Nervous System

Frontotemporal dementia and Lewy body dementia

Clinical Overview and When to Suspect FTD or DLB

Frontotemporal dementia (FTD) and dementia with Lewy bodies (DLB) are the two most important non-Alzheimer dementias tested on boards.

Suspect FTD when:

— Young-onset dementia with prominent behavioral disinhibition, apathy, or language dysfunction (not memory loss)

— Personality change precedes or overshadows memory impairment

Suspect DLB when:

— Older adult with fluctuating cognition, recurrent well-formed visual hallucinations, and spontaneous parkinsonism

— REM sleep behavior disorder (acting out dreams) precedes or accompanies cognitive decline

Board pearl: FTD = personality/behavior first, memory relatively spared early. DLB = visual hallucinations + parkinsonism + cognitive fluctuations. Alzheimer's = memory loss first.

FTD: neurodegeneration of frontal and temporal lobes → behavioral/personality changes or progressive aphasia, typically onset age 45–65

DLB: α-synuclein deposits in cortex → cognitive fluctuations, visual hallucinations, and parkinsonism

FTD — Presentation Patterns and Key History

Three major clinical variants:

— Disinhibition (socially inappropriate behavior, impulsivity, loss of manners)

— Apathy/inertia, loss of empathy or sympathy

— Compulsive/ritualistic behaviors, hyperorality (craving sweets, eating non-food items)

— Executive dysfunction early; episodic memory and visuospatial function relatively preserved

— Fluent speech but progressive loss of word/object meaning

— Anomia, impaired single-word comprehension

— Effortful, halting speech with grammatical errors

— Apraxia of speech; comprehension relatively preserved

History clues: age <65, personality change, socially inappropriate behavior, lack of insight, family history (FTD has highest heritability among dementias — ~40% familial)

Next best step: Collateral history from family is critical — patients with bvFTD typically lack insight into their behavioral changes.

Behavioral variant FTD (bvFTD) — most common:

Semantic variant primary progressive aphasia (svPPA):

Nonfluent/agrammatic variant PPA (nfvPPA):

DLB — Presentation Patterns and Key History

Core clinical features (≥2 → probable DLB):

Supportive features:

— Severe neuroleptic sensitivity (antipsychotics → life-threatening rigidity)

— Autonomic dysfunction (orthostatic hypotension, constipation, urinary incontinence)

— Depression, apathy, anxiety

— Repeated falls and syncope

Key distinction: DLB vs Parkinson's disease dementia (PDD) → the "1-year rule": if dementia begins within 1 year of parkinsonism → DLB; if parkinsonism precedes dementia by >1 year → PDD. Same underlying pathology (α-synuclein) but different clinical trajectory.

Board pearl: Visual hallucinations in an elderly patient with parkinsonism who has NOT been started on levodopa → think DLB, not drug-induced hallucinations.

Fluctuating cognition — variations in attention and alertness (lucid periods alternating with confusion/drowsiness)

Recurrent visual hallucinations — well-formed, detailed (people, animals)

REM sleep behavior disorder (RBD) — loss of normal atonia during REM → acting out dreams, can precede dementia by years

Spontaneous parkinsonism — bradykinesia, rigidity, resting tremor (typically symmetric, less tremor-dominant than PD)

Diagnostic Workup — Imaging

FTD imaging:

— bvFTD → bilateral frontal ("knife-edge" atrophy of frontal gyri)

— svPPA → left anterior temporal lobe atrophy

— nfvPPA → left posterior frontal / insular atrophy

DLB imaging:

Next best step: For suspected DLB with diagnostic uncertainty, DaT-SPECT is the most useful confirmatory test. For FTD, MRI showing frontal/temporal atrophy in a young patient with behavioral change is often sufficient.

MRI brain (preferred): asymmetric frontal and/or anterior temporal lobe atrophy

FDG-PET: frontal and anterior temporal hypometabolism (more sensitive than structural MRI early in disease)

MRI brain: relatively preserved medial temporal lobes/hippocampi (unlike Alzheimer's)

FDG-PET: occipital hypometabolism ("cingulate island sign" — relative sparing of posterior cingulate with occipital hypometabolism)

DaT-SPECT (ioflupane): ↓ dopamine transporter uptake in basal ganglia — distinguishes DLB from Alzheimer's (highly specific)

Polysomnography: confirms RBD (REM without atonia)

Diagnostic Workup — Labs, Biomarkers, and Criteria

Laboratory evaluation (rule out reversible causes):

Biomarkers:

— Genetic testing considered when strong family history: C9orf72 (most common — also linked to ALS), MAPT, GRN

— MIBG myocardial scintigraphy: ↓ cardiac uptake (postganglionic sympathetic denervation) — supports DLB/PDD

Neuropsychological testing:

Board pearl: Normal hippocampal volume on MRI in a patient with dementia + visual hallucinations + parkinsonism → DLB, not Alzheimer's.

