Multiple memory deficits in patients with multiple sclerosis. Exploring the working memory system

Electrophysiological evidence for a defect in the processing of temporal sound patterns in multiple sclerosis

OBJECTIVES

To assess the processing of spectrotemporal sound patterns in multiple sclerosis by using auditory evoked potentials (AEPs) to complex harmonic tones.

METHODS

22 patients with definite multiple sclerosis but mild disability and no auditory complaints were compared with 15 normal controls. Short latency AEPs were recorded using standard methods. Long latency AEPs were recorded to synthesised musical instrument tones, at onset every two seconds, at abrupt frequency changes every two seconds, and at the end of a two second period of 16/s frequency changes. The subjects were inattentive but awake, reading irrelevant material.

RESULTS

Short latency AEPs were abnormal in only 4 of 22 patients, whereas long latency AEPs were abnormal to one or more stimuli in 17 of 22. No significant latency prolongation was seen in response to onset and infrequent frequency changes (P1, N1, P2) but the potentials at the end of 16/s frequency modulations, particularly the P2 peaking approximately 200 ms after the next expected change, were significantly delayed.

CONCLUSION

The delayed responses appear to be a mild disorder in the processing of change in temporal sound patterns. The delay may be conceived of as extra time taken to compare the incoming sound with the contents of a temporally ordered sensory memory store (the long auditory store or echoic memory), which generates a response when the next expected frequency change fails to occur. The defect cannot be ascribed to lesions of the afferent pathways and so may be due to disseminated brain lesions visible or invisible on magnetic resonance imaging.

The internal auditory clock: what can evoked potentials reveal about the analysis of temporal sound patterns, and abnormal states of consciousness?

Whereas in vision a large amount of information may in theory be extracted from instantaneous images, sound exists only in its temporal extent, and most of its information is contained in the pattern of changes over time. The "echoic memory" is a pre-attentive auditory sensory store in which sounds are apparently retained in full temporal detail for a period of a few seconds. From the long-latency auditory evoked potentials to spectro-temporal modulation of complex harmonic tones, at least two automatic sound analysis processes can be identified whose time constants suggest participation of the echoic memory. When a steady tone changes its pitch or timbre, "change-type" CP1, CN1 and CP2 potentials are maximally recorded near the vertex. These potentials appear to reflect a process concerned with the distribution of sound energy across the frequency spectrum. When, on the other hand, changes occur in the temporal pattern of tones (in which individual pitch changes are occurring at a rate sufficiently rapid for the C-potentials to be refractory), a large mismatch negativity (or MN1) and following positivity (MP2) are generated. The amplitude of these potentials is influenced by the degree of regularity of the pattern, larger responses being generated to a "deviant" tone when the pitch and time of occurrence of the "standards" are fully specified by the preceding pattern. At the sudden cessation of changes, on resumption of a steady pitch, a mismatch response is generated whose latency is determined with high precision (in the order of a few milliseconds) by the anticipated time of the next change, which did not in fact occur. The mismatch process, therefore, functions as spectro-temporal auditory pattern analyser, whose consequences are manifested each time the pattern changes. Since calibration of the passage of time is essential for all conscious and subconscious behaviour, is it possible that some states of unconsciousness may be directly due to disruption of internal "clocks"? Abnormal mismatch potentials may provide a manifestation of a disordered auditory time-sense, sometimes being abolished in comatose patients while the C-potentials and similar responses to the onset of tones are preserved. Both C- and M-potentials were usually found to be preserved, however, in patients who had emerged from coma and were capable of discriminating sounds. Substantially intact responses were also recorded from three patients who were functionally in a "vegetative" state. The C- and M-potentials were once again dissociated in a group of patients with multiple sclerosis, only the mismatch potentials being found to be significantly delayed. This subclinical impairment of a memory-based process responsible for the detection of change in temporal sound patterns may be related to defects in other memory domains such as working memory.

