Visual system damage and network maladaptation are associated with cognitive performance in neuromyelitis optica spectrum disorders

Alterations of brain structural and functional connectivity networks topology and decoupling in pediatric myelin oligodendrocyte glycoprotein antibody-associated disease

OBJECTIVE

To investigate the alteration in structural and functional connectivity networks (SCN and FCN) as well as their coupling in pediatric myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), and determine if these properties could serve as potential biomarkers for the disease.

MATERIALS AND METHODS

In total of 32 children with MOGAD and 30 age- and sex-matched healthy controls (HC) were employed to construct the SCN and FCN, respectively. The graph-theoretical analyses of the global properties, node properties of the 90 brain nodes, and the structural-functional connectivity (SC-FC) coupling of the two networks were performed. The graph-theoretical properties that exhibited significant differences were analyzed using partial correlation analysis in conjunction with the clinical scales, including the expanded disability status scale (EDSS), modified Rankin scale (mRS), and pediatric cerebral performance category (PCPC) of the MOGAD group. Subsequently, a machine learning model was developed to discriminate between MOGAD and the HC group, aiming to explore the potential of these properties as biomarkers.

RESULTS

The SCN of the MOGAD group exhibited aberrant global properties, including an increased characteristic path length (Lp) and a decreased global efficiency (Eg), along with reduced nodal properties such as degree centrality (Dc), nodal efficiency (Ne), and local efficiency in multiple nodes. The FCN of the MOGAD group only exhibited decreased Dc, Ne, and betweenness centrality in two nodes of nodal properties. Besides, MOGAD showed a significant decrease in SC-FC coupling compared to the HC group. The analysis of partial correlation revealed significant correlations between several properties and the scales of EDSS and mRS in the MOGAD group. The machine learning method was used to extract six features and establish the model, achieving a classification accuracy of 82.3% for MOGAD.

CONCLUSIONS

Pediatric MOGAD showed a more pronounced impairment in the SCN along with decoupling of SC-FC. Both partial correlation analysis and discriminant modeling suggest that alterations in brain network properties have the potential as biomarkers for assessing brain damage in MOGAD.

Cognitive and psychopathological features of neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease: A narrative review

Clinicians are becoming increasingly aware of the cognitive and psychopathological consequences of neurological diseases, which were once thought to manifest with motor and sensory impairments only. The cognitive profile of multiple sclerosis, in particular, is now well-characterised. Similar efforts are being made to better characterise the cognitive profile of other central nervous system inflammatory demyelinating autoimmune disorders. This review discusses the current understanding of the cognitive and psychological features of neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD). Detailed analysis of the cognitive sequelae of the above conditions can not only assist with understanding disease pathogenesis but also can guide appropriate management of the symptoms and consequently, improve the quality of life and long-term outcomes for these patients. This narrative review will also identify research gaps and provide recommendations for future directions in the field.

Temporal and topological properties of dynamic networks reflect disability in patients with neuromyelitis optica spectrum disorders

Approximately 36% of patients with neuromyelitis optica spectrum disorders (NMOSD) suffer from severe visual and motor disability (blindness or light perception or unable to walk) with abnormalities of whole-brain functional networks. However, it remains unclear how whole-brain functional networks and their dynamic properties are related to clinical disability in patients with NMOSD. Our study recruited 30 NMOSD patients (37.70 ± 11.99 years) and 45 healthy controls (HC, 41.84 ± 11.23 years). The independent component analysis, sliding-window approach and graph theory analysis were used to explore the static strength, time-varying and topological properties of large-scale functional networks and their associations with disability in NMOSD. Compared to HC, NMOSD patients showed significant alterations in dynamic networks rather than static networks. Specifically, NMOSD patients showed increased occurrence (fractional occupancy; P < 0.001) and more dwell times of the low-connectivity state (P < 0.001) with fewer transitions (P = 0.028) between states than HC, and higher fractional occupancy, increased dwell times of the low-connectivity state and lower transitions were related to more severe disability. Moreover, NMOSD patients exhibited altered small-worldness, decreased degree centrality and reduced clustering coefficients of hub nodes in dynamic networks, related to clinical disability. NMOSD patients exhibited higher occurrence and more dwell time in low-connectivity states, along with fewer transitions between states and decreased topological organizations, revealing the disrupted communication and coordination among brain networks over time. Our findings could provide new perspective to help us better understand the neuropathological mechanism of the clinical disability in NMOSD.

