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Add comprehensive articles on Vascular Dementia and Wallerian Degeneration

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- Created a detailed article for Vascular Dementia covering key facts, terminology, imaging findings, differential diagnoses, pathology, clinical issues, and diagnostic checklist.
- Developed an extensive article on Wallerian Degeneration including key facts, terminology, imaging features, differential diagnoses, pathology, clinical issues, and diagnostic checklist.
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---
title: "Primary Progressive Aphasia"
docid: "5dca11fe-b5ee-404c-b22e-4008b7571844"
breadcrumbs:
- "Nuclear Medicine"
- "Central Nervous System"
- "Neurodegeneration"
- "Primary Progressive Aphasia"
---
# KEY FACTS
- ## Terminology
- Group of heterogeneous neurodegenerative disorders characterized by prominent language and word-finding difficulties
- This includes logopenic-variant primary progressive aphasia (lvPPA), semantic-variant primary progressive aphasia (svPPA), and nonfluent/agrammatic-variant primary progressive aphasia (nfvPPA)
- ## Imaging
- Hypometabolism within critical brain areas on F-18 FDG PET
- lvPPA: Left precuneus and temporoparietal region
- svPPA: Left anterior temporal lobe
- nfvPPA: Left inferior frontal lobe and insula
- ## Top Differential Diagnoses
- Alzheimer disease (AD)
- Frontotemporal dementia (FTD) (behavioral variant)
- Vascular dementia
- ## Pathology
- lvPPA is within AD spectrum
- svPPA and nfvPPA are within FTD spectrum
- ## Clinical Issues
- Progressive language and word-finding difficulties
- lvPPA: Impaired single-word retrieval, impaired repetition of sentences/phrases
- svPPA: Impaired single-word comprehension/naming, object knowledge
- nfvPPA: Agrammatism in language production, apraxia of speech
- No cure exists for primary progressive aphasias
- Patients with lvPPA may be eligible for amyloid-binding therapies
- Engagement of social services and supportive care can aid with patients, families, and caregivers
# TERMINOLOGY
- ## Abbreviations
- Primary progressive aphasia (PPA)
- ## Definitions
- Group of heterogeneous neurodegenerative disorders characterized by prominent language and word-finding difficulties
- Classically grouped, given their language-predominant symptoms, though they are separate pathologic processes
# IMAGING
- ## General Features
- ### Best diagnostic clue
- Hypometabolism within critical brain areas on F-18 FDG PET
- Classically involves left cerebral hemisphere, given majority of people are left language dominant
- MR will demonstrate volume loss in affected areas in late-stage disease
- ### Location
- Logopenic-variant PPA (lvPPA): Involves left precuneus and left temporoparietal region
- Semantic-variant PPA (svPPA): Involves left anterior temporal lobe
- Nonfluent/agrammatic PPA (nfvPPA): Involves left inferior frontal lobe and left insula
- ## Imaging Recommendations
- ### Best imaging tool
- F-18 FDG PET
- Prominent, asymmetric hypometabolism within affected left cerebral hemispheric structures
- MR
- Initially used to assess for alternative etiologies that could cause symptoms (i.e., neoplasm, infarct, infection, trauma)
- Qualitative and quantitative volume assessment can be performed to identify areas of neurodegeneration in late-stage disease
- Amyloid PET
- Positive in majority of lvPPA cases
- Negative in svPPA and nfvPPA
- Interpreted as "scant to few" (negative) or "moderate to frequent" (positive) β-amyloid neuritic plaques (Aβs)
- ### Protocol advice
- MR
- DWI/ADC, T2/FLAIR, and SWI/GRE performed to assess for alternative etiologies (vascular insults, neoplasms, infection)
- 3D T1 MR to assess for subtle volume loss; can perform quantitative volumetric analysis
- F-18 FDG PET
- Patient preparation
- Patient should fast, stop IV fluids containing dextrose, and stop parenteral feeding for 4-6 hours; blood sugar should be < 150 mg/dL
- Place patient in quiet, dimly lit room for 30 minutes prior to examination
- Radiopharmaceutical: F-18 FDG
- Dose: 7-10 mCi (260-370 MBq)
- Dosimetry: Bladder is critical organ
- Image acquisition: 45-60 minutes post injection
- Amyloid PET
- No patient preparation necessary
- Radiopharmaceutical: F-18 florbetapir (or other amyloid-based tracers)
- Dose: ~ 10 mCi (370 MBq) for F-18 florbetapir
- Dosimetry: Gallbladder, bowel, intestines are critical organs
- Image acquisition: 30-50 minutes post injection for F-18 florbetapir
# DIFFERENTIAL DIAGNOSIS
- [Alzheimer Disease (Classic Type)](/document/alzheimer-disease/2aad3ac4-44fd-43e5-8e50-a86987483af3)
- Most common dementia
- Memory impairment is prominent symptom
- Language difficulties typically reserved for advanced disease
