Cognitive Profiles of Amyotrophic Lateral Sclerosis Differ in Resting-State Functional Connectivity: An fMRI Study

Autonomic dysfunction in neurodegenerative disease

In addition to their more studied cognitive and motor effects, neurodegenerative diseases are also associated with impairments in autonomic function - the regulation of involuntary physiological processes. These autonomic impairments manifest in different ways and at different stages depending on the specific disease. The neural networks responsible for autonomic regulation in the brain and body have characteristics that render them particularly susceptible to the prion-like spread of protein aggregation involved in neurodegenerative diseases. Specifically, the axons of these neurons - in both peripheral and central networks - are long and poorly myelinated axons, which make them preferential targets for pathological protein aggregation. Moreover, cortical regions integrating information about the internal state of the body are highly connected with other brain regions, which increases the likelihood of intersection with pathological pathways and prion-like spread of abnormal proteins. This leads to an autonomic 'signature' of dysfunction, characteristic of each neurodegenerative disease, that is linked to the affected networks and regions undergoing pathological aggregation.

Distinct Longitudinal Changes in EEG Measures Reflecting Functional Network Disruption in ALS Cognitive Phenotypes

Amyotrophic lateral sclerosis (ALS) is characterised primarily by motor system degeneration, with clinical evidence of cognitive and behavioural change in up to 50% of cases. We have shown previously that resting-state EEG captures dysfunction in motor and cognitive networks in ALS. However, the longitudinal development of these dysfunctional patterns, especially in networks linked with cognitive-behavioural functions, remains unclear. Longitudinal studies on non-motor changes in ALS are essential to further develop our understanding of disease progression, improve care and enhance the evaluation of new treatments. To address this gap, we examined 124 ALS individuals with 128-channel resting-state EEG recordings, categorised by cognitive impairment (ALSci, n = 25), behavioural impairment (ALSbi, n = 58), or non-impaired (ALSncbi, n = 53), with 12 participants meeting the criteria for both ALSci and ALSbi. Using linear mixed-effects models, we characterised the general and phenotype-specific longitudinal changes in brain network, and their association with cognitive performance, behaviour changes, fine motor symptoms, and survival. Our findings revealed a significant decline in [Formula: see text]-band spectral power over time in the temporal region along with increased [Formula: see text]-band power in the fronto-temporal region in the ALS group. ALSncbi participants showed widespread β-band synchrony decrease, while ALSci participants exhibited increased co-modulation correlated with verbal fluency decline. Longitudinal network-level changes were specific of ALS subgroups and correlated with motor, cognitive, and behavioural decline, as well as with survival. Spectral EEG measures can longitudinally track abnormal network patterns, serving as a candidate stratification tool for clinical trials and personalised treatments in ALS.

Spinal cord neurone loss and foot placement changes in a rat knock-in model of amyotrophic lateral sclerosis Type 8

Amyotrophic lateral sclerosis is an age-dependent cell type-selective degenerative disease. Genetic studies indicate that amyotrophic lateral sclerosis is part of a spectrum of disorders, ranging from spinal muscular atrophy to frontotemporal dementia that share common pathological mechanisms. Amyotrophic lateral sclerosis Type 8 is a familial disease caused by mis-sense mutations in VAPB. VAPB is localized to the cytoplasmic surface of the endoplasmic reticulum, where it serves as a docking point for cytoplasmic proteins and mediates inter-organelle interactions with the endoplasmic reticulum membrane. A gene knock-in model of amyotrophic lateral sclerosis Type 8 based on the VapBP56S mutation and VapB gene deletion has been generated in rats. These animals display a range of age-dependent phenotypes distinct from those previously reported in mouse models of amyotrophic lateral sclerosis Type 8. A loss of motor neurones in VapBP56S/+ and VapBP56S/P56S animals is indicated by a reduction in the number of large choline acetyl transferase-staining cells in the spinal cord. VapB-/- animals exhibit a relative increase in cytoplasmic TDP-43 levels compared with the nucleus, but no large protein aggregates. Concomitant with these spinal cord pathologies VapBP56S/+ , VapBP56S/P56S and VapB-/- animals exhibit age-dependent changes in paw placement and exerted pressures when traversing a CatWalk apparatus, consistent with a somatosensory dysfunction. Extramotor dysfunction is reported in half the cases of motor neurone disease, and this is the first indication of an associated sensory dysfunction in a rodent model of amyotrophic lateral sclerosis. Different rodent models may offer complementary experimental platforms with which to understand the human disease.

