Metabolic brain changes across different levels of cognitive impairment in ALS: a 18F-FDG-PET study

Frequency and Early Predictors of Cognitive Deterioration in Amyotrophic Lateral Sclerosis: A Longitudinal Population-Based Study

OBJECTIVE

The objective is to evaluate cognitive and behavioral progression and identify early predictors of these changes in a cohort of amyotrophic lateral sclerosis (ALS) patients.

METHODS

A total of 161 ALS patients were tested at diagnosis (T0), and 107 were re-tested after 1 year (T1) using cognitive/behavioral tests. All patients underwent whole-genome sequencing, and 46 patients (ALS-normal cognition [CN]) underwent [18F]Fluorodeoxyglucose positron emission tomography.

RESULTS

Of the 161 patients, 107 were re-rested at T1; non-retested patients included 10 with frontotemporal dementia and 44 who were either non-testable or deceased. At T0, 67 patients (62.6%) were classified as ALS-CN, whereas 40 (38.4%) showed some degree of cognitive/behavioral impairment. Eighteen ALS-CN patients (26.9%) experienced cognitive decline at T1. Phenoconverters had lower baseline scores in letter fluency (Letter Fluency Test [FAS]) (p < 0.001), Edinburgh Cognitive and Behavioral ALS Screen (ECAS) verbal fluency score (p = 0.017). Both tests were independently predictive of phenoconversion in binary logistic regression models, with optimal cut-off scores of 28.75 and 14.2, with good sensitivity and specificity. Other predictors included older age, lower education, and ALS-related genetic variants. Phenoconverters were hypometabolic in the left temporal lobe. Thirteen (32.5%) of the 40 patients with cognitive impairment at T0 worsened by T1, with FAS (p = 0.02) and the ECAS verbal fluency score (p = 0.023) predicting further decline.

INTERPRETATION

Approximately 30% of ALS patients experienced cognitive/behavioral decline within the first year after diagnosis. FAS and ECAS verbal fluency were predictive of cognitive phenoconversion. Our findings highlight the importance of early detection of at-risk individuals and the need for longitudinal cognitive assessments to monitor disease progression. ANN NEUROL 2025;97:1122-1133.

Mild cognitive impairment in amyotrophic lateral sclerosis: current view

Amyotrophic lateral sclerosis (ALS) is a fatal multi-system neurodegenerative disorder with no effective treatment or cure. Although primarily characterized by motor degeneration, cognitive dysfunction is an important non-motor symptom that has a negative impact on patient and caregiver burden. Mild cognitive deficits are present in a subgroup of non-demented patients with ALS, often preceding motor symptoms. Detailed neuropsychological assessments reveal deficits in a variety of cognitive domains, including those of verbal fluency and retrieval, language, executive function, attention and verbal memory. Mild cognitive impairment (MCI), a risk factor for developing dementia, affects between 10% and over 50% of ALS patients. Neuroimaging revealed atrophy of frontal and temporal cortices, disordered white matter Integrity, volume reduction in amygdala and thalamus, hypometabolism in the frontal and superior temporal gyrus and anterior insula. Neuronal loss in non-motor brain areas, associated with TDP-43 deposition, one of the morphological hallmarks of ALS, is linked to functional disruption of frontostriatal and frontotemporo-limbic connectivities as markers for cognitive deficits in ALS, the pathogenesis of which is still poorly understood. Early diagnosis by increased cerebrospinal fluid or serum levels of neurofilament light/heavy chain or glial fibrillary acidic protein awaits confirmation for MCI in ALS. These fluid biomarkers and early detection of brain connectivity signatures before structural changes will be helpful not only in establishing early premature diagnosis but also in clarifying the pathophysiological mechanisms of MCI in ALS, which might serve as novel targets for prohibition/delay and future adequate treatment of this debilitating disorder.

Sex-related differences in amyotrophic lateral sclerosis: A 2-[18F]FDG-PET study

PURPOSE

We investigated sex-related brain metabolic differences in Amyotrophic Lateral Sclerosis (ALS) and healthy controls (HC).