Cognitive impairment in Neuromyelitis Optica Spectrum Disorder: A retrospective study using the Brief International cognitive Assessment for Multiple Sclerosis (BICAMS)

BACKGROUND

Neuromyelitis Optica Spectrum Disorder (NMOSD) is an inflammatory disease of the central nervous system. The study aimed to characterize the neuropsychological profile of NMOSD by comparing them with multiple sclerosis (MS) patients and healthy controls.

METHOD

Sixty-four participants were included:19 NMOSD, 27 MS, and 18 healthy controls. The neuropsychological protocol included the Portuguese version of Montreal Cognitive Assessment, the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS), Verbal Fluency (phonemic and semantic), the Hospital Anxiety and Depression Scale, and the Expanded Disability Status Scale for clinical groups.

RESULTS

NMOSD patients had significant lower cognitive performance when compared to HC mainly in information processing speed, concentration, language processing, and in executive functions (cognitive flexibility, sustained, and divided attention). No significant differences were observed between NMOSD and MS patients. Three predictors for cognitive impairment, according to BICAMS criteria, were found: depression, disease duration, and the level of disability.

CONCLUSION

The neuropsychological profile found in the present study for NMOSD is consistent with the previous findings. Information regarding the predictors of cognitive impairment in both diseases and their different associations are important for future research and for guiding interventions more suitable for the neuropsychological needs of affected patients.

Paths to hippocampal damage in neuromyelitis optica spectrum disorders

AIMS

Many patients with neuromyelitis optica spectrum disorders (NMOSD) suffer from cognitive impairment affecting memory, processing speed and attention and suffer from depressive symptoms. Because some of these manifestations could trace back to the hippocampus, several magnetic resonance imaging (MRI) studies have been performed in the past, with a number of groups describing volume loss of the hippocampus in NMOSD patients, whereas others did not observe such changes. Here, we addressed these discrepancies.

METHODS

We performed pathological and MRI studies on the hippocampi of NMOSD patients, combined with detailed immunohistochemical analysis of hippocampi from experimental models of NMOSD.

RESULTS

We identified different pathological scenarios for hippocampal damage in NMOSD and its experimental models. In the first case, the hippocampus was compromised by the initiation of astrocyte injury in this brain region and subsequent local effects of microglial activation and neuronal damage. In the second case, loss of hippocampal volume was seen by MRI in patients with large tissue-destructive lesions in the optic nerves or the spinal cord, and the pathological work-up of tissue derived from a patient with such lesions revealed subsequent retrograde neuronal degeneration affecting different axonal tracts and neuronal networks. It remains to be seen whether remote lesions and associated retrograde neuronal degeneration on their own are sufficient to cause extensive volume loss of the hippocampus, or whether they act in concert with small astrocyte-destructive, microglia-activating lesions in the hippocampus that escape detection by MRI, either due to their small size or due to the chosen time window for examination.

CONCLUSIONS

Different pathological scenarios can culminate in hippocampal volume loss in NMOSD patients.

Cognition in patients with neuromyelitis optica spectrum disorders: A prospective multicentre study of 217 patients (CogniNMO-Study)

BACKGROUND

There is limited and inconsistent information on the prevalence of cognitive impairment in neuromyelitis optica spectrum disorders (NMOSD).

OBJECTIVE

To assess cognitive performance and changes over time in NMOSD.

METHODS

This study included data from 217 aquaporin-4-IgG-seropositive (80%) and double-seronegative NMOSD patients. Cognitive functions measured by Symbol Digit Modalities Test (SDMT), Paced Auditory Serial-Addition Task (PASAT), and/or Multiple Sclerosis Inventory Cognition (MuSIC) were standardized against normative data (N = 157). Intraindividual cognitive performance at 1- and 2-year follow-up was analyzed. Cognitive test scores were correlated with demographic and clinical variables and assessed with a multiple linear regression model.

