Diffusion tensor MRI changes in gray structures of the frontal-subcortical circuits in amyotrophic lateral sclerosis

MRI biomarkers and neuropsychological assessments of hippocampal and parahippocampal regions affected by ALS: A systematic review

BACKGROUND AND OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a progressive motor and extra-motor neurodegenerative disease. This systematic review aimed to examine MRI biomarkers and neuropsychological assessments of the hippocampal and parahippocampal regions in patients with ALS.

METHODS

A systematic review was conducted in the Scopus and PubMed databases for studies published between January 2000 and July 2023. The inclusion criteria were (1) MRI studies to assess hippocampal and parahippocampal regions in ALS patients, and (2) studies reporting neuropsychological data in patients with ALS.

RESULTS

A total of 46 studies were included. Structural MRI revealed hippocampal atrophy, especially in ALS-FTD, involving specific subregions (CA1, dentate gyrus). Disease progression and genetic factors impacted atrophy patterns. Diffusion tensor imaging (DTI) showed increased mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and decreased fractional anisotropy (FA) in the hippocampal tracts and adjacent regions, indicating loss of neuronal and white matter integrity. Functional MRI (fMRI) revealed reduced functional connectivity (FC) between the hippocampus, parahippocampus, and other regions, suggesting disrupted networks. Perfusion MRI showed hypoperfusion in parahippocampal gyri. Magnetic resonance spectroscopy (MRS) found changes in the hippocampus, indicating neuronal loss. Neuropsychological tests showed associations between poorer memory and hippocampal atrophy or connectivity changes. CA1-2, dentate gyrus, and fimbria atrophy were correlated with worse memory.

CONCLUSIONS

The hippocampus and the connected regions are involved in ALS. Hippocampal atrophy disrupted connectivity and metabolite changes correlate with cognitive and functional decline. Specific subregions can be particularly affected. The hippocampus is a potential biomarker for disease monitoring and prognosis.

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.

Non-Motor Symptoms of Amyotrophic Lateral Sclerosis: A Multi-Faceted Disorder

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive degeneration of motor pathways. A growing body of evidence from recent years suggests that ALS results in a wide range of non-motor symptoms as well, which can have a significant impact on patients' quality of life. These symptoms could also, in turn, provide useful information as biomarkers for disease progression, and can shed insight on ALS mechanisms. Here we aim to review a wide range of non-motor symptoms of ALS, with emphasis on their importance to research and clinical treatment of patients.

Effectiveness of sorting tests for detecting cognitive decline in older adults with dementia and other common neurodegenerative disorders: A meta-analysis

The demand for simple, accurate and time-efficient screens to detect cognitive decline at point-of-care is increasing. Sorting tests are often used to detect the 'executive' deficits that are commonly associated with behavioural-variant frontotemporal dementia (bvFTD), but their potential for use as a cognitive screen with older adults is unclear. A comprehensive search of four databases identified 142 studies that compared the sorting test performance (e.g. WCST, DKEFS-ST) of adults with a common neurodegenerative disorder (e.g. Alzheimer's disease, vascular dementia, bvFTD, Parkinson's disease) and cognitively-healthy controls. Hedges' g effect sizes were used to compare the groups on five common test scores (Category, Total, Perseveration, Error, Description). The neurodegenerative disorders (combined) showed large deficits on all scores (g -1.0 to -1.3), with dementia (combined subtypes) performing more poorly (g -1.2 to -2.1), although bvFTD was not disproportionately worse than the other dementias. Overall, sorting tests detected the cognitive impairments caused by common neurodegenerative disorders, especially dementia, highlighting their potential suitability as a cognitive screen for older adults.

An overview of screening instruments for cognition and behavior in patients with ALS: selecting the appropriate tool for clinical practice

Objective: Patients with amyotrophic lateral sclerosis (ALS) not only show motor deficits, but may also have cognitive and/or behavioral impairments. Recognizing these impairments is crucial as they are associated with lower quality of life, shorter survival, and increased caregiver burden. Therefore, ALS-specific neuropsychological screening instruments have been developed that can account for motor and speech difficulties. This study provides an overview and comparison of these screeners. Methods: A systematic review was conducted using Medline and Embase. Articles describing cognitive/behavioral screening instruments assessed in ALS patients were included. Screening instruments were compared on multiple factors, such as domains, adaptability, required time, and validation. Results: We included 99 articles, reporting on nine cognitive screeners (i.e. ACE-R, ALS-BCA, ALS-CBS, ECAS, FAB, MMSE, MoCA, PSSFTS, and UCSF-SB), of which five ALS-specific. Furthermore, eight behavioral screeners (i.e. ALS-FTD-Q, AES, BBI, DAS, FBI, FrSBe, MiND-B, and NPI) were reported on, of which three ALS-specific. Conclusion: Considering the broad range of cognitive domains, adaptability, and satisfying validity, the ALS-CBS and ECAS appear to be the most suitable screeners to detect cognitive and behavioral changes in ALS. The BBI appears to be the best option to screen for behavioral changes in ALS, since all relevant domains are assessed, motor-related problems are considered, and has a satisfactory validity. The MiND-B and ALS-FTD-Q are promising as well. In general, all screening instruments would benefit from additional validation research to gain greater insights into test characteristics and to aid clinicians in selecting screening tools for use in clinical practice.

