Frontotemporal Lobar Degenerations

Slide 1 · Frontotemporal Lobar

Degenerations

Anatomic patterns · Protein pathology · Clinicopathologic interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Distinguish frontotemporal lobar degeneration (FTLD) from the clinical label frontotemporal dementia (FTD).

Compare FTLD-tau and FTLD-TDP using protein biology, genes and inclusion morphology.

Recognize characteristic changes of Pick disease and the limitations of clinical subtype prediction.

Integrate protein pathology with clinical presentation and anatomical vulnerability.

Slide 3 · FTLD defines a heterogeneous pathologic group

Anatomic target

Focal degeneration predominantly affecting frontal and/or temporal lobes.

Clinical expression

Early changes in behavior, personality or language are common.

Protein classification

Abnormal tau or TDP-43 inclusions define the major pathologic patterns.

Slide 4 · FTLD and FTD are related, not identical

FTLD: Pathology

FTD: Clinical syndrome

Describes the pattern of lobar neurodegeneration.

Specifies the tissue lesion and proteinopathy.

Definitive classification relies on neuropathology.

Used in clinical settings for frontotemporal dementias.

Describes behavioral and language presentations.

Does not uniquely predict the deposited protein.

Slide 5 · Focal degeneration gives clinical specificity

Simplified lobar schematic—not anatomical imaging

Frontal

Temporal

Frontal-predominant damage: Disturbances of personality and behavior.

Temporal language-network involvement: Progressive aphasic manifestations.

Regional involvement may be mixed and becomes broader with progression.

Slide 6 · Behavioral change can be the initial signal

Alterations in personality and behavior may precede prominent memory loss.

Behavior-led presentations are clinically recognizable, but not pathologically uniform.

Progression can add language deficits and more generalized cognitive decline.

Slide 7 · Language deficits can dominate presentation

Aphasia may precede major memory disturbance in frontotemporal dementia.

Language-led and behavior-led forms overlap as the disease evolves.

Clinical language presentation by itself does not establish tau versus TDP-43 pathology.

Slide 8 · Two common initial clinical emphases

Behavior-dominant

Language-dominant

Early personality alteration.

Early behavioral disturbance.

Language impairment may emerge later.

Early progressive aphasia.

Personality/behavior change may follow.

Global deficits eventually develop.

Slide 9 · Clinical syndromes show overlapping features

Not rigid categories

The textbook recognizes several variants organized by dominant symptoms.

Cross-domain evolution

Behavioral and aphasic symptoms are not mutually exclusive.

Protein heterogeneity

A clinical variant cannot be equated with one aggregate type.

Slide 10 · FTLD versus Alzheimer disease: Presenting emphasis

Feature

FTLD (typical emphasis)

Alzheimer disease (typical emphasis)

Early prominent change

Personality, behavior, language

Forgetfulness and memory disturbance

Later disease

Global dementia may develop

Language, skilled actions and other domains deteriorate

Definitive pathology

Proteinopathy and distribution

Amyloid-β plaques with tau tangles

Slide 11 · Focal impairment can progress to global dementia

Focal frontal/temporal degeneration

Selective network dysfunction

Dominant early syndrome

Behavior or aphasia

Progressive cortical involvement

Additional cognitive domains

Global dementia

Advanced clinical stage

An initially focal syndrome does not imply a persistently restricted disease.

Slide 12 · Motor dysfunction does not exclude FTLD

Primary presentation

Possible additional findings

Personality, behavior or language changes typically dominate.

Early memory impairment need not be the chief problem.

Some patients develop extrapyramidal motor symptoms.

Certain subtypes show nigral degeneration at autopsy.

Slide 13 · Early-onset dementia: An important context

Younger onset

FTLD is among the more common causes of early-onset dementia.

Textbook comparison

FTLD and AD occur with similar frequency below age 65.

Interpretation

This textbook statement is population/context dependent; It is not a universal risk estimate.

Slide 14 · Why clinical examination cannot provide full classification

Can suggest

Cannot establish on its own

A frontal or temporal functional syndrome.

A pattern of dominant behavioral or aphasic deficits.

Probable neurodegenerative disease.

The molecular protein of the inclusions.

The definitive neuropathologic subtype.

Whether tau- or TDP-43-related histology is present.

Slide 15 · FTLD classification centers on abnormal proteins

FTLD-tau

Cytoplasmic tau inclusions in affected neurons; May include Pick bodies.

FTLD-TDP

Abnormal TDP-43-containing inclusions in neuronal compartments and processes.

Other inclusion proteins

FUS is also linked to FTLD in the chapter’s neurodegeneration table; Not the main focus here.

