Cognitive impairment in amyotrophic lateral sclerosis and its relation to motor disabilities

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.

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.

Uncinate fasciculus microstructure and verbal episodic memory in amyotrophic lateral sclerosis: a diffusion tensor imaging and neuropsychological study

The present study evaluates the integrity of uncinate fasciculus (UF) and the association between UF microstructure and verbal episodic memory (as one of the cognitive functions linked to UF) in non-demented patients with amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI). We studied 21 patients with ALS and 11 healthy, demographically-comparable volunteers. Fractional anisotropy, apparent diffusion coefficient, axial and radial diffusivity were the DTI metrics examined. Episodic memory was evaluated with Babcock Story Recall Test and Rey Auditory Verbal Learning Test (RAVLT) for patients; measures of immediate and delayed recall and retention for both tests and sum of words recalled through five learning trials for RAVLT were considered. Patients with ALS showed significant bilateral reduction of axial diffusivity in the UF as compared to controls. Furthermore, there were several significant relations between various DTI metrics (mostly in left hemisphere) and memory measures (specifically for the RAVLT). UF microstructural changes may contribute to ALS-related memory impairment, with word-list learning performance relying more upon the integrity of frontal and temporal connections than memory components associated with story recall.

Prose memory impairment in amyotrophic lateral sclerosis patients is related to hippocampus volume

BACKGROUND AND PURPOSE

Thirty per cent of amyotrophic lateral sclerosis (ALS) patients have non-motor symptoms, including executive and memory deficits. The in vivo anatomical basis of memory deficits in ALS has not been elucidated. In this observational study, brain atrophy in relation to memory function was investigated in ALS patients and controls.

METHODS

Twenty-six ALS patients without dementia and 21 healthy volunteers matched for gender, age and education level underwent comprehensive neuropsychological evaluation and T1- and T2-weighted 3 T magnetic resonance imaging scanning of the brain. Grey and white matter brain volumes were analysed using voxel-based morphometry and age related white matter changes were assessed. The most frequently abnormal memory test (<2 SD below normative data corrected for age, gender and education) was correlated with regional brain volume variations by multiple regression analyses with age, gender and total grey matter volumes as covariates.

RESULTS

Immediate and delayed story recall scores were abnormal in 23% of ALS patients and correlated to bilateral hippocampus grey matter volume (r = 0.52 for both memory tests; P < 0.05; corrected for age, gender and total grey matter volume). This correlation was not found in healthy controls with similar age, education, anxiety and depression levels and white matter changes.

CONCLUSIONS

Prose memory impairment is a frequent finding in this cohort and is associated with hippocampus volume in ALS patients without dementia. These findings complement previous hippocampus changes in imaging studies in ALS and suggest involvement of the hippocampus in cognitive dysfunction of ALS.

Memory deficits in amyotrophic lateral sclerosis are not exclusively caused by executive dysfunction: a comparative neuropsychological study of amnestic mild cognitive impairment

Background

Recent work suggests that ALS and frontotemporal dementia can occur together and share at least in part the same underlying pathophysiology. However, it is unclear at present whether memory deficits in ALS stem from a temporal lobe dysfunction, or are rather driven by frontal executive dysfunction. In this study we sought to investigate the nature of memory deficits by analyzing the neuropsychological performance of 40 ALS patients in comparison to 39 amnestic mild cognitive impairment (aMCI) patients and 40 healthy controls (HC). The neuropsychological battery tested for impairment in executive functions, as well as memory and visuo-spatial skills, the results of which were compared across study groups. In addition, we calculated composite scores for memory (learning, recall, recognition) and executive functions (verbal fluency, cognitive flexibility, working memory). We hypothesized that the nature of memory impairment in ALS will be different from those exhibited by aMCI patients.

Results

Patient groups exhibited significant differences in their type of memory deficit, with the ALS group showing impairment only in recognition, whereas aMCI patients showed short and delayed recall performance deficits as well as reduced short-term capacity. Regression analysis revealed a significant impact of executive function on memory performance exclusively for the ALS group, accounting for one fifth of their memory performance. Interestingly, merging all sub scores into a single memory and an executive function score obscured these differences.

Conclusion

The presented results indicate that the interpretation of neuropsychological scores needs to take the distinct cognitive profiles in ALS and aMCI into consideration. Importantly, the observed memory deficits in ALS were distinctly different from those observed in aMCI and can be explained only to some extent in the context of comorbid (coexisting) executive dysfunction. These findings highlight the qualitative differences in temporal lobe dysfunction between ALS and aMCI patients, and support temporal lobe dysfunction as a mechanism underlying the distinct cognitive impairments observed in ALS.