Visuoperceptual impairment in MS patients: nature and possible neural origins

Failures on visuoperceptual neuropsychological tasks (on neuropsychological tests of visuo-spatial perception or on tests concerning semantic properties of visual objects), may indicate focal deficits of visuoperceptual function, or could be the result of (an)other (peripheral) visual deficit(s), or be the effect of a more general cognitive decline. In multiple sclerosis (MS) patients exhibiting sufficient visual acuity and not showing severe cognitive deterioration, impairment on a comprehensive set of 31 visuoperceptual neuropsychological tasks was compared with spatial resolution deficits (SRD), temporal resolution deficits (TRD) for visual stimuli, abnormal pattern shift visual evoked potential (PSVEP) responses, and failing scores on neuropsychological tasks other than visuoperceptual tasks. Impairment on the visuoperceptual neuropsychological tasks was highly independent from the other abnormal visual and cognitive neurological impairments examined, suggesting that it mostly represented focal deficits. Only TRD in both eyes related to this impairment and this relationship was rather weak. Thus in some MS patients a slowed visual information processing may be one of the combined deficits underlying visuoperceptual neuropsychological task impairment. Given that SRD and TRD were not related to another stage of MS and reflect disturbances of a P (parvocellular channel and ventral stream projections) and M (magnocellular channel and dorsal stream projections) visual-system function respectively, demyelination of a certain M pathway may become a co-determinant of visuoperceptual neuropsychological task impairment more rapidly than damage to a certain P pathway.

A 12-week, open trial of donepezil hydrochloride in patients with multiple sclerosis and associated cognitive impairments

Cognitive dysfunction occurs in up to 65% of patients with multiple sclerosis (MS), but there is no effective treatment for the symptoms. The authors conducted a 12-week, open-pilot study to assess the efficacy and tolerability of donepezil HCl administered in patients with MS and cognitive impairment. Seventeen patients at a long-term care facility with Mini-Mental State Examination scores of < or = 25 received 5 mg of donepezil HCl for a 4-week period, followed by 8 weeks of 10 mg of donepezil HCl. Cognitive, neurologic, functional, and behavioral assessments were conducted at baseline and at 4 and 12 weeks. Statistically significant improvement was observed in several cognitive domains including attention, memory, and executive functioning, as well as different aspects of behavior. These data suggest that donepezil HCl merits further study as a potentially viable treatment option for patients with cognitive impairment associated with MS.

Verbal learning strategies in patients with multiple sclerosis

Word list learning was studied in patients with a definite diagnosis of Multiple Sclerosis and in Normal Control subjects by means of the selective reminding procedure of Buschke and Fuld in two learning conditions: (1) using unrelated items and (2) paired-associate items. The Multiple Sclerosis patients displayed poor learning in both conditions. To identify the functional locus of their deficit, stochastic Markov chain analyses were performed, which allowed individual measurements of encoding, automatic and intentional retrieval abilities. On both tasks, encoding on the first trial and automatic retrieval on the subsequent trials were impaired in Multiple Sclerosis patients, whereas intentional retrieval, both with and without reminding by the examiner, appeared to be preserved. As all of the impaired abilities require a normal speed of information processing, the salient learning deficit of the Multiple Sclerosis patients could be tentatively traced back to the slowing down of their mental activity.

The effect of importance level, delay, and rate of forgetting on prose recall in multiple sclerosis

Memory deficits are frequently seen in patients with multiple sclerosis (MS). The focus of this study was to examine semantic encoding and the rate of forgetting in MS patients. The prose passages of the Wechsler Memory Scale Logical Memory subtest were used to examine MS patients' semantic sensitivity to the idea units of a story. The stories were divided into high, medium, and low idea units, reflecting their overall importance to the meaning of the story. MS patients recalled fewer idea units than controls, but both groups favored the main ideas relative to the nonessential details at both the immediate and delayed recall of the passages. Likewise, MS patients forgot information at a much faster rate than controls. Implications of this faster forgetting rate in MS patients are discussed from an applied setting.

Changes in short-term memory processes in patients with multiple sclerosis

In this study we compared the performance of 39 multiple sclerosis (MS) patients with 28 age-, sex- and education-matched controls on both the Mini-Mental State Examination, a global cognitive assessment tool, and the Sternberg Short-Term memory scanning task, a standardized test of short-term memory (STM) processes. While the STM span of our MS patients did not differ from that of our controls, STM scanning time of the MS group was reliably slower than that of the controls and a significant correlation was observed between STM scanning time and duration but not severity of illness. Our results suggest that processing stages other than the manipulation of data within the STM buffer are also affected by MS.

