Spatial cognition in young children with spinal muscular atrophy

Cognitive impairment in children with 5q-associated spinal muscular atrophy type 1: two case reports and the review of the literature

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused by mutations in the survival motor neuron 1 (SMN1) gene on chromosome 5, leading to the degeneration of lower motor neurons. There are few studies on cognitive impairment comorbid with SMA. Here, we report two cases of severe cognitive impairment in Chinese children with SMA type 1, marking the first such reports in this demographic. We propose that severe cognitive dysfunction may be a comorbidity of SMA. Clinicians should consider SMA in patients presenting with severe muscle weakness and atrophy accompanied by cognitive impairments, to avoid misdiagnosis and oversight.

Exploring variability in cognitive functioning in patients with spinal muscular atrophy: a scoping review

The cognitive functioning of individuals with spinal muscular atrophy (SMA) is not well understood, prompting a call for more research to better grasp cognitive involvement in SMA. This study aims to explore recent findings regarding cognitive outcomes in SMA patients, including correlations between clinical features and cognitive abilities. The investigation seeks to identify commonly used measures for assessing cognitive function in this patient population. A scoping review following the Joanna Briggs Institute methodology examined literature until December 2023. Two databases were searched along with relevant article references using specific terms such as "spinal muscular atrophy," "SMA," "cognitive," "abilities," "functions," "intellective," or "intellectual." Screening focused on titles and abstracts from English language peer-reviewed journals. After the initial research, 1452 articles were identified. Subsequent screening and selection led to the inclusion of 13 articles in the review. Among these studies, four indicated a cognitive trend within the normal range for SMA patients. In four other studies, the majority of patients fell within the normal range. However, smaller proportions were observed to be either above or below the norm compared to the controls. Three studies reported noted cognitive performance below the average, while two showed above-average scores. The scoping review suggests that most SMA patients have cognitive abilities similar to the general population, with types II and III showing even lesser impact. However, certain cognitive domains may be affected in type I patients, highlighting the need for further research to fully understand cognitive involvement in SMA.

Impaired Neurodevelopment in Children with 5q-SMA - 2 Years After Newborn Screening

OBJECTIVE

Numerous studies have consistently found that reduced SMN protein expression does not severely affect cognitive function in SMA patients. However, the average intelligence quotient of SMA patients has ranged above to below average in different studies. The cognitive development of SMA patients identified through newborn screening remains largely unknown.

METHODS

40 of 47 eligible SMA patients (23 females/17 males) from 39 families identified through newborn screening between January 2018 and December 2020 underwent developmental testing using Bayley III (BSID) after the 2 years of age. The mean age was 29.25 months (23-42 months). 17 patients had 2, 11 patients had 3 and 12 patients had ≥4 copies of SMN2.

RESULTS

cognitive scale: mean 94.55 (SD 24.01); language scale: mean 86.09 (SD 26.41); motor scale: 81.28 (SD 28.07). Overall, the cognitive scales show that 14 children were below average, 20 children were average and 6 children were above average. 10/14 children with below average scores had 2 SMN2 copies. The post-hoc pairwise comparisons showed that the cognition main scale was significantly more sensitive to the number of SMN2 copies than the motor main scale of the BSID (MΔ= 10.27, p = 0.014). There is also evidence that cognition scored higher than the language main scale (MΔ= 7.11, p = 0.090).

CONCLUSION

The impaired cognitive development of SMA children with 2 SMN2 copies, despite early initiation of therapy, underscores the critical role of the SMN protein in the early stages of brain development.

Profile of cognitive abilities in spinal muscular atrophy type II and III: what is the role of motor impairment?

There has recently been some concern on possible cognitive impairment in patients with Spinal Muscular Atrophy (SMA). The aim of this study was to assess cognitive profiles in type II and III SMA with a focus on individual indexes and possible correlations with motor function. 57 type II and III individuals, aged 3.5-17 years, were consecutively enrolled in a prospective, multicentric study. Cognitive function was assessed using age-appropriate Weschler Scales. Motor function was concomitantly assessed using disease-specific functional scales. Only 2 individuals (3%) had a intellectual disability of mild degree while the others were within normal range, with no significant difference in relation to SMA type, gender or functional status. While the overall quotients were mostly within normal range, some indexes showed wider variability. A significant positive medium correlation was found between Processing Speed Index and motor functional scores. Working memory had lower scores in type III patients compared to type II. Intellectual disability is uncommon in type II and III SMA. Motor functional abilities may play a role in some of the items contributing to the overall cognitive profile.

