Frontiers in Psychology (Apr 2015)
Rapid recovery from aphasia after infarction of Wernicke’s area
Abstract
Introduction Wernicke’s area (the posterior superior temporal gyrus) is a critical brain region for language. However language function does recover over time to varying extents in many patients with damage to Wernicke’s area (Kertesz et al., 1993). In this study, we characterized the nature and time course of language recovery in detail in two patients with acute infarction of Wernicke’s area. We focused on the first three months post stroke, and especially on the first two weeks, since previous studies have shown that the greatest gains take place during this period (Pedersen et al., 1995; Basso, 1992). We relied primarily on quantitative analysis of conversational speech samples, as an efficient means of probing multiple language domains in the clinically and logistically challenging acute/subacute period (Holland et al., 1985). Methods Two patients with acute ischemic infarction of Wernicke’s area participated in the study after providing informed consent: VG, an 85-year-old female retired nurse, and JI, a 76-year-old male security guard. Conversational speech samples were elicited every day from 2 days to 16 days post-stroke, and also at 1 month and approximately 3 months. A brief aphasia battery was also administered at a subset of time points. Five minutes of connected speech per time point were transcribed using ELAN (Wittenburg et al., 2006), and coded with CHAT (MacWhinney et al., 2011). Multiple speech/language measures were derived from the coded samples using a custom MATLAB program. Patterns of change over time were investigated with principal components analysis and correlations between language measures and log-transformed time post stroke. Results Both patients presented acutely with Wernicke’s aphasia, but demonstrated rapid recovery. In both patients, almost all speech/language measures improved essentially in parallel with a logarithmic time course, with increases in words per minute (Fig. 1a,b), mean length of utterance, frequency of embeddings (Fig. 1c,d), frequency of bound morphemes, and aphasia battery scores for confrontation naming, sentence comprehension, repetition, and reading aloud. Both patients showed decreases in the frequency of phonemic errors and neologisms (Fig. 1e,f), semantic errors and lexical access impairments, fillers, false starts, and retracings (Fig. 1g,h). Morphosyntactic errors reduced in frequency only in patient VG and not in JI. Single word comprehension improved only in patient JI and not in VG. The patients showed opposite changes in the ratio of open to closed class words, reflecting resolution of agrammatic features in VG, and less empty speech in JI (Fig. 1i,j). Neither patient met criteria for Wernicke’s aphasia for more than a few days, both evolving quickly to conduction aphasia. Discussion Quantitative analysis of connected speech samples and language testing following infarction of Wernicke’s area revealed rapid improvements in almost all speech/language measures, spanning phonological, syntactic and semantic domains. The greatest changes occurred early, with recovery slowing over time, and the data were well fit by logarithmic recovery curves. Despite the importance of Wernicke’s area, the rapidity and extent of recovery observed suggest that other brain regions can be rapidly recruited to support many of the functions of Wernicke’s area (Weiller et al., 1995).
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