Potential of neuroimaging as a biomarker in amyotrophic lateral sclerosis: from structure to metabolism

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by motor neuron degeneration. The development of ALS involves metabolite alterations leading to tissue lesions in the nervous system. Recent advances in neuroimaging have significantly improved our understanding of the underlying pathophysiology of ALS, with findings supporting the corticoefferent axonal disease progression theory. Current studies on neuroimaging in ALS have demonstrated inconsistencies, which may be due to small sample sizes, insufficient statistical power, overinterpretation of findings, and the inherent heterogeneity of ALS. Deriving meaningful conclusions solely from individual imaging metrics in ALS studies remains challenging, and integrating multimodal imaging techniques shows promise for detecting valuable ALS biomarkers. In addition to giving an overview of the principles and techniques of different neuroimaging modalities, this review describes the potential of neuroimaging biomarkers in the diagnosis and prognostication of ALS. We provide an insight into the underlying pathology, highlighting the need for standardized protocols and multicenter collaborations to advance ALS research.

Alterations in regional homogeneity and functional connectivity in the cerebellum of patients with sporadic amyotrophic lateral sclerosis

OBJECTIVE

The purpose of this study was to examine the cerebellum's local and global functional characteristics in individuals with sporadic amyotrophic lateral sclerosis (sALS) and their correlation with clinical data.

METHODS

Resting-state functional magnetic resonance imaging was performed on 39 patients with sALS and on 23 healthy controls. Regional homogeneity (ReHo) in the cerebellum of all participants was analyzed, and the cerebellar regions with differences in ReHo were considered regions of interest (ROIs). In addition, the functional connectivity between the ROIs and other brain regions was analyzed.

RESULTS

In patients with sALS, ReHo increased in parts of the posterior cerebellar lobe. Then, the two regions with increased ReHo of the cerebellum were used as seeds, and further analysis revealed that the connectivity of the right cerebellum to the right medial superior frontal gyrus, left lingual gyrus (calcarine sulcus), left precentral gyrus, left supplementary motor area, and right Crus II was significantly increased.

CONCLUSION

The results demonstrate that resting-state functional connectivity changes in both motor and extra-motor regions of the cerebellum in patients with sALS, and that the cerebellum plays a pathophysiological role in sALS.

Understanding depression with amyotrophic lateral sclerosis: a short assessment of facts and perceptions

Depression with an average prevalence of 25-40% is a serious condition in amyotrophic lateral sclerosis (ALS) that can impact quality of life and survival of patients and caregiver burden, yet the underlying neurobiology is poorly understood. Preexisting depression has been associated with a higher risk of developing ALS, while people with ALS have a significantly higher risk of developing depression that can cause multiple complications. Depression may be a prodromal or subclinical symptom prior to motor involvement, although its relations with disease progression and impairment of quality of life are under discussion. Unfortunately, there are no studies existing that explore the pathogenic mechanisms of depression associated with the basic neurodegenerative process, and no specific neuroimaging data or postmortem findings for the combination of ALS and depression are currently available. Experience from other neurodegenerative processes suggests that depressive symptoms in ALS may be the consequence of cortical thinning in prefrontal regions and other cortex areas, disruption of mood-related brain networks, dysfunction of neurotransmitter systems, changing cortisol levels and other, hitherto unknown mechanisms. Treatment of both ALS and depression is a multidisciplinary task, depression generally being treated with a combination of antidepressant medication, physiotherapy, psychological and other interventions, while electroconvulsive therapy and deep brain stimulation might not be indicated in the majority of patients in view of their poor prognosis. Since compared to depression in other neurodegenerative diseases, our knowledge of its molecular basis in ALS is missing, multidisciplinary clinicopathological studies to elucidate the pathomechanism of depression in motor system disorders including ALS are urgently warranted.

Functional network dynamics revealed by EEG microstates reflect cognitive decline in amyotrophic lateral sclerosis

Recent electroencephalography (EEG) studies have shown that patterns of brain activity can be used to differentiate amyotrophic lateral sclerosis (ALS) and control groups. These differences can be interrogated by examining EEG microstates, which are distinct, reoccurring topographies of the scalp's electrical potentials. Quantifying the temporal properties of the four canonical microstates can elucidate how the dynamics of functional brain networks are altered in neurological conditions. Here we have analysed the properties of microstates to detect and quantify signal-based abnormality in ALS. High-density resting-state EEG data from 129 people with ALS and 78 HC were recorded longitudinally over a 24-month period. EEG topographies were extracted at instances of peak global field power to identify four microstate classes (labelled A-D) using K-means clustering. Each EEG topography was retrospectively associated with a microstate class based on global map dissimilarity. Changes in microstate properties over the course of the disease were assessed in people with ALS and compared with changes in clinical scores. The topographies of microstate classes remained consistent across participants and conditions. Differences were observed in coverage, occurrence, duration, and transition probabilities between ALS and control groups. The duration of microstate class B and coverage of microstate class C correlated with lower limb functional decline. The transition probabilities A to D, C to B and C to B also correlated with cognitive decline (total ECAS) in those with cognitive and behavioural impairments. Microstate characteristics also significantly changed over the course of the disease. Examining the temporal dependencies in the sequences of microstates revealed that the symmetry and stationarity of transition matrices were increased in people with late-stage ALS. These alterations in the properties of EEG microstates in ALS may reflect abnormalities within the sensory network and higher-order networks. Microstate properties could also prospectively predict symptom progression in those with cognitive impairments.

