White matter tract damage in the behavioral variant of frontotemporal and corticobasal dementia syndromes.

Fernanda Tovar-Moll,Ivanei Edson Bramati,Jorge Moll,Ricardo De Oliveira-Souza,Roland Zahn,Michael Tierney,Alyson Cavanagh,Jordan Grafman,Karl Herholz

doi:10.1371/journal.pone.0102656

Abstract

The phenotypes of the behavioral variant of frontotemporal dementia and the corticobasal syndrome present considerable clinical and anatomical overlap. The respective patterns of white matter damage in these syndromes have not been directly contrasted. Beyond cortical involvement, damage to white matter pathways may critically contribute to both common and specific symptoms in both conditions. Here we assessed patients with the behavioral variant of frontotemporal dementia and corticobasal syndrome with whole-brain diffusion tensor imaging to identify the white matter networks underlying these pathologies. Twenty patients with the behavioral variant of frontotemporal dementia, 19 with corticobasal syndrome, and 15 healthy controls were enrolled in the study. Differences in tract integrity between (i) patients and controls, and (ii) patients with the corticobasal syndrome and the behavioral variant of frontotemporal dementia were assessed with whole brain tract-based spatial statistics and analyses of regions of interest. Behavioral variant of frontotemporal dementia and the corticobasal syndrome shared a pattern of bilaterally decreased white matter integrity in the anterior commissure, genu and body of the corpus callosum, corona radiata and in the long intrahemispheric association pathways. Patients with the behavioral variant of frontotemporal dementia showed greater damage to the uncinate fasciculus, genu of corpus callosum and forceps minor. In contrast, corticobasal syndrome patients had greater damage to the midbody of the corpus callosum and perirolandic corona radiata. Whereas several compact white matter pathways were damaged in both the behavioral variant of frontotemporal dementia and corticobasal syndrome, the distribution and degree of white matter damage differed between them. These findings concur with the distinctive clinical manifestations of these conditions and may improve the in vivo neuroanatomical and diagnostic characterization of these disorders.

Highlights

The nosology of the frontotemporal dementias has been debated since they were recognized as distinct from the dementia of Alzheimer’s disease on clinical, pathologic and genetic criteria [1]
Overall cognitive impairment did not statistically differ between the patient groups, but, as expected, psychopathology was more severe in behavioral variant of frontotemporal dementia (bvFTD) than in corticobasal syndrome (CBS) due to higher degrees of apathy, disinhibition and aberrant motor behaviors in bvFTD
Patients with CBS were significantly older than both controls and bvFTD patients, all differences remained statistically significant after covarying age in the relevant comparisons (Table 1)

Summary

Introduction

The nosology of the frontotemporal dementias has been debated since they were recognized as distinct from the dementia of Alzheimer’s disease on clinical, pathologic and genetic criteria [1]. Several studies have pointed to a specific cortical and subcortical pattern of atrophy in these neurodegenerative syndromes [4], the involvement of the white matter (WM), especially of its compact fiber tracts, needs to be further investigated. These syndromes usually show specific cortical and subcortical patterns of atrophy, they share regions of injury [4]. Assessing the extension and pattern of WM damage in CBS and bvFTD may contribute to a deeper understanding of the anatomical network and clinicoanatomical correlations in dementias pertaining to the Pick-frontotemporal complex

Methods

Results

Conclusion