TSH, B₁₂, RPR/VDRL, CBC, CMP, HIV (if risk factors)

These are standard for ALL dementias

FTD: CSF Alzheimer biomarkers (Aβ42, tau, p-tau) typically normal or non-Alzheimer pattern → helps exclude AD

DLB: CSF α-synuclein assays emerging but not yet standard

FTD: executive dysfunction, behavioral dyscontrol; memory and visuospatial relatively spared

DLB: prominent visuospatial/executive deficits early; attention fluctuates; memory can be impaired but less so than in AD early

FTD — First-Line Management

No FDA-approved disease-modifying therapy for FTD.

Symptomatic management:

— SSRIs (e.g., sertraline, citalopram, trazodone) — first-line for behavioral disturbances

— Trazodone also useful for sleep disturbance and agitation

Important — what NOT to use:

Non-pharmacologic:

Next best step: When a patient with FTD has behavioral symptoms → start SSRI + caregiver education. Avoid cholinesterase inhibitors.

Behavioral symptoms (disinhibition, agitation, compulsions):

Apathy: no consistently effective pharmacotherapy; structured activities, caregiver education

Language variants (PPA): speech-language therapy for compensatory strategies

Cholinesterase inhibitors (donepezil, rivastigmine) → NOT effective in FTD; may worsen behavioral symptoms

Memantine → limited/no benefit in FTD

Antipsychotics: use with extreme caution; reserved for severe agitation/psychosis only when non-pharmacologic measures fail

Caregiver education and support (critical — high caregiver burnout)

Environmental modifications, structured routines

Physical exercise, occupational therapy

DLB — First-Line Management

Cognitive symptoms:

— DLB has a cholinergic deficit even greater than AD → often robust response

— Can also improve visual hallucinations and behavioral symptoms

Visual hallucinations:

— AVOID haloperidol, risperidone, olanzapine → severe neuroleptic sensitivity in DLB (rigidity, obtundation, NMS-like reaction, ↑ mortality)

Parkinsonism:

— Risk: can exacerbate hallucinations (balance motor benefit vs. psychosis)

— Avoid dopamine agonists (higher hallucination risk)

RBD:

Board pearl: DLB + antipsychotic use → life-threatening sensitivity reaction is a classic board trap. If psychosis must be treated, quetiapine or pimavanserin are safest.

Cholinesterase inhibitors (rivastigmine preferred, also donepezil) — first-line

Mild/non-distressing → reassurance, environmental modifications

Distressing → optimize cholinesterase inhibitor first

If antipsychotic needed → ONLY use quetiapine or pimavanserin (5-HT2A inverse agonist)

Carbidopa-levodopa at lowest effective dose — may help motor symptoms

Melatonin — first-line (safest)

Low-dose clonazepam — if melatonin insufficient

Bedroom safety measures (remove sharp objects, pad bed rails)

Treatment Algorithms and Decision Logic

Dementia with behavioral change → Is it FTD or Alzheimer's?

Dementia with hallucinations → Is it DLB or AD with psychosis?

Dementia with parkinsonism → DLB vs PDD vs PSP vs CBD:

Key management principle: In all dementias, non-pharmacologic interventions (caregiver support, structured environment, physical activity) form the foundation. Medications address specific symptom domains.

Next best step: Categorize the dementia by predominant feature (behavioral, language, hallucinations, motor) before selecting therapy.