Multiple sclerosis: the disease and its manifestations

Multiple sclerosis is an immune-mediated inflammatory demyelinating disease of the central nervous system clinically characterized by relapses and remissions of neurological disturbance. A typical relapse, exemplified by optic neuritis, increases in severity over a week or two and after approximately one month begins to remit. Resolution takes place over the course of two to three months. In the early stages, clinical recovery is virtually complete, though persistent abnormalities of conduction can usually be detected by evoked potential techniques and persistent structural abnormalities can be detected by magnetic resonance imaging (MRI). These techniques, together with cerebrospinal fluid examination for oligoclonal IgG, provide supporting evidence for the diagnosis which, in the absence of a specific test, nevertheless remains primarily clinical. The course of the disease is very variable, but after a number of years neurological deficit begins to accumulate after each relapse. In most patients, the relapsing and remitting phase of the disease is followed by a phase of continuous progression of disability. Cognitive disturbances can be detected in many patients even quite early in the course of the illness. Deficits in attention, memory and executive skills may be prominent and tend to become increasingly prominent as neurological deficit increases, although this is not always the case. There is some correlation between the extent of MRI abnormalities in the cerebral white matter and the severity of cognitive deficit. Depression and anxiety are commonly experienced but are poorly correlated to the lesion load seen on MRI. In contrast, the much rarer psychotic symptoms, euphoria and emotional lability are closely linked to the severity of white matter disease.

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

The aim of the present study was to determine whether a cognitive decline, related to multiple sclerosis (MS), also involves deficits in semantic memory. Semantic memory function was evaluated by studying the conscious understanding of conceptual meanings. A group of MS patients with cognitive decline was presented with four tasks concerning concepts, their attributes and relationships to other concepts. The tasks were designed to measure spontaneous, cued and recognition performance separately. The patients had difficulties in understanding conceptual meanings. Easing the retrieval demands of the tasks did not help them to improve their performance which was poorer than the control group's on every task used. The results indicate a retrieval deficit combined with an underlying storage deficit in the semantic memory of MS patients with cognitive decline.

Awareness of remembering achieved through automatic and conscious processes in multiple sclerosis

Fifty multiple sclerosis (MS) and forty-one matched control subjects were administered a word stem completion task and the California Verbal Learning. Test (CVLT). As predicted, priming in a conventional "implicit" task did not differ for MS and control groups, and under "explicit" instructions verbal list recall was significantly lower in the MS group with recognition intact. Application of the process dissociation procedure (Jacoby, Toth, & Yonelinas, 1993) to the word stem task demonstrated that conscious and unconscious processes both contribute to remembering in MS. Exploratory analyses found no group differences in words remembered under inclusion nor exclusion conditions, though preliminary estimates for MS automatic processing exceeded those for controls. As predicted, prospective metamemory judgments reflected subsequent performance for both groups in the inclusion but not the exclusion condition. By contrast, retrospective monitoring for both groups reflected memory performance in both conditions. However post hoc analyses demonstrated that those MS subjects who employed more automatic processing were less aware retrospectively of their successful remembering under exclusion than MS subjects who used less automatic processing.

Assessment of memory in multiple sclerosis patients using the Memory Assessment Scale

Previous assessment of memory function in multiple sclerosis patients has yielded mixed findings regarding the type and severity of memory deficits, which may be due to (1) differential selection of scales for memory assessment; (2) limited, inconsistent or weak reliability and validity data for the memory scales employed; (3) poor standardization techniques; (4) lack of theoretical foundation for the measure; and (5) limited control of confounding variables, e.g., education, age and the use of nonverbal memory tests. The purpose of the present study was to assess memory function in multiple sclerosis subjects using the verbal subtests of the Memory Assessment Scale, a relatively new measure designed to overcome many of the aforementioned problems. Participants included 57 patients diagnosed as relapsing-remitting, 47 diagnosed as chronic progressive (two generally recognized types of multiple sclerosis), and 132 control participants. A multivariate analysis controlling for age and verbal IQ was significant (Wilks = 5.64, p < .001). One way follow-up tests showed both groups with multiple sclerosis had significantly diminished performance across all memory variables when compared with controls, with the exception of List Clustering Acquisition. This indicated that the patients used clustering (mentally grouping similar words together) as often as controls did. These findings provide support for the presence of significant and consistent verbal memory impairment in multiple sclerosis patients and the particular importance of using psychometrically sound measures in the assessment of this population.

