Primary Progressive Aphasia and its variants

What Primary Progressive Aphasia is

Primary Progressive Aphasia is a clinical syndrome characterised by the insidious onset and gradual progression of language difficulty as the dominant feature, with relative preservation of other cognitive domains in the early stages. The condition was first described by Marsel Mesulam in the 1980s and is now classified within the Frontotemporal Dementia spectrum (ICD-11 6D83), although the Logopenic Variant is most commonly an atypical Alzheimer's Disease.

The three variants (Gorno-Tempini 2011 criteria)

Non-fluent Variant PPA

Effortful, halting speech with simplified grammar (agrammatism) and impaired articulation (apraxia of speech). Comprehension of single words is preserved; comprehension of complex sentences is often impaired. Reading aloud may be effortful but word meaning is usually retained.

Imaging shows left perisylvian (frontal operculum and anterior insula) atrophy. Underlying pathology is most commonly tau or TDP-43.

Semantic Variant PPA

Fluent but increasingly empty speech, with prominent naming difficulty and loss of word meaning. People may use "thing" or "that" or general placeholders. Single-word comprehension is impaired. Object recognition can be affected.

Imaging shows left anterior temporal lobe atrophy. Underlying pathology is TDP-43 in most cases.

Logopenic Variant PPA

Word-finding pauses with impaired sentence repetition. Speech is non-fluent because of frequent pauses but grammar is preserved. Phonological errors (saying a similar-sounding wrong word) are characteristic.

Imaging shows left temporo-parietal atrophy. Underlying pathology is most commonly Alzheimer's Disease.

How they are diagnosed

• Careful history with examples of the language difficulty;
• Structured cognitive testing (Addenbrooke's Cognitive Examination) with attention to fluency, naming, repetition and reading;
• Formal Speech and Language Therapy assessment using standardised language batteries;
• Structural Magnetic Resonance Imaging looking for asymmetric or focal atrophy;
• FDG-PET where Magnetic Resonance Imaging is inconclusive (NICE NG97 1.2.23);
• Cerebrospinal Fluid biomarkers or amyloid PET may help where Logopenic Variant is suspected and Alzheimer's confirmation matters for trials.

Treatment

No medication slows PPA. Treatment is centred on Speech and Language Therapy, which has the strongest evidence base for any intervention in PPA:

• Word-retrieval strategies and lexical retraining (more effective in early disease);
• Augmentative and alternative communication aids in later disease;
• Family training in supportive communication;
• Group therapy and PPA support groups for peer connection.

Cholinesterase Inhibitors are sometimes tried in Logopenic Variant PPA given its Alzheimer's Pathology, with mixed evidence. They are not recommended for Non-Fluent or Semantic Variant.

Practical considerations

The communication difficulty in PPA carries specific practical implications:

• Written communication, photographs and pre-prepared cards become valuable supports;
• Restaurants, banks and other services may need to be aware to allow time and use simple language;
• Driving may be affected by the cognitive load of speech production rather than visuospatial skill; DVLA review applies;
• Decision-making about work, finance and care often requires more time and structured communication.

Family communication

Practical tips for family communication:

• Allow time; do not finish sentences unless invited;
• Use single-message statements;
• Avoid open questions; use closed options;
• Use a writing pad alongside speech;
• Engage Speech and Language Therapy as early as possible.

Where The Dementia Service fits in

PPA is often under-recognised because cognitive scores can be in the normal range despite substantial language difficulty. The Dementia Service can provide structured assessment with onward Speech and Language Therapy and FDG-PET referral where indicated.