Memory-related white matter tract integrity in amyotrophic lateral sclerosis: an advanced neuroimaging and neuropsychological study

Quantitative susceptibility mapping in amyotrophic lateral sclerosis: automatic quantification of the magnetic susceptibility in the subcortical nuclei

Objective: Previous studies have suggested a link between dysregulation of cortical iron levels and neuronal loss in amyotrophic lateral sclerosis (ALS) patients. However, few studies have reported differences in quantitative susceptibility mapping (QSM) values in subcortical nuclei between patients with ALS and healthy controls (HCs). Methods: MRI was performed using a 3 Tesla Prisma scanner (64-channel head coil), including 3D T1-MPRAGE and multi-echo 3D GRE for QSM reconstruction. Automated QSM segmentation was used to measure susceptibility values in the subcortical nuclei, which were compared between the groups. Correlations with clinical scales were analyzed. Group comparisons were performed using independent t-tests, with p < 0.05 considered significant. Correlations were assessed using Pearson's correlation, with p < 0.05 considered significant. Cohen's d was reported to compare the standardized mean difference (SMD) of QSM. Results: Twelve patients with limb-onset ALS (mean age 48.7 years, 75% male) and 13 age-, sex-, and handedness-matched HCs (mean age 44.6 years, 69% male) were included. Compared to HCs, ALS patients demonstrated significantly lower susceptibility in the left caudate nucleus (CN) (SMD = -0.845), right CN (SMD = -0.851), whole CN (SMD = -1.016), and left subthalamic nucleus (STN) (SMD = -1.000). Susceptibility in the left putamen (SMD = -0.857), left thalamus (SMD = -1.081), and whole thalamus (SMD = -0.968) was significantly higher in the patients. The susceptibility of the substantia nigra (SN), CN, and pulvinar was positively correlated with disease duration. Conclusions: QSM detects abnormal iron accumulation patterns in the subcortical gray matter of ALS patients, which correlates with disease characteristics, supporting its potential as a neuroimaging biomarker.

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.

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.

MRI biomarkers for memory-related impairment in amyotrophic lateral sclerosis: a systematic review

Introduction: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder associated with cognitive and behavioral impairments and motor symptoms. Magnetic resonance imaging (MRI) biomarkers have been investigated as potential tools for detecting and monitoring memory-related impairment in ALS. Our objective was to examine the importance of identifying MRI biomarkers for memory-related impairment in ALS, motor neuron disease (MND), and ALS frontotemporal dementia (FTD) (ALS-FTD) patients. Methods: PubMed and Scopus databases were searched. Keywords covering magnetic resonance imaging, ALS, MND, and memory impairments were searched. There were a total of 25 studies included in our work here. Results: The structural MRI (sMRI) studies reported gray matter (GM) atrophy in the regions associated with memory processing, such as the hippocampus and parahippocampal gyrus (PhG), in ALS patients. The diffusion tensor imaging (DTI) studies showed white matter (WM) alterations in the corticospinal tract (CST) and other tracts that are related to motor and extra-motor functions, and these alterations were associated with memory and executive function impairments in ALS. The functional MRI (fMRI) studies also demonstrated an altered activation in the prefrontal cortex, limbic system, and other brain regions involved in memory and emotional processing in ALS patients. Conclusion: MRI biomarkers show promise in uncovering the neural mechanisms of memory-related impairment in ALS. Nonetheless, addressing challenges such as sample sizes, imaging protocols, and longitudinal studies is crucial for future research. Ultimately, MRI biomarkers have the potential to be a tool for detecting and monitoring memory-related impairments in ALS.

Hippocampal Metabolic Alterations in Amyotrophic Lateral Sclerosis: A Magnetic Resonance Spectroscopy Study

BACKGROUND

Magnetic resonance spectroscopy (MRS) in amyotrophic lateral sclerosis (ALS) has been overwhelmingly applied to motor regions to date and our understanding of frontotemporal metabolic signatures is relatively limited. The association between metabolic alterations and cognitive performance in also poorly characterised.

MATERIAL AND METHODS

In a multimodal, prospective pilot study, the structural, metabolic, and diffusivity profile of the hippocampus was systematically evaluated in patients with ALS. Patients underwent careful clinical and neurocognitive assessments. All patients were non-demented and exhibited normal memory performance. 1H-MRS spectra of the right and left hippocampi were acquired at 3.0T to determine the concentration of a panel of metabolites. The imaging protocol also included high-resolution T1-weighted structural imaging for subsequent hippocampal grey matter (GM) analyses and diffusion tensor imaging (DTI) for the tractographic evaluation of the integrity of the hippocampal perforant pathway zone (PPZ).

