Retrosplenial cortex (BA 29) volumes in behavioral variant frontotemporal dementia and alzheimer's disease

Background: The retrosplenial cortex (RSC) is a crucial transit region between the hippocampus and cingulate cortex and has been implicated in spatial navigation and memory. Importantly, RSC atrophy is a predilection site of Alzheimer's (AD) pathology, but there have been no studies assessing structural changes in the RSC in behavioral variant frontotemporal dementia (bvFTD). Methods: A manual tracing method was used to calculate regional RSC volume in MRI scans from patients with bvFTD (n = 15) and AD (n = 15), as well as age- and sex-matched controls (n = 15). Results: RSC volumes were significantly reduced in the AD (p < 0.001), but not the bvFTD cohort (p > 0.1) compared to age-matched controls. RSC volumes discriminated bvFTD from AD in over 90% of the cases. Conclusion: These findings provide further evidence that RSC atrophy is specific to AD, which might explain the commonly observed spatial disorientation in this patient group.