Neurodegeneration of brain networks in the amyotrophic lateral sclerosis–frontotemporal lobar degeneration (ALS–FTLD) continuum: evidence from MRI and MEG studies

Abstract

Brain imaging techniques, especially those based on magnetic resonance imaging (MRI) and magnetoencephalography (MEG), have been increasingly applied to study multiple large-scale distributed brain networks in healthy people and neurological patients. With regard to neurodegenerative disorders, amyotrophic lateral sclerosis (ALS), clinically characterized by the predominant loss of motor neurons and progressive weakness of voluntary muscles, and frontotemporal lobar degeneration (FTLD), the second most common early-onset dementia, have been proven to share several clinical, neuropathological, genetic, and neuroimaging features. Specifically, overlapping or mildly diverging brain structural and functional connectivity patterns, mostly evaluated by advanced MRI techniques-such as diffusion tensor and resting-state functional MRI (DT-MRI, RS-fMRI)-have been described comparing several ALS and FTLD populations. Moreover, though only pioneering, promising clues on connectivity patterns in the ALS-FTLD continuum may derive from MEG investigations. We will herein overview the current state of knowledge concerning the most advanced neuroimaging findings associated with clinical and genetic patterns of neurodegeneration across the ALS-FTLD continuum, underlying the possibility that network-based approaches may be useful to develop novel biomarkers of disease for adequately designing and monitoring more appropriate treatment strategies.

Classification of amyotrophic lateral sclerosis by brain volume, connectivity, and network dynamics

“…Our results indicated a reduction in resting state functional connectivity within the DMN, as well as between the DMN and both the SMN and the FPN, in ALS as compared with HC. Specifically, the observed reduction was primarily related to the functional connectivity between the PCC and all other brain regions, supporting findings of previous investigations (for an overview of functional connectivity reductions in DMN see Chiò et al, 2014; Trojsi, Sorrentino, Sorrentino, & Tedeschi, 2018; Turner et al, 2012; for specific reductions of PCC functional connectivity see Bueno et al, 2018; Bueno et al, 2019; Matías‐Guiu et al, 2016; Mohammadi et al, 2009). The PCC and the DMN in general underly self‐referential and episodic memory processing (for an overview see Menon, 2011).…”

Brain functional networks become more connected as amyotrophic lateral sclerosis progresses: a source level magnetoencephalographic study

“…In a large, fMRI based study, Schulthess et al revealed increased functional connectivity, with a topography linked to the spreading of the pTDP-43 pathology ( Schulthess et al, 2016 ). The reported evidence might be compatible with the idea that hyper connectedness might relate to neuronal damage in ALS ( Trojsi et al, 2017 ).…”

Mindfulness Meditation Is Related to Long-Lasting Changes in Hippocampal Functional Topology during Resting State: A Magnetoencephalography Study

“…As expected, we did not find difference in the global metrics comparing meditators to controls. Global metrics capture widespread reorganization in the brain activity, and those are found to be altered typically in processes that cause diffuse damage to the brain, such as neurological diseases [32, 56–58]. Our results showed that the connectedness or the brain network (Leaf fraction), its scale-freeness (Degree divergence), and its resiliency versus targeted attacks (Tree hierarchy) are not affected by VM.…”