Sematic memory deficit in multiple sclerosis; impaired understanding of conceptual meanings

The role of language ability in verbal fluency of individuals with multiple sclerosis

BACKGROUND

While cognitive deficits in memory and processing speed have been well-documented in individuals with multiple sclerosis (MS), language is largely considered to be intact. Verbal fluency deficits observed in MS are often attributed to impaired processing speed and executive functions rather than language ability. The current study evaluates the contribution of various cognitive factors to verbal fluency including language ability, oral-motor speed, processing speed, and executive functions.

METHODS

We analyzed pre-existing data from seventy-four (74) individuals with MS who completed a battery of neuropsychological tests designed to assess individual ability for various cognitive factors. We conducted linear multiple regression analyses with letter and category verbal fluency as outcome variables and performance on other cognitive domains (e.g., processing speed, executive functioning) as predictors.

RESULTS

Both vocabulary and processing speed predicted letter fluency while only vocabulary predicted category fluency. These findings suggest that the observed verbal fluency deficits in MS may reflect both impaired language ability and processing speed.

CONCLUSION

We propose that further research on language ability in MS is needed to determine if comprehensive neuropsychological test batteries for persons with MS should include tests of language ability to fully understand the cognitive profile of any given patient. Given the importance of language ability, it may be necessary to conduct a more thorough assessment of language in individuals with MS who experience a deficit in this domain.

Language disorders in multiple sclerosis: A systematic review

BACKGROUND

Although cognitive impairments are common in patients with multiple sclerosis (MS), language impairments are not well defined.

OBJECTIVE

The goal of this review was to examine the presence and nature of language disorders associated with MS.

METHOD

A search of PubMed and PsycINFO databases was conducted using combinations of the following terms: language disorders, language pathology, language impairment, multiple sclerosis, communication, language and speech. Studies were chosen based on the original language of the text, year of publication, peer-review status and specificity of the results regarding language and communication disorders.

RESULTS

This review covers 30 articles from 13 countries. The studies involved patients with different types of MS. Various language impairments were reported in MS. However, since the methods used in the studies varied widely, it is difficult to draw any conclusions thus far.

CONCLUSION

Given the various cognitive deficits in MS, it is expected that higher language abilities would be affected. This aspect should be investigated in future studies.

Cognition in multiple sclerosis

PURPOSE OF REVIEW

A broad overview of cognition in multiple sclerosis (MS) is provided, taking account of its impact on the lives of patients, how cognitive impairment relates to disease and magnetic resonance variables, which cognitive domains are most vulnerable, the influence of depression and fatigue and what treatment options are available.

RECENT FINDINGS

The current focus is on cognitive reserve, which seems to offer some protection from the cognitive impact of MS. There is also considerable momentum with new MRI techniques and growing interest in PET studies.

SUMMARY

Cognition in MS is a priority for patients. Although understanding of the natural history of MS cognitive deficits is reasonably well understood, treatment options require further work before precise recommendations can be made on an individual basis.

Cognitive impairment in patients with multiple sclerosis using the Brief Repeatable Battery-Neuropsychology test

AIMS

To assess the cognitive impairment of multiple sclerosis (MS) patients using the Brief Repeatable Battery-Neuropsychology (BRB-N) test.

METHODS

The performance of 59 patients with MS in the BRB-N test was assessed and compared with 152 matched healthy controls (HC).

RESULTS

In most tests, MS patients performed worse than controls. Age and educational level strongly influenced the performance of the subjects. The Symbol Digit Modality Test (SDMT) best correlated with the other individual tests and contributed most to the general BRB-N factor. Furthermore, a correlation between physical disability and performance in some BRB-N tests was observed. Indeed, patients with progressive MS and greater physical disability performed worse in some tests than less disabled patients with relapsing MS. By creating a global BRB-N Z score, we found that patients generally performed 0.7 standard deviation (SD) below the level of controls. We obtained cut-off values stratified by age and education to determinate cognitive impairment in MS patients.

CONCLUSIONS

Our data show that cognitive impairment is prevalent amongst MS patients, and that a single cognitive measurement might be useful for monitoring patients during the progression of this illness.