METHODS

We collected two equal-sized groups of male (m-ALS) and female ALS (f-ALS) patients (n = 130 each), who underwent 2-[18F]FDG-PET at diagnosis, matched for site of onset, cognitive status and King's stage. We included 168 age-matched healthy controls, half female (f-HC) and half male (m-HC). We compared brain metabolism of males and females separately for ALS and HC, including age as covariate. A differential network analysis was performed to evaluate brain connectivity.

RESULTS

M-ALS showed relative hypometabolism of bilateral medial frontal, parietal and occipital cortices, and left temporal cortex, compared to f-ALS. In node-wise comparison, f-ALS showed significantly higher connectivity in right middle cingulate cortex and left superior and medial frontal gyrus. In HC we did not find any sex-related differences.

CONCLUSION

Sex resulted a major determinant of brain metabolism and connectivity in ALS patients.

Education moderates the association between motor involvement and executive status in ALS

BACKGROUND

This study aimed to determine whether educational attainment-a common proxy of cognitive reserve (CR)-influences the association between motor and cognitive/behavioural outcomes in a large cohort of ALS patients without dementia.

METHODS

N = 726 ALS patients without FTD were assessed for motor (ALSFRS-R), cognitive (Edinburgh Cognitive and Behavioural ALS Screen, ECAS) and behavioural outcomes (ECAS-Carer Interview, ECAS-CI). CR was operationalized via educational attainment (in years). Moderation models were run on each subscale of the cognitive section of the ECAS and on the ECAS-CI by addressing ALSFRS-R as the predictor and education as the moderator.

RESULTS

Education was associated with both the ALSFRS-R and all the cognitive subscales of the ECAS, while not with the ECAS-CI. As to moderation models, a significant Education*ALSFRS-R interaction was detected solely with regard to the ECAS-Executive-with its simple slope-based decomposition revealing that higher ALSFRS-R scores were associated with higher scores on the ECAS-Executive for patients with low (p < 0.001) and average (p = 0.007), while not high, levels of education.

DISCUSSION

Education seems to moderate the association between motor involvement and executive status in ALS patients without dementia, thus possibly exerting a protective role towards both motor function and cognition in this population.

Current potential diagnostic biomarkers of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) currently lacks the useful diagnostic biomarkers. The current diagnosis of ALS is mainly depended on the clinical manifestations, which contributes to the diagnostic delay and be difficult to make the accurate diagnosis at the early stage of ALS, and hinders the clinical early therapeutics. The more and more pathogenesis of ALS are found at the last 30 years, including excitotoxicity, the oxidative stress, the mitochondrial dysfunction, neuroinflammation, the altered energy metabolism, the RNA misprocessing and the most recent neuroimaging findings. The findings of these pathogenesis bring the new clues for searching the diagnostic biomarkers of ALS. At present, a large number of relevant studies about the diagnostic biomarkers are underway. The ALS pathogenesis related to the diagnostic biomarkers might lessen the diagnostic reliance on the clinical manifestations. Among them, the cortical altered signatures of ALS patients derived from both structural and functional magnetic resonance imaging and the emerging proteomic biomarkers of neuronal loss and glial activation in the cerebrospinal fluid as well as the potential biomarkers in blood, serum, urine, and saliva are leading a new phase of biomarkers. Here, we reviewed these current potential diagnostic biomarkers of ALS.