RESULTS

ALS patients exhibited higher hippocampal tNAA, tNAA/tCr and tCho bilaterally, despite the absence of volumetric and PPZ diffusivity differences between the two groups. Furthermore, superior memory performance was associated with higher hippocampal tNAA/tCr bilaterally. Both longer symptom duration and greater functional disability correlated with higher tCho levels.

CONCLUSION

Hippocampal 1H-MRS may not only contribute to a better academic understanding of extra-motor disease burden in ALS, but given its sensitive correlations with validated clinical metrics, it may serve as practical biomarker for future clinical and clinical trial applications. Neuroimaging protocols in ALS should incorporate MRS in addition to standard structural, functional, and diffusion sequences.

Structural Plasticity of the Hippocampus in Neurodegenerative Diseases

Neuroplasticity is the capacity of neural networks in the brain to alter through development and rearrangement. It can be classified as structural and functional plasticity. The hippocampus is more susceptible to neuroplasticity as compared to other brain regions. Structural modifications in the hippocampus underpin several neurodegenerative diseases that exhibit cognitive and emotional dysregulation. This article reviews the findings of several preclinical and clinical studies about the role of structural plasticity in the hippocampus in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. In this study, literature was surveyed using Google Scholar, PubMed, Web of Science, and Scopus, to review the mechanisms that underlie the alterations in the structural plasticity of the hippocampus in neurodegenerative diseases. This review summarizes the role of structural plasticity in the hippocampus for the etiopathogenesis of neurodegenerative diseases and identifies the current focus and gaps in knowledge about hippocampal dysfunctions. Ultimately, this information will be useful to propel future mechanistic and therapeutic research in neurodegenerative diseases.

Frontotemporal Pathology in Motor Neuron Disease Phenotypes: Insights From Neuroimaging

Frontotemporal involvement has been extensively investigated in amyotrophic lateral sclerosis (ALS) but remains relatively poorly characterized in other motor neuron disease (MND) phenotypes such as primary lateral sclerosis (PLS), progressive muscular atrophy (PMA), spinal muscular atrophy (SMA), spinal bulbar muscular atrophy (SBMA), post poliomyelitis syndrome (PPS), and hereditary spastic paraplegia (HSP). This review focuses on insights from structural, metabolic, and functional neuroimaging studies that have advanced our understanding of extra-motor disease burden in these phenotypes. The imaging literature is limited in the majority of these conditions and frontotemporal involvement has been primarily evaluated by neuropsychology and post mortem studies. Existing imaging studies reveal that frontotemporal degeneration can be readily detected in ALS and PLS, varying degree of frontotemporal pathology may be captured in PMA, SBMA, and HSP, SMA exhibits cerebral involvement without regional predilection, and there is limited evidence for cerebral changes in PPS. Our review confirms the heterogeneity extra-motor pathology across the spectrum of MNDs and highlights the role of neuroimaging in characterizing anatomical patterns of disease burden in vivo. Despite the contribution of neuroimaging to MND research, sample size limitations, inclusion bias, attrition rates in longitudinal studies, and methodological constraints need to be carefully considered. Frontotemporal involvement is a quintessential clinical facet of MND which has important implications for screening practices, individualized management strategies, participation in clinical trials, caregiver burden, and resource allocation. The academic relevance of imaging frontotemporal pathology in MND spans from the identification of genetic variants, through the ascertainment of presymptomatic changes to the design of future epidemiology studies.

Hippocampal connectivity in Amyotrophic Lateral Sclerosis (ALS): more than Papez circuit impairment

Emerging evidence suggests that memory deficit in amyotrophic lateral sclerosis (ALS), a neurodegenerative disease with varying impairment of motor abilities and cognitive profile, may be independent from executive dysfunction. Our multimodal magnetic resonance imaging (MRI) approach, including resting state functional MRI (RS-fMRI), diffusion tensor imaging (DTI) and voxel-based morphometry (VBM), aimed to investigate structural and functional changes within and beyond the Papez circuit in non-demented ALS patients (n = 32) compared with healthy controls (HCs, n = 21), and whether these changes correlated with neuropsychological measures of verbal and non-verbal memory. We revealed a decreased functional connectivity between bilateral hippocampus, bilateral parahippocampal gyri and cerebellum in ALS patients compared with HCs. Between-group comparisons revealed white matter abnormalities in the genu and body of the corpus callosum and bilateral cortico-spinal tracts, superior longitudinal and uncinate fasciculi in ALS patients (p < .05, family-wise error corrected). Interestingly, changes of Digit Span forward performance were inversely related to RS-fMRI signal fluctuations in the cerebellum, while changes of both episodic and visual memory scores were inversely related to mean and radial diffusivity abnormalities in several WM fiber tracts, including middle cerebellar peduncles. Our findings revealed that ALS patients showed significant functional and structural connectivity changes across the regions comprising the Papez circuit, as well as more extended areas including cerebellum and frontal, temporal and parietal areas, supporting the theory of a multi-system pathology in ALS that spreads from cortical to subcortical structures.