Age <65, personality change first, executive dysfunction, frontal atrophy → FTD → SSRI

Age >65, memory loss first, hippocampal atrophy → AD → cholinesterase inhibitor ± memantine

Visual hallucinations + parkinsonism + fluctuating cognition + RBD → DLB → rivastigmine; DaT-SPECT if uncertain

Late-stage AD with hallucinations (no parkinsonism, no fluctuations) → AD psychosis → cautious low-dose antipsychotic

Dementia-first or within 1 year → DLB

PD for years → dementia later → PDD

Vertical gaze palsy + falls → PSP

Asymmetric rigidity + apraxia + alien limb → CBD

Special Populations — Elderly and Frail Patients

— Orthostatic hypotension from autonomic dysfunction → fall risk → check orthostatics at every visit

— Cholinesterase inhibitors can cause bradycardia, syncope → start low, titrate slowly

— Polypharmacy risk: review all medications — anticholinergics worsen cognition in DLB

— Young-onset behavioral change → may be initially treated as depression, bipolar disorder, or personality disorder

— Average diagnostic delay: 3–4 years

Board pearl: A 55-year-old with "new-onset psychiatric illness" (disinhibition, personality change, compulsive behavior) + normal memory → consider bvFTD before diagnosing a primary psychiatric disorder.

DLB patients are typically elderly (onset 60–80) and often frail:

FTD patients are often younger (45–65) but may be misdiagnosed with psychiatric illness:

Elderly FTD patients (onset >65) may overlap with AD clinically → MRI atrophy pattern + biomarkers help differentiate

Driving safety: both FTD and DLB impair judgment and visuospatial function early → formal driving evaluation should be recommended

Special Populations — Genetic FTD and Young Patients

FTD genetics (highest familial rate of any dementia):

— C9orf72 hexanucleotide repeat expansion → most common genetic cause of both FTD and ALS; FTD-ALS overlap

— MAPT (microtubule-associated protein tau) → tau-positive FTD

— GRN (progranulin) → TDP-43 positive FTD

When to offer genetic testing:

Implications:

Board pearl: FTD patient who develops fasciculations, muscle wasting, and dysarthria → C9orf72 expansion causing FTD-ALS overlap. This is a high-yield association.

~40% of FTD patients have a family history; ~10% are autosomal dominant

Key genes:

Strong family history of FTD, ALS, or both

Young onset (<50)

FTD-ALS phenotype (behavioral change + upper/lower motor neuron signs)

C9orf72 carriers may develop ALS → monitor for fasciculations, weakness, dysphagia

Genetic counseling essential before testing (implications for asymptomatic family members)

No disease-modifying therapy yet, but clinical trials are gene-specific

Complications of FTD and DLB

FTD complications:

DLB complications:

Board pearl: If a demented patient develops severe rigidity and altered mental status after receiving haloperidol → suspect DLB with neuroleptic sensitivity → stop antipsychotic immediately, supportive care.

Progressive loss of social functioning, legal/financial problems from disinhibition

Hyperorality → weight gain, choking risk

Motor neuron disease (ALS overlap) → respiratory failure, dysphagia → aspiration pneumonia

Complete dependence within 6–8 years from diagnosis on average

Caregiver burnout (behavioral symptoms are more distressing than memory loss)

Falls → hip fractures, subdural hematomas (parkinsonism + orthostatic hypotension + fluctuating attention)

Neuroleptic sensitivity syndrome → if inadvertently given typical or potent atypical antipsychotics → rigidity, fever, AMS, ↑ CK (resembles NMS) → can be fatal

Aspiration pneumonia (dysphagia from parkinsonism)

Depression and anxiety (up to 60%)

Rapid cognitive decline (faster than typical AD in many cases)

Emergencies and When to Escalate Care

Neuroleptic sensitivity crisis (DLB):

Acute behavioral crisis (FTD):

Aspiration pneumonia (both):

When to refer:

Triggered by antipsychotic exposure (even single dose)

Presentation: severe rigidity, ↑ temperature, autonomic instability, AMS

Management: immediately discontinue offending agent, IV fluids, cooling, ICU if unstable

Consider dantrolene if NMS-like features; supportive care

Severe agitation, aggression, or dangerous disinhibited behavior

First: ensure safety (patient, caregiver, staff)

Non-pharmacologic de-escalation first

If medication needed: low-dose trazodone or lorazepam (short-term); avoid antipsychotics if possible

Inpatient psychiatric or geriatric unit if not manageable outpatient

Dysphagia screening, speech therapy evaluation

If recurrent → consider PEG tube discussion (goals of care conversation)

Uncertain diagnosis → behavioral neurology/dementia specialist

Genetic FTD → genetic counseling

DLB with medication-refractory hallucinations → movement disorder specialist

All patients → palliative care involvement early for goals-of-care planning

Key Differentials — FTD vs Other Conditions

FTD vs Alzheimer's disease:

FTD vs primary psychiatric disorders:

FTD vs normal pressure hydrocephalus (NPH):

svPPA vs Alzheimer's anomia:

Board pearl: A 58-year-old diagnosed with "late-onset bipolar" who doesn't respond to mood stabilizers and has progressive personality change → reconsider FTD and obtain brain MRI.