ECAS correlation with metabolic alterations on FDG-PET imaging in ALS

Background: Cognitive impairment is observed in up to 50% of patients with amyotrophic lateral sclerosis (ALS). The Edinburgh Cognitive and Behavioral ALS Screen (ECAS) is an ALS-specific multi-domain screening tool. Few studies have examined the relationship between ECAS scores and [18F]fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) findings. Objective: To assess the relationship between ECAS scores and glucose metabolism patterns on [18F]FDG -PET images in ALS. Methods: We collected [18F]FDG-PET images from 65 patients with ALS and 39 healthy controls. ECAS scores were collected on all patients and we calculated the correlation to [18F]FDG-PET in order to investigate the potential links between cognition and glucose metabolism. Results: We observed hypometabolism in the frontal cortex, insula, and limbic system, together with hypermetabolism in the cerebellum in patients with ALS compared to controls. A lower ECAS total score was associated with lower glucose metabolism in the right orbitofrontal gyrus and higher glucose metabolism in lateral occipital, medial occipital, and cerebellar regions, among patients with ALS. Similar results, although less widespread, were observed in the analyses of ECAS ALS-specific scores. Conclusions: The metabolic patterns in [18F]FDG -PET show that changes in the glucose metabolism of corresponding areas are related to cognitive dysfunction in ALS, and can be detected using the ECAS.

Prevalence and motor-functional correlates of frontotemporal-spectrum disorders in a large cohort of non-demented ALS patients

BACKGROUND

This study aimed at (1) delivering generalizable estimates of the prevalence of frontotemporal-spectrum disorders (FTSDs) in non-demented ALS patients and (2) exploring their motor-functional correlates.

METHODS

N = 808 ALS patients without FTD were assessed for motor-functional outcomes-i.e., disease duration, severity (ALSFRS-R), progression rate (ΔFS), and stage (King's and Milano-Torino-MiToS-systems)-cognition-via the cognitive section of the Edinburgh Cognitive and Behavioural ALS Screen (ECAS)-and behaviour-via the ECAS-Carer Interview. Neuropsychological phenotypes were retrieved via Strong's revised criteria-i.e., ALS cognitively and behaviourally normal (ALScbn) or cognitively and/or behaviourally impaired (ALSci/bi/cbi).

RESULTS

Defective ECAS-Total performances were detected in ~ 29% of patients, with the ECAS-Executive being failed by the highest number of patients (~ 30%), followed by the ECAS-Language, -Fluency, and -Memory (~ 15-17%) and -Visuospatial (~ %8). Apathy was the most frequent behavioural change (~ 28%), followed by loss of sympathy/empathy (~ 13%); remaining symptoms were reported in < 4% of patients. The distribution of Strong's classifications was as follows: ALScbn: 46.7%; ALSci/bi/cbi: 22.9%/20.0%/10.4%. Multinomial regressions on Strong's classifications revealed that lower ALSFRS-R scores were associated with a higher probability of ALSbi and ALScbi classifications (p ≤ .008). Higher King's and MiToS stages were associated with a higher probability of ALSbi classification (p ≤ .031).

CONCLUSIONS

FTSDs affect ~ 50% of non-demented ALS patients, with cognitive deficits being as frequent as behavioural changes. A higher degree of motor-functional involvement is associated with worse behavioural outcomes-with this link being weaker for cognitive deficits.

Cerebral glucose metabolic correlates of cognitive and behavioural impairments in amyotrophic lateral sclerosis

OBJECTIVE

Half of ALS patients are cognitively and/or behaviourally impaired. As cognition/behaviour and cerebral glucose metabolism can be correlated by means of 18F-Fluorodeoxyglucose positron emission tomography (FDG-PET), we aimed to utilise FDG-PET, first, to replicate group-level differences in glucose metabolism between non-demented ALS patients separated into non-impaired (ALSni), cognitively impaired (ALSci), behaviourally impaired (ALSbi), and cognitively and behaviourally impaired (ALScbi) groups; second, to investigate glucose metabolism and performance in various cognitive domains; and third, to examine the impact of partial volume effects correction (PVEC) of the FDG-PET data on the results.

METHODS

We analysed neuropsychological, clinical, and imaging data from 67 ALS patients (30 ALSni, 21 ALSci, 5 ALSbi, and 11 ALScbi). Cognition was assessed with the Edinburgh Cognitive and Behavioural ALS Screen, and two social cognition tests. FDG-PET and structural MRI scans were acquired for each patient. Voxel-based statistical analyses were undertaken on grey matter volume (GMV) and non-corrected vs. PVE-corrected FDG-PET scans.