Neuropsychological aspects of multiple sclerosis: a quantitative review

Neuropsychological studies of multiple sclerosis (MS) from a 20-year period were reviewed using meta-analytic and vote-count techniques. Mean effect sizes comparing MS and healthy control groups on variables categorized by neuropsychological domain were small to moderate in magnitude; all were statistically significant (M(r) = .22 (.13) to .46 (.15), rW = .23 to .43, all p < .05). Interhemispheric transfer, general cognitive ability, and learning/memory were more highly related to MS than were visuoperceptual, visuospatial, and visuoconstructional ability, language and conceptual ability (all p < .05); other domains were generally intermediate. Despite previous reports to the contrary, disease subtype was not shown to be consistently related to neuropsychological status independently of other potential explanatory variables. Findings were interpreted with regard to future research and clinical activities involving patients with MS, including selection of tests for brief neuropsychological screening examinations.

The question of disproportionate impairments in visual and auditory information processing in multiple sclerosis

The present study was conducted to investigate the hypothesis that subjects with MS have a disproportionate impairment in the phonological loop of working memory and whether such impairment is domain-specific. This was assessed by comparing performance in subjects with MS across both the visual (using the Paced Visual Serial Addition Test: PVSAT) and auditory (using the Paced Auditory Serial Addition Test: PASAT) domains. In addition, we assessed the role of processing speed in mediating performance deficits. The results showed that: (1) Although all subjects performed better on the PVSAT versus the PASAT, no disproportionate modality-specific differences were observed in the MS group relative to controls; and (2) the rate of decline across trials in the MS and healthy control groups did not differ on either the PVSAT or PASAT. Implications of the results are discussed within the context of a working memory model.

Serial position and temporal cue effects in multiple sclerosis: two subtypes of defective memory mechanisms

Neurocognitive studies of multiple sclerosis (MS) have identified a robust long-term memory deficit. We hypothesized that this is due in part to the limited representation and use of serial order information. MS patients and controls were studied with a supraspan list learning procedure with post-encoding retrieval and recognition trials. MS patients demonstrated post-encoding negative recency with normal recognition, and word order recall was impaired. These findings appear to be in part to difficulty using temporal order cues in long-term memory. Two dissociable memory deficits were identified, suggesting that there are at least two neurocognitive mechanisms underlying memory impairment in MS.

Selective impairment of auditory processing in chronic fatigue syndrome: a comparison with multiple sclerosis and healthy controls

The most consistent deficit observed in individuals with Chronic Fatigue Syndrome has been in efficiency of information processing. To examine the possibility of a modality-specific impairment, the present study examined subjects with Chronic Fatigue Syndrome, multiple sclerosis, and healthy controls on an auditory-versus visual-paced serial-addition test. 20 subjects with Chronic Fatigue Syndrome, 20 subjects with clinically definite Multiple Sclerosis, and 20 sedentary healthy controls were compared. One-half of the subjects in each group were administered the Paced Auditory Serial Addition Test and the other half were administered the Paced Visual Serial Addition Test. The group with Chronic Fatigue Syndrome was differentially impaired on the auditory relative to the visual processing task. The group with Multiple Sclerosis was equally impaired on both versions of the task. The results are discussed within the framework of Baddeley's model of working memory.

Memory deficits and early cognitive deterioration in MS

INTRODUCTION

In the present study, the pattern of memory and learning deficits in two cognitively different, but clinically and demographically similar, multiple sclerosis (MS) groups was compared.

MATERIAL & METHODS

23 patients represented the cognitively preserved MS group and 22 patients the MS group with early cognitive decline. A control group of 35 healthy controls was also included. The cognitive status of the subjects was defined using the Mild Deterioration Battery (MDB). Furthermore, all subjects were given a set of memory and learning tests and were instructed to evaluate the frequency of their memory and learning difficulties. The Mini-Mental State Examination (MMSE) was also administered to all subjects.

RESULTS

The cognitively deteriorated patients, even those with normal MMSE performance, showed widespread memory and learning deficits, but adequate self-evaluation of their everyday memory and learning difficulties. The preserved group, in turn, performed similarly to the controls.

