Unexpected brain-language relationships in aphasia: Evidence from transcortical sensory aphasia associated with frontal lobe lesions

The syndrome of transcortical sensory aphasia (TCSA) is usually associated with extraperisylvian lesions of the left hemisphere that involve either po sterior cortical regions (temporal-occipital cortex and inferior parietal c ortex) or subcortical structures (thalamus). In exceptional cases, TCSA occ urs in association with anterior perisylvian lesions involving the left Bro ca's area and its adjoining regions. This unconventional brain-language rel ationship is intriguing, because it contradicts the tenets of traditional a phasiology. This article reviews the extant literature of TCSA cases with f rontal lesions. In the second section, the author assesses new cases of TCS A with frontal lesions in a two-part study. In Study 1 the issue of whether the language profile of TCSA with frontal lesions fits well with the diagn ostic criteria of TCSA was investigated by comparing the language scores of the Western Aphasia Battery (WAB) in three groups of TCSA: Group 1: eight patients with posterior hemispheric damage; Group 2: seven patients with an terior hemispheric damage; and Group 3: four patients with anterior plus po sterior hemispheric damage. Group comparisons failed to reveal statisticall y significant differences in demographic data and in nearly all WAB subtest s. In Study 2, the pattern of language deficits was further investigated in three patients with TCSA and frontal lesions using cognitive neuropsycholo gycal investigations. Patients' performance is discussed taking into accoun t recent advances in the functional anatomy of language processing systems and in the interindividual differences in the organisation of language netw orks.