Clinical characteristics of cortical multiple sclerosis

There are several articles in this special issue in which authors eloquently describe neurobehavioural and cognitive complications of multiple sclerosis with relevant neuropsychological assessments and neuroimaging findings. However behavioural and cognitive presentation of multiple sclerosis remains poorly understood. Two years ago, we reported a series of patients with multiple sclerosis who presented with neurobehavioural symptoms and had neuropsychological deficits consistent with cortical dysfunction. Based on previous case reports, pathological studies of cerebral cortex in multiple sclerosis and advanced neuroimaging studies we suggested that neurobehavioural presentation of multiple sclerosis represents a new variant called "cortical multiple sclerosis". The condition is characterised by predominant or exclusive cortical pathology presenting with neurobehavioural symptoms, such as depression, amnesia or distinct cortical syndromes. Since the publication of our report, there has been further neuroimaging and neuropathological findings that further supported the above concept. In addition, observation of more patients with this condition helped us to formulate a logical approach in the detection of these patients. This article focuses on their clinical characteristics.

Verbal fluency deficits in multiple sclerosis

A quantitative review of 35 studies with 3673 participants was conducted to estimate and compare the magnitude of deficits upon tests of phonemic and semantic fluency for participants with multiple sclerosis (MS) relative to healthy controls. Participants with MS were substantially but similarly impaired on tests of phonemic and semantic fluency. These deficits were larger than deficits on measures of verbal intelligence, confrontation naming and another widely used measure of executive functioning, the Wisconsin Card Sorting Test, but were of a comparable or smaller magnitude relative to deficits on the oral version of the Symbol Digit Modalities Test (SDMT). This is consistent with other research suggesting that measures of verbal fluency and the SDMT may be amongst the most sensitive neuropsychological measures to cognitive impairment in MS. Increased neurological disability and a chronic progressive (as opposed to a relapsing remitting) disease course were associated with larger deficits on tests of phonemic and semantic fluency. However, it is suggested that this latter finding is attributable to the distinct clinical features of chronic progressive and relapsing remitting sub-types. Thus, patients who follow a chronic progressive course tend to be older, have an increased duration of illness and experience greater neurological disability. Once these variables were controlled for, differences between the two sub-types were substantially attenuated.

Cognitive impairment as marker of diffuse brain abnormalities in early relapsing remitting multiple sclerosis

OBJECTIVES

To establish the frequency of cognitive impairment in a population based sample of patients with recently diagnosed relapsing-remitting multiple sclerosis (RRMS), and to determine the relation between cognitive abnormalities and the extent of macroscopic and microscopic tissue damage revealed by magnetic resonance imaging (MRI) and magnetisation transfer (MT) imaging.

METHODS

58 patients with RRMS consecutively diagnosed in the previous six months in Aquitaine and 70 healthy controls underwent a battery of neuropsychological tests. Lesion load and atrophy indices (brain parenchymal fraction and ventricular fraction) were measured on brain MRI. MT ratio (MTR) histograms were obtained from lesions, normal appearing white matter (NAWM), and normal appearing grey matter (NAGM). Gadolinium enhanced lesions were counted.

RESULTS

44 RRMS patients could be individually matched with healthy controls for age, sex, and education. Patients performed worse in tests of verbal and spatial memory, attention, information processing speed, inhibition, and conceptualisation. Measures of attention and information processing speed were correlated with lesion load, mean NAWM MTR, and the peak location of the NAGM MTR histogram in the patients. Multivariate regression analysis showed that lesion load and mean NAWM MTR were among the MR indices that were most significantly associated with impairment of attention and information processing speed in these early RRMS cases.

CONCLUSIONS

Cognitive impairment appears to be common in the early stages of RRMS, mainly affecting attention, information processing speed, memory, inhibition, and conceptualisation. The severity of these deficits reflects the extent of the lesions and the severity of tissue disorganisation outside lesions.

Cognitive impairment in relapsing and primary progressive multiple sclerosis: mostly a matter of speed

Based on the assumption that cognitive impairment in MS is consistent with subcortical dementia, a battery of neuropsychological tests was assembled that included measures of executive function (Tower of London and Wisconsin Card Sorting Test), verbal learning and memory (a paired associates learning test), and speeded information processing (Stroop Color Word Interference Test). The battery was administered to patients with relapsing and primary progressive MS and to healthy controls. Differences between patients and controls occurred on several of the measures. However, when differences with respect to fatigue and depression were statistically controlled, the only differences that remained significant involved measures relating to the speed of information processing. Patients performed more slowly than controls, with the disparity being greater for relapsing patients than for those with primary progressive disease. The slowing was evident on measures of automatic as well as controlled processing and regardless of whether speed was an explicit feature of successful performance or recorded unobstrusively while the patient concentrated on planning a correct solution to a problem. Parallels were noted between cognitive slowing associated with MS and that of normal aging.