Selective attention and the three-process memory model for the interpretation of verbal free recall in amyotrophic lateral sclerosis

The present study investigates selective attention and verbal free recall in amyotrophic lateral sclerosis (ALS) and examines the contribution of selective attention, encoding, consolidation, and retrieval memory processes to patients' verbal free recall. We examined 22 non-demented patients with sporadic ALS and 22 demographically related controls using Stroop Neuropsychological Screening Test (SNST; selective attention) and Rey Auditory Verbal Learning Test (RAVLT; immediate & delayed verbal free recall). The item-specific deficit approach (ISDA) was applied to RAVLT to evaluate encoding, consolidation, and retrieval difficulties. ALS patients performed worse than controls on SNST (p < .001) and RAVLT immediate and delayed recall (p < .001) and showed deficient encoding (p = .001) and consolidation (p = .002) but not retrieval (p = .405). Hierarchical regression analysis revealed that SNST and ISDA indices accounted for: (a) 91.1% of the variance in RAVLT immediate recall, with encoding (p = .016), consolidation (p < .001), and retrieval (p = .032) significantly contributing to the overall model and the SNST alone accounting for 41.6%; and (b) 85.2% of the variance in RAVLT delayed recall, with consolidation (p < .001) and retrieval (p = .008) significantly contributing to the overall model and the SNST alone accounting for 39.8%. Thus, selective attention, encoding, and consolidation, and to a lesser extent of retrieval, influenced both immediate and delayed verbal free recall. Concluding, selective attention and the memory processes of encoding, consolidation, and retrieval should be considered while interpreting patients' impaired free recall. (JINS, 2012, 18, 1-10).

The use of P300-based BCIs in amyotrophic lateral sclerosis: from augmentative and alternative communication to cognitive assessment

The use of augmentative and alternative communication (AAC) tools in patients with amyotrophic lateral sclerosis (ALS), as effective means to compensate for the progressive loss of verbal and gestural communication, has been deeply investigated in the recent literature. The development of advanced AAC systems, such as eye-tracking (ET) and brain-computer interface (BCI) devices, allowed to bypass the important motor difficulties present in ALS patients. In particular, BCIs could be used in moderate to severe stages of the disease, since they do not require preserved ocular-motor ability, which is necessary for ET applications. Furthermore, some studies have proved the reliability of BCIs, regardless of the severity of the disease and the level of physical decline. However, the use of BCI in ALS patients still shows some limitations, related to both technical and neuropsychological issues. In particular, a range of cognitive deficits in most ALS patients have been observed. At the moment, no effective verbal-motor free measures are available for the evaluation of ALS patients' cognitive integrity; BCIs could offer a new possibility to administer cognitive tasks without the need of verbal or motor responses, as highlighted by preliminary studies in this field. In this review, we outline the essential features of BCIs systems, considering advantages and challenges of these tools with regard to ALS patients and the main applications developed in this field. We then outline the main findings with regard to cognitive deficits observed in ALS and some preliminary attempts to evaluate them by means of BCIs. The definition of specific cognitive profiles could help to draw flexible approaches tailored on patients' needs. It could improve BCIs efficacy and reduce patients' efforts. Finally, we handle the open question, represented by the use of BCIs with totally locked in patients, who seem unable to reliably learn to use such tool.

Reduced cognitive function in Chinese patients with early amyotrophic lateral sclerosis and associated factors

The aims of this study were to investigate the cognitive function of Chinese amyotrophic lateral sclerosis (ALS) patients. Twenty-two patients with ALS were enrolled and a group of 60 healthy individuals were enrolled as a control group. The Extended Scale for Dementia (ESD) was used to evaluate cognitive function and the Hamilton Depression Scale was used for the assessment of depression. In addition, the Modified Norris Scale was used to assess medulla oblongata and limb function. The overall ESD scores were significantly lower in the ALS patients; however, no correlation was found between individual scores of cognitive function and the overall Modified Norris Scale scores. A majority of ALS patients had significantly reduced cognitive function, suggesting the pathological involvement of areas in the brain outside the motor area. This study shows that through the assessment of cognitive function, abnormalities in cognitive function in ALS patients can be identified.

Cognitive functioning in sporadic amyotrophic lateral sclerosis: a six month longitudinal study

OBJECTIVE

To observe changes in cognition over six months in subjects with recently diagnosed sporadic amyotrophic lateral sclerosis (ALS).

METHODS

The study used a between-group and within-group longitudinal design. Nineteen ALS subjects and eight matched caregivers were recruited to participate in baseline neuropsychological assessments that were repeated six months later. Between group comparisons for these variables were undertaken at baseline and six months later. Within group/across time comparisons for these variables were carried out for both groups. Individual analyses for the neuropsychological variables using z scores were done for the ALS subjects using their baseline performance as the basis for comparison with their six month performance.

RESULTS

The between-group and within-group comparisons did not show significant differences in cognitive function over time. In individual analyses, however, seven of 19 ALS subjects (36.84%) developed abnormal neuropsychological performance over six months.

CONCLUSIONS

Early in the disease course, over one third of the ALS subjects developed cognitive deficits over six months. These findings support the hypothesis that cognitive deficits in ALS become more prominent over time.

Only subtle cognitive deficits in non-bulbar amyotrophic lateral sclerosis patients

Neuropsychological investigations of amyotrophic sclerosis (ALS) patients revealed considerable discrepancies regarding neurocognitive functions. Some, but not all studies have suggested executive dysfunctioning and memory impairment, and there is a wide range of applied neuropsychological tests and results. In this study, we investigated the neuropsychological performance of 15 non-bulbar ALS patients, 14 patients with neuromuscular symptoms, and 15 healthy controls. To avoid confounding effects of motor disability, performance was assessed using exclusively motor-free tests of frontal lobe functioning (specific memory functions, conditional-associative learning, attention, and executive functions). ALS patients exhibited poorer performance in two conditions (semantic and alternating condition, respectively) of the Verbal Fluency Test, suggesting a subtle executive deficit. No deficits were found in tests of memory, conditional-associative learning, or attention. Assessed mood status was not related to neuropsychological performance. Verbal memory (CVLT) and verbal fluency (lexical condition) were positively associated with duration of disease. Our results support the view that there are only subtle cognitive deficits in ALS patients and we assume a possible effect of practice on cognitive tasks following reduced daily motor activity.