RESULTS

ALSci and ALScbi had lower cognitive scores than ALSni. In contrast to both ALSni and ALSci, ALScbi showed widespread hypometabolism in the superior- and middle-frontal gyri in addition to the right temporal pole. Correlations were observed between the GMV, the FDG-PET signal, and various cognitive scores. The FDG-PET results were largely unaffected by PVEC.

INTERPRETATION

Our study identified widespread differences in hypometabolism in the ALScbi-ni but not in the ALSci-ni group comparison, raising the possibility that cerebral metabolism may be more closely related to the presence of behavioural changes than to mild cognitive deficits.

Prognostic value of motor and extramotor involvement in ALS

OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder resulting in upper and lower motor neuron loss. ALS often has a focal onset of weakness, which subsequently spreads to other body regions. Survival is limited to two to five years after disease onset, often due to respiratory failure. Cognitive impairment is present in approximately 30% to 50% of patients and in 10%-15% of patients, the clinical criteria of frontotemporal dementia (FTD) are met.

METHODS

In this retrospective single-center ALS cohort study, we examined the occurrence of cognitive and behavioral impairment in relation to motor impairment at disease presentation and studied its impact on survival.

RESULTS

The degree of lower motor neuron involvement was associated with a worse survival, but there was no effect for upper motor neuron involvement. Patients who were cognitively normal had a significantly better survival compared to patients with cognitive or behavioral impairment and to patients with comorbid FTD. There was no significant difference regarding survival between patients with FTD and patients with cognitive or behavioral impairment.

CONCLUSIONS

The extent of motor and extramotor involvement in patients with ALS at disease presentation holds complementary prognostic information.

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.

PET and SPECT Imaging of ALS: An Educational Review

Amyotrophic lateral sclerosis (ALS) is a disease leading to progressive motor degeneration and ultimately death. It is a complex disease that can take a significantly long time to be diagnosed, as other similar pathological conditions must be ruled out for a definite diagnosis of ALS. Noninvasive imaging of ALS has shed light on disease pathology and altered biochemistry in the ALS brain. Other than magnetic resonance imaging (MRI), two types of functional imaging, positron emission tomography (PET) and single photon emission computed tomography (SPECT), have provided valuable data about what happens in the brain of ALS patients compared to healthy controls. PET imaging has revealed a specific pattern of brain metabolism through [18F]FDG, while other radiotracers have uncovered neuroinflammation, changes in neuronal density, and protein aggregation. SPECT imaging has shown a general decrease in regional cerebral blood flow (rCBF) in ALS patients. This educational review summarizes the current state of ALS imaging with various PET and SPECT radiopharmaceuticals to better understand the pathophysiology of ALS.

Brain metabolic signatures in patients with genetic and nongenetic amyotrophic lateral sclerosis

AIMS

To study the brain metabolic signature in Chinese amyotrophic lateral sclerosis (ALS) patients and compare the difference in brain metabolic patterns between ALS with and without genetic variants.

METHODS

We included 146 patients with ALS and 128 healthy controls (HCs). All patients with ALS underwent genetic testing to screen for ALS related genetic variants and were then divided into genetic (n = 22) and nongenetic ALS (n = 93) subgroups. All participants underwent brain 18 F-FDG-PET scans. Group comparisons were performed using the two-sample t-test model of SPM12.

RESULTS

We identified a large of hypometabolic clusters in ALS patients as compared with HCs, especially in the bilateral basal ganglia, midbrain, and cerebellum. Moreover, hypometabolism in the bilateral temporal lobe, precentral gyrus and hypermetabolism in the left anterior cingulate, occipital lobe, and bilateral frontal lobe were also found in ALS patients as compared with HCs. Compared with nongenetic ALS patients, genetic ALS patients showed hypometabolism in the right postcentral gyrus, precuneus, and middle occipital gyrus. The incidence of sensory disturbance in patients with genetic ALS was higher than that in patients with nongenetic ALS (5 of 22 [22.72%] vs. 7 of 93 [7.52%], p = 0.036).