Visual object recognition deficits in early Parkinson's disease

The nature of the visual perception deficits in Parkinson's disease (PD) has remained unclear. The present study explored whether there emerge deficits in the different stages of visual object recognition in early PD. Twenty-eight patients and 14 healthy controls were studied. A set of reaction time tasks were applied to measure the different stages of object recognition. The results indicate some selective problems in both basic perceptual and semantic visual processing at an early stage of cognitive deterioration in PD.

Visual object recognition in early Alzheimer's disease: deficits in semantic processing

OBJECTIVES

The purpose of the present study was to divide visual object recognition into different stages and to reveal which of these stages are impaired in early Alzheimer's disease (AD).

METHODS

Performance in object detection, familiarity detection, semantic name and word categorization, and identification with naming were studied by using two-choice reaction-time tasks. Ten patients with newly diagnosed AD and 14 healthy subjects were studied.

RESULTS

Patients with early AD had impairments in several stages of the object recognition process. After controlling for the basic visuomotor slowness, they were as fast and as accurate as the controls in object detection, but had difficulties in all stages that required semantic processing.

CONCLUSIONS

Semantic memory impairments contribute to the deficits in visual object recognition in early AD. Thus, the semantic memory deficit may be manifested in several ways in the difficulties that AD patients experience in everyday life.

Conscious and unconscious uses of memory in multiple sclerosis

Conscious and unconscious uses of memory and priming were studied in 30 patients with multiple sclerosis (MS) and 15 normal control (NC) subjects. MS patients were classified into two subgroups according to their cognitive status; 15 of them were cognitively deteriorated (the MS-D group) and 15 cognitively preserved (the MS-P group). A process dissociation procedure [J. Mem. Lang. 30 (1991) 513] was used to separate conscious and unconscious memory performance in a word stem completion task. The results showed that the MS-D group had deficient conscious memory performance, but had intact unconscious memory as well as priming. The MS-P group showed normal conscious and unconscious uses of memory and priming. Thus, in MS-related cognitive decline, conscious memory seems to be vulnerable, whereas unconscious memory remains intact. The results provide neuropsychological support for the distinction between conscious and unconscious memory processes. Moreover, the results show the importance of studying cognitively homogenous MS groups as opposed to heterogenous ones, in order to find the underlying mechanisms of memory deficits in MS. Interestingly, the neural systems needed for the unconscious use of memory do not seem to deteriorate even in MS patients with deficient overall cognitive capacity. This finding encourages the development of future rehabilitation programs, suggesting that unconscious remembering might help MS patients with deficient conscious memory to cope with their daily activities.

Visual object recognition in multiple sclerosis

Deficits in tasks measuring visual processing have been earlier reported in studies of MS. Yet, the nature and severity of visual-processing deficits in MS remains unclear. We used a new method in order to measure the different stages of visual processing in object recognition: shape recognition, familiarity recognition, semantic categorization, and identification with naming. Six two-choice reaction-time tasks were presented to 30 MS patients and 15 healthy controls. The patients were divided into cognitively preserved and cognitively deteriorated study groups according to their cognitive status. The purpose was to find out whether deficits at specific stages of visual processing can be found in cognitively deteriorated MS patients. Cognitively deteriorated MS patients did not perform as well as cognitively preserved MS patients or healthy controls. They were slower already at the early stage of visual processing where discrimination of whole objects from scrambled ones was required. They also had higher error rates in tasks requiring object familiarity detection and object identification with naming. Thus, cognitively deteriorated MS patients had difficulties in visual shape recognition and semantic-lexical processing. However, variation of performances was large within both of the patient groups indicating that even patients without a generalized cognitive decline may have deficits in some stages of the visual processing. We suggest that because of the heterogeneity of the patients, every single case needs to be examined separately in order to identify the possible deficits in visual processing.