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 posterior cortical regions (temporal-occipital cortex and inferior parietal cortex) or subcortical structures (thalamus). In exceptional cases, TCSA occurs in association with anterior perisylvian lesions involving the left Broca's area and its adjoining regions. This unconventional brain-language relationship is intriguing, because it contradicts the tenets of traditional aphasiology. This article reviews the extant literature of TCSA cases with frontal lesions. In the second section, the author assesses new cases of TCSA 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 diagnostic 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 anterior hemispheric damage; and Group 3: four patients with anterior plus posterior hemispheric damage. Group comparisons failed to reveal statistically significant differences in demographic data and in nearly all WAB subtests. In Study 2, the pattern of language deficits was further investigated in three patients with TCSA and frontal lesions using cognitive neuropsychologycal investigations. Patients' performance is discussed taking into account recent advances in the functional anatomy of language processing systems and in the interindividual differences in the organisation of language networks.