The Spectrum of Cognitive Dysfunction in Amyotrophic Lateral Sclerosis: An Update

Cognitive dysfunction is an important non-motor symptom in amyotrophic lateral sclerosis (ALS) that has a negative impact on survival and caregiver burden. It shows a wide spectrum ranging from subjective cognitive decline to frontotemporal dementia (FTD) and covers various cognitive domains, mainly executive/attention, language and verbal memory deficits. The frequency of cognitive impairment across the different ALS phenotypes ranges from 30% to 75%, with up to 45% fulfilling the criteria of FTD. Significant genetic, clinical, and pathological heterogeneity reflects deficits in various cognitive domains. Modern neuroimaging studies revealed frontotemporal degeneration and widespread involvement of limbic and white matter systems, with hypometabolism of the relevant areas. Morphological substrates are frontotemporal and hippocampal atrophy with synaptic loss, associated with TDP-43 and other co-pathologies, including tau deposition. Widespread functional disruptions of motor and extramotor networks, as well as of frontoparietal, frontostriatal and other connectivities, are markers for cognitive deficits in ALS. Cognitive reserve may moderate the effect of brain damage but is not protective against cognitive decline. The natural history of cognitive dysfunction in ALS and its relationship to FTD are not fully understood, although there is an overlap between the ALS variants and ALS-related frontotemporal syndromes, suggesting a differential vulnerability of motor and non-motor networks. An assessment of risks or the early detection of brain connectivity signatures before structural changes may be helpful in investigating the pathophysiological mechanisms of cognitive impairment in ALS, which might even serve as novel targets for effective disease-modifying therapies.

Frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) is one of the most common causes of early-onset dementia and presents with early social-emotional-behavioural and/or language changes that can be accompanied by a pyramidal or extrapyramidal motor disorder. About 20-25% of individuals with FTLD are estimated to carry a mutation associated with a specific FTLD pathology. The discovery of these mutations has led to important advances in potentially disease-modifying treatments that aim to slow progression or delay disease onset and has improved understanding of brain functioning. In both mutation carriers and those with sporadic disease, the most common underlying diagnoses are linked to neuronal and glial inclusions containing tau (FTLD-tau) or TDP-43 (FTLD-TDP), although 5-10% of patients may have inclusions containing proteins from the FUS-Ewing sarcoma-TAF15 family (FTLD-FET). Biomarkers definitively identifying specific pathological entities in sporadic disease have been elusive, which has impeded development of disease-modifying treatments. Nevertheless, disease-monitoring biofluid and imaging biomarkers are becoming increasingly sophisticated and are likely to serve as useful measures of treatment response during trials of disease-modifying treatments. Symptomatic trials using novel approaches such as transcranial direct current stimulation are also beginning to show promise.

Relationship between temporal dynamics of intrinsic brain activity and motor function remodeling in patients with acute BGIS

Background

patients with acute basal ganglia ischemic stroke (BGIS) show changes in local brain activity represented by the amplitude of low-frequency fluctuation (ALFF), but the time-varying characteristics of this local nerve activity are still unclear. This study aimed to investigate the abnormal time-varying local brain activity of patients with acute BGIS by using the ALFF method combined with the sliding-window approach.

Methods

In this study, 34 patients with acute BGIS with motor dysfunction and 44 healthy controls (HCs) were recruited. The dynamic amplitude of low-frequency fluctuation (dALFF) was employed to detect the alterations in brain activity induced by acute BGIS patients. A two-sample t-test comparison was performed to compare the dALFF value between the two groups and a Spearman correlation analysis was conducted to assess the relationship between the local brain activity abnormalities and clinical characteristics.