Frontotemporal degeneration in amyotrophic lateral sclerosis (ALS): a longitudinal MRI one-year study

OBJECTIVE

Advanced neuroimaging techniques may offer the potential to monitor disease progression in amyotrophic lateral sclerosis (ALS), a neurodegenerative, multisystem disease that still lacks therapeutic outcome measures. We aim to investigate longitudinal functional and structural magnetic resonance imaging (MRI) changes in a cohort of patients with ALS monitored for one year after diagnosis.

METHODS

Resting state functional MRI, diffusion tensor imaging (DTI), and voxel-based morphometry analyses were performed in 22 patients with ALS examined by six-monthly MRI scans over one year.

RESULTS

During the follow-up period, patients with ALS showed reduced functional connectivity only in some extramotor areas, such as the middle temporal gyrus in the left frontoparietal network after six months and in the left middle frontal gyrus in the default mode network after one year without showing longitudinal changes of cognitive functions. Moreover, after six months, we reported in the ALS group a decreased fractional anisotropy (P = .003, Bonferroni corrected) in the right uncinate fasciculus. Conversely, we did not reveal significant longitudinal changes of functional connectivity in the sensorimotor network, as well as of gray matter (GM) atrophy or of DTI metrics in motor areas, although clinical measures of motor disability showed significant decline throughout the three time points.

CONCLUSION

Our findings highlighted that progressive impairment of extramotor frontotemporal networks may precede the appearance of executive and language dysfunctions and GM changes in ALS. Functional connectivity changes in cognitive resting state networks might represent candidate radiological markers of disease progression.

Papez Circuit Gray Matter and Episodic Memory in Amyotrophic Lateral Sclerosis and Behavioural Variant Frontotemporal Dementia

Amyotrophic lateral sclerosis and behavioural variant frontotemporal dementia are two different diseases recognized to overlap at clinical, pathological and genetic characteristics. Both conditions are traditionally known for relative sparing of episodic memory. However, recent studies have disputed that with the report of patients presenting with marked episodic memory impairment. Besides that, structural and functional changes in temporal lobe regions responsible for episodic memory processing are often detected in neuroimaging studies of both conditions. In this study, we investigated the gray matter features associated with the Papez circuit in amyotrophic lateral sclerosis, behavioural variant frontotemporal dementia and healthy controls to further explore similarities and differences between the two conditions. Our non-demented amyotrophic lateral sclerosis patients showed no episodic memory deficits measured by a short-term delayed recall test while no changes in gray matter of the Papez circuit were found. Compared with the amyotrophic lateral sclerosis group, the behavioural variant frontotemporal dementia group had lower performance on the short-term delayed recall test and marked atrophy in gray matter of the Papez circuit. Bilateral atrophy of entorhinal cortex and mammillary bodies distinguished behavioural variant frontotemporal dementia from amyotrophic lateral sclerosis patients as well as atrophy in left cingulate, left hippocampus and right parahippocampal gyrus. Taken together, our results suggest that sub-regions of the Papez circuit could be differently affected in amyotrophic lateral sclerosis and behavioural variant frontotemporal dementia.

Extra-motor cerebral changes and manifestations in primary lateral sclerosis

Primary lateral sclerosis (PLS) is classically considered a 'pure' upper motor neuron disorder. Motor cortex atrophy and pyramidal tract degeneration are thought to be pathognomonic of PLS, but extra-motor cerebral changes are poorly characterized. In a prospective neuroimaging study, forty PLS patients were systematically evaluated with a standardised imaging, genetic and clinical protocol. Patients were screened for ALS and HSP associated mutations, as well as C9orf72 hexanucleotide repeats. Clinical assessment included composite reflex scores, spasticity scales, functional rating scales, and screening for cognitive and behavioural deficits. The neuroimaging protocol evaluated cortical atrophy patterns, subcortical grey matter changes and white matter alterations in whole-brain and region-of-interest analyses. PLS patients tested negative for known ALS- and HSP-associated mutations and C9orf72 repeat expansions. Voxel-wise analyses revealed anterior cingulate, dorsolateral prefrontal, insular, opercular, orbitofrontal and bilateral mesial temporal grey matter changes and white matter alterations in the fornix, brainstem, temporal lobes, and cerebellum. Significant thalamus, caudate, hippocampus, putamen and accumbens nucleus volume reductions were also identified. Extra-motor clinical manifestations were dominated by verbal fluency deficits, language deficits, apathy and pseudobulbar affect. Our clinical and radiological evaluation confirms considerable extra-motor changes in a population-based cohort of PLS patients. Our data suggest that PLS should no longer be considered a neurodegenerative disorder selectively affecting the pyramidal system. PLS is associated with widespread extra-motor changes and manifestations which should be carefully considered in the multidisciplinary management of this low-incidence condition.