CONCLUSION

Widespread memory and learning deficits are associated with relatively mild cognitive decline in MS. These deficits were observable in the intermediate-length screening battery, the MDB, but not in the MMSE. The present study suggests that the accuracy of patients' own evaluations of their memory and other cognitive problems is superior to the results of very brief screening batteries, like the MMSE. Therefore, brief screening in neuropsychological assessment of MS patients is not recommendable.

Retrieval from semantic memory may be normal in multiple sclerosis patients: a study of free word association

Increased effort of retrieval from memory is considered to be a feature of cognition in subcortical neurological diseases, such as multiple sclerosis (MS). Free word association provides a means to investigate alterations in automatic and effortful retrieval. Using this procedure we investigated whether in MS free word association would shift from commonality towards idiosyncrasy, as a result of effortful, controlled retrieval. The MS group consisted of a cohort of outpatients, who suffered from chronic but quiescent MS. The patients responded with perfectly normal association patterns. Apparently, impairment of retrieval, or more specifically increased effort of retrieval, from memory does not hold true generally in MS. In patients with obvious physical handicaps (mean Kurtzke DSS = 4 +/- 2) we could not demonstrate abnormal associative processes.

Alphanumeric sequencing: a report on a brief measure of information processing used among persons with multiple sclerosis

Alphanumeric Sequencing involves the alternating recitation of counting and the alphabet. We report data on the use of this measure with two clinical samples of persons with multiple sclerosis, having either the chronic progressive (n = 23) or relapsing-remitting form (n = 52) of the disease. Patients were administered Alphanumeric Sequencing and several other tests of information-processing speed/capacity and short-term memory. Chronic progressive MS patients performed worse than 23 healthy controls on both the speed and error components of the test, while relapsing-remitting patients were worse than 35 controls only on the total time to complete the task. The time score was correlated with several measures of information processing and short-term memory.

The nature of memory impairments in multiple sclerosis: acquisition versus retrieval

The present study was designed to examine whether verbal memory impairment in multiple sclerosis (MS) is attributable to impaired information acquisition or compromised retrieval. Twenty-three MS and 23 control subjects were administered a 10-item verbal list-learning task. Subjects were trained to a specific criterion on the verbal test in order to assure equal information acquisition. Following a 30-min delay, retrieval and recognition performance was evaluated. MS subjects required significantly more trials to reach criterion on the task relative to controls, but the groups did not differ on tests of recall and recognition. Performance was correlated with rate of information processing speed. These results suggest that verbal memory impairment among MS subjects is a consequence of inadequate initial learning and not a function of impaired retrieval.

Working memory impairment among persons with chronic progressive multiple sclerosis

We examined short-term memory (STM) among a group of 23 definite, chronic progressive multiple sclerosis (MS) patients, all of whom had experienced recent significant disease activity, and a control group matched closely on age and education. MS patients were impaired, relative to controls, on the majority of the measures used. Although there were no significant differences between groups on the Mini Mental State Examination, patients performed more poorly on digits forward and backward, the Brown-Peterson test, and the logical memory scale of the Revised Wechsler Memory Scale (both immediate and delayed). Performance on tests sensitive to central processing capacity was significantly correlated with measures of STM. Working memory was significantly impaired in this sample of chronic progressive MS patients. In conjunction with previous research showing deficient information processing and prefrontal dysfunction among this population, the findings suggest that an impairment of central information processing may be a fundamental aspect of the mnestic and cognitive decline observed in many chronic progressive MS patients.

Event-related auditory evoked potentials and multiple sclerosis

Long latency event-related auditory evoked potentials, particularly the P300 wave, constitute an objective electrophysiological index of cognitive function. For this reason, these potentials have been studied in a series of 101 patients with multiple sclerosis (MS), classified according to McAlpine's criteria into definite, probable and possible cases. The patients were also classified as depressed or non-depressed according to the DSM-III and Research Diagnostic Criteria. They were also subjected to a battery of psychometric tests. In the patient population the N200 and P300 latencies were increased, as were the P200 latencies, when compared with a control population. This electrophysiological pattern had previously been observed in other conditions characterised by subcortical lesions. Partial correlations (at constant disease duration) between the disability score and the cognitive deficit were found to be significant. Patients with an increased P300 latency had a greater disability and the P300 latency was significantly correlated with the duration of the illness. The N200 and P300 latencies were increased in depressed MS subjects, but this increase did not reach the level of significance. Depression was more frequent in the more severely handicapped patients. This suggests that the origin of the depression seen in multiple sclerosis is only partly organic, and that it is one of the factors contributing to the subcortical cognitive deficit in multiple sclerosis. Progressive forms of the disease exhibited the most profound cognitive deficit, and the most marked increase in P300 latency.