Slide 16 · Three levels of description must stay separate

Clinical phenotype

Behavior-led or aphasic syndrome

Neuroanatomic lesion

Frontal/temporal lobar atrophy

Molecular pathology

Tau, TDP-43, or another protein

A clinical syndrome is not equivalent to a protein-defined diagnosis.

Slide 17 · Sporadic and heritable FTLD coexist

Sporadic disease

Inherited forms

Most FTLD cases are sporadic.

Absence of family history does not exclude the diagnosis.

Genetic examples include MAPT, C9orf72, TARDBP and GRN.

Familial forms illuminate how proteins become dysregulated.

Slide 18 · Shared histopathologic response to degeneration

Neuronal injury

Loss in involved cortical regions

Reactive tissue response

Gliosis in affected areas

Abnormal inclusions

Protein-dependent cellular pathology

The atrophy seen grossly reflects loss of neuronal tissue, accompanied by gliosis.

Slide 19 · Topography links pathology to phenotype

Simplified lobar schematic—not anatomical imaging

Frontal

Temporal

Atrophy is variable in severity and distribution among FTLD forms.

Clinically dominant deficits often correspond to the affected lobar territories.

Distribution alone does not prove the molecular subtype.

Slide 20 · FTLD-tau is a tau accumulation disorder

Core lesion

Variable inclusion pattern

Progressive neuronal loss and reactive gliosis in involved cortex.

Cytoplasmic neuronal inclusions containing tau.

Some inclusions resemble Alzheimer-type tangles.

Others are rounded and smooth: Pick bodies.

Slide 21 · Physiologic tau is associated with microtubules

Tau protein

Microtubule-associated protein

Microtubule binding

Function regulated in part by phosphorylation

Neuronal function

Normal cytoskeletal support

Binding becomes less favorable as tau phosphorylation increases.

Slide 22 · Phosphorylation changes tau behavior

Increased tau phosphorylation

Lower microtubule-binding affinity

More unbound tau

Greater propensity to aggregate

Tau accumulation

Cytoplasmic protein inclusions

A biochemical association, not a fully resolved explanation of neurotoxicity.

Slide 23 · Tau isoform balance is biologically relevant

Alternative mRNA splicing

MAPT transcripts encode multiple tau isoforms.

Physiologic balance

Relative abundance of isoforms contributes to normal neuronal function.

Disease association

An altered isoform ratio may encourage aggregation and dysfunction.

Slide 24 · MAPT mutations provide a genetic route to FTLD-tau

MAPT mutation

Tau coding/splice regulation affected

Abnormal tau behavior

Altered binding or isoform balance

Inclusions

Tau aggregates and progressive degeneration

Sporadic FTLD-tau also occurs without a detected inherited MAPT cause.

Slide 25 · MAPT mutation mechanism I: Altered tau protein

Molecular event

Pathologic interpretation

Missense mutations may alter tau phosphorylation behavior.

This shifts tau away from microtubule binding.

Aggregation becomes more favorable.

Insoluble inclusions occur in vulnerable neurons.

Slide 26 · MAPT mutation mechanism II: Altered RNA splicing

Molecular event

Pathologic interpretation

Some variants affect splice-related RNA structure.

Many relevant variants are intronic.

Relative tau isoform expression changes.

Abnormal isoform balance can provoke dysfunction and aggregation.

Slide 27 · Tau toxicity may involve two mechanisms

Loss of physiologic function

Aggregated tau is less available for its normal microtubule-associated role.

Toxic gain of function

Abnormally phosphorylated aggregated tau may itself impair neurons.

Open mechanistic issue

The relative contributions to neuronal death remain unresolved.

Slide 28 · Do not equate tau aggregation with a proven pathway

Observed

Abnormal tau phosphorylation and inclusion formation

Plausible contributors

Functional depletion plus toxic aggregates

Unresolved

How aggregated tau produces neuronal death

Separate morphologic association from a demonstrated causal step.

Slide 29 · FTLD-tau and Alzheimer disease are not synonymous

Feature

FTLD-tau

Alzheimer disease

Defining accumulated proteins

Tau predominant; no defining amyloid-β plaque pathology

Amyloid-β deposition plus tau tangles

Common clinical emphasis

Behavior and/or language first

Memory disturbance early

Shared finding

Tau-related neuronal inclusions

Tau-related neuronal inclusions

Slide 30 · Microscopy in FTLD-tau: Three central findings

Neuronal loss in the affected cortical regions.

Reactive gliosis accompanying loss of cortical neurons.

