Cognitive Fatigability is Independent of Subjective Cognitive Fatigue and Mood in Multiple Sclerosis

Slowing processing speed is associated with cognitive fatigue in newly diagnosed multiple sclerosis patients

OBJECTIVE

To further investigate objective measures of cognitive fatigue (CF), defined as the inability to sustain performance over time, in newly diagnosed multiple sclerosis (MS) patients, by conducting a performance analysis on the Paced Auditory Serial Addition Test (PASAT) based on the type of errors (omissions vs. incorrect responses) committed.

METHOD

Sixty-two newly diagnosed patients with MS (pwMS) and 41 healthy controls (HC) completed the PASAT. Analysis of the change in performance during the test was performed by comparing the number of correct responses, incorrect responses, and omissions in the 1^st versus the 3^rd tertile of the PASAT.

RESULTS

A significant decline in accuracy over time was observed to be related to an increment in the number of omissions, significantly more pronounced in pwMS than in HC. No change in the number of incorrect responses throughout the PASAT was observed for either group.

CONCLUSIONS

CF can be detected even in newly diagnosed pwMS and might objectively manifest as a progressive increase in omissions during a sustained highly demanding task (i.e., PASAT). This pattern may reflect slowed processing speed and increased fatigue in pwMS. Focusing on omissions on the PASAT instead of correct responses only may improve its specificity as an objective measure of CF.

Smell as a Disease Marker in Multiple Sclerosis

Existing data suggest that people with multiple sclerosis (pwMS) are at an elevated risk for experiencing olfactory impairment. We investigated if smell dysfunction can be used as an MS disease marker. This is a cross-sectional, case−control study. All data were collected prospectively from 171 participants, 115 pwMS and 56 controls (age and sex stratified and matched to the patients), who reported smell, taste, and nasal breathing, and completed the Greek-validated questionnaires for nasal obstruction (NOSE), nasal-symptoms QoL (SNOT-22), and olfaction-associated QoL (QOD). The smell was assessed with the “Sniffin’ sticks” (odor threshold (OT), discrimination (OD), identification (OI) test, and total TDI). We recorded the pwMS disease characteristics (Expanded Disability Status Scale-EDSS, the disease type and duration), cognitive function, emotional status, fatigue, and impact of MS in everyday activities. A TDI < 30.75 (hyposmia) was detected in 30.8% of the patients. The patients’ OD and TDI scores were significantly lower than the controls’ (p = 0.005, and 0.015, respectively). The hyposmia correlated with disease severity and duration. The EDSS score correlated negatively with OD (r = −0.299, p = 0.001) and TDI (r = −0.242, p = 0.01). The disease duration correlated negatively with OD (r = −0.305, p = 0.001, OI (r = −0.253, p = 0.008) and TDI (r = −0.3, p = 0.001). The information processing speed (SDMT) correlated with OD, OT, and TDI (r = 0.302, p = 0.002; r = 0.242, p = 0.016; r = 0.326, p = 0.001). The olfactory function is changing in MS in accordance with disease progression.

Current perspectives on the diagnosis and management of fatigue in multiple sclerosis

INTRODUCTION

Fatigue is a common and debilitating symptom among multiple sclerosis (MS) patients with a prevalence up to 81% and with a considerable impact on quality of life. However, its subjective nature makes it difficult to define and quantify in clinical practice. Research aimed at a more precise definition and knowledge of this construct is thus continuously growing.

AREAS COVERED

This review summarizes the most relevant updates available on PubMed up to July 1^st 2022 regarding: the assessment methods that aim to measure the concept of fatigue (as opposed to fatigability), the possible treatment pathways currently available to clinicians, interconnection with the pathophysiological substrates and with the common comorbidities of MS, such as depression and mood disorders.

EXPERT OPINION

The in-depth study of fatigue can help to better understand its actual impact on MS patients and can stimulate clinicians towards a more valid approach, through a targeted analysis of this symptom. Considering fatigue from a multidimensional perspective allows the use of patient-tailored methods for its identification and subsequent treatment by different professional figures. Better identification of methods and treatment pathways would reduce the extremely negative impact of fatigue on MS patients' quality of life.

Ocrelizumab in Patients with Active Primary Progressive Multiple Sclerosis: Clinical Outcomes and Immune Markers of Treatment Response

Ocrelizumab is a B-cell-depleting monoclonal antibody approved for the treatment of relapsing-remitting multiple sclerosis (RRMS) and active primary progressive MS (aPPMS). This prospective, uncontrolled, open-label, observational study aimed to assess the efficacy of ocrelizumab in patients with aPPMS and to dissect the clinical, radiological and laboratory attributes of treatment response. In total, 22 patients with aPPMS followed for 24 months were included. The primary efficacy outcome was the proportion of patients with optimal response at 24 months, defined as patients free of relapses, free of confirmed disability accumulation (CDA) and free of T1 Gd-enhancing lesions and new/enlarging T2 lesions on the brain and cervical MRI. In total, 14 (63.6%) patients and 13 patients (59.1%) were classified as responders at 12 and 24 months, respectively. Time exhibited a significant effect on mean absolute and normalized gray matter cerebellar volume (F = 4.342, p = 0.23 and F = 4.279, p = 0.024, respectively). Responders at 24 months exhibited reduced peripheral blood ((%) of CD19+ cells) plasmablasts compared to non-responders at the 6-month point estimate (7.69 ± 4.4 vs. 22.66 ± 7.19, respectively, p = 0.043). Response to ocrelizumab was linked to lower total and gray matter cerebellar volume loss over time. Reduced plasmablast depletion was linked for the first time to sub-optimal response to ocrelizumab in aPPMS.

