Understanding and managing cognitive dysfunction in multiple sclerosis

Memory in multiple sclerosis: A reappraisal using the item specific deficit approach

OBJECTIVE

As many as 65% of people with multiple sclerosis (MS) have clinically significant memory impairment, but the nature of this deficit is controversial. Some investigations suggest that an inability to retrieve newly learned information from memory is prominent, whereas others imply that compromised acquisition accounts for impairment. Prior research has not simultaneously evaluated acquisition and retrieval processes in MS, and fewer have attempted to account for initial acquisition when studying retrieval. The Item Specific Deficit Approach (ISDA) offers a method of quantifying acquisition, retrieval, and retention processes, with the latter two mechanisms being adjusted for initial acquisition. To simultaneously quantify acquisition and retrieval abilities, the ISDA was applied to list learning performance in two independent samples of people with MS and corresponding healthy comparison groups.

PARTICIPANTS AND METHODS

Study 1 included 85 people with MS and 47 healthy individuals. Study 2 involved a separate sample of 79 people with MS and 22 healthy people. They were administered neuropsychological batteries, and participants with MS were classified as globally impaired or unimpaired. The California Verbal Learning Test-II was administered to assess new-learning in both studies, and responses were scored using the ISDA.

RESULTS

Both studies revealed that cognitively impaired people with MS manifest weaknesses involving acquisition and retrieval. Nearly identical effect sizes emerged across samples, with cognitive impairment achieving a medium effect upon acquisition and a large effect upon retrieval.

CONCLUSIONS

These findings accord well with previous research showing diminished acquisition and retrieval among people with MS. The results may also reconcile contradictory findings in the extant literature by showing that memory impairment in MS is not exclusively attributable to either acquisition or retrieval. Rather, both processes may manifest across people with MS. The replication across samples with nearly identical effect sizes implies that these effects are reliable and possess external validity. These data hold implications for memory rehabilitation interventions involving people with MS, and suggest that acquisition and retrieval processes should be addressed in treatment. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Pain is associated with prospective memory dysfunction in multiple sclerosis

Prospective memory (PM) pertains to the execution of a future goal or behavior. Initial research implies that people with multiple sclerosis (MS) are apt to show impaired prospective memory for activities of daily living. Yet, PM impairment does not occur in all people with MS. Thus, some other variable besides disease status alone may contribute to PM dysfunction in people with MS. Chronic pain may be such a variable. Approximately 50-70% of people with MS experience significant pain, and such pain has been thought to diminish memory function. To investigate this possibility, 96 patients with MS and 29 healthy subjects were administered the Memory for Intentions Screening Test (MIST; Woods, S. P., Iudicello, J. E., Moran, L. M, Carey, C. L., Dawson, M. S., & Grant, I. (2008). HIV-associated prospective memory impairment increases risk of dependence in everyday functioning. Neuropsychology, 22, 110-117.), a well-validated measure of prospective memory, and the Medical Outcomes Study Pain Effects Scale (PES; Fischer, J. S., Rudick, R. A., Cutter, G. R., & Reingold, S. C. (1999). The multiple sclerosis functional composite measure (MSFC): An integrated approach to MS clinical outcome assessment. National MS Society Clinical Outcomes Assessment Task Force. Multiple Sclerosis, 5, 244-250.) to assess chronic pain. After controlling for demographic variables and disability severity, subjective pain accounted for significant variance in PM, particularly for time-based intentions over sustained delay periods. These data accord well with assertions that pain may degrade ability to remember new intentions and suggests that pain is associated with PM dysfunction in people with MS.

Cerebellar abnormalities contribute to disability including cognitive impairment in multiple sclerosis

The cerebellum is known to be involved not only in motor but also cognitive and affective processes. Structural changes in the cerebellum in relation to cognitive dysfunction are an emerging topic in the field of neuro-psychiatric disorders. In Multiple Sclerosis (MS) cerebellar motor and cognitive dysfunction occur in parallel, early in the onset of the disease, and the cerebellum is one of the predilection sites of atrophy. This study is aimed at determining the relationship between cerebellar volumes, clinical cerebellar signs, cognitive functioning and fatigue in MS. Cerebellar volumetry was conducted using T1-weighted MPRAGE magnetic resonance imaging of 172 MS patients. All patients underwent a clinical and brief neuropsychological assessment (information processing speed, working memory), including fatigue testing. Patients with and without cerebellar signs differed significantly regarding normalized cerebellar total volume (nTCV), normalized brain volume (nBV) and whole brain T2 lesion volume (LV). Patients with cerebellar dysfunction likewise performed worse in cognitive tests. A regression analysis indicated that age and nTCV explained 26.3% of the variance in SDMT (symbol digit modalities test) performance. However, only age, T2 LV and nBV remained predictors in the full model (r² = 0.36). The full model for the prediction of PASAT (Paced Auditory Serial Addition Test) scores (r² = 0.23) included age, cerebellar and T2 LV. In the case of fatigue, only age and nBV (r² = 0.17) emerged as significant predictors. These data support the view that cerebellar abnormalities contribute to disability, including cognitive impairment in MS. However, this contribution does not seem to be independent of, and may even be dominated by wider spread MS pathology as reflected by nBV and T2 LV.

Physical activity associated with increased resting-state functional connectivity in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system, resulting in physical, cognitive and affective disturbances, with notable declines in the ability to learn and retain new information. In this study, we examined if higher levels of physical activity in MS individuals were associated with an increased resting-state connectivity of the hippocampus and cortex, resulting in better performance on a task of episodic memory. Forty-five individuals with a clinically definite diagnosis of MS were recruited for the study. Consistent with previous reports, hippocampus was functionally connected to the posteromedial cortex, parahippocampal gyrus, superior frontal gyrus, and the medial frontal cortex. Higher levels of physical activity in MS patients were associated with an increased coherence between the hippocampus and the posteromedial cortex (PMC). The increased connectivity between these two regions, in turn, was predictive of better relational memory, such that MS patients who showed an increased coherence between the left (not right) hippocampus and the PMC also showed better relational memory. Results of the study are interpreted in light of the challenge of disentangling effects of physical activity from effects of disease severity and its neuropathological correlates.