Cognitive function in bulbar- and spinal-onset amyotrophic lateral sclerosis. A longitudinal study in 52 patients

We performed a longitudinal study of frontal and temporal lobe functions in patients with amyotrophic lateral sclerosis (ALS) and compared the evolution of cognitive performance with that of motor deficits in patients with spinal and bulbar-onset of the disease. Fifty two patients suffering from sporadic ALS according to the El Escorial criteria were examined; 37 patients had a spinal, 15 a bulbar onset of the disease. The data profile included examinations at entry (E1), every four months at follow-up (E2, E3, E4) and after 18 months (E5), if possible. Neuropsychological testing covered the domains of executive functions, memory and attentional control. ALS patients showed executive dysfunctions that were most prominently represented by deficits of non-verbal and verbal fluency and concept formation. Memory-related deficits were also present but less expressed. The same held true for phasic and tonic alertness and divided attention. In contrast to motor functions declining concomitantly with disease progression, cognitive deficits appeared in early disease, were essentially present at initial testing and did not substantially decline on follow-up. A subgroup analysis revealed that bulbar-onset ALS patients performed consistently poorer in many cognitive tests than spinal-onset ones with special reference to verbal and non-verbal fluency and interference control. This subgroup difference persisted or even increased throughout follow-up. We conclude that there is a fronto-temporal pattern of cognitive dysfunction in ALS expressing itself early in the course of the disease and mainly with bulbar forms. The cognitive deficits do not progress in synchrony with motor decline, but distinctly more slowly. We suggest that cognitive dysfunctions reflect functional and possibly morphological deficits outside the primary motor system that is specific for the nature and evolution of the disease and might also give clues to etiopathogenesis.

Word retrieval in amyotrophic lateral sclerosis: a functional magnetic resonance imaging study

The cognitive impairment revealed in some non- demented amyotrophic lateral sclerosis (ALS) patients is characterized by executive dysfunction with widely repeated deficits on tests of verbal (letter) fluency. However, conflicting evidence exists of an impairment on other word retrieval tasks, such as confrontation naming, which do not place heavy demands on executive processes. Previous research has demonstrated intact confrontation naming in the presence of verbal fluency deficits, although naming deficits have been described in other studies. In this investigation, functional MRI (fMRI) techniques were employed to explore whether word retrieval deficits and underlying cerebral abnormalities were specific to letter fluency, which are more likely to indicate executive dysfunction, or were also present in confrontation naming, indicating language dysfunction. Twenty-eight non-demented ALS patients were compared with 18 healthy controls. The two groups were matched for age, intelligence quotient, years of education, and anxiety and depression scores. Two compressed-sequence overt fMRI activation paradigms were employed, letter fluency and confrontation naming, which were developed for use with an older and potentially impaired population. In ALS patients relative to controls, the letter fluency fMRI task revealed significantly impaired activation in the middle and inferior frontal gyri and anterior cingulate gyrus, in addition to regions of the parietal and temporal lobes. The confrontation naming fMRI task also revealed impaired activation in less extensive prefrontal regions, including the inferior frontal gyrus and regions of the temporal, parietal and occipital lobes. These changes were present despite matched performance between patients and controls during each activation paradigm. The pattern of dysfunction corresponded to the presence of cognitive deficits on both letter fluency and confrontation naming in the ALS group. This study provides evidence of cerebral abnormalities in ALS in the network of regions involved in language and executive functions. Moreover, the findings further illustrate the heterogeneity of cognitive and cerebral change in ALS.

The basic aspects of therapeutics in amyotrophic lateral sclerosis

Once thought to be a single pathological disease state, amyotrophic lateral sclerosis (ALS) is now recognized to be the limited phenotypic expression of a complex, heterogeneous group of biological processes, resulting in an unrelenting loss of motor neurons. On average, individuals affected with the disease live <5 years. In this article, the complex nature of the pathogenesis of ALS, including features of age dependency, environmental associations, and genetics, is reviewed. Once held to be uncommon, it is now clear that ALS is associated with a frontotemporal dementia and that this process may reflect disturbances in the microtubule-associated tau protein metabolism. The motor neuron ultimately succumbs in a state where significant disruptions in neurofilament metabolism, mitochondrial function, and management of oxidative stress exist. The microenvironment of the neuron becomes a complex milieu in which high levels of glutamate provide a source of chronic excitatory neurotoxicity, and the contributions of activated microglial cells lead to further cascades of motor neuron death, perhaps serving to propagate the disease once established. The final process of motor neuron death encompasses many features of apoptosis, but it is clear that this alone cannot account for all features of motor neuron loss and that aspects of a necrosis-apoptosis continuum are at play. Designing pharmacological strategies to mitigate against this process thus becomes an increasingly complex issue, which is reviewed in this article.