Memory and "frontal lobe" dysfunction in multiple sclerosis

The characteristics of memory disturbance in multiple sclerosis (MS) are briefly reviewed and the interactions of conceptual and memory dysfunction in MS are considered. Although conceptual functions such as abstraction and problem solving traditionally have been considered to be frontal lobe functions, there is now convincing evidence from studies of patients with focal brain lesions that these capacities are not localized to the frontal lobes. Thus, the concept of frontal lobe dysfunction in MS is without empirical support. Nevertheless, studies examining the relationship between memory and conceptual impairment in MS have value for both basic and clinical neuroscience.

Brain magnetic resonance imaging correlates of cognitive impairment in multiple sclerosis

We evaluated the correlations between cognitive impairment, clinical and brain magnetic resonance imaging (MRI) findings in 100 patients with multiple sclerosis (MS). The performance on one or more neuropsychological tests was abnormal in 47% of the 64 patients who completed the entire neuropsychological battery; the cognitive impairment was mild in 14 (22%) and severe in 16 (25%). Performance on any single neuropsychological test was unrelated to clinical parameters (age, duration of the disease, disability). The neuropsychological performance of relapsing-remitting patients was better than in patients with a chronic-progressive disease. The mean scores for almost all the neuropsychological tests were significantly lower in patients with severe ventricular dilatation and corpus callosum atrophy than in patients in whom these structures were little affected. Mean scores for WMS, performance Intelligence Quotient (IQ), total IQ and Token Test (TT) were also significantly correlated with the widening of cortical sulci and total lesional scores. Our data support the contention that the involvement of pathways that are critical for a given cognitive process as well as the progression of the axonal degeneration and sclerosis seem to play important roles in the pathophysiology of cognitive dysfunction in MS.

Clinically isolated lesions of the type seen in multiple sclerosis: a cognitive, psychiatric, and MRI follow up study

There is a dearth of longitudinal studies on psychometric and psychiatric change in multiple sclerosis (MS) particularly on the evolution of these abnormalities early in the disease process. A 4 1/2 year follow up study documenting magnetic resonance imaging (MRI), psychometric, and psychiatric abnormalities was undertaken in a group of 48 patients with clinically isolated lesions--for example, optic neuritis--which are frequently the harbinger of MS. At follow up about half the subjects had developed clinically definite MS, with memory deficits becoming apparent. Deficits in attention documented at initial assessment were present but unchanged in those subjects who still had a clinically isolated lesion status. However, after MS was categorised into a relapsing-remitting or chronic progressive course, patients with a chronic progressive course were found to have significantly deteriorated with regard to auditory attention tasks. T1 relaxation times in apparently normal white matter correlated with certain indices of cognitive impairment. In developing a model to explain the pathogenesis of intellectual and emotional change in MS, the interaction of organic, psychological, and social factors needs to be emphasised.

Neuropsychological assessment in MS: clinical, neurophysiological and neuroradiological relationships

We assessed cognitive performance and its relationship with clinical and anatomic disease severity in MS with mild to moderate handicap; 34 definite MS and 18 healthy subjects matched for age and education were submitted to a neuropsychological test battery. Both groups were examined for anxiety. MS patients underwent magnetic resonance imaging examination. MS performed worse than controls on all WAIS-P subtests and had learning, short- and long-term verbal memory impairment. Cognitive deficits were not related to abnormal emotional states, but were found to be associated with attentional process and information-processing speed impairment. Cognitive impairment did not correlate with severity of physical disability. The most severe memory deficits were found in patients with extensive periventricular damage.

