About foreign accent syndrome

Abstract

The foreign accent syndrome (FAS) is a rare speech disorder characterized by the emergence of foreign accent. Until now, more than 100 cases of FAS have been reported and the impression of accent change is regarded to be the result of a combination of segmental deficits (i.e., phonetic distortions and phonemic paraphasias), and supra-segmental changes (i.e., stress, pitch, or rhythm variation known as disprosody). The most common etiology for FAS involves a stroke, followed by other causes. As for the anatomical substrate for FAS, most of the cases involve the lesion in the left frontal lobe, especially in the left pre-central gyrus. However, various lesions were reported to develop FAS, including the right hemisphere, the brain stem, and the cerebellum. Because of such a heterogeneous etiology and lesion location, it is controversial whether there is consistency or universality enough to treat it as a "syndrome".

Here, we reviewed the literature of FAS with a neurogenic origin to elucidate the characteristics and mechanism of FAS. As a result, we suggested that the Japanese FAS cases could be classified into two subtypes, i.e., the "English accent type" and the "Chinese/Korean accent type" depending on the types of speech error. In addition, the lesion network mapping analysis using the lesions of the previous FAS cases without aphasia suggested that the common disrupted functional network might be localized to the middle portion of the precentral gyrus, known as the larynx / phonation area.