Immunohistochemical study on the distribution of alpha-synuclein in the central nervous system of transgenic mice expressing a human Cu/Zn superoxide dismutase mutation

We used the SOD1(G93A) transgenic mice as an in vivo model of amyotrophic lateral sclerosis (ALS) and performed immunohistochemical studies to investigate whether alpha-synuclein is involved in the pathogenesis of ALS. In the spinal cord of transgenic mice, immunohistochemistry showed intense staining of alpha-synuclein mainly in the anterior horn. In the hippocampus of transgenic mice, differential increases in the staining density of alpha-synuclein were observed. In the cerebellar cortex of transgenic mice, the prominent immunostaining of alpha-synuclein was found in the molecular and granular layers. The present study provides the first in vivo evidence that alpha-synuclein immunoreactivity was increased in the central nervous system of SOD(G93A) transgenic mice, suggesting that alpha-synuclein might play an important role in the pathogenesis of ALS. However, the functional implications of these increases require elucidation.

Memory deficits and retrieval processes in ALS

Subtle neuropsychological deficits have been described in patients affected by amyotrophic lateral sclerosis (ALS) without dementia. Overall, selective impairment in memory function has been reported, but the source of memory impairment in ALS has yet to be defined. We performed neuropsychological screening in 20 ALS patients. Semantic encoding and post-encoding cue effects on the retrieval of word lists were investigated in the ALS patients and normal controls. Severity of memory impairment was correlated to cerebral blood perfusion detected by single photon emission computed tomography (SPECT). ALS patients showed moderate impairments in frontal and memory tests. Short-term memory was normal, while serial position retrieval of word lists with normal recency effect but poor primacy effect showed long-term memory deficit. ALS patients performed better in cued encoding than in cued post-encoding recall condition. In the cued post-encoding condition, the primacy effect in word list recall improved significantly in controls, but not in ALS patients, as compared with both the free recall and cued encoding conditions. SPECT hypoperfusion was observed in frontal and temporal areas in ALS patients. ALS patients showed a long-term memory deficit which did not improve in cued post-encoding condition as it does for controls. We hypothesize abnormal retrieval processes related to frontal lobe dysfunction which entails difficulties in generating stable long-memory traces at encoding.

Immunohistochemical study on the distribution of homocysteine in the central nervous system of transgenic mice expressing a human Cu/Zn SOD mutation

In the present study, we used the transgenic mice expressing a human Cu/Zn SOD mutation (SOD1(G93A)) as an in vivo model of ALS and performed immunohistochemical studies to investigate the changes of homocysteine in the central nervous system of symptomatic transgenic mice. In control and presymptomatic transgenic mice, homocysteine-immunoreactive astrocytes were not detected in any region. In symptomatic transgenic mice, homocysteine-immunoreactive astrocytes were distributed in the spinal cord, brainstem and cerebellar nuclei of transgenic mice. In the hippocampal formation of transgenic mice, pyramidal cells in the CA1-3 regions and granule cells in the dentate gyrus showed homocysteine immunoreactivity. The present study provides the first in vivo evidence that homocysteine immunoreactive astrocytes were found in the central nervous system of symptomatic SOD(G93A) transgenic mice, suggesting that reactive astrocytes may play an important role in the pathogenesis and progress of ALS. This study also suggests that increased expression of homocysteine in the hippocampal neurons might reflect a role of homocysteine in an abnormality of hippocampal function of ALS.

Visual and auditory event-related potentials in sporadic amyotrophic lateral sclerosis

OBJECTIVES

To investigate the relationship between amyotrophic lateral sclerosis (ALS) and cognitive function by means of oddball event-related potentials (ERPs) and to determine the usefulness of this methodology in the cognitive status assessment of physically disabled patients.

METHODS

Visual and auditory oddball ERPs were recorded in 16 consecutive sporadic ALS patients. A comprehensive battery of neuropsychological (NP) tests assessed intelligence, executive functions, attention, memory, word fluency, visuo-motor and visual-constructive skills.

RESULTS

All patients performed visual and auditory ERPs and 75% of cases showed abnormal N200 and/or P300 waves. Ten patients (62.5%) carried out the entire psychometric evaluation with significant impairment on tests of executive function and attention. A significant correlation between delayed visual (P<0.04) and auditory (P<0.04) P300 latency and impaired NP tests was found.

CONCLUSIONS

In agreement with literature data, our findings confirm the hypothesis of cognitive impairment in ALS patients especially on attention and executive functions suggesting a more extensive degeneration beyond the motor areas. ALS causes severe physical disabilities and such a condition may interfere with NP testing. Thus, the P300 seems to be a useful tool for the assessment of cognition and attention when severe physical deficits are present.

Frontal lobe dysfunction in amyotrophic lateral sclerosis

The aim of the present study was to investigate the involvement of frontal lobe dysfunction in amyotrophic lateral sclerosis (ALS) using ocular motor paradigms and neuropsychological testing. Fifty-one patients with ALS participated in the following ocular motor tasks: (1) a three-choice task and (2) a remembered saccade task. The patients underwent a clinical and neuropsychological evaluation. One-third of ALS patients presented with signs of frontal dysfunction, as determined by their high distractibility factors (DF) in the three-choice task and their performances in both the Wisconsin and Stroop tests. ALS patients exhibited longer latencies to eye movement than controls in the performance of the remembered saccade task, specifically in performance of both remembered and delayed saccades, but saccade accuracy was not impaired. Finally, performance indices of the ocular motor tasks, in particular the DF, was correlated only with the degree of dysarthria.

