Generalization and maintenance of treatment gains in primary progressive aphasia (PPA): a systematic review

Background: Cognitive-linguistic treatments and interventions targeting communication have been developed within the context of primary progressive aphasia (PPA), however knowledge about the scope of generalization and maintenance of therapy gains considering PPA subtypes remains scarce and awaits systematic investigation. Aims: To analyse the effects of semantic therapy on generalization and maintenance of treatment outcomes in individuals with PPA, considering its different subtypes. Methods & Procedures: Central, PubMed, Medline, Web of Knowledge and Scopus were used to retrieve articles of interest. A total of 25 non-randomized studies published between 2000 and 2016 met the eligibility criteria and therefore were included in this study. Main Contribution: This systematic review provides evidence-based information for clinical practice in PPA. Generalization and maintenance effects post-treatment for each PPA variant are analysed and discussed. Several factors are described as important to maximize the scope for generalization and maintenance of treatment gains. Conclusions & Implications: Generalization is particularly hard to achieve in the semantic variant, as in the face of degraded semantic knowledge learning is rigid and context dependent. In contrast, non-fluent and logopenic variants offer better scope for generalization. Maintenance patterns do not seem to be influenced by PPA subtype, but rather by other factors such as continued practice, treatment length and frequency of sessions. In the future, clinicians should consider the PPA subtype when planning the treatment protocol.