Tau-immunoreactive fibrillary cytoplasmic inclusions in residual neurons.

Some subtypes also contain abnormal tau in glial cells.

Slide 31 · Glial inclusions broaden the cellular substrate

Neurons

Cortical neuronal inclusions dominate the core description.

Glia

Some FTLD-tau forms contain additional glial tau inclusions.

Diagnostic point

Protein immunoreactivity must be interpreted with cell type and anatomical distribution.

Slide 32 · Pick disease is a distinct FTLD-tau subtype

Gross feature

Severe frontal and temporal atrophy, often asymmetric.

Cellular feature

Swollen Pick cells and characteristic cytoplasmic Pick bodies.

Protein feature

Pick bodies are tau-positive neuronal inclusions.

Slide 33 · Pick disease may cause knife-edge gyral atrophy

Simplified lobar schematic—not anatomical imaging

Frontal

Temporal

Atrophy may be especially severe in the frontal and temporal lobes.

Gyri can become wafer thin, producing a “knife-edge” appearance.

Frequently asymmetric atrophy helps characterize the gross pattern.

Slide 34 · Pick disease shows a selective lobar distribution

Typically affected

Relatively spared

Frontal lobes.

Temporal lobes.

Asymmetry is frequent.

Posterior two-thirds of the superior temporal gyrus.

Parietal and occipital lobes usually minimally involved.

Slide 35 · Pick disease: Cortical loss favors superficial layers

Conceptual cortical laminae, superficial → deep

Layer I

Layer II

Layer III

Layer IV

Layer V

Layer VI

Predominant neuronal loss in outer three layers

Neuronal loss is especially marked in the outer three cortical layers.

Laminar selectivity is a microscopic counterpart of cortical thinning.

Layer emphasis contributes to the pathologic pattern but is not sufficient alone.

Slide 36 · Pick cells: Swollen residual neurons

Some surviving cortical neurons have a chromatolysis-like swelling.

These swollen neurons as Pick cells.

Pick cells should be distinguished from the intracellular Pick body inclusions.

Slide 37 · Pick bodies are rounded cytoplasmic inclusions

Simplified cellular schematic—not a tissue section

Pick bodies are round to oval and filamentous.

They occur within neuronal cytoplasm.

They are not synonymous with neuronal swelling (Pick cells).

Slide 38 · Pick bodies: Complementary staining evidence

Silver impregnation

Tau immunohistochemistry

Pick bodies stain intensely with appropriate silver stains.

The inclusion is round to oval and cytoplasmic.

Pick bodies are immunoreactive for tau.

Tau labeling confirms the principal deposited protein.

Slide 39 · Not every FTLD-tau inclusion is a Pick body

Pattern

Typical description

Interpretation

Tangle-like

Fibrillary tau inclusion resembling AD-type tangles

Tau-positive, not necessarily Pick disease

Pick-body type

Rounded or oval neuronal cytoplasmic inclusion

Defines the characteristic Pick disease morphology

Glial tau inclusion

Tau-positive cytoplasmic lesion in glia

Found in some FTLD-tau subtypes

Slide 40 · FTLD-TDP is a distinct proteinopathy

Protein

Disease lesion

TDP-43: Transactive response DNA-binding protein 43.

An RNA-binding protein normally enriched in the nucleus.

TDP-43-containing inclusions replace the tau-dominant profile.

Associated with neuronal loss, gliosis and lobar atrophy.

Slide 41 · Physiologic TDP-43 supports RNA processing

Nuclear TDP-43

Normally distributed diffusely in nucleus

RNA processing

RNA-binding activities

Cellular stress context

Participates in stress-granule biology

Abnormal redistribution and inclusion formation characterize FTLD-TDP.

Slide 42 · Stress granules are RNA–protein assemblies

Cellular stress

Translation may be halted

Granule assembly

RNA and protein complexes form

Transient sequestration

Free mRNAs are retained during stress

TDP-43 contributes to stress-granule biology; The source does not define a simple granule-to-inclusion mechanism.

Slide 43 · Normal TDP-43 distribution is predominantly nuclear

Simplified cellular schematic—not a tissue section

Normal immunoreactivity is diffuse within the neuronal nucleus.

Physiologic nuclear localization is the reference against which disease is recognized.

A nuclear signal is different from an abnormal intranuclear inclusion.

Slide 44 · Cytoplasmic TDP-43 inclusions are abnormal

Simplified cellular schematic—not a tissue section

TDP-43 appears as discrete neuronal cytoplasmic inclusions.

Affected cells often lose normal diffuse nuclear TDP-43 immunoreactivity.

