The numerical taxonomy of acute and chronic aphasic syndromes

Summary Acute (n=179) and chronic (n=113) aphasic populations were studied by numerical taxonomy. Clustering based on the objective and standardized language scores of the WAB yielded significant differences for the acute and chronic groups. The overlap between objective clustering and clinical typology, also based on test scores, was sufficient to allow us to interpret the data in clinical terms. The decrease of the global cluster and of Wernicke's cluster and the appearance of new clusters, such as the mixed global-Broca's, the partially recovered Broca's — mild anomic, and the recovered Wernicke's-semantic groups, and the further dichotomy of afferent and efferent conduction clusters were observed. Recovering patients are often reclassified as anomics; this changes the anomic clusters, loading one with patients who fall into the recovered category. Chronic clusters appeared more distinct with less overlap. The trends in both data sets were investigated by principal components analysis. This showed that all language scores contributed to the first component in both populations fairly evenly. Therefore, the main contribution to the first component was severity (the combination of scores). Comprehension and fluency were the major contributors to the second root in both populations, indicating the diagnostic significance of these parameters. Repetition featured more prominently in the second root of the acute, than the chronic population.