CONCLUSIONS

Our investigation provided unprecedented evidence of relative hypometabolism in the midbrain and cerebellum in ALS patients. Genetic ALS patients showed a specific signature of brain metabolism and a higher incidence of sensory disturbance, indicating that genetic factors may be an underlying cause affecting the brain metabolism and increasing the risk of sensory disturbance in ALS.

Analysis of positron emission tomography hypometabolic patterns and neuropsychiatric symptoms in patients with dementia syndromes

AIMS

To estimate the proportions of specific hypometabolic patterns and their association with neuropsychiatric symptoms (NPS) in patients with cognitive impairment (CI).

METHODS

This multicenter study with 1037 consecutive patients was conducted from December 2012 to December 2019. ¹⁸ F-FDG PET and clinical/demographic information, NPS assessments were recorded and analyzed to explore the associations between hypometabolic patterns and clinical features by correlation analysis and multivariable logistic regression models.

RESULTS

Patients with clinical Alzheimer's disease (AD, 81.6%, 605/741) and dementia with Lewy bodies (67.9%, 19/28) mostly had AD-pattern hypometabolism, and 76/137 (55.5%) of patients with frontotemporal lobar degeneration showed frontal and anterior temporal pattern (FT-P) hypometabolism. Besides corticobasal degeneration, patients with behavioral variant frontotemporal dementia (36/58), semantic dementia (7/10), progressive non-fluent aphasia (6/9), frontotemporal lobar degeneration and amyotrophic lateral sclerosis (3/5), and progressive supranuclear palsy (21/37) also mostly showed FT-P hypometabolism. The proportion of FT-P hypometabolism was associated with the presence of hallucinations (R = 0.171, p = 0.04), anxiety (R = 0.182, p = 0.03), and appetite and eating abnormalities (R = 0.200, p = 0.01) in AD.

CONCLUSION

Specific hypometabolic patterns in FDG-PET are associated with NPS and beneficial for the early identification and management of NPS in patients with CI.

Simultaneous PET/MRI: The future gold standard for characterizing motor neuron disease-A clinico-radiological and neuroscientific perspective

Neuroimaging assessment of motor neuron disease has turned into a cornerstone of its clinical workup. Amyotrophic lateral sclerosis (ALS), as a paradigmatic motor neuron disease, has been extensively studied by advanced neuroimaging methods, including molecular imaging by MRI and PET, furthering finer and more specific details of the cascade of ALS neurodegeneration and symptoms, facilitated by multicentric studies implementing novel methodologies. With an increase in multimodal neuroimaging data on ALS and an exponential improvement in neuroimaging technology, the need for harmonization of protocols and integration of their respective findings into a consistent model becomes mandatory. Integration of multimodal data into a model of a continuing cascade of functional loss also calls for the best attempt to correlate the different molecular imaging measurements as performed at the shortest inter-modality time intervals possible. As outlined in this perspective article, simultaneous PET/MRI, nowadays available at many neuroimaging research sites, offers the perspective of a one-stop shop for reproducible imaging biomarkers on neuronal damage and has the potential to become the new gold standard for characterizing motor neuron disease from the clinico-radiological and neuroscientific perspectives.

Paraneoplastic Cerebellar Syndrome Presented as Cerebellar Hypermetabolism in a Patient With Occult Breast Carcinoma

ABSTRACT

A 47-year-old woman presented with an acute cerebellar syndrome. Neither cerebellar atrophy nor an infarction or tumor was shown on MRI. A diagnostic CT demonstrated enlarged axillary lymph nodes, but no primary tumor. Puncture of these nodes showed non-small cell carcinoma. 18F-FDG PET/CT imaging was performed and suggested an occult breast carcinoma, which was confirmed by pathological examination. It also showed cerebellar hypermetabolism, consistent with a PCS (paraneoplastic cerebellar syndrome). This case shows that 18F-FDG PET imaging may be of value in patients in which a PCS is considered clinically, particularly in patients suspicious for an occult malignancy.