RESULTS

NMOSD patients were impaired in SDMT (p = 0.007), MuSIC semantic fluency (p < 0.001), and MuSIC congruent speed (p < 0.001). No significant cognitive deterioration was found at follow-up. SDMT scores were related to motor and visual disability (p_Bon < 0.05). No differences were found between aquaporin-4-IgG-seropositive and double-seronegative NMOSD.

CONCLUSIONS

A subset of NMOSD patients shows impairment in visual processing speed and in semantic fluency regardless of serostatus, without noticeable changes during a 2-year observation period. Neuropsychological measurements should be adapted to physical and visual disabilities.

Static and Dynamic Characteristics of Functional Network Connectivity in Neurologically Asymptomatic Patients Undergoing Maintenance Hemodialysis: A Resting-State Functional MRI Study

BACKGROUND

The characteristics of static functional network connectivity (sFNC) and dynamic FNC (dFNC) in neurologically asymptomatic patients undergoing maintenance hemodialysis are unknown. Elucidating these characteristics may improve our understanding of the mechanisms of neuropathological damage in these patients.

PURPOSE

To explore the static and dynamic characteristics of FNC in neurologically asymptomatic patients undergoing maintenance hemodialysis and the relationship between FNC-related parameters with the neuropsychological scores and blood biomarkers.

STUDY TYPE

Retrospective.

POPULATION

A total of 23 neurologically asymptomatic patients undergoing maintenance hemodialysis and 25 healthy controls matched for age, sex, and years of education.

FIELD STRENGTH/SEQUENCE

A 3.0 T MRI/functional MRI and three-dimensional-T1 structural imaging ASSESSMENT: Independent components; spatial map intensity; sFNC and dFNC strengths; and time attribute parameters (mean dwell time, fractional window, and number of transitions) were determined. Neuropsychological tests were performed. Blood biochemical tests were performed for the patients but not healthy controls.

STATISTICAL TESTS

Chi-squared test, one-sample t-test, two-sample t-test, partial correlation analysis, and family-wise error and false discovery rate correction. P < 0.05 denoted statistical significance.

RESULTS

Significant group differences in the strengths of sFNC and dFNC between networks were found. The sFNC strength between the visual and sensorimotor networks was significantly associated with the global cognitive function score (i.e. the Montreal Cognitive Assessment [MoCA]) (r = 0.606). The sFNC strength between the salience and default mode networks was significantly associated with anxiety scores (r = 0.458). In state 1, positive correlations were found between the mean dwell time and backward digital span task score (r = 0.562), fractional window and MoCA score (r = 0.576), and fractional window and backward digital span task score (r = 0.592).

DATA CONCLUSION

Neurologically asymptomatic patients undergoing maintenance hemodialysis had defective sFNC and dFNC. Our results provide a new perspective on the mechanism of neuropathological damage in patients undergoing maintenance hemodialysis.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 1.

Reduced GABA levels in the medial prefrontal cortex are associated with cognitive impairment in patients with NMOSD

BACKGROUND

Cognitive impairment is a symptom present in part of patients with neuromyelitis optica spectrum disorder (NMOSD) and its pathophysiology is unknown. Dysfunction of the GABAergic/glutamatergic pathways involving inhibitory and excitatory neurotransmitters have been implicated in several neurological disorders. This study aimed to investigate the changes in inhibitory gamma-aminobutyric acid (GABA) and excitatory glutamate and glutamine (Glx) neurotransmitter levels and their correlations with cognitive functions in patients with NMOSD.

METHODS

A total of 29 patients with NMOSD and 28 sex-, age-, and education-matched healthy controls (HCs) were included in the study. All participants underwent clinical and cognitive assessments and proton magnetic resonance spectroscopy scanning. Meshcher-Garwood point-resolved spectroscopy was used to measure GABA and Glx levels in the medial prefrontal cortex (mPFC) and left thalamus. Total creatine (tCr) was applied as an internal reference. The GABA and Glx levels in the patient group were compared with those in HCs and correlated with cognitive scores and clinical variables.