- F-18 FDG PET demonstrates more symmetric temporoparietal hypometabolism
- Positive on amyloid PET
- [Frontotemporal Dementia (Behavioral Variant)](/document/frontotemporal-dementia/9f9eda8c-7e3c-4292-9861-4b8abc2c6474)
- Classically presents with behavioral and personality changes
- F-18 FDG PET demonstrates symmetric anterior frontal and temporal hypometabolism
- MR demonstrates corresponding atrophy in frontotemporal lobes
- [Vascular Dementia](/document/multiinfarct-dementia/3823c4d4-5e98-46da-a717-892fef54b382)
- 2nd most common cause of dementia
- MR shows scattered infarcts of varying ages, typically in deep gray nuclei or within vascular territory
- Left middle cerebral artery (MCA) territory infarcts can affect areas involved in language and communication
- ## Limbic-Predominant Age-Related TDP-43 Encephalopathy (LATE)
- Recently described neurodegenerative disease that classically occurs in older adult patients (> 80 years old)
- Typically does not present with language difficulties
- F-18 FDG PET demonstrates hypometabolism within anterior temporal lobes and insula, usually bilateral
# PATHOLOGY
- ## General Features
- Undetermined cause, likely secondary to combination of genetic, lifestyle, and environmental factors
- ## Staging, Grading, & Classification
- Diagnostic criteria
- lvPPA
- Core criteria: Impaired single-word retrieval, impaired repetition of sentences/phrases
- Other features: Speech errors in spontaneous speech, spared single-word comprehension and object knowledge, spared motor speech, absence of frank agrammatism
- svPPA
- Core criteria: Impaired confrontation naming, impaired single-word comprehension
- Other features: Impaired object knowledge, surface dyslexia/dysgraphia, spared repetition, spared speech production
- nfvPPA
- Core criteria: Agrammatism in language production, effortful/halting speech with speech sound errors and distortions (apraxia)
- Other features: Impaired comprehension of syntactically complex sentences, spared single-word comprehension, spared object knowledge
- ## Gross Pathologic & Surgical Features
- Late-stage disease demonstrates prominent volume loss within affected regions
- Increased sulcal volume within left cerebral hemisphere
- lvPPA is believed to be within Alzheimer disease (AD) spectrum
- Associated with Aβ and τ neurofibrillary tangles (τ-NFT) (80% of cases)
- svPPA and nfvPPA are believed to be within frontotemporal dementia spectrum
- svPPA is associated with TDP-43
- nfvPPA is associated with 4-repeat τ isoform (4R-τ)
# CLINICAL ISSUES
- ## Presentation
- ### Most common signs/symptoms
- Progressive word-finding and language difficulties
- lvPPA: Impaired single-word retrieval, impaired repetition of sentences/phrases
- svPPA: Impaired single-word comprehension/naming, object knowledge
- nfvPPA: Agrammatism in language production, apraxia of speech
- Delayed diagnosis can occur given lack of apparent memory loss or behavioral symptoms
- ### Other signs/symptoms
- Late-stage disease will have memory loss/dementia
- Psychiatric issues (i.e., depression, anxiety) may be present
- ## Natural History & Prognosis
- Progressive language and word-finding difficulties
- End-stage disease presents with near-complete inability to communicate
- Memory loss is less evident in early disease and can present later in disease course
- Significant distinction from AD, where memory loss is primary symptom and language difficulties are seen later in disease course
- No prominent behavioral, anger, or dysexecutive symptoms
- Distinct from behavioral-variant frontotemporal dementia, where behavioral issues are evident early in disease course
- ## Treatment
- No cure exists for PPAs
- lvPPA patients may be eligible for amyloid-targeting therapy
- No disease-modifying therapies exist for svPPA or nfvPPA
- Speech therapy and rehabilitation can aid in improving communication with caregivers/family
- Engagement of social services and supportive care can aid with patients, families, and caregivers
# DIAGNOSTIC CHECKLIST
- ## Image Interpretation Pearls
- F-18 FDG PET
- Asymmetric hypometabolism within left temporoparietal region (lvPPA), left temporal pole (svPPA), or left inferior frontal lobe and insula (nfvPPA)
- MR
- Asymmetric left cerebral hemispheric volume loss within affected areas
- ## Reporting Tips
- Identify asymmetric hypometabolism if present
- Describe key brain areas that are affected to convey specificity of underlying disease process
- Exclude alternative etiologies and identify normal areas of metabolism on F-18 FDG PET
- Consider additional imaging, such as amyloid PET, for suspected lvPPA, which would be beneficial for assessing candidacy for amyloid-targeting therapies
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