Symptom Interconnectivity in Multiple Sclerosis: A Narrative Review of Potential Underlying Biological Disease Processes

Introduction

Fatigue, cognitive impairment, depression, and pain are highly prevalent symptoms in multiple sclerosis (MS). These often co-occur and may be explained by a common etiology. By reviewing existing literature, we aimed to identify potential underlying biological processes implicated in the interconnectivity between these symptoms.

Methods

A literature search was conducted to identify articles reporting research into the biological mechanisms responsible for the manifestation of fatigue, cognitive impairment, depression, and pain in MS. PubMed was used to search for articles published from July 2011 to July 2021. We reviewed and assessed findings from the literature to identify biological processes common to the symptoms of interest.

Results

Of 693 articles identified from the search, 252 were selected following screening of titles and abstracts and assessing reference lists of review articles. Four biological processes linked with two or more of the symptoms of interest were frequently identified from the literature: (1) direct neuroanatomical changes to brain regions linked with symptoms of interest (e.g., thalamic injury associated with cognitive impairment, fatigue, and depression), (2) pro-inflammatory cytokines associated with so-called ‘sickness behavior,’ including manifestation of fatigue, transient cognitive impairment, depression, and pain, (3) dysregulation of monoaminergic pathways leading to depressive symptoms and fatigue, and (4) hyperactivity of the hypothalamic–pituitary-adrenal (HPA) axis as a result of pro-inflammatory cytokines promoting the release of brain noradrenaline, serotonin, and tryptophan, which is associated with symptoms of depression and cognitive impairment.

Conclusion

The co-occurrence of fatigue, cognitive impairment, depression, and pain in MS appears to be associated with a common set of etiological factors, namely neuroanatomical changes, pro-inflammatory cytokines, dysregulation of monoaminergic pathways, and a hyperactive HPA axis. This association of symptoms and biological processes has important implications for disease management strategies and, eventually, could help find a common therapeutic pathway that will impact both inflammation and neuroprotection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-022-00368-2.

Predictors of cognitive fatigue and fatigability in multiple sclerosis

BACKGROUND

Persons with multiple sclerosis (PwMS) commonly experience cognitive fatigue (CF), defined as a decrease in cognitive performance with sustained activity, yet CF remains understudied. Further, the relationship between subjective CF and objective CF, or cognitive fatiguability, has not been fully elucidated in previous studies. Understanding the predictors of cognitive fatigue may scaffold the development of interventions that target this symptom. The objective of this prospective study was to evaluate the extent to which depression, anxiety, information processing speed, and sleep quality predict subjective and objective CF.

METHODS

PwMS were recruited from one academic MS clinic in London (ON) Canada. Objective CF was measured by the Paced Auditory Serial Addition Test (PASAT), where performance on the last third of the PASAT is compared to performance on the 1st third, a validated measurement of objective CF. Subjective CF was measured by the cognitive component of the Modified Fatigue Impact Scale (MFIS). Additionally, depression, anxiety, information processing speed, and sleep quality data was collected. All assessments took place on the same day. Pearson's r was calculated to examine the relationship among all continuous outcome measures while linear regression analyses were used to examine predictors of subjective and objective CF.

RESULTS

The sample consisted of 53 subjects who were mostly female (37; 69.8%) with a mean age of 44.2 years; the majority (47; 88.7%) had relapsing MS. Objective CF and subjective CF were not significantly related (r = - 0.16). Further, there was no statistically significant predictors of objective CF noted. In contrast, subjective CF demonstrated a statistically significant relationship with the Symbol Digit Modalities Test (SDMT; r = - 0.29, p = .05), Hospital Anxiety and Depression Scale (HADS), depression subscale (r = 0.61, p < .001), HADS anxiety subscale (r = 0.54, p < .001), and sleep quality (r = 0.33, p = .02). Additionally, all variables predicted subjective CF, R²_adj = 0.384 [F (6, 40) = 5.783, p = .0002]. In particular, anxiety significantly predicted subjective CF when controlling for depression, information speed, and sleep quality.

CONCLUSION

This study demonstrated that subjective CF is significantly predicted by anxiety, and strongly influenced by information processing impairment and depression. Addressing underlying affective factors, such as anxiety or depression, may help alleviate perceived or subjective CF among PwMS, thus improving their function and quality of life. Further studies with a larger sample size or longitudinal follow up may help define predictors of objective CF.