The Relations Between Recognition Disorders of Familiar People and Other Unique Entities in Patients with Semantic and Behavioral Variants of Right Frontotemporal Degeneration: A Review of Single-Case Studies

Introduction: An association between recognition disorders of familiar people and other unique entities (UEs), such as famous buildings, is often reported in patients showing a right variant of frontotemporal degeneration (FTD). However, the clinical context and the modality-specific or semantic nature of these disorders have not been clarified by group studies of these patients. Aims of the study: Since a recent consensus statement from the International Working Group on FTD has called for the clarification of these issues, I undertook a review of single-case reports that explored this issue. This review allowed me to identify 11 papers reporting patients affected by a ‘semantic’ or a ‘behavioral’ variant of right FTD. Results: A detailed analysis of these patients suggested the following: (a) the incidence of this association is similar in the ‘semantic’ and ‘behavioral’ variants of right FTD; (b) this association is not systematically observed in patients with a ‘prosopagnosic’ form of the ‘semantic variant, whereas it is more frequent in the ‘properly semantic’ and in the ‘behavioral’ variants; and (c) in these two last groups of patients, the association between poor recognition of familiar people and of other unique entities is usually observed both in the verbal and in the pictorial modalities. Discussion: These results seem to indicate that recognition defects concerning both familiar people and other UEs are due to modality-specific and semantic disorders mainly affecting the right hemisphere’s pictorial knowledge.