilson's disease - Leigh's disease - Leukodystrophies - Lipid storage diseases - Mitochondrial mutations

9.4 Historical/Unique Populations¶

Kuru: Cannibalism-associated rapidly progressive dementia in tribal New Guinea; contributed to discovery of human prion disease ALS-Parkinsonism-Dementia Complex of Guam (Lytico-Bodig Disease): Polyproteinopathy often with tau, TDP-43, and α -synuclein aggregation; incidence has declined sharply over past 60 years; root cause uncertain

10. KEY POINTS & CLINICAL PEARLS¶

Essential clinical pearls for the evaluation and management of dementia syndromes.

Key Clinical Pearls¶

Topic	Pearl
Diagnosis	Three major questions: (1) What is the clinical diagnosis? (2) What is treatable/reversible? (3) Can the physician help alleviate caregiver burden?
History	Acute/subacute onset suggests delirium; slowly progressive memory loss over years suggests AD/LATE
Personality Change	Early personality change, disinhibition, weight gain, compulsive eating suggests FTD, not AD
Visual Hallucinations	Early visual hallucinations, RBD, parkinsonism, Capgras syndrome, delirium-proneness suggests DLB

Topic	Pearl
Medication Review	Removal of cognition-impairing drugs is critical - review medications in every patient
Reversible Causes	Never miss depression, NPH, alcohol dependence, medication side effects, B12 deficiency, hypothyroidism
Cognitive Testing	MMSE and MOCA may be normal in MCI and early AD - use more comprehensive testing when in doubt
Negative Amyloid PET	In older amnestic patients with hippocampal atrophy, negative amyloid PET strongly suggests LATE
Anti-Ab Therapy	Lecanemab and donanemab require positive amyloid biomarkers (PET or CSF) before treatment
Behavioral Management	Before using psychoactive drugs for behavior, rule out hunger, constipation, UTI, pain, electrolyte imbalance, drug toxicity
Memantine Caution	Use memantine with great caution or not at all in DLB - risk of worsening agitation/confusion
Antipsychotic Risk	All antipsychotics carry increased mortality risk in dementia patients - use judiciously
Cholinesterase Inhibitors	May help psychiatric symptoms (apathy, hallucinations, depression) in DLB, potentially avoiding more toxic drugs
Seizures	Levetiracetam and lamotrigine preferred anticonvulsants due to favorable cognitive profiles
Mixed Pathology	Most late-onset dementia shows multiple pathologies at autopsy - pure diagnoses are rare in elderly