Microstructural correlates of Edinburgh Cognitive and Behavioural ALS Screen (ECAS) changes in amyotrophic lateral sclerosis

Edinburgh Cognitive and Behavioural ALS Screen (ECAS) was designed for testing patients with amyotrophic lateral sclerosis (ALS), a multi-system neurodegenerative disease characterized by progressive physical disability. In this study, we aim to explore the potential brain microstructural substrates associated with performance on ECAS in the early stages of ALS, using a whole-brain tract-based spatial statistics diffusion tensor imaging approach. Thirty-six non-demented ALS patients, assessed using ECAS, and 35 age-, sex- and education-matched healthy controls underwent magnetic resonance imaging at 3 Tesla. The ALS patients showed decreased fractional anisotropy (FA) in the cortico-spinal tracts and corpus callosum (CC) and significant association between verbal fluency score, among ALS-specific ECAS scores, and FA measures in several long association fiber tracts in the frontal, temporal and parietal lobes. Furthermore, the ALS non-specific total score was inversely related to axial diffusivity (AD) in the mediodorsal nucleus of the thalamus, with more extended areas of correlation in the CC, when considering only the memory subscore. Our results point towards microstructural degeneration across motor and extra-motor areas in ALS, underlining that alterations in verbal fluency performances may be related to impairment of frontotemporal connectivity, while alterations of memory may be associated with damage of thalamocortical circuits.

Frontostriatal grey matter atrophy in amyotrophic lateral sclerosis A visual rating study

Amyotrophic lateral sclerosis (ALS) is characterised by frontostriatal grey matter changes similar to those in frontotemporal dementia (FTD). However, these changes are usually detected at a group level, and simple visual magnetic resonance imaging (MRI) cortical atrophy scales may further elucidate frontostriatal changes in ALS.

The Clinical and Radiological Spectrum of Hippocampal Pathology in Amyotrophic Lateral Sclerosis

Hippocampal pathology in Amyotrophic Lateral Sclerosis (ALS) remains surprisingly under recognized despite compelling evidence from neuropsychology, neuroimaging and neuropathology studies. Hippocampal dysfunction contributes significantly to the clinical heterogeneity of ALS and requires structure-specific cognitive and neuroimaging tools for accurate in vivo evaluation. Recent imaging studies have generated unprecedented insights into the presymptomatic and longitudinal processes affecting this structure and have contributed to the characterisation of both focal and network-level changes. Emerging neuropsychology data suggest that memory deficits in ALS may be independent from executive dysfunction. In the era of precision medicine, where the development of individualized care strategies and patient stratification for clinical trials are key priorities, the comprehensive review of hippocampal dysfunction in ALS is particularly timely.

Brain signature of mild stages of cognitive and behavioral impairment in amyotrophic lateral sclerosis

We aimed to assess the brain signature of cognitive and behavioral impairment in C9orf72-negative non-demented ALS patients. The study included 50 amyotrophic lateral sclerosis (ALS) patients (out of 75 initially recruited) and 38 healthy controls. High-resolution T1-weighted and spin-echo diffusion tensor images were acquired in a 3T MRI scanner. The multi atlas-based analysis protocol and the FreeSurfer tool were employed for gray matter assessment, and fiber tractography for white matter evaluation. Cognitively impaired ALS patients (n = 12) had bilateral amygdalae and left thalamic volumetric reduction compared to non-impaired ALS patients. Behaviorally impaired ALS patients (n = 14) had lower fractional anisotropy (FA) at the fornix in comparison with healthy subjects. These parameters did correlate with cognitive/behavioral scores, but not with motor-functional parameters in the ALS cohort. We believe that basal ganglia and fornix damage might be related to cognitive and behavioral impairment across ALS-frontotemporal dementia continuum. Also, distinct anatomical areas seem to influence the behavioral and cognitive status of these individuals.