Morphology reflects protein redistribution/aggregation, not simply overexpression.

Slide 45 · TDP-43 may form intranuclear inclusions

Simplified cellular schematic—not a tissue section

Some neurons contain TDP-43-positive intranuclear inclusions.

This is an inclusion, rather than the normal diffuse nuclear staining pattern.

Needle-like intranuclear inclusions correlate strongly with GRN mutations.

Slide 46 · TDP-43 inclusions also occur in neuronal processes

Simplified cellular schematic—not a tissue section

Abnormal TDP-43 aggregates may form thread-like neuronal process inclusions.

The pathologic deposits are not restricted to neuronal cell bodies.

Immunohistochemistry clarifies protein composition and cellular location.

Slide 47 · TDP-43 inclusions undergo disease-associated modification

Phosphorylation

Aggregated TDP-43 in FTLD-TDP is phosphorylated.

Ubiquitination

The same inclusions can be ubiquitinated.

Pathology readout

Abnormal protein localization, morphology and modification support tissue interpretation.

Slide 48 · FTLD-TDP: Regional distribution of inclusions

Simplified lobar schematic—not anatomical imaging

Frontal

Temporal

Inclusions are frequent in frontal and temporal cortices.

The striatum and hippocampal dentate gyrus may also be affected.

Regional neuronal loss and gliosis coexist with the inclusions.

Slide 49 · Gross morphology alone does not sort tau from TDP

Feature

FTLD-tau

FTLD-TDP

Gross change

Frontal/temporal atrophy of variable severity

Similar variable frontal/temporal atrophy

Tissue response

Neuronal loss and reactive gliosis

Neuronal loss and reactive gliosis

Key separator

Tau-positive inclusions

TDP-43-positive inclusions

Slide 50 · Inherited FTLD-TDP highlights three genetic routes

C9orf72

Repeat expansion

TARDBP

TDP-43 sequence

GRN

Progranulin deficiency

Different inherited abnormalities converge on TDP-43 protein pathology.

Slide 51 · C9orf72: Hexanucleotide repeat expansion

Variant class

Expanded hexanucleotide repeat in the 5′ region of C9orf72.

Clinical spectrum

Associated with FTLD-TDP and amyotrophic lateral sclerosis.

Molecular uncertainty

The precise path to TDP-43 aggregation is not fully defined.

Slide 52 · C9orf72 connects FTLD and ALS

FTLD expression

ALS relationship

Behavioral or language-led cognitive syndrome.

Frontal and temporal neurodegeneration.

The same expanded repeat can be found across the FTLD–ALS spectrum.

Clinical syndrome alone does not establish an exclusive molecular diagnosis.

Slide 53 · C9orf72 inflammation hypothesis remains incomplete

C9orf72 expansion

Gene dosage/function may be altered

Possible neuroinflammatory role

Haploinsufficiency implicated by evidence

TDP-43 inclusions

Mechanistic link remains uncertain

Do not present the inflammatory route as a proven complete causal chain.

Slide 54 · TARDBP mutations directly involve the inclusion protein

Gene product

Disease connection

TARDBP encodes TDP-43 itself.

Pathogenic variants are relatively uncommon in familial FTLD-TDP.

Variants can also appear in inherited ALS.

Functional dysregulation and aggregate toxicity may both contribute.

Slide 55 · TDP-43 dysfunction: Loss and gain of function

Loss of normal activity

Disrupted nuclear RNA-related functions may contribute to neuronal injury.

Toxic protein accumulation

Aberrant aggregate species may exert additional cellular toxicity.

Interpretive caution

The source describes both mechanisms as potentially contributory, not quantified causes.

Slide 56 · GRN mutations cause progranulin deficiency

GRN loss-of-function mutation

Reduced progranulin production

Haploinsufficiency

Progranulin insufficiency

FTLD-TDP phenotype

Inflammatory dysregulation and TDP-43 pathology

The route from inflammation to aggregation has unresolved steps.

Slide 57 · Progranulin links FTLD-TDP with brain inflammation

Protein

Progranulin is a secreted protein.

Biological role

Implicated in regulating inflammation in the brain.

FTLD context

Reduced progranulin is associated with a proinflammatory state and TDP-43 pathology.

Slide 58 · GRN-associated FTLD differs from C9orf72-associated FTLD

GRN

C9orf72 / TARDBP

Progranulin haploinsufficiency.

Robbins does not link GRN mutations with ALS.

Genetic abnormalities may be associated with both FTLD and ALS.

Shared molecular spectrum does not mean identical clinical presentation.

