Subtype classification in primary progressive aphasia using operationalized criteria

Introduction: According to guidelines by Gorno-Tempini et al. (2011), primary progressive aphasia (PPA) is classified into a nonfluent (nfvPPA), a semantic (svPPA) and a logopenic variant (lvPPA). Not all patients can be assigned to one of these subtypes (10-41%; Utianski et al., 2019). However, the classification scheme does not provide clear guidance on when task performance is considered impaired. A few studies have proposed operationalized criteria for classifying the variants in English-speaking patients (e.g., Wicklund et al., 2014). The present study aimed to determine how well the classification system can be applied to German patients with PPA using criteria and norm data from established speech-/language batteries.

Methods: 35 native German-speaking patients (15 f) who met the core criteria for PPA, participated in the study. Assessment of speech-/language functions included subtests of the Aachen Aphasia Test and of the Nonverbal Semantics Test, as well as ratings of motor speech performance (Hierarchical Word Lists, Bogenhausen Dysarthria Scales). Definitions of impaired task performance were established for all variables, using published norms where available.

Results: 26 participants (74.3%) could be clearly assigned to one of the main PPA variants (25.7% PPA unclassifiable). 10 patients each met the clinical criteria for nfvPPA and svPPA (28.6% each). 6 patients (17.1%) were classified as lvPPA.

Conclusions: The criteria defined for performance impairment allowed for a PPA classification in the majority of cases. With 25.7%, the proportion of unclassifiable cases was within the range of previously published studies. This suggests the general feasibility of the approach.