RESULTS

Patients with NMOSD showed lower GABA+/tCr levels in the mPFC compared with HCs (P = 0.028). The GABA+/tCr levels in the mPFC were significantly associated with verbal memory performance (r = 0.462, P = 0.027) and overall cognition (r = 0.440, P = 0.035) in the NMOSD group. The GABA+/tCr levels in the left thalamus or Glx/tCr levels in both regions were not significantly different between groups, nor were they related to any cognitive domain in patients with NMOSD (all P values > 0.05).

CONCLUSION

The GABA+ levels in the mPFC decreased and correlated with cognitive dysfunction in patients with NMOSD, suggesting that the changes in regional GABA+ levels might be a potential metabolic feature of cognitive decline in patients with NMOSD.

Clinical and neuroimaging findings in MOGAD-MRI and OCT

Myelin oligodendrocyte glycoprotein antibody-associated disorders (MOGAD) are rare in both children and adults, and have been recently suggested to be an autoimmune neuroinflammatory group of disorders that are different from aquaporin-4 autoantibody-associated neuromyelitis optica spectrum disorder and from classic multiple sclerosis. In-vivo imaging of the MOGAD patient central nervous system has shown some distinguishing features when evaluating magnetic resonance imaging of the brain, spinal cord and optic nerves, as well as retinal imaging using optical coherence tomography. In this review, we discuss key clinical and neuroimaging characteristics of paediatric and adult MOGAD. We describe how these imaging techniques may be used to study this group of disorders and discuss how image analysis methods have led to recent insights for consideration in future studies.

The prevalence of cognitive impairment in patients with neuromyelitis optica spectrum disorders (NMOSD): A systematic review and meta-analysis

OBJECTIVE

To estimate pooled prevalence of cognitive impairment in neuromyelitis opticaspectrum disorders (NMOSD) cases.

METHODS

We searched PubMed, Scopus, EMBASE, Web of Science, and google scholar. We also searched the gray literature including references of the included studies, and conference abstracts which were published up to 20th October 2020. The search strategy included the MeSH and text words as (((Cognitive Dysfunctions) OR Cognitive Impairment) OR Cognitive Declines) OR Mild Cognitive Impairment) OR Mental Deterioration) AND (Neuromyelitis Optica spectrum disorder OR NMOSD OR Devic syndrome OR Neuromyelitis Optica spectrum disorders).

RESULTS

The literature search revealed 1830 articles, after deleting duplicates 1434 remained. For the meta-analysis, 25 studies were included. Totally, 761 NMOSD patients were evaluated and 329 patients had cognitive impairment. Mean age ranged from 34-53 years. The prevalence of cognitive impairment ranged from 3% to 75%.The pooled prevalence of cognitive impairment was 44%, 95%CI(35%-54%), (I²=89.1%, P<0.001) which shows a high statistical heterogeneity . By excluding the abstract of Jung et al which was published in 2009, we found that the pooled prevalence was 34% (95% CI:31-37%) (I²=0) CONCLUSION: Cognitive impairment should be considered in NMOSD patients as its pooled prevalence is estimated as 44%.

Cognitive impairment in NMOSD-More questions than answers

INTRODUCTION

Neuromyelitis optica spectrum disorder (NMOSD) is a type of central nervous system antibody-mediated disease which affects mainly optic nerves and spinal cord, but may also present with acute brainstem syndrome, acute diencephalic syndrome, and cerebral syndrome with typical brain lesions. One of the most disabling symptoms, diagnosed in 29%-67% of cases, is cognitive dysfunction, with such processes as memory, processing speed, executive function, attention, and verbal fluency being predominantly affected. However, description of cognition in NMOSD patients is still a relatively new area of research.

METHODS

A systematic MEDLINE search was performed to retrieve all studies that investigated cognitive impairment and its clinical correlates in patients with NMOSD.

RESULTS

We summarize the current knowledge on cognitive impairment profile, neuropsychological tests used to examine NMOSD patients, clinical and demographical variables affecting cognition, and magnetic resonance imaging correlates. We provide a comparison of cognitive profile of patients with multiple sclerosis and NMOSD.

CONCLUSION

Patients with NMOSD are at significant risk of cognitive deficits. However, the knowledge of cognitive symptoms in NMOSD and potential modifying interventions is still scarce. Further accumulation of clinical data may facilitate effective therapeutic interventions.