The imaging signature of C9orf72 hexanucleotide repeat expansions: implications for clinical trials and therapy development

While C9orf72-specific imaging signatures have been proposed by both ALS and FTD research groups and considerable presymptomatic alterations have also been confirmed in young mutation carriers, considerable inconsistencies exist in the literature. Accordingly, a systematic review of C9orf72-imaging studies has been performed to identify consensus findings, stereotyped shortcomings, and unique contributions to outline future directions. A formal literature review was conducted according to the STROBE guidelines. All identified papers were individually reviewed for sample size, choice of controls, study design, imaging modalities, statistical models, clinical profiling, and identified genotype-associated pathological patterns. A total of 74 imaging papers were systematically reviewed. ALS patients with GGGGCC repeat expansions exhibit relatively limited motor cortex involvement and widespread extra-motor pathology. C9orf72 positive FTD patients often show preferential posterior involvement. Reports of thalamic involvement are relatively consistent across the various phenotypes. Asymptomatic hexanucleotide repeat carriers often exhibit structural and functional changes decades prior to symptom onset. Common shortcomings included sample size limitations, lack of disease-controls, limited clinical profiling, lack of genetic testing in healthy controls, and absence of post mortem validation. There is a striking paucity of longitudinal studies and existing presymptomatic studies have not evaluated the predictive value of radiological changes with regard to age of onset and phenoconversion. With the advent of antisense oligonucleotide therapies, the meticulous characterisation of C9orf72-associated changes has gained practical relevance. Neuroimaging offers non-invasive biomarkers for future clinical trials, presymptomatic ascertainment, diagnostic and prognostic applications.

The Characteristics of Cognitive Impairment in ALS Patients Depend on the Lateralization of Motor Damage

(1) Background: Cognitive features of patients with amyotrophic lateral sclerosis (ALS) have never been specifically analyzed according to the lateralization of motor impairment. In the present study we investigated the cognitive performances of ALS patients to describe the relationship between motor and cognitive dysfunction, according to site and side of disease onset. (2) Methods: Six-hundred and nine ALS patients underwent a comprehensive neuropsychological evaluation at diagnosis in Turin ALS Centre Tests included—mini-mental state examination (MMSE), frontal assessment battery (FAB), trail-making test A/B (TMT A-B), digit span forward and backward (digit span FW/digit span BW), letter fluency test (FAS), category fluency test (CAT), Rey auditory verbal learning test (RAVLT), Babcock story recall test (BSRT), Rey-Osterrieth complex figure test (ROCFT), Wisconsin card sorting test (WCST), Raven’s coloured progressive matrices (CPM47). Cognitive performances of patients, grouped by side and site of onset, were statistically compared using z-scores, as appropriate. (3) Results: Bulbar patients and bilateral spinal onset patients (S_bil) were generally characterized by lower cognitive performances in most neuropsychological tests, when compared to patients with lateralized onset (right-side spinal onset, S_ri and left-side spinal onset, S_le). Digit span backward and visual memory task (ROCFT) median z-scores were significantly higher, reflecting a better cognitive performance, in S_ri patients when compared to bulbar/S_bil patients, while verbal memory tasks (RAVLT and BRST) resulted in significantly higher scores in S_le patients. Our results are in keeping with hemispheric functional lateralization of language and visuospatial abilities. (4) Conclusions: In ALS patients, as in other neurodegenerative diseases, we found a direct relationship between lateralized motor and cognitive features.

Amygdala pathology in amyotrophic lateral sclerosis and primary lateral sclerosis

Temporal lobe studies in motor neuron disease overwhelmingly focus on white matter alterations and cortical grey matter atrophy. Reports on amygdala involvement are conflicting and the amygdala is typically evaluated as single structure despite consisting of several functionally and cytologically distinct nuclei. A prospective, single-centre, neuroimaging study was undertaken to comprehensively characterise amygdala pathology in 100 genetically-stratified ALS patients, 33 patients with PLS and 117 healthy controls. The amygdala was segmented into groups of nuclei using a Bayesian parcellation algorithm based on a probabilistic atlas and shape deformations were additionally assessed by vertex analyses. The accessory basal nucleus (p = .021) and the cortical nucleus (p = .022) showed significant volume reductions in C9orf72 negative ALS patients compared to controls. The lateral nucleus (p = .043) and the cortico-amygdaloid transition (p = .024) were preferentially affected in C9orf72 hexanucleotide carriers. A trend of total volume reduction was identified in C9orf72 positive ALS patients (p = .055) which was also captured in inferior-medial shape deformations on vertex analyses. Our findings highlight that the amygdala is affected in ALS and our study demonstrates the selective involvement of specific nuclei as opposed to global atrophy. The genotype-specific patterns of amygdala involvement identified by this study are consistent with the growing literature of extra-motor clinical features. Mesial temporal lobe pathology in ALS is not limited to hippocampal pathology but, as a key hub of the limbic system, the amygdala is also affected in ALS.