Amyotrophic Lateral Sclerosis-Frontotemporal Dementia: Shared and Divergent Neural Correlates Across the Clinical Spectrum

BACKGROUND AND OBJECTIVES

A significant overlap between amyotrophic lateral sclerosis (ALS) and behavioral variant of frontotemporal dementia (bvFTD) has been observed at clinical, genetic, and pathologic levels. Within this continuum of presentations, the presence of mild cognitive or behavioral symptoms in patients with ALS has been consistently reported, although it is unclear whether this is to be considered a distinct phenotype or rather a natural evolution of ALS. Here, we used mathematical modeling of MRI connectomic data to decipher common and divergent neural correlates across the ALS-frontotemporal dementia (FTD) spectrum.

METHODS

We included 83 patients with ALS, 35 patients with bvFTD, and 61 healthy controls, who underwent clinical, cognitive, and MRI assessments. Patients with ALS were classified according to the revised Strong criteria into 54 ALS with only motor deficits (ALS-cn), 21 ALS with cognitive or behavioral involvement (ALS-ci/bi), and 8 ALS with bvFTD (ALS-FTD). First, we assessed the functional and structural connectivity patterns across the ALS-FTD spectrum. Second, we investigated whether and where MRI connectivity alterations of patients with ALS with any degree of cognitive impairment (i.e., ALS-ci/bi and ALS-FTD) resembled more the pattern of damage of one (ALS-cn) or the other end (bvFTD) of the spectrum, moving from group-level to single-subject analysis.

RESULTS

As compared with controls, extensive structural and functional disruption of the frontotemporal and parietal networks characterized bvFTD (bvFTD-like pattern), while a more focal structural damage within the sensorimotor-basal ganglia areas characterized ALS-cn (ALS-cn-like pattern). ALS-ci/bi patients demonstrated an ALS-cn-like pattern of structural damage, diverging from ALS-cn with similar motor impairment for the presence of enhanced functional connectivity within sensorimotor areas and decreased functional connectivity within the bvFTD-like pattern. On the other hand, patients with ALS-FTD resembled both structurally and functionally the bvFTD-like pattern of damage with, in addition, the structural ALS-cn-like damage in the motor areas.

DISCUSSION

Our findings suggest a maladaptive role of functional rearrangements in ALS-ci/bi concomitantly with similar structural alterations compared to ALS-cn, supporting the hypothesis that ALS-ci/bi might be considered as a phenotypic variant of ALS, rather than a consequence of disease worsening.

Pathophysiological Underpinnings of Extra-Motor Neurodegeneration in Amyotrophic Lateral Sclerosis: New Insights From Biomarker Studies

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) lie at opposing ends of a clinical, genetic, and neuropathological continuum. In the last decade, it has become clear that cognitive and behavioral changes in patients with ALS are more frequent than previously recognized. Significantly, these non-motor features can impact the diagnosis, prognosis, and management of ALS. Partially overlapping neuropathological staging systems have been proposed to describe the distribution of TAR DNA-binding protein 43 (TDP-43) aggregates outside the corticospinal tract. However, the relationship between TDP-43 inclusions and neurodegeneration is not absolute and other pathophysiological processes, such as neuroinflammation (with a prominent role of microglia), cortical hyperexcitability, and synaptic dysfunction also play a central role in ALS pathophysiology. In the last decade, imaging and biofluid biomarker studies have revealed important insights into the pathophysiological underpinnings of extra-motor neurodegeneration in the ALS-FTLD continuum. In this review, we first summarize the clinical and pathophysiological correlates of extra-motor neurodegeneration in ALS. Next, we discuss the diagnostic and prognostic value of biomarkers in ALS and their potential to characterize extra-motor neurodegeneration. Finally, we debate about how biomarkers could improve the diagnosis and classification of ALS. Emerging imaging biomarkers of extra-motor neurodegeneration that enable the monitoring of disease progression are particularly promising. In addition, a growing arsenal of biofluid biomarkers linked to neurodegeneration and neuroinflammation are improving the diagnostic accuracy and identification of patients with a faster progression rate. The development and validation of biomarkers that detect the pathological aggregates of TDP-43 in vivo are notably expected to further elucidate the pathophysiological underpinnings of extra-motor neurodegeneration in ALS. Novel biomarkers tracking the different aspects of ALS pathophysiology are paving the way to precision medicine approaches in the ALS-FTLD continuum. These are essential steps to improve the diagnosis and staging of ALS and the design of clinical trials testing novel disease-modifying treatments.

