Functional Connectivity Changes in Behavioral, Semantic, and Nonfluent Variants of Frontotemporal Dementia

Abstract

Frontotemporal dementia (FTD) affects behavior, language, and personality. This study aims to explore functional connectivity changes in three FTD variants: behavioral (bvFTD), semantic (svPPA), and nonfluent variant (nfvPPA). Seventy-six patients diagnosed with FTD by international criteria and thirty-two controls were investigated. Functional connectivity from resting functional magnetic resonance imaging (fMRI) was estimated for the whole brain. Two types of analysis were done: network basic statistic and topological measures by graph theory. Several hubs in the limbic system and basal ganglia were compromised in the behavioral variant apart from frontal networks. Nonfluent variants showed a major disconnection with respect to the behavioral variant in operculum and parietal inferior. The global efficiency had lower coefficients in nonfluent variants than behavioral variants and controls. Our results support an extensive disconnection among frontal, limbic, basal ganglia, and parietal hubs.

Qualitative and Quantitative Analyses of Brain ¹⁸Fluoro-Deoxy-Glucose Positron Emission Tomography in Primary Progressive Aphasia

“…Table 2, at QL in 9 (patients 1-9) of the 18 (50%) cases, the HA were in the temporoparietal cortex and in limbic structures, in most cases bilaterally and predominantly in the left hemisphere, with the highest negative z score value mainly in the temporoparietal and temporal lateral cortex at QN. At QL in 6 of 18 (33.3%) patients (10)(11)(12)(13)(14)(15), the HA were in the frontoparietal and frontotemporal regions with the highest negative z score value at QN, in the prefrontal and temporal regions. However, in the remaining 3 of 18 (16.7%) patients (16)(17)(18) in whom the HA at QL appeared widespread and irregular in both cortical hemispheres, QN localized the highest z score negative value in the prefrontal and parietal areas bilaterally.…”

“…Globally, the combined use of QL and QN evidenced that the two procedures concordantly permitted to achieve a correct diagnosis in 8 of 18 (44.4%) cases, as lvPPA in 4 cases (5)(6)(7)(8) and as nfvPPA in 4 cases (12)(13)(14)(15). In the other 10 of 18 (55.6%) patients, only QN could be useful for the correct diagnosis, as lvPPA in 5 cases (1,2,3,11,16) and as nfvPPA in the remaining 5 cases (4,9,10,17,18).…”

“…However, MRI has low sensitivity in the early phases, in particular in nfvPPA and lvPPA [9,10], and only after disease progression, when atrophy affects larger areas, the diagnosis could be supported [11]. Moreover, the suggested use of functional MRI, despite of being able to define language network changes [11][12][13], is still limited.…”

Análisis de conectividad estructural cerebral en demencia frontotemporal, a partir de imágenes de resonancia de difusión

“…El análisis de grafos ha revelado características importantes de la organización del cerebro, como una arquitectura eficiente de "pequeño mundo" (que combina un alto nivel de segregación con un alto nivel de eficiencia global) y regiones de red altamente conectadas, denominadas "hubs" [19]. En relación con la DFT, la mayoría de los estudios han utilizado un acercamiento desde la conectividad funcional a través de la modalidad de resonancia magnética funcional para estudiar posibles alteraciones en las conexiones cerebrales de estos pacientes [19][20][21][22]. Esta técnica pretende mostrar redes cerebrales funcionalmente conectadas midiendo cambios sincronizados y dependientes del tiempo en los niveles de oxigenación de la sangre que perfunde el cerebro.…”

“…Dichas investigaciones previas han reportado alteraciones topológicas de las redes, como reducción en la eficiencia global y en la conectividad interregional entre las regiones frontal, temporal, occipital, y subcortical, en pacientes de bvDFT en comparación con los controles [19,21]. En cuanto a las variantes lingüísticas, los estudios respaldan una disminución de la conectividad en comparación con los controles, con afectaciones marcadas en el lóbulo temporal y una amplia gama de regiones corticales y en regiones de asociación visual y auditiva [20]. De esta manera el deterioro progresivo de los dominios cognitivos podría ser un reflejo de las alteraciones en la integridad funcional en los sistemas cerebrales.…”