"Switchboard" malfunction in motor neuron diseases: Selective pathology of thalamic nuclei in amyotrophic lateral sclerosis and primary lateral sclerosis

The thalamus is a key cerebral hub relaying a multitude of corticoefferent and corticoafferent connections and mediating distinct extrapyramidal, sensory, cognitive and behavioural functions. While the thalamus consists of dozens of anatomically well-defined nuclei with distinctive physiological roles, existing imaging studies in motor neuron diseases typically evaluate the thalamus as a single structure. Based on the unique cortical signatures observed in ALS and PLS, we hypothesised that similarly focal thalamic involvement may be observed if the nuclei are individually evaluated. A prospective imaging study was undertaken with 100 patients with ALS, 33 patients with PLS and 117 healthy controls to characterise the integrity of thalamic nuclei. ALS patients were further stratified for the presence of GGGGCC hexanucleotide repeat expansions in C9orf72. The thalamus was segmented into individual nuclei to examine their volumetric profile. Additionally, thalamic shape deformations were evaluated by vertex analyses and focal density alterations were examined by region-of-interest morphometry. Our data indicate that C9orf72 negative ALS patients and PLS patients exhibit ventral lateral and ventral anterior involvement, consistent with the ‘motor’ thalamus. Degeneration of the sensory nuclei was also detected in C9orf72 negative ALS and PLS. Both ALS groups and the PLS cohort showed focal changes in the mediodorsal-paratenial-reuniens nuclei, which mediate memory and executive functions. PLS patients exhibited distinctive thalamic changes with marked pulvinar and lateral geniculate atrophy compared to both controls and C9orf72 negative ALS. The considerable ventral lateral and ventral anterior pathology detected in both ALS and PLS support the emerging literature of extrapyramidal dysfunction in MND. The involvement of sensory nuclei is consistent with sporadic reports of sensory impairment in MND. The unique thalamic signature of PLS is in line with the distinctive clinical features of the phenotype. Our data confirm phenotype-specific patterns of thalamus involvement in motor neuron diseases with the preferential involvement of nuclei mediating motor and cognitive functions. Given the selective involvement of thalamic nuclei in ALS and PLS, future biomarker and natural history studies in MND should evaluate individual thalamic regions instead overall thalamic changes.

Hippocampal structural and functional integrity in multiple sclerosis patients with or without memory impairment: a multimodal neuroimaging study

The increasing evidence for a pure amnestic-like profile in multiple sclerosis (MS) introduces the role of hippocampal formation in MS episodic memory function. The aim of the present study was to investigate structural and functional hippocampal changes in mildly-disabled MS patients with and without memory impairment. Thirty-one MS patients with or without memory impairment and 16 healthy controls (HC) underwent MRI in a 3.0 T MRI scanner. Patients were categorized as memory preserved (MP) and memory impaired (MI) based on verbal and visual memory scores extracted from the Brief Repeatable Neuropsychological Battery. The acquisition protocol included high-resolution 3D-T1-weighted, diffusion weighted imaging and echo-planar imaging sequences for the analysis of hippocampal gray matter (GM) density, perforant pathway area (PPA) tractography, and hippocampal functional connectivity (FC), respectively. Compared to HC, we found decreased left and bilateral hippocampal GM density in MP and MI patients, respectively, decreased fractional anisotropy and increased radial diffusivity on left PPA in MI patients, and reduced FC in MI between left hippocampus and left superior frontal gyrus, precuneus/posterior cingulated cortex and lateral occipital gyrus/angular gyrus. The only differences between MP and MI were found in FC. Specifically, MP patients showed FC changes between left hippocampus and right temporo-occipital fusiform/lingual gyrus (increased FC) as well as supramarginal gyrus (decreased FC). In conclusion, we highlight the early detection of structural hippocampal changes in MS without neuropsychologically-detected memory deficits and decreased hippocampal FC in MS patients with impaired memory performance, when both GM density and PPA integrity are affected.