Combining structural and metabolic markers in a quantitative MRI study of motor neuron diseases

OBJECTIVE

To assess the performance of a combination of three quantitative MRI markers (iron deposition, basal neuronal metabolism, and regional atrophy) for differential diagnosis between amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS).

METHODS

In total, 33 ALS, 12 PLS, and 28 healthy control (HC) subjects underwent a 3T MRI study including single- and multi-echo sequences for gray matter (GM) volumetry and quantitative susceptibility mapping (QSM) and a pseudo-continuous arterial spin labeling (ASL) sequence for cerebral blood flow (CBF) measurement. Mean values of QSM, CBF, and GM volumes were extracted in the motor cortex, basal ganglia, thalamus, amygdala, and hippocampus. A generalized linear model was applied to the three measures to binary discriminate between groups. The diagnostic performances were evaluated via receiver operating characteristic analyses.

RESULTS

A significant discrimination was obtained: between ALS and HCs in the left and right motor cortex, where QSM increases were respectively associated with disability scores and disease duration; between PLS and ALS in the left motor cortex, where PLS patients resulted significantly more atrophic; between ALS and HC in the right motor cortex, where GM volumes were associated with upper motor neuron scores. Significant discrimination between ALS and HC was achieved in subcortical structures only combining all three parameters.

INTERPRETATION

While increased QSM values in the motor cortex of ALS patients is a consolidated finding, combining QSM, CBF, and GM volumetry shows higher diagnostic potential for differentiating ALS patients from HC subjects and, in the motor cortex, between ALS and PLS.

Cognitive and Behavioral Manifestations in ALS: Beyond Motor System Involvement

Amyotrophic lateral sclerosis (ALS) has long been considered to be a purely motor disorder. However, it has become apparent that many ALS patients develop cognitive and behavioral manifestations similar to frontotemporal dementia and the term amyotrophic lateral sclerosis-frontotemporal spectrum disorder (ALS-FTSD) is now used in these circumstances. This review is intended to be an overview of the cognitive and behavioral manifestations commonly encountered in ALS patients with the goal of improving case-oriented management in clinical practice. We introduce the principal ALS-FTSD subtypes and comment on their principal clinical manifestations, neuroimaging findings, neuropathological and genetic background, and summarize available therapeutic options. Diagnostic criteria for ALS-FTSD create distinct categories based on the type of neuropsychological manifestations, i.e., changes in behavior, impaired social cognition, executive dysfunction, and language or memory impairment. Cognitive impairment is found in up to 65%, while frank dementia affects about 15% of ALS patients. ALS motor and cognitive manifestations can worsen in parallel, becoming more pronounced when bulbar functions (affecting speech, swallowing, and salivation) are involved. Dementia can precede or develop after the appearance of motor symptoms. ALS-FTSD patients have a worse prognosis and shorter survival rates than patients with ALS or frontotemporal dementia alone. Important negative prognostic factors are behavioral and personality changes. From the clinician's perspective, there are five major distinguishable ALS-FTSD subtypes: ALS with cognitive impairment, ALS with behavioral impairment, ALS with combined cognitive and behavioral impairment, fully developed frontotemporal dementia in combination with ALS, and comorbid ALS and Alzheimer's disease. Although the most consistent ALS and ALS-FTSD pathology is a disturbance in transactive response DNA binding protein 43 kDa (TDP-43) metabolism, alterations in microtubule-associated tau protein metabolism have also been observed in ALS-FTSD. Early detection and careful monitoring of cognitive deficits in ALS are crucial for patient and caregiver support and enable personalized management of individual patient needs.