Slide 59 · GRN mutations: Needle-like intranuclear inclusions

Simplified cellular schematic—not a tissue section

Needle-like TDP-43-positive intranuclear inclusions show a strong association with GRN mutation.

Morphologic association supports, but does not independently replace, molecular testing.

Other FTLD-TDP inclusions may coexist.

Slide 60 · Genetic pathways: What is altered?

Gene

Protein / variant

Major teaching implication

MAPT

Tau; missense or splicing changes

FTLD-tau protein dysregulation

C9orf72

Expanded hexanucleotide repeat

FTLD-TDP–ALS disease spectrum

TARDBP

TDP-43 protein

FTLD-TDP; also familial ALS

GRN

Progranulin; loss of function

FTLD-TDP, inflammation link; not ALS in source

Slide 61 · FTLD-tau versus FTLD-TDP: Tissue distinctions

Criterion

FTLD-tau

FTLD-TDP

Accumulating protein

Tau

TDP-43

Mutation examples

MAPT

C9orf72, TARDBP, GRN

Typical cellular site

Neuronal cytoplasmic; some glial

Neuronal cytoplasm, nuclei, processes

Specific association

Pick bodies in Pick disease

Needle-like nuclear inclusions with GRN

Common lesion

Cortical neuronal loss and gliosis

Cortical neuronal loss and gliosis

Slide 62 · Clinicopathologic interpretation uses complementary axes

Clinical syndrome

Behavioral / aphasic predominance

Topographic atrophy

Frontal and/or temporal distribution

Neuropathologic protein

Tau versus TDP-43

Protein subtype cannot be deduced securely from the first two axes.

Slide 63 · Applied case: Behavior-led presentation

An adult develops progressive personality change and disturbed behavior. Memory loss is less conspicuous early. Over time, language and global cognition decline.

What anatomic pattern is suggested—and what cannot be inferred?

Hypothetical teaching vignette

Slide 64 · Case analysis: Behavior-led presentation

Most compatible syndrome

Frontotemporal dementia clinical phenotype.

Suggested pathology

FTLD is a plausible anatomic pathologic correlate.

Important limit

Neither tau nor TDP-43 inclusions can be inferred reliably from presentation alone.

Slide 65 · Applied case: A distinctive neuropathologic lesion

Autopsy demonstrates severe, asymmetric frontal and temporal atrophy, superficial cortical neuronal loss, ballooned neurons and rounded tau-positive neuronal cytoplasmic inclusions.

Which FTLD-tau subtype best fits this pattern?

Hypothetical teaching vignette

Slide 66 · Case analysis: Pick disease

Gross clue

Marked asymmetric frontal/temporal atrophy.

Cellular clues

Pick cells plus round tau-positive Pick bodies.

Diagnosis

Pick disease, a morphologically distinctive FTLD-tau form.

Slide 67 · Applied case: TDP-43 pathology and genetics

A degenerating frontal cortex contains TDP-43-positive cytoplasmic inclusions, nuclear immunoreactivity loss and numerous needle-like neuronal intranuclear inclusions.

Which gene association should be considered?

Hypothetical teaching vignette

Slide 68 · Case analysis: Intranuclear TDP-43 inclusions

Protein family

The pathologic aggregate is TDP-43, not tau.

Clue

Needle-like neuronal intranuclear inclusions correlate with GRN mutation.

Interpretive limit

A morphologic association should not be treated as standalone genetic proof.

Slide 69 · Critical interpretation: Avoid three category errors

Do not use “FTD” (clinical) and “FTLD” (pathologic) as fully interchangeable labels.

Do not assign a tau/TDP subtype from behavioral versus aphasic presentation alone.

Do not treat a pathogenesis hypothesis (for example inflammation → aggregation) as fully established.

Do not interpret simplified teaching diagrams as diagnostic microscopy.

Slide 70 · Integrated high-yield synthesis

Anatomy → syndrome

Frontal/temporal neuronal loss explains early behavioral and aphasic deficits.

Protein → subtype

Tau and TDP-43 inclusions define major pathologic patterns.

Genetics → mechanism

MAPT, C9orf72, TARDBP and GRN help explain distinct molecular routes.

Slide 71 · References and source limitations

Primary textbook

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. 2026. Chapter 28: The Central Nervous System; Frontotemporal Lobar Degenerations, pp. 1164–1166.

Source qualification

The lecture is derived from the supplied topic extraction and adjacent textbook content. The available Markdown contains interleaved two-column passages; no original chapter PDF or licensed textbook plates were supplied. Conceptual illustrations are native editable schematics, not patient/pathology images.