Results

Compared with HCs, the activity of neurons in the left temporal pole (TP), parahippocampal gyrus (paraHIP), middle occipital gyrus (MOG), dorsolateral superior frontal gyrus (SFGdl), medial cingulate cortex (MCC), right rectus, precuneus (PCu) and right cerebellum crus1 were significantly increased in patients with BGIS. In addition, we found that there was a negative correlation (r = -0.458, p = 0.007) between the dALFF value of the right rectus and the scores of the National Institutes of Health Stroke Scale (NIHSS), and a positive correlation (r = 0.488, 0.499, p < 0.05) with the scores of the Barthel Index scale (BI) and the Fugl Meyer motor function assessment (FMA). ROC analysis results demonstrated that the area under the curves (AUC) of the right rectus was 0.880, p<0.001.

Conclusion

The pattern of intrinsic brain activity variability was altered in patients with acute BGIS compared with HCs. The abnormal dALFF variability might be a potential tool to assess motor function in patients with acute BGIS and potentially inform the diagnosis of this disease.

Aberrant Multimodal Connectivity Pattern Involved in Default Mode Network and Limbic Network in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that progressively affects bulbar and limb function. Despite increasing recognition of the disease as a multinetwork disorder characterized by aberrant structural and functional connectivity, its integrity agreement and its predictive value for disease diagnosis remain to be fully elucidated. In this study, we recruited 37 ALS patients and 25 healthy controls (HCs). High-resolution 3D T1-weighted imaging and resting-state functional magnetic resonance imaging were, respectively, applied to construct multimodal connectomes. Following strict neuroimaging selection criteria, 18 ALS and 25 HC patients were included. Network-based statistic (NBS) and the coupling of grey matter structural-functional connectivity (SC-FC coupling) were performed. Finally, the support vector machine (SVM) method was used to distinguish the ALS patients from HCs. Results showed that, compared with HCs, ALS individuals exhibited a significantly increased functional network, predominantly encompassing the connections between the default mode network (DMN) and the frontoparietal network (FPN). The increased structural connections predominantly involved the inter-regional connections between the limbic network (LN) and the DMN, the salience/ventral attention network (SVAN) and FPN, while the decreased structural connections mainly involved connections between the LN and the subcortical network (SN). We also found increased SC-FC coupling in DMN-related brain regions and decoupling in LN-related brain regions in ALS, which could differentiate ALS from HCs with promising capacity based on SVM. Our findings highlight that DMN and LN may play a vital role in the pathophysiological mechanism of ALS. Additionally, SC-FC coupling could be regarded as a promising neuroimaging biomarker for ALS and shows important clinical potential for early recognition of ALS individuals.

Basal ganglia alterations in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) has traditionally been associated with brain damage involving the primary motor cortices and corticospinal tracts. In the recent decades, most of the research studies in ALS have focused on extra-motor and subcortical brain regions. The aim of these studies was to detect additional biomarkers able to support the diagnosis and to predict disease progression. The involvement of the frontal cortices, mainly in ALS cases who develop cognitive and/or behavioral impairment, is amply recognized in the field. A potential involvement of fronto-temporal and fronto-striatal connectivity changes in the disease evolution has also been reported. On this latter regard, there is still a shortage of studies which investigated basal ganglia (BG) alterations and their role in ALS clinical manifestation and progression. The present review aims to provide an overview on the magnetic resonance imaging studies reporting structural and/or functional BG alterations in patients with ALS, to clarify the role of BG damage in the disease clinical evolution and to propose potential future developments in this field.

Cognitive reserve protects ALS-typical cognitive domains: A longitudinal study

BACKGROUND AND OBJECTIVES

To determine whether cognitive reserve (CR) as measured by verbal intelligence quotient, educational length, and achievement protects amyotrophic lateral sclerosis (ALS) patients' verbal fluency, executive functioning, and memory against brain volume loss over a period of 12 months.

METHODS

This cohort study was completed between 2013 and 2016 with a follow-up duration of 12 months. ALS patients were recruited from two specialist out-patient clinics in Rostock and Magdeburg in Germany. Participants underwent cognitive testing and magnetic resonance imaging both at baseline and again after 12 months. The cognitive domains assessed included verbal memory in addition to executive functions such as verbal fluency, working memory, shifting and selective attention.

RESULTS

Thirty-eight ALS patients took part; 25 patients had no cognitive impairment (ALSni), and 13 were cognitively impaired (ALSci). On average, patients lost 294 mm3 in their superior frontal gyri, 225 mm3 in their orbitofrontal gyri, and 15.97 mm3 in their hippocampi over 12 months. There was strong evidence that CR protected letter fluency from further decline (Bayes factor [BF] >10) and moderate evidence that it supported learning effects in letter flexibility (BF >3). However, there is a lack of evidence supporting the notion that working memory, shifting, selective attention or verbal memory (BF = 1) are protected.

DISCUSSION

As CR is easily determined and protects ALS-specific cognitive domains over time, it should be regarded as a valuable predictive marker.