Mapping the human middle longitudinal fasciculus through a focused anatomo-imaging study: shifting the paradigm of its segmentation and connectivity pattern

Τhe middle longitudinal fasciculus (MdLF) was initially identified in humans as a discrete subcortical pathway connecting the superior temporal gyrus (STG) to the angular gyrus (AG). Further anatomo-imaging studies, however, proposed more sophisticated but conflicting connectivity patterns and have created a vague perception on its functional anatomy. Our aim was, therefore, to investigate the ambiguous structural architecture of this tract through focused cadaveric dissections augmented by a tailored DTI protocol in healthy participants from the Human Connectome dataset. Three segments and connectivity patterns were consistently recorded: the MdLF-I, connecting the dorsolateral Temporal Pole (TP) and STG to the Superior Parietal Lobule/Precuneus, through the Heschl's gyrus; the MdLF-II, connecting the dorsolateral TP and the STG with the Parieto-occipital area through the posterior transverse gyri and the MdLF-III connecting the most anterior part of the TP to the posterior border of the occipital lobe through the AG. The lack of an established termination pattern to the AG and the fact that no significant leftward asymmetry is disclosed tend to shift the paradigm away from language function. Conversely, the theory of "where" and "what" auditory pathways, the essential relationship of the MdLF with the auditory cortex and the functional role of the cortical areas implicated in its connectivity tend to shift the paradigm towards auditory function. Allegedly, the MdLF-I and MdLF-II segments could underpin the perception of auditory representations; whereas, the MdLF-III could potentially subserve the integration of auditory and visual information.

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.

Structural and functional papez circuit integrity in amyotrophic lateral sclerosis

Cognitive impairment in amyotrophic lateral sclerosis (ALS) is heterogeneous but now recognized as a feature in non-demented patients and no longer exclusively attributed to executive dysfunction. However, despite common reports of temporal lobe changes and memory deficits in ALS, episodic memory has been less explored. In the current study, we examined how the Papez circuit-a circuit known to participate in memory processes-is structurally and functionally affected in ALS patients (n = 20) compared with healthy controls (n = 15), and whether these changes correlated with a commonly used clinical measure of episodic memory. Our multimodal MRI approach (cortical volume, voxel-based morphometry, diffusion tensor imaging and resting state functional magnetic resonance) showed reduced gray matter in left hippocampus, left entorhinal cortex and right posterior cingulate as well as increased white matter fractional anisotropy and decreased mean diffusivity in the left cingulum bundle (hippocampal part) of ALS patients compared with controls. Interestingly, thalamus, mammillary bodies and fornix were preserved. Finally, we report a decreased functional connectivity in ALS patients in bilateral hippocampus, bilateral anterior and posterior parahippocampal gyrus and posterior cingulate. The results revealed that ALS patients showed statistically significant structural changes, but more important, widespread prominent functional connectivity abnormalities across the regions comprising the Papez circuit. The decreased functional connectivity found in the Papez network may suggest these changes could be used to assess risk or assist early detection or development of memory symptoms in ALS patients even before structural changes are established.

Tracking a Fast-Moving Disease: Longitudinal Markers, Monitoring, and Clinical Trial Endpoints in ALS

Amyotrophic lateral sclerosis (ALS) encompasses a heterogeneous group of phenotypes with different progression rates, varying degree of extra-motor involvement and divergent progression patterns. The natural history of ALS is increasingly evaluated by large, multi-time point longitudinal studies, many of which now incorporate presymptomatic and post-mortem assessments. These studies not only have the potential to characterize patterns of anatomical propagation, molecular mechanisms of disease spread, but also to identify pragmatic monitoring markers. Sensitive markers of progressive neurodegenerative change are indispensable for clinical trials and individualized patient care. Biofluid markers, neuroimaging indices, electrophysiological markers, rating scales, questionnaires, and other disease-specific instruments have divergent sensitivity profiles. The discussion of candidate monitoring markers in ALS has a dual academic and clinical relevance, and is particularly timely given the increasing number of pharmacological trials. The objective of this paper is to provide a comprehensive and critical review of longitudinal studies in ALS, focusing on the sensitivity profile of established and emerging monitoring markers.

Gray matter and white matter changes in non-demented amyotrophic lateral sclerosis patients with or without cognitive impairment: A combined voxel-based morphometry and tract-based spatial statistics whole-brain analysis

The phenotypic heterogeneity in amyotrophic lateral sclerosis (ALS) implies that patients show structural changes within but also beyond the motor cortex and corticospinal tract and furthermore outside the frontal lobes, even if frank dementia is not detected. The aim of the present study was to investigate both gray matter (GM) and white matter (WM) changes in non-demented amyotrophic lateral sclerosis (ALS) patients with or without cognitive impairment (ALS-motor and ALS-plus, respectively). Nineteen ALS-motor, 31 ALS-plus and 25 healthy controls (HC) underwent 3D-T1-weighted and 30-directional diffusion-weighted imaging on a 3 T MRI scanner. Voxel-based morphometry and tract-based spatial-statistics analysis were performed to examine GM volume (GMV) changes and WM differences in fractional anisotropy (FA), axial and radial diffusivity (AD, RD, respectively). Compared to HC, ALS-motor patients showed decreased GMV in frontal and cerebellar areas and increased GMV in right supplementary motor area, while ALS-plus patients showed diffuse GMV reduction in primary motor cortex bilaterally, frontotemporal areas, cerebellum and basal ganglia. ALS-motor patients had increased GMV in left precuneus compared to ALS-plus patients. We also found decreased FA and increased RD in the corticospinal tract bilaterally, the corpus callosum and extra-motor tracts in ALS-motor patients, and decreased FA and increased AD and RD in motor and several WM tracts in ALS-plus patients, compared to HC. Multimodal neuroimaging confirms motor and extra-motor GM and WM abnormalities in non-demented cognitively-impaired ALS patients (ALS-plus) and identifies early extra-motor brain pathology in ALS patients without cognitive impairment (ALS-motor).