Complex cognitive disruption in frontal dementia related to motor neuron disease

We describe a patient in whom motor neuron disease and frontal dementia showed concomitant development. This patient underwent a detailed and sequential neurolinguistic assessment, which indicated an alteration in language planning, language comprehension, and morphosyntactic operations. He showed also attention deficit, abstract reasoning disturbances, and prosopoagnosia which became worse during the year follow-up. We suggest that a more specific and sensitive neurolinguistic and neuropsychological test battery must be used to detect and study the entire disruption of cognitive processes in frontal dementia related to motor neuron disease.

Immunohistochemical study on the distribution of Bcl-2 and Bax in the central nervous system of the transgenic mice expressing a human Cu/Zn SOD mutation

In the present study, we performed immunohistochemical studies to investigate the changes of Bcl-2 and Bax in the central nervous system of the transgenic mice expressing a human Cu/Zn SOD mutation. In contrast to the controls, a high density of Bcl-2-IR astrocytes were detected all around the gray matter of the spinal cord of the mutant transgenic mice. Bcl-2-IR astrocytes were also detected in the cerebellum and brainstem of transgenic mice. Specific immunoreactivity for Bax was seen in the spinal cord and brainstem of transgenic mice. Immunostaining for Bax was identified only in neurons and not in glial cells. Our present study demonstrated the distribution of Bcl-2 and Bax in detail using immunohistochemical methods through the central nervous system of the transgenic mice, for the first time.

Cognitive change in motor neurone disease/amyotrophic lateral sclerosis (MND/ALS)

A motor neuronopathy complicating frontotemporal dementia (FTD) has been recognised and designated FTD/motor neurone disease (MND). FTD is characterised by profound character change and altered social conduct, and executive deficits, reflecting focal degeneration of the frontal and temporal neocortex. The motor neuronopathy comprises bulbar palsy and limb amyotrophy. The major histological change is typically of microvacuolation of the cerebral cortex, with atrophy of the bulbar neurones and anterior horn cells of the spinal cord. Ubiquitinated inclusion bodies occur in large pyramidal cortical neurones and in surviving cranial nerve nuclei and anterior horn cells. Evidence is emerging that some patients with classical MND/amyotrophic lateral sclerosis (ALS), who are thought not to be demented, develop cognitive deficits in the realm of frontal executive functions. Moreover, frontal lobe abnormalities have been demonstrated by neuroimaging. The findings point to a link between FTD/MND and cMND/ALS and suggest that a proportion of patients with cMND/ALS go on to develop FTD. Patients with cMND/ALS may not be equally vulnerable. The hypothesis is that patients who present with bulbar palsy and amyotrophy, rather than corticospinal and corticobulbar features, may be most susceptible to the development of FTD.

Verbal fluency and executive dysfunction in amyotrophic lateral sclerosis (ALS)

Neuropsychological investigations of amyotrophic lateral sclerosis (ALS) patients have revealed variable results on specific tests, despite a similar overall cognitive profile of predominantly executive dysfunction with some evidence of memory impairment. The most striking and consistent deficit is found using tests of verbal fluency. The current investigation explored why verbal fluency is particularly sensitive to the impairment in ALS, by investigating some of the underlying cognitive processes: (i) intrinsic response generation; (ii) phonological loop functions; and (iii) simple word retrieval. Twenty-two ALS patients and 25 healthy controls were investigated. The battery included: (i) written and spoken letter-based fluency, category fluency, design fluency; (ii) the Phonological Similarities effect and Word Length Effect; and (iii) computerised sentence completion and confrontational naming. The tests were designed to control for motor speed and to accommodate for the range of disabilities that are present in ALS patients. Significant impairments were found on some tests of intrinsic response generation, namely the Written Verbal Fluency Test, Category Fluency Test (generation of animal names) and Design Fluency Test. Phonological loop functions appeared to be intact with evidence of both the Phonological Similarities and Word Length Effects, but the ALS patients displayed significantly reduced working memory capacity. No deficits were found on tests of simple word retrieval. The findings indicate that verbal fluency impairments in ALS patients result from a higher order dysfunction, implicating deficits in the supervisory attentional system or central executive component of working memory, and are not caused or exaggerated by an impairment in phonological loop functions or in primary linguistic abilities. The study also demonstrates the importance of controlling for differences in motor speed, which may have served to exaggerate the presence of cognitive deficits in ALS patients reported by some other studies.

Immunocytochemical study on the distribution of nitrotyrosine in the brain of the transgenic mice expressing a human Cu/Zn SOD mutation

In the previous study, we reported increased NOS expression in the astrocytes in the spinal cord of the transgenic mice that are used as ALS animal model. In the present study, we performed immunocytochemical studies to investigate the changes of nitrotyrosine-immunoreactivity in the brains of the transgenic mice, and demonstrated in vivo evidence of peroxynitrite-mediated oxidative damage in the pathogenesis of ALS. In the spinal cord of the transgenic mice, immunocytochemistry showed intensely stained nitrotyrosine-IR glial cells with the appearance of astrocytes, but no nitrotyrosine-IR glial cells were observed in the spinal cord of the control mice. In the transgenic mice, nitrotyrosine-IR neurons were observed in the hypoglossal nucleus, lateral reticular nucleus, medullary reticular formation and cerebellar nuclei. Interestingly, nitrotyrosine-IR neurons were observed in the hippocampal formation and septal area of the transgenic mice. In the hippocampus, nitrotyrosine-IR neurons in the CA1 region showed intense staining, and the immunoreactivity was localized mainly in the pyramidal cell layer. Recent studies have shown that antioxidants and selective neuronal NOS inhibitor increase survival in the SOD1 transgenic mouse model of FALS. It is possible that therapy with these agents may slow the neurodegenerative process in human ALS, perhaps through reduction of nitrotyrosine formation.