High resolution in-vivo diffusion imaging of the human hippocampus

The human hippocampus is a key target of many imaging studies given its capacity for neurogenesis, role in long term potentiation and memory, and nearly ubiquitous involvement in neurological and psychiatric conditions. Diffusion tensor imaging (DTI) has detected microstructural abnormalities of the human hippocampus associated with various disorders, but acquisitions have typically been limited to low spatial resolution protocols designed for whole brain (e.g. > 2 mm isotropic, >8 mm³ voxels), limiting regional specificity and worsening partial volume effects. The purpose here was to develop a simple DTI protocol using readily available standard single-shot EPI at 3T, capable of yielding much higher spatial resolution images (1 x 1 x 1 mm³) of the human hippocampus in a 'clinically feasible' scan time of ~6 min. A thin slab of twenty 1 mm slices oriented along the long axis of the hippocampus enabled efficient coverage and a shorter repetition time, allowing more diffusion weighted images (DWIs) per slice per unit time. In combination with this strategy, a low b value of 500 s/mm² was chosen to help overcome the very low SNR of a 1 x 1 x 1 mm³ EPI acquisition. 1 mm isotropic mean DWIs (averaged over 120-128 DWIs) showed excellent detail of the hippocampal architecture (e.g. morphology and digitations, sub-regions, stratum lacunosum moleculare - SLM) that was not readily visible on 2 mm isotropic diffusion images. Diffusion parameters within the hippocampus were consistent across subjects and fairly homogenous across sub-regions of the hippocampus (with the exception of the SLM and tail). However, it is expected that DTI parameters will be sensitive to microstructural changes associated with a number of clinical disorders (e.g. epilepsy, dementia) and that this practical, translatable approach for high resolution acquisition will facilitate localized detection of hippocampal pathology.

Automatic thalamus and hippocampus segmentation from MP2RAGE: comparison of publicly available methods and implications for DTI quantification

PURPOSE

In both structural and functional MRI, there is a need for accurate and reliable automatic segmentation of brain regions. Inconsistent segmentation reduces sensitivity and may bias results in clinical studies. The current study compares the performance of publicly available segmentation tools and their impact on diffusion quantification, emphasizing the importance of using recently developed segmentation algorithms and imaging techniques.

METHODS

Four publicly available, automatic segmentation methods (volBrain, FSL, FreeSurfer and SPM) are compared to manual segmentation of the thalamus and hippocampus imaged with a recently proposed T1-weighted MRI sequence (MP2RAGE). We evaluate morphometric accuracy on 22 healthy subjects and impact on diffusivity measurements obtained from aligned diffusion-weighted images on a subset of 10 subjects.

RESULTS

Compared to manual segmentation, the highest Dice similarity index of the thalamus is obtained with volBrain using a local library ([Formula: see text], [Formula: see text]) followed by volBrain using an external library ([Formula: see text], [Formula: see text]), FSL ([Formula: see text], [Formula: see text]), FreeSurfer ([Formula: see text], [Formula: see text]) and SPM ([Formula: see text], [Formula: see text]). The same order is found for hippocampus with volBrain local ([Formula: see text], [Formula: see text]), volBrain external ([Formula: see text], [Formula: see text]), FSL ([Formula: see text], [Formula: see text]), FreeSurfer ([Formula: see text], [Formula: see text]) and SPM ([Formula: see text], [Formula: see text]). For diffusivity measurements, volBrain provides values closest to those obtained from manual segmentations. volBrain is the only method where FA values do not differ significantly from manual segmentation of the thalamus.

CONCLUSIONS

Overall we find that volBrain is superior in thalamus and hippocampus segmentation compared to FSL, FreeSurfer and SPM. Furthermore, the choice of segmentation technique and training library affects quantitative results from diffusivity measures in thalamus and hippocampus.

Structural brain correlates of cognitive and behavioral impairment in MND

OBJECTIVE

To assess the structural correlates of cognitive and behavioral impairment in motor neuron diseases (MND) using multimodal MRI.

METHODS

One hundred one patients with sporadic MND (56 classic amyotrophic lateral sclerosis, 31 upper motor neuron phenotype, and 14 lower motor neuron phenotype) and 51 controls were enrolled. Patients were classified into MND with a pure motor syndrome (MND-motor) and with cognitive/behavioral symptoms (MND-plus). Cortical thickness measures and diffusion tensor (DT) metrics of white matter (WM) tracts were assessed. A random forest approach was used to explore the independent role of cortical and WM abnormalities in explaining major cognitive and behavioral symptoms.