The Impact of Limited Previous Motor Experience on Action Possibility Judgments in People with Spinal Muscle Atrophy

Previous studies have shown that people with limited motor capabilities may rely on previous motor experience when making action possibility judgments for others. In the present study, we examined if having limited previous motor experience, as a consequence of spinal muscle atrophy (SMA), alters action possibility judgments. Participants with SMA and neurologically healthy (NH) sex- and age-matched controls performed a perceptual-motor judgment task using the Fitts's law paradigm. Participants observed apparent motion videos of reciprocal aiming movements with varying levels of difficulty. For each movement, participants predicted the shortest movement time (MT) at which a neurologically healthy young adult could accurately perform the task. Participants with SMA predicted significantly longer MTs compared to controls; however, the predicted MTs of both SMA and NH participants exhibited a Fitts's law relationship (i.e., the predicted MTs significantly increased as movement difficulty increased). Overall, these results provide evidence that participants with SMA who have limited, or no motor experience may make more conservative action possibility judgments for others. Critically, our finding that the pattern of action possibility judgments was not different between SMA and NH groups suggests that limited previous motor experience may not completely impair action possibility judgments.

Cognitive performance of adult patients with SMA before and after treatment initiation with nusinersen

BACKGROUND

Spinal muscular atrophy (SMA) is a genetic neuromuscular disease caused by mutations of the SMN1 gene. Deficient SMN protein causes irreversible degeneration of alpha motor neurons characterized by progressive muscle weakness and atrophy. Considering that SMA is a multi-systemic disorder and SMN protein was found to be expressed in cortical structures, the cognitive profile of adult patients with SMA has recently been of particular interest. With nusinersen, a novel, disease-modifying drug has been established, but its effects on neuropsychological functions have not been validated yet. Aim of this study was to investigate the cognitive profile of adult patients with SMA during treatment initiation with nusinersen and to reveal improvement or deterioration in cognitive performance.

METHODS

This monocentric longitudinal study included 23 patients with SMA type 2 and 3. All patients were assessed with the Edinburgh Cognitive and Behavioral ALS Screen (ECAS) before and after 14 months of treatment initiation with nusinersen. Additionally, motor function was evaluated by Hammersmith Functional Motor Scale Expanded (HFMSE), Revised Upper Limb Module (RULM) and Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R).

RESULTS

Of the treatment-naive patients, only three were below the age- and education-matched cut-off for cognitive impairment in the ECAS total score. Significant differences between SMA type 2 and 3 were only detected in the domain of Language. After 14 months of treatment, patients showed significant improvement of absolute scores in all three ALS-specific domains, in the non-ALS-specific domain of Memory, in both subscores and in the ECAS total score. No associations were detected between cognitive and functional outcome measures.

CONCLUSIONS

In some adult patients with SMA abnormal cognitive performance in ALS-specific functions of the ECAS was evident. However, the presented results suggest no clinically significant cognitive changes during the observed treatment period with nusinersen.

Neuromuscular Diseases Affect Number Representation and Processing: An Exploratory Study

Spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD) both are rare genetic neuromuscular diseases with progressive loss of motor ability. The neuromotor developmental course of those diseases is well documented. In contrast, there is only little evidence about characteristics of general and specific cognitive development. In both conditions the final motor outcome is characterized by an inability to move autonomously: children with SMA never accomplish independent motoric exploration of their environment, while children with DMD do but later lose this ability again. These profound differences in developmental pathways might affect cognitive development of SMA vs. DMD children, as cognition is shaped by individual motor experiences. DMD patients show impaired executive functions, working memory, and verbal IQ, whereas only motor ability seems to be impaired in SMA. Advanced cognitive capacity in SMA may serve as a compensatory mechanism for achieving in education, career progression, and social satisfaction. This study aimed to relate differences in basic numerical concepts and arithmetic achievement in SMA and DMD patients to differences in their motor development and resulting sensorimotor and environmental experiences. Horizontal and vertical spatial-numerical associations were explored in SMA/DMD children ranging between 6 and 12 years through the random number generation task. Furthermore, arithmetic skills as well as general cognitive ability were assessed. Groups differed in spatial number processing as well as in arithmetic and domain-general cognitive functions. Children with SMA showed no horizontal and even reversed vertical spatial-numerical associations. Children with DMD on the other hand revealed patterns in spatial numerical associations comparable to healthy developing children. From the embodied Cognition perspective, early sensorimotor experience does play a role in development of mental number representations. However, it remains open whether and how this becomes relevant for the acquisition of higher order cognitive and arithmetic skills.