Fronto-temporal dementia and motor neuron disease: a neuropsychological study

The neuropsychological follow-up study of a 58-year-old man suffering from Motor Neuron Disease (ALS/MND) and Fronto-Temporal Dementia (FTD) is reported. Neuromuscular signs first appeared at the age of 51 and slowly progressed to late bulbar involvement; behavioural symptoms of the frontal type first appeared around age 53; lastly, several neuropsychological symptoms suggestive of worsening temporal involvement supervened at age 57. Our patient died at 59 of respiratory failure with the classic clinical and neuroradiological picture of FTD. A short discussion addresses the controversial issue of the coupling of ALS/MND with Dementia and its possible interpretation as the expression of a chance association of relatively common diseases, versus that of a single multifaceted disease. The role of a detailed neuropsychological assessment is highlighted, within the context of increasingly specific diagnostic criteria for FTD.

Amyotrophic lateral sclerosis with dementia. Case report

A patient is described in whom a profound and rapidly progressive dementia occurred in association with clinical features of amyotrophic lateral sclerosis. A magnetic resonance imaging showed signs of frontal and especially left temporal atrophy. The pattern of dementia indicated impaired frontotemporal lobe functions, evidenced by reduced tracer uptake in the frontotemporal lobes on brain single photon emission computed tomography. Neuropathological examination in this patient revealed mild frontotemporal atrophy with spongiform changes and neuronal loss affecting mainly layers II and III of the frontotemporal cortices. There was atrophy of the hypoglossal nuclei. The spinal cord changes were consistent with motor neuron disease. The patient showed an irreversible and progressive course. A review of the relevant literature was made.

Recognition memory deficits in amyotrophic lateral sclerosis assessed with event-related brain potentials

OBJECTIVES

Amyotrophic lateral sclerosis (ALS) has been shown to cause neuropsychological deficits. The present investigation sought to delineate memory deficits by recording cognitive event-related potentials (ERPs).

SUBJECTS AND METHODS

Eight ALS patients and 8 matched controls were subjected to a 2-phase recognition memory test. During the first phase words were presented consecutively on a video-screen with one-third of the words being repeated. The subject had to press buttons according to whether a word had been repeated or not. During the second phase (delay 1 h) a second list containing 33% old items from phase 1 and 66% new words was shown with an old/new decision required.

RESULTS

ALS patients showed less accurate recognition in the second phase. The ERPs of the controls showed a reliable difference between old and new items in both phases. This difference was nearly absent in the patients in both phases.

CONCLUSION

The ERP pattern suggests abnormal memory processes in ALS. The results are compared with data from similar experiments in Huntington's and Alzheimer's disease and are interpreted in terms of an encoding deficit in ALS.

Dementia of frontal type and dementias with subcortical gliosis

The group of Frontotemporal dementias (FTD) is composed of non-Alzheimer forms of dementia characterized clinically by behavioural and personality change leading to apathy and mutism. The disorder is associated with a progressive atrophy of the frontal, anterior temporal and anterior parietal lobes of the brain with several types of underlying pathology. One type (frontal lobe degeneration) is characterized by a microvacuolar degeneration of the outer cortical laminae along with a mild and mainly subpial gliosis and a loss of nerve cells, mostly from layers II and III. Another type shows transcortical tissue cavitation and florid gliosis with neuronal degeneration characterized by the presence of tau and ubiquitin positive inclusion bodies and alpha beta-crystallin-positive ballooned neurones: such changes have been termed 'Pick-type histology', and form the basis for the modern definition of 'Pick's disease'. The aetiological relationship between these two histological types is presently unknown. Both histologies can be differently distributed topographically throughout the brain to produce syndromes of progressive language disorder, when affecting bitemporal lobes or the left hemisphere preferentially, or progressive apraxia when parietal and motor regions are involved. Either pathology can be combined with or overlaps with that of classical motor neurone disease to produce motor neurone disease dementia. The underlying cause of FTD is unknown but genetic factors are strongly implicated. About half of cases show a previous family history of a similar disorder. In several families bearing a FTD clinical and pathological phenotype, linkage to chromosome 17 has been established but the pathology of this group appears distinctive and its relation to other forms of FTD awaits further elucidation. It is still possible that the many clinical and pathological variants of FTD may reflect different phenotypic expressions of a particular genetic change(s) at a single locus on this chromosome.

Relation between cognitive dysfunction and pseudobulbar palsy in amyotrophic lateral sclerosis

OBJECTIVES

To examine the relation between cognitive dysfunction and pseudobulbar features in patients with amyotrophic lateral sclerosis (ALS).