FTD: younger onset, behavioral/personality change first, executive dysfunction, frontal/temporal atrophy, normal hippocampi

AD: older onset, episodic memory loss first, hippocampal atrophy, ↑ tau / ↓ Aβ42 in CSF

bvFTD can mimic late-onset depression, bipolar disorder, OCD, or schizophrenia

Clues favoring FTD: progressive course, lack of prior psychiatric history, neuroimaging showing frontal atrophy, poor response to psychiatric medications

NPH: triad of gait apraxia ("magnetic gait"), urinary incontinence, dementia → ventriculomegaly out of proportion to atrophy on CT/MRI

FTD: no gait abnormality early, prominent behavioral symptoms, cortical atrophy

svPPA: loss of semantic knowledge (doesn't know what a word means) + anterior temporal atrophy

AD anomia: retrieval deficit (knows the concept, can't find the word) + posterior temporal/parietal atrophy

Key Differentials — DLB vs Other Conditions

DLB vs Parkinson's disease dementia (PDD):

DLB vs Alzheimer's disease:

DLB vs delirium:

DLB vs progressive supranuclear palsy (PSP):

Next best step: In a patient with dementia + parkinsonism, ask about visual hallucinations, cognitive fluctuations, RBD, and falls — the pattern distinguishes DLB from PSP, CBD, and PDD.

Same pathology (cortical α-synuclein)

Distinction is clinical: 1-year rule (dementia within 1 year of motor symptoms = DLB; motor symptoms >1 year before dementia = PDD)

Both respond to cholinesterase inhibitors; both have neuroleptic sensitivity

DLB: visual hallucinations, parkinsonism, fluctuating cognition, RBD, preserved hippocampi, occipital hypometabolism

AD: memory-predominant, no parkinsonism early, hippocampal atrophy, temporoparietal hypometabolism

Fluctuating cognition in DLB can mimic delirium → key difference: delirium has an identifiable acute precipitant (infection, medications, metabolic), DLB fluctuations are chronic and recurrent without a trigger

PSP: vertical gaze palsy (especially downgaze), early falls backward, axial rigidity > limb rigidity, no hallucinations

DLB: visual hallucinations, fluctuating cognition, RBD

Preventive Care, Screening, and Follow-Up — FTD

Follow-up strategy:

Advance care planning:

Caregiver support:

Board pearl: FTD patients lose decision-making capacity early in the disease due to impaired judgment and insight → advance directives should be addressed at diagnosis.

No validated screening tool for FTD in general population

Early recognition depends on clinician awareness of behavioral red flags in young patients

Clinic visits every 3–6 months with caregiver present (patient lacks insight)

Track: behavioral symptoms (standardized scales), functional status (ADLs/IADLs), nutrition/weight, caregiver burden

Speech therapy referral for PPA variants

Swallowing assessment as disease progresses (especially FTD-ALS)

Discuss early — FTD patients lose capacity faster than AD patients due to impaired judgment

Address: healthcare proxy, financial power of attorney, driving cessation, living will

Genetic implications for family members if familial mutation identified

Connect to FTD-specific support groups (e.g., AFTD)

Screen caregivers for depression and burnout at each visit

Respite care resources

Preventive Care, Screening, and Follow-Up — DLB

Follow-up strategy:

Monitoring parameters for cholinesterase inhibitors:

Driving:

Long-term planning:

Board pearl: At every visit for DLB, check the medication list — even a well-meaning provider may have prescribed an anticholinergic or a contraindicated antipsychotic.

Visits every 3–6 months; monitor cognitive fluctuations, hallucinations, motor function, falls, autonomic symptoms

Medication reconciliation at every visit — avoid anticholinergics, antipsychotics (except quetiapine/pimavanserin), and first-generation antihistamines

Fall prevention: physical therapy, home safety evaluation, orthostatic hypotension management (compression stockings, midodrine, fludrocortisone if needed)

Heart rate (risk of bradycardia)

GI side effects (nausea, diarrhea)

Weight loss

DLB patients typically need to stop driving early — fluctuating attention + visuospatial dysfunction + parkinsonism = unsafe

Formal driving evaluation recommended

Goals-of-care conversations early (median survival from diagnosis: 5–8 years)