Cognitive Impairment in Adult Patients with 5q-Associated Spinal Muscular Atrophy

In previous studies, a below-average, average, or above-average intelligence quotient (IQ) in children with SMA was detected but, aside from a severe physical disability, the cognitive performance of adult SMA patients has not yet been evaluated. The intelligence test used in this study, the Wechsler Adult Intelligence Scale, fourth edition (WAIS-IV), was used to measure major intelligence components of adult SMA patients. The WAIS-IV determines four index scores representing verbal comprehension, perceptual reasoning, working memory, and processing speed. Due to time-dependent demands on motor function, the processing speed index score was excluded. IQ index scores of 33 adult SMA patients did not differ from IQ index scores of the normal population. In SMA type-3 patients, the index scores for verbal comprehension, perceptual reasoning, and working memory did not differ from the normal population but showed a trend of IQ scores towards lower points. Patients with SMA type 2 had lower IQ index scores for working memory (90.33 ± 12.95; p = 0.012) and perceptual reasoning (90.73 ± 12.58; p = 0.013) than the normal population. This study provided further evidence that SMA is a multi-systemic disease and may refute the widespread hypothesis that SMA patients might improve their cognitive skills to compensate for their physical impairment.

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.

Executive function is inversely correlated with physical function: the cognitive profile of adult Spinal Muscular Atrophy (SMA)

Background

Spinal muscular atrophy (SMA) issues from mutations in the survival of motor neuron (SMN) 1 gene. Loss or reduction of the SMN protein results in progressive muscle weakness. Whether this protein deficiency also affects cortical function remains unclear. While no data on adult patients exists so far, prior studies in children with SMA indicate cognitive abilities equal or even superior to healthy controls. This may suggest a possible compensatory—neuropsychological and interactional—process. The goal of this study was to assess the cognitive profile of adult patients with SMA, with a special focus on social cognition as a potential candidate for enhanced cognitive function through compensatory processes.

Methods

In a cross-sectional design, N = 31 adult SMA patients (types II and III) were assessed for language, verbal fluency, memory, visuospatial abilities and executive function with the Edinburgh Cognitive and Behavioural ALS Screen and for social cognition with the Reading the Mind in the Eyes Test. Physical function was evaluated using the Hammersmith Functional Motor Scale Expanded. N = 19 neurologically healthy controls were matched with patients for age, sex and years of education.

Results

In none of the abovementioned cognitive domains significant differences between SMA patients and controls were found. Among patients, no differences between type II SMA and type III SMA were detected for any domain. However, a trend towards better social cognition in patients with type II SMA, compared to those with type III SMA was observed. Furthermore, a significant inverse correlation of physical function and executive function was detected: lower motor function was associated with a better executive function.

Conclusions

This study shows cognitive abilities in adult SMA in the normal range for all assessed domains. Thus, reduction of SMN protein has no obvious negative impact on cognitive function. Executive functions are identified as the only cognitive domain correlated with disease severity. Therefore, executive functions may play a role in the adaptation to physical restrictions in SMA, making them a promising target for future research.

Cognitive Performance of Patients with Adult 5q-Spinal Muscular Atrophy and with Amyotrophic Lateral Sclerosis

Motor neuron diseases, such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS), share several clinical similarities while differing substantially in etiology, disease onset and progression. Cognitive dysfunction, a clinically relevant non-motor feature in a substantial proportion of ALS patients, has been less frequently investigated in SMA. In this prospective multicenter cross-sectional study, cognitive function was assessed by the Edinburgh Cognitive (and Behavioural) ALS Screen (ECAS) and a German vocabulary test (Wortschatztest, WST) in 34 adult patients with SMA types 2-4 and in 34 patients with ALS. Demographic and clinical parameters were assessed to identify factors that potentially influence cognitive function. While SMA and ALS patients were comparable in the vocabulary test, on average, SMA patients performed better than ALS patients in the cognitive domains of memory, language and executive function. Better cognitive abilities in SMA patients seemed to be related to the early onset, rather than the extent or the duration, of their physical handicap. Future studies should focus on disease-specific cognitive functions in SMA.

