Frontotemporal Degeneration With TDP-C At The Anterior Temporal Lobe.

The anatomical distribution of most neurodegenerative diseases displays considerable interindividual variations. In contrast, FTLD-TDP type C (TDP-C) shows a consistent predilection for the anterior temporal lobe (ATL). The relatively selective atrophy of ATL in TDP-C patients has highlighted the importance this region for complex cognitive and behavioral functions. This review includes observations on 28 TDP-C cases, 18 with semantic primary progressive aphasia and 10 with other syndromes. Longitudinal imaging allowed the delineation of progression trajectories. At post-mortem examination, the pathognomonic feature of TDP-C consisted of long, thick neurites found predominantly in superficial cortical layers. These neurites may represent dystrophic apical dendrites of Layer III and V pyramidal neurons that are known to play pivotal roles in complex cortical computations. Other types of FTLD-TDP, such as TDP-A and TDP-B are not associated with long dystrophic neurites in the cerebral cortex and do not display similar predilection patterns for ATL. Research is beginning to identify molecular, structural and immunological differences between pathologic TDP-43 in TDP-C versus TDP-A and B. Parallel investigations based on proteomics, somatic mutations, and GWAS are detecting molecular features that could conceivably mediate the selective vulnerability of ATL to TDP-C. Future work will focus on characterizing the distinctive features of the abnormal TDP-C neurites, the mechanisms of neurotoxicity, initial cellular targets within the ATL, trajectory of spread, and the nature of ATL-specific markers that modulate vulnerability to TDP-C. This article is protected by copyright. All rights reserved.