METHODS

The performance of two patient groups, ALS with pseudobulbar palsy (n = 24) and ALS without pseudobulbar palsy (n = 28), was compared with 28 healthy age matched controls on an extensive neuropsychological battery. Tests used were the national adult reading test, short form of the WAIS-R, recognition memory test, Kendrick object learning test, paired associate learning, Wisconsin card sorting test, verbal fluency, Stroop and negative priming tests, a random movement joystick test, and a computerised Tower of Hanoi test.

RESULTS

Tests of executive function showed a pronounced deficit on written verbal fluency in both ALS groups in comparison to controls, which tended to be more prominent in patients with ALS with pseudobulbar palsy. The random movement joystick test (a non-verbal test of intrinsic movement generation) showed an impairment in the generation of random sequences in patients with pseudobulbar palsy only. The computerised Tower of Hanoi showed a subtle planning impairment (shorter planning times) in all the patients with ALS compared with controls on trials requiring more complex solutions. In addition the pseudobulbar patients displayed shorter planning times on complex trials, and tended to solve these trials less accurately. There was also evidence of a deficit for all patients with ALS in comparison with controls on total errors and number of categories achieved on the Wisconsin card sorting test and a strong tendency towards an impairment on a task of selective attention and cognitive inhibition (negative priming). A word recognition memory deficit was showed across both ALS groups.

CONCLUSIONS

This study elicited cognitive deficits (involving predominantly executive processes, with some evidence of memory impairment) in patients with ALS and further strengthened the link between ALS and frontal lobe dysfunction, this being more prominent in patients with pseudobulbar palsy. However, cognitive impairments suggestive of extramotor cortical involvement were not exclusive to this subgroup.

Prevalence and correlates of neuropsychological deficits in amyotrophic lateral sclerosis

OBJECTIVE

To determine the prevalence and correlates of neuropsychological impairment in a large cohort (n = 146) of patients with typical, sporadic (non-familial) amyotrophic lateral sclerosis.

METHODS

A battery of neuropsychological tests was administered to patients with amyotrophic lateral sclerosis who were attending a monthly outpatient clinic or who were in hospital undergoing diagnostic tests.

RESULTS

Comparing individual patient's scores with relevant normative data, 35.6% of the patients displayed evidence of clinically significant impairment, performing at or below the 5th percentile on at least two of the eight neuropsychological measures. Deficits were most common in the areas of problem solving, attention/mental control, continuous visual recognition memory, word generation, and verbal free recall. Impairment was most prevalent in patients with dysarthria (48.5%), but 27.4% of non-dysarthric patients were also impaired. Impaired patients had more severe or widespread symptoms of amyotrophic lateral sclerosis than non-impaired patients, and had fewer years of education.

CONCLUSION

Neither the conventional wisdom that cognition is intact in nearly all patients with amyotrophic lateral sclerosis, nor more recent suggestions that cognition is often at least mildly impaired seems to be correct. A minority of patients with amyotrophic lateral sclerosis displayed evidence of significant impairment. Dysarthria, low education, and greater severity of motor symptoms were risk factors for impairment.

Nonverbal visual attention, but not recognition memory of learning, processes are impaired in motor neurone disease

Pathology outside the motor system is being increasingly recognised in motor neurone disease (MND) and up to 3% of patients may have overt dementia of frontal lobe type; it is not clear whether milder cognitive disturbance is a more frequent feature of the disease. Standard neuropsychological testing can be difficult in MND and we therefore used the microcomputer-controlled Cambridge Neuropsychological Test Automated Battery (CANTAB), which allows accurate assessment in the presence of motor and bulbar dysfunction. The results of subtests evaluating nonverbal visual attention, recognition memory and learning from a large (n = 50) group of patients with MND compared to normal (n = 27) and neurological disease (n = 23) control groups are presented in this report. The MND group showed significant impairment in a focal attention (visual search) task, but no deficits in memory or learning. Inspection of the visual search data showed that up to a quarter of the MND patients scored two or more standard deviations below the mean control score. It is suggested that this reflects pathology in fronto-striatal circuitry.

Cognition, language, and speech in amyotrophic lateral sclerosis: a review

Amyotrophic lateral sclerosis (ALS) is a progressive, adult-onset neurodegenerative disorder manifesting as a relentless loss of motor capabilities and, ultimately, death. Traditionally thought to affect solely the lower motor neurons and corticospinal tracts, recent studies suggest that the pathogenic process of ALS is more extensive, involving dysfunction of cortical grey and white matter with clinical correlates of impairment in cognition and language. The impact of speech and motor deficits are discussed in relation to the issues of assessment of cognition and language. Three case studies are presented for illustrative purposes. Finally, direction for future research to investigate cognitive dysfunction in ALS are presented.

Parkinsonism in motor neuron disease: case report and literature review

This report describes a patient who had clinical features of both motor neuron disease and Parkinson's disease. Neuropathological examination and immunocytochemical studies showed that he had motor neuron disease of the progressive muscular atrophy type, and Lewy body Parkinson's disease, with intracytoplasmic inclusion bodies characteristic of both conditions. This is the first detailed description of these two diseases occurring concurrently in the same patient. A review of all previously reported cases of combined motor neuron disease and parkinsonism has led to the following conclusions: (1) that these two neuropathologically defined diseases occur together very infrequently, but (2) that parkinsonism and substantia nigra degeneration are not uncommon as part of the multi-system disease process underlying motor neuron disease.