Functional Abnormalities of Cerebellum and Motor Cortex in Spinal Muscular Atrophy Mice

Spinal muscular atrophy (SMA) is a devastating genetic neuromuscular disease. Diffuse neuropathology has been reported in SMA patients and mouse models, however, functional changes in brain regions have not been studied. In the SMNΔ7 mouse model, we identified three types of differences in neuronal function in the cerebellum and motor cortex from two age groups: P7-9 (P7) and P11-14 (P11). Microelectrode array studies revealed significantly lower spontaneous firing and network activity in the cerebellum of SMA mice in both age groups, but it was more profound in the P11 group. In the motor cortex, however, neural activity was not different in either age group. Whole-cell patch-clamp was used to study the function of output neurons in both brain regions. In cerebellar Purkinje cells (PCs) of SMA mice, the input resistance was larger at P7, while capacitance was smaller at P11. In the motor cortex, no difference was observed in the passive membrane properties of layer V pyramidal neurons (PN5s). The action potential threshold of both types of output neurons was depolarized in the P11 group. We also observed lower spontaneous excitatory and inhibitory synaptic activity in PN5s and PCs respectively from P11 SMA mice. Overall, these differences suggest functional alterations in the neural network in these motor regions that change during development. Our results also suggest that neuronal dysfunction in these brain regions may contribute to the pathology of SMA. Comprehensive treatment strategies may consider motor regions outside of the spinal cord for better outcomes.

Cognitive performance of children with spinal muscular atrophy: A systematic review

Spinal muscular atrophy (SMA) is genetic and progressive, caused by large bi-allelic deletions in the SMN1 gene, or the association of a large deletion and a null variant.

Cognition-Action Trade-Offs Reflect Organization of Attention in Infancy

This chapter discusses what cognition-action trade-offs in infancy reveal about the organization and developmental trajectory of attention. We focus on internal attention because this aspect is most relevant to the immediate concerns of infancy, such as fluctuating levels of expertise, balancing multiple taxing skills simultaneously, learning how to control attention under variable conditions, and coordinating distinct psychological domains. Cognition-action trade-offs observed across the life span include perseveration during skill emergence, errors and inefficient strategies during decision making, and the allocation of resources when attention is taxed. An embodied cognitive-load account interprets these behavioral patterns as a result of limited attentional resources allocated across simultaneous, taxing task demands. For populations where motor errors could be costly, like infants and the elderly, attention is typically devoted to motor demands with errors occurring in the cognitive domain. In contrast, healthy young adults tend to preserve their cognitive performance by modifying their actions.

Current Status of the Utilization of Powered Wheelchair in Preschool Children with Locomotive Disability in Japan

[Purpose] This study aimed to elucidate the actual state of powered wheelchair (PWC) prescription for preschool children with disabilities in Japan, and also to determine the approximate number of preschool children with disabilities who would potentially benefit from PWC use. [Subjects and Methods] A total of 318 facilities providing rehabilitation for disabled children in Japan were enrolled in the study. A questionnaire about PWC use for preschoolers was mailed to the facilities. Each study items were analyzed employing the Fisher's exact test. [Results] Of the 318 facilities, consent to participate in this study was obtained from 108 (return rate: 34.0%). After PWC provision, many facilities reported improvement in quality of life indices for preschool children with disabilities. It was revealed that there were 6 preschool children from 2 to 6 years of age with disabilities who might acquire a means of independent locomotion through PWC provision and thereby experience improved quality of life. [Conclusion] There was no negative comment from the facilities studied about the prescription and provision of PWC for preschool children with disabilities.

Self-locomotion and spatial language and spatial cognition: insights from typical and atypical development

Various studies have shown that occurrence of locomotion in infancy is correlated with the development of spatial cognitive competencies. Recent evidence suggests that locomotor experience might also be important for the development of spatial language. Together these findings suggest that locomotor experience might play a crucial role in the development of linguistic-cognitive spatial skills. However, some studies indicate that, despite their total deprivation of locomotor experience, young children with spinal muscular atrophy (SMA) have the capacity to acquire and use rich spatial representations including good spatial language. Nonetheless, we have to be cautious about what the striking performances displayed by SMA children can reveal on the link between motor and spatial development, as the dynamics of brain development in atypically developing children are different from typically developing children.

Independent mobility after early introduction of a power wheelchair in spinal muscular atrophy

Weakness resulting from spinal muscular atrophy causes severe limitations in functional mobility. The early introduction of power mobility has potential to enhance development and mitigate disability. These outcomes are achieved by simulating normal skill acquisition and by promoting motor learning, visuospatial system development, self-exploration, cognition, and social development. There are few reports on early power mobility in spinal muscular atrophy, and it is typically not prescribed until school age. The authors evaluated 6 children under age 2 years with neuromuscular disease (5 spinal muscular atrophy, 1 congenital muscular dystrophy) for power mobility. Parents recorded the practice hours necessary to achieve independence using the Power Mobility Skills Checklist. Four children achieved independence in all items on the checklist by 7.9 months (range: 73-458 days). Introduction of early power mobility is feasible in spinal muscular atrophy patients under age 2 years and should be introduced in late infancy when children typically acquire locomotor skills.