Machine Learning in Amyotrophic Lateral Sclerosis: Achievements, Pitfalls, and Future Directions

Background: Amyotrophic Lateral Sclerosis (ALS) is a relentlessly progressive neurodegenerative condition with limited therapeutic options at present. Survival from symptom onset ranges from 3 to 5 years depending on genetic, demographic, and phenotypic factors. Despite tireless research efforts, the core etiology of the disease remains elusive and drug development efforts are confounded by the lack of accurate monitoring markers. Disease heterogeneity, late-stage recruitment into pharmaceutical trials, and inclusion of phenotypically admixed patient cohorts are some of the key barriers to successful clinical trials. Machine Learning (ML) models and large international data sets offer unprecedented opportunities to appraise candidate diagnostic, monitoring, and prognostic markers. Accurate patient stratification into well-defined prognostic categories is another aspiration of emerging classification and staging systems. Methods: The objective of this paper is the comprehensive, systematic, and critical review of ML initiatives in ALS to date and their potential in research, clinical, and pharmacological applications. The focus of this review is to provide a dual, clinical-mathematical perspective on recent advances and future directions of the field. Another objective of the paper is the frank discussion of the pitfalls and drawbacks of specific models, highlighting the shortcomings of existing studies and to provide methodological recommendations for future study designs. Results: Despite considerable sample size limitations, ML techniques have already been successfully applied to ALS data sets and a number of promising diagnosis models have been proposed. Prognostic models have been tested using core clinical variables, biological, and neuroimaging data. These models also offer patient stratification opportunities for future clinical trials. Despite the enormous potential of ML in ALS research, statistical assumptions are often violated, the choice of specific statistical models is seldom justified, and the constraints of ML models are rarely enunciated. Conclusions: From a mathematical perspective, the main barrier to the development of validated diagnostic, prognostic, and monitoring indicators stem from limited sample sizes. The combination of multiple clinical, biofluid, and imaging biomarkers is likely to increase the accuracy of mathematical modeling and contribute to optimized clinical trial designs.

The changing landscape of motor neuron disease imaging: the transition from descriptive studies to precision clinical tools

PURPOSE OF REVIEW

Neuroimaging in motor neuron disease (MND) has traditionally been seen as an academic tool with limited direct relevance to individualized patient care. This has changed radically in recent years as computational imaging has emerged as a viable clinical tool with true biomarker potential. This transition is not only fuelled by technological advances but also by important conceptual developments.

RECENT FINDINGS

The natural history of MND is now evaluated by presymptomatic, postmortem and multi-timepoint longitudinal imaging studies. The anatomical spectrum of MND imaging has also been expanded from an overwhelmingly cerebral focus to innovative spinal and muscle applications. In contrast to the group-comparisons of previous studies, machine-learning and deep-learning approaches are increasingly utilized to model real-life diagnostic dilemmas and aid prognostic classification. The focus from evaluating focal structural changes has shifted to the appraisal of network integrity by connectivity-based approaches. The armamentarium of MND imaging has also been complemented by novel PET-ligands, spinal toolboxes and the availability of magnetoencephalography and high-field magnetic resonance (MR) imaging platforms.

SUMMARY

In addition to the technological and conceptual advances, collaborative multicentre research efforts have also gained considerable momentum. This opinion-piece reviews emerging trends in MND imaging and their implications to clinical care and drug development.

Clinical and Radiological Markers of Extra-Motor Deficits in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is now universally recognized as a complex multisystem disorder with considerable extra-motor involvement. The neuropsychological manifestations of frontotemporal, parietal, and basal ganglia involvement in ALS have important implications for compliance with assistive devices, survival, participation in clinical trials, caregiver burden, and the management of individual care needs. Recent advances in neuroimaging have been instrumental in characterizing the biological substrate of heterogeneous cognitive and behavioral deficits in ALS. In this review we discuss the clinical and radiological aspects of cognitive and behavioral impairment in ALS focusing on the recognition, assessment, and monitoring of these symptoms.

Evaluating the cerebral correlates of survival in amyotrophic lateral sclerosis

Objective

To evaluate cerebral degenerative changes in ALS and their correlates with survival using 3D texture analysis.