Reactive astrocytes are widespread in the cortical gray matter of amyotrophic lateral sclerosis

The distribution of reactive astrocytes was examined in the cortical gray matter of non-motor and motor regions from cases of familial and sporadic amyotrophic lateral sclerosis (ALS) and compared to that of beta-amyloid deposits. By glial fibrillary acidic protein immunocytochemistry, patches of reactive astrocytes, characterized by multiple reactive astrocytes in a circular or patch-like formation, occurred in 12 of 15 ALS cases examined. These patches of reactive astrocytes were not restricted to the motor cortex but were found in the gray matter in ALS in all examined brain regions, including frontal, temporal, inferior parietal, cingulate, occipital, and motor cortices, from both familial and sporadic ALS cases. Reactive astrocytes were also found in the subpial region and at the gray/white matter junction. Because patches of astrocytes can occur in association with senile plaques, beta-amyloid was localized. By immunostaining, beta-amyloid deposits were observed in five of the 15 ALS cases: three cases had only early plaques, two had both early and classic plaques. The number of ALS cases with both astrocyte patches and amyloid plaques was four of 15, but typically astrocyte patches in ALS occurred without any evidence of an association with beta-amyloid deposits. Therefore, the astrocyte patches in ALS are not the result of beta-amyloid deposition. The widespread occurrence of reactive astrocytes, as patches in the cortical gray matter and in the subpial region and at the gray/white matter junction, is evidence of a widespread pathology in ALS cortex in both familial and sporadic forms of the disease.

Reversible cognitive decline during high-dose alpha-interferon treatment

The cognitive effects of high-dose human leukocyte alpha-interferon (IFN-alpha) treatment were evaluated among 15 patients with the newly diagnosed spinal form of amyotrophic lateral sclerosis (ALS). To confirm the earlier findings showing reversible effects on cognitive performance and to exclude confounding effects, a randomized blinded placebo controlled study was conducted. Twelve patients with continuous intravenous IFN-alpha-infusion treatment over five days and 3 placebo control patients were neuropsychologically evaluated. The neuropsychological examination included tests of intelligence, memory, complex mental processing, visuoconstructional skills, writing, and calculation. A clear difference in the performance profiles of the placebo and the IFN-alpha-treated patient groups was detected: The IFN-alpha group showed significant deterioration during treatment in the digit span backwards task, logical verbal memory task, calculation ability, and writing time, while improvement was seen after treatment. Concomitant fever did not explain the findings. In the placebo group an improvement indicating a learning effect in the three consecutive measurements was found. The reversible cognitive deterioration indicates a clear CNS effect during the IFN-alpha treatment.

Cognitive and memory deficits in untreated Parkinson's disease and amyotrophic lateral sclerosis patients: a comparative study

We investigated the profile of cognitive and memory deficits of 22 Parkinson's disease (PD), 24 amyotrophic lateral sclerosis (ALS) patients and 26 age-matched controls. The patients were at the early phase of the disease and untreated. The ALS patients exhibited deficits in simple visuoperceptual functions and in complex visuoperceptual reasoning (Digit Symbol and Block Design tests), whereas the PD patients showed deficits only in simple visuoperceptual functions. Moreover, both ALS and PD patients had impairment in tasks requiring set shifting from one reaction to another that may suggest frontal lobe dysfunction. The ALS and PD patients also showed impairment in the task of learning a word list with effort-demanding organization of the material to be remembered. However, preserved delayed recall of logical passages suggests that memory, per se, is not impaired in ALS or in PD. The patterns of errors in a test of recognition of learned words imply, at least partially, different underlying deficits in the two diseases. An inability to inhibit irrelevant information may contribute to memory impairment in ALS patients, whereas the memory deficit in PD may derive from lowered motivation or initiating behaviour.

Hippocampal and neocortical ubiquitin-immunoreactive inclusions in amyotrophic lateral sclerosis with dementia

Amyotrophic lateral sclerosis (ALS) patients with dementia were found to have ubiquitin-immunoreactive (IR) inclusions in the dentate granule cells of the hippocampus. These inclusions were also present in some patients with minor cognitive changes but otherwise typical ALS. Ubiquitin-IR inclusions were also found in neurons of superficial layers of the frontal and temporal cortex and in the entorhinal cortex in patients with ALS and dementia. These ubiquitin-IR inclusions were non-argyrophilic, and were not labelled by antibodies which identify Alzheimer's neurofibrillary tangles and Pick bodies, nor were they typical of cortical Lewy bodies. Our findings indicate that ubiquitin-IR inclusions in small neurons of the hippocampus, entorhinal area and neocortex are a characteristic feature of degeneration of non-motor cortex in ALS, and are particularly associated with cognitive impairment and dementia of frontal lobe type.

Motor neuron disease and dementia reported among 13 members of a single family

All 49 members of four generations of a family were identified. In the first three generations eight members were afflicted with dementia, whereas in the fourth generation only one was demented but three of four were afflicted with motor neuron disease and they also had slight cognitive deficiencies. The pattern of heredity is compatible with dominant autosomal inheritance. Neuropsychological testing revealed affection mostly of the frontal lobes. A pedigree and six case reports are presented.