Cerebellar lesion studies of cognitive function in children and adolescents - limitations and negative findings

An increasing number of human lesion and functional brain imaging studies appear to support the hypothesis that the cerebellum contributes to a wide range of non-motor functions, including attention, language and visuospatial functions. Various abnormalities have been reported in standard neuropsychological tests in children and adolescents who have been treated for cerebellar tumors. This review focuses on limitations of lesion studies and negative findings in children and adolescents with focal cerebellar lesions. Frequently cited early findings have not been replicated in later studies or have been explained by motor components of the tasks. Such discrepancies may relate to a number of methodological problems. In addition to impaired motor function, it is unclear to what extent deficits in neuropsychological tests are caused by unspecific effects such as increased intracranial pressure and depression. Effects of extracerebellar lesions are frequently not considered. Although a role of the cerebellum in specific aspects of non-motor functions seems obvious it is still an open question which cognitive functions are involved, why and to what extent. It is a matter of ongoing discussion whether or not cognitive dysfunction belongs to the symptoms of cerebellar disease. Overall, disorders appear to be mild and far less frequent than disorders observed following lesions of cerebral areas. The aim of the review is to demonstrate that many findings frequently cited to support cerebellar involvement in cognition are insufficient to prove the hypothesis. There is ongoing need of well-controlled lesion studies, which show that disorders are due to cerebellar lesions independent of motor dysfunction and other confounding factors.

Locomotion autonome et cognition spatiale: le paradoxe de l'amyotrophie spinale infantile

Various studies have shown that occurrence of locomotion in infancy is correlated with the development of visuospatial cognitive competencies, suggesting that locomotor experience might play a central role in spatial development, especially in the realm of manual search for hidden objects. However, recent studies indicate that young children with spinal muscular atrophy (SMA), a hereditary neuromuscular disease which results in severe motor impairments, excel in some spatial cognitive skills. Indeed, striking cognitive performances are exhibited by young SMA children in some areas such as the ability to search successfully for hidden objects and the acquisition of the spatial vocabulary. The performances of SMA children suggest that, despite their total deprivation of locomotor experience, they have the capacity to acquire and use rich spatial representations. As a result, locomotor impairment does not appear to be a key risk factor for dramatic slowing down or deviation in the development of spatial search skills.

Can Infant Cognitive Psychology Be Helpful in Understanding Learning Processes?

Since teaching and learning has become a major economic activity of modern society, different learning models can be considered in order to increase its effectiveness and efficiency. For a long time infant cognitive psychology was influenced by nativist theories and, thus, early learning has been underestimated and insufficiently studied. However, in recent years, infant psychology has described developmental sequences, learning situations, and social mechanisms that influence development. Thus, infant psychology appears again to be developmental. Since infant learning is fast and efficient, this paper proposes that it can be considered as a model for teaching and learning in older children and adults. Some examples of early acquired knowledge and some acquisition situations are presented. Conversely, some examples of later failures are exposed. The relevant theoretical contexts are discussed. The consequences of learning mechanisms observed in infants for pedagogy are considered.

Cerebellar agenesis II: motor and language functions

In a former study of a patient with cerebellar agenesis (HK) mild motor deficits, problems in delay eyeblink conditioning and mild to moderate deficits in IQ, planning behavior, visuospatial abilities, visual memory, and attention were found. The present study reports additional findings in the same patient. In the motor domain, impairments in fine motor manipulations, trace eyeblink conditioning and motor imagination in a functional magnetic resonance (fMRI) study were found. Based on fMRI findings; however, cortical areas involved in a tapping task did not significantly differ from a healthy control group. In the cognitive domain, deficits in speech comprehension as well as verbal learning and declarative memory were present. No significant affective symptoms were observed. Although problems in executive, visuospatial and language tasks are in agreement with the so-called cerebellar cognitive affective syndrome-other possibilities remain. Non-motor impairments in HK might also be a consequence of lacking motor abilities in development and motor deficits may interfere with the performance of parts of the cognitive tasks. In addition, lack of promotion and learning opportunities in childhood may contribute and mental retardation based on extracerebellar dysfunction cannot be excluded.