Methods

A total of 157 participants were included in this analysis from four neuroimaging studies. Voxel-wise texture analysis on T1-weighted brain magnetic resonance images (MRIs) was conducted between patients and controls. Patients were divided into long- and short-survivors using the median survival of the cohort. Neuroanatomical differences between the two survival groups were also investigated.

Results

Whole-brain analysis revealed significant changes in image texture (FDR P < 0.05) bilaterally in the motor cortex, corticospinal tract (CST), insula, basal ganglia, hippocampus, and frontal regions including subcortical white matter. The texture of the CST correlated (P < 0.05) with finger- and foot-tapping rate, measures of upper motor neuron function. Patients with a survival below the media of 19.5 months demonstrated texture change (FDR P < 0.05) in the motor cortex, CST, basal ganglia, and the hippocampus, a distribution which corresponds to stage 4 of the distribution TDP-43 pathology in ALS. Patients with longer survival exhibited texture changes restricted to motor regions, including the motor cortex and the CST.

Interpretation

Widespread gray and white matter pathology is evident in ALS, as revealed by texture analysis of conventional T1-weighted MRI. Length of survival in patients with ALS is associated with the spatial extent of cerebral degeneration.

Macaque parvocellular mediodorsal thalamus: dissociable contributions to learning and adaptive decision-making

Distributed brain networks govern adaptive decision‐making, new learning and rapid updating of information. However, the functional contribution of the rhesus macaque monkey parvocellular nucleus of the mediodorsal thalamus (MDpc) in these key higher cognitive processes remains unknown. This study investigated the impact of MDpc damage in cognition. Preoperatively, animals were trained on an object‐in‐place scene discrimination task that assesses rapid learning of novel information within each session. Bilateral neurotoxic (NMDA and ibotenic acid) MDpc lesions did not impair new learning unless the monkey had also sustained damage to the magnocellular division of the MD (MDmc). Contralateral unilateral MDpc and MDmc damage also impaired new learning, while selective unilateral MDmc damage produced new learning deficits that eventually resolved with repeated testing. In contrast, during food reward (satiety) devaluation, monkeys with either bilateral MDpc damage or combined MDpc and MDmc damage showed attenuated food reward preferences compared to unoperated control monkeys; the selective unilateral MDmc damage left performance intact. Our preliminary results demonstrate selective dissociable roles for the two adjacent nuclei of the primate MD, namely, MDpc, as part of a frontal cortical network, and the MDmc, as part of a frontal‐temporal cortical network, in learning, memory and the cognitive control of behavioural choices after changes in reward value. Moreover, the functional cognitive deficits produced after differing MD damage show that the different subdivisions of the MD thalamus support distributed neural networks to rapidly and fluidly incorporate task‐relevant information, in order to optimise the animals’ ability to receive rewards.

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.

Resting state fMRI correlates of Theory of Mind impairment in amyotrophic lateral sclerosis

Theory of Mind (ToM), the ability to recognize thoughts and emotions of another, may be one of the cognitive domains affected in amyotrophic lateral sclerosis (ALS), a neurodegenerative disease now recognized as a multi-system disorder. The present study aimed to identify early dysfunctions of brain resting state functional magnetic resonance imaging (RS-fMRI) networks in a group of ALS patients longitudinally explored for impairment of "cognitive" and "affective" ToM subcomponents. RS-fMRI connectivity was investigated in a group of 21 patients with ALS (i.e., 9 with bulbar-onset or ALS-B and 12 with limb-onset or ALS-L) in early stages of disease and 15 healthy controls (HCs). The same subjects were assessed, at baseline and after six months, for neuropsychological performances, including cognitive and affective ToM and multi-domain cognitive functions. The RS-fMRI study showed a decreased connectivity in frontotemporal areas within the main cognitive resting state networks, including the default mode (DMN), the right and left fronto-parietal (R-, L-FPN), and the salience (SLN) networks, in the entire ALS group. As exploratory results, comparing the ALS-B subgroup to the ALS-L one, we revealed a widespread decrease of RS-fMRI signals in the left middle frontal gyrus for L-FPN and SLN and in the left superior frontal gyrus for SLN. At baseline, no ToM or other cognitive abnormalities were reported in the entire group of ALS patients compared to HCs, although, after six months, the ALS-B subset exhibited a significant impairment of both affective and cognitive ToM subcomponents, whereas the ALS-L group showed significant impairment of the cognitive subcomponent alone. Our findings provide original evidence of the deficit of both ToM subcomponents during the ALS course, supporting the hypothesis of a biologically more aggressive character of ALS-B. Moreover, early RS-fMRI abnormalities in cognitive networks may underlie and precede the clinical appearance of ToM alterations in ALS.