Palliative care referral when appropriate

Assess for depression at each visit — high prevalence in DLB

Ethical, Legal, and Patient Safety Considerations

— FTD patients often lack insight into their behavioral changes → may refuse evaluation or treatment

— Capacity assessment should be formalized when clinical decisions arise

— Early establishment of healthcare proxy and durable power of attorney is essential

— Both FTD and DLB impair driving ability (judgment, attention, visuospatial)

— Physician may have legal obligation to report unsafe drivers (varies by state/jurisdiction)

— When patient refuses to stop driving, involve DMV, family, and document discussion

— FTD patients (especially bvFTD with disinhibition and poor judgment) are vulnerable to financial abuse

— Recommend early involvement of legal counsel for estate planning

— Avoid chemical restraints with antipsychotics, especially in DLB

— CMS regulations: antipsychotic use in dementia must be justified and alternatives documented

— Aggressive behavior in FTD or DLB can endanger caregivers → safety planning is part of management

Board pearl: Prescribing haloperidol to a DLB patient for agitation represents a patient safety error — this is a testable medicolegal pitfall.

Capacity and consent:

Driving safety:

Financial exploitation:

Restraint and antipsychotic use:

Caregiver safety:

High-Yield Associations and Rapid-Fire Facts

FTD + ALS → C9orf72 repeat expansion (most common shared genetic cause)

Pick bodies (intraneuronal tau inclusions) → classic FTD histology ("Pick disease")

TDP-43 inclusions → most common FTD pathology overall (more than tau)

FTD: frontal/temporal atrophy with relative sparing of posterior cortex

DLB: Lewy bodies = intracytoplasmic α-synuclein inclusions in cortex

DLB: preserved hippocampi on MRI (unlike AD)

DLB: occipital hypometabolism on FDG-PET (unlike AD = temporoparietal)

DaT-SPECT ↓ uptake → supports DLB diagnosis (differentiates from AD)

Neuroleptic sensitivity → hallmark of DLB (not seen in AD or FTD)

Cholinesterase inhibitors: effective in DLB and PDD, NOT in FTD

SSRIs: first-line for behavioral FTD symptoms

Melatonin: first-line for REM sleep behavior disorder in DLB

FTD average survival: 6–8 years from symptom onset

DLB average survival: 5–8 years from diagnosis

Both FTD and DLB progress faster than typical AD

Board Question Stem Patterns

58M, personality change, disinhibition, compulsive eating, apathy, MRI: frontal atrophy → bvFTD → SSRI + caregiver education

72F, visual hallucinations (seeing children in her room), fluctuating alertness, shuffling gait, resting tremor → DLB → rivastigmine; avoid antipsychotics

Dementia patient given haloperidol → severe rigidity, AMS, fever → DLB with neuroleptic sensitivity → stop antipsychotic, supportive care

65M, dementia, parkinsonism, DaT-SPECT shows ↓ uptake bilaterally → DLB confirmed → cholinesterase inhibitor

55F, progressive non-fluent speech, effortful, agrammatic, left inferior frontal atrophy → nfvPPA (FTD variant) → speech therapy

60M, behavioral change + fasciculations + tongue atrophy + FH of ALS → FTD-ALS → test for C9orf72

Patient with DLB, distressing hallucinations despite rivastigmine → Add quetiapine or pimavanserin (NEVER haloperidol)

50M, "late-onset bipolar disorder" unresponsive to lithium, MRI: frontal atrophy → Reconsider bvFTD

Elderly patient, dementia, preserved hippocampi on MRI, occipital hypometabolism on PET → DLB, not AD

DLB patient with REM sleep behavior disorder → Melatonin first-line; clonazepam if refractory

One-Line Recap

Frontotemporal dementia presents with early behavioral/personality change (bvFTD) or progressive aphasia (PPA variants) in patients typically aged 45–65, with frontal/temporal atrophy on MRI, no benefit from cholinesterase inhibitors, managed with SSRIs for behavioral symptoms and caregiver support, while dementia with Lewy bodies is characterized by fluctuating cognition, well-formed visual hallucinations, spontaneous parkinsonism, and REM sleep behavior disorder in elderly patients, diagnosed with supportive DaT-SPECT showing ↓ dopaminergic uptake, treated with cholinesterase inhibitors (rivastigmine first-line) and melatonin for RBD, with the critical safety rule of avoiding typical and most atypical antipsychotics due to life-threatening neuroleptic sensitivity, and both conditions require early advance care planning, caregiver support, and referral to dementia specialists.