RESULTS

There were 48 MND-motor and 53 MND-plus patients. Relative to controls, both patient groups showed a distributed cortical thinning of the bilateral precentral gyrus, insular and cingulate cortices, and frontotemporal regions. In all regions, there was a trend toward a more severe involvement in MND-plus cases, particularly in the temporal lobes. Both patient groups showed damage to the motor callosal fibers, which was more severe in MND-plus. MND-plus patients also showed a more severe involvement of the extra-motor WM tracts. The best predictors of executive and non-executive deficits and behavioral symptoms in MND were diffusivity abnormalities of the corpus callosum and frontotemporal tracts, including the uncinate, cingulum, and superior longitudinal fasciculi.

CONCLUSIONS

Cortical thinning and WM degeneration are highly associated with neuropsychological and behavioral symptoms in patients with MND. DT MRI metrics seem to be the most sensitive markers of extra-motor deficits within the MND spectrum.

Amyotrophic lateral sclerosis-associated mutant profilin 1 increases dendritic arborisation and spine formation in primary hippocampal neurons

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease and familial ALS accounts for 10% of cases. The identification of familial ALS mutations in the actin-binding protein profilin 1 directly implicates actin dynamics and regulation in the pathogenesis of ALS. The mechanism by which these mutations cause ALS is unknown. In this study we show that expression of the ALS-associated actin-binding deficient mutant of PFN1 (PFN1(C71G)) results in increased dendritic arborisation and spine formation, and cytoplasmic inclusions in cultured mouse hippocampal neurons.

Diffusion imaging changes in grey matter in Alzheimer's disease: a potential marker of early neurodegeneration

Alzheimer's disease (AD) is recognized to have a long presymptomatic period, during which there is progressive accumulation of molecular pathology, followed by inexorable neuronal damage. The ability to identify presymptomatic individuals with evidence of neurodegenerative change, to stage their disease, and to track progressive changes will be important for early diagnosis and for prevention trials. Despite recent advances, particularly in magnetic resonance imaging, our ability to identify early neurodegenerative changes reliably is limited. The development of diffusion-weighted magnetic resonance imaging, which is sensitive to microstructural changes not visible with conventional volumetric techniques, has led to a number of diffusion imaging studies in AD; these have largely focused on white matter changes. However, in AD cerebral grey matter is affected very early, with pathological studies suggesting that grey matter changes predate those in white matter. In this article we review the growing number of studies that assess grey matter diffusivity changes in AD. Although use of the technique is still at a relatively early stage, results so far have been promising. Initial studies identified changes in diffusion measures in the hippocampi of patients with mild cognitive impairment, which predated macroscopic volume loss, with positive predictive value for progression to AD dementia. More recent studies have identified abnormalities in multiple neocortical areas (particularly the posterior cingulate) at various stages of disease progression. Studies of patients who carry genetic mutations predisposing to autosomal dominant familial AD have shown cortical and subcortical grey matter diffusivity changes several years before the expected onset of the first clinical symptoms. The technique is not without potential methodological difficulties, especially relating to partial volume effects, although recent advances appear to be reducing such issues. Going forward, further utilization of grey matter diffusion measurements in AD may improve our understanding with regards to the timing and nature of the earliest presymptomatic neurodegenerative changes. This imaging technique may also be useful in comparing and contrasting subtle variations in different disease subgroups, and as a sensitive outcome measure for presymptomatic clinical trials in AD and other neurodegenerative diseases.

Microstructural white matter changes underlying cognitive and behavioural impairment in ALS--an in vivo study using DTI

Background

A relevant fraction of patients with amyotrophic lateral sclerosis (ALS) exhibit a fronto-temporal pattern of cognitive and behavioural disturbances with pronounced deficits in executive functioning and cognitive control of behaviour. Structural imaging shows a decline in fronto-temporal brain areas, but most brain imaging studies did not evaluate cognitive status. We investigated microstructural white matter changes underlying cognitive impairment using diffusion tensor imaging (DTI) in a large cohort of ALS patients.

Methods

We assessed 72 non-demented ALS patients and 65 matched healthy control subjects using a comprehensive neuropsychological test battery and DTI. We compared DTI measures of fiber tract integrity using tract-based spatial statistics among ALS patients with and without cognitive impairment and healthy controls. Neuropsychological performance and behavioural measures were correlated with DTI measures.

Results

Patients without cognitive impairment demonstrated white matter changes predominantly in motor tracts, including the corticospinal tract and the body of corpus callosum. Those with impairments (ca. 30%) additionally presented significant white matter alterations in extra-motor regions, particularly the frontal lobe. Executive and memory performance and behavioural measures were correlated with fiber tract integrity in large association tracts.

Conclusion

In non-demented cognitively impaired ALS patients, white matter changes measured by DTI are related to disturbances of executive and memory functions, including prefrontal and temporal regions. In a group comparison, DTI is able to observe differences between cognitively unimpaired and impaired ALS patients.