Endogenous event-related potentials as indices of dementia in multiple sclerosis patients

Auditory event-related potentials (ERPs) were recorded in a "double oddball" paradigm requiring an easy and a hard pitch discrimination from multiple sclerosis (MS) patients with and without dementia, and a group of age and sex matched normal subjects. Cognitive function was assessed by a short battery of neuropsychologic (NP) tests, and the two groups of MS patients were selected on the basis of substantial non-overlapping degrees of cognitive deficit in the demented as compared to the non-demented group. The N100, P200 and P300 ERP components were longer in latency in the demented patients, and the N100-P300 interval was prolonged as well, compared to the non-demented patients, whose ERP latencies did not differ from those of the normal subjects. Increased P300 latency was associated with poorer performance on the NP tests, especially those sensitive to impairment of learning and retrieval from memory. The reaction times of both patient groups were prolonged as compared to the controls, whereas the accuracy of the demented patients was significantly poorer than that of the non-demented patients.

Neuropsychological assessment in multiple sclerosis: a follow-up study with magnetic resonance imaging

Nineteen moderately impaired patients with clinically definite multiple sclerosis and an initially relapsing-remitting course were included in a neuropsychological and magnetic resonance imaging (MRI) follow-up study. The average test/re-test interval was about 2 years. The neuropsychological findings were indicative of a very mild overall impairment; the patients, as a group, showed no evidence of cognitive deterioration in the follow-up period. A numerical estimation of the severity of cerebral demyelination shown by MRI did not indicate a significant change. No correlation between cognitive performance variations and MRI changes was found.

Korsakoff's syndrome as the initial presentation of multiple sclerosis

A 37-year-old man presented with an acute amnestic syndrome of Korsakoff's type and an upper brain-stem oculomotor syndrome. After a moderate improvement with steroid therapy, he developed progressive behavioural changes due to a frontal lobe syndrome, in addition to motor and visual impairment. Memory performance was investigated on several occasions during an 11-year follow-up. Diagnosis of laboratory-supported definite multiple sclerosis was established and magnetic resonance imaging showed disseminated white matter lesions, especially in both medial temporal lobes. No other cause than multiple sclerosis was found for the amnestic syndrome. Among the rare cases of Korsakoff's syndrome in the course of multiple sclerosis, this is to our knowledge the first case in which a memory deficit was the initial manifestation of the disease.

Cognitive abnormalities in multiple sclerosis: a psychometric and MRI study

This study reports the cognitive abnormalities of a group of 58 patients with definite multiple sclerosis (MS). The psychometric functions measured were: 'IQ deficit', verbal and visual memory, abstracting ability, visual and auditory attention and naming ability. The presence of brain pathology was investigated using magnetic resonance imaging (MRI). A group of 46 physically disabled controls without significant brain disease was used for comparison. Normative MRI data were obtained from a group of 40 normal volunteers. The psychometric performance of the MS group was compared to the previously reported findings in patients with clinically isolated syndromes. MS patients had widespread cognitive deficits sparing naming ability and affecting verbal memory less severely than other intellectual functions. The overall performance on psychometric tests was related to the severity of the MRI abnormalities and to the duration of the illness, but was not significantly influenced by the presence of psychiatric morbidity or the degree of physical disability. Patients with clinically isolated syndromes occupied an intermediate position between MS patients and disabled controls in terms of cognitive and MRI abnormalities.

Memory and learning in outpatients with quiescent multiple sclerosis

In 22 (56%) of 39 quiet-stage multiple sclerosis (MS) patients with at least average intelligence quotients, performances in memory and learning tasks were normal, as compared with those of a control group (24 healthy volunteers). Of the remaining 44% (n = 17), 2 patients were amnesic and 5 had been judged to have suffered cognitive decline. Auditory word learning was particularly vulnerable; however, acquisition rate was not significantly different between MS patients and controls.

Cognitive and psychiatric abnormalities in multiple sclerosis

In multiple sclerosis, behavioral changes, including alterations in cognitive functions and psychiatric abnormalities, have been recognized with increasing frequency in recent years. Multiple sclerosis formerly was thought to be primarily a disorder of the brain stem and spinal cord; however, functional changes that can be attributed, at least in part, to cerebral dysfunction are being recognized. Certain cognitive functions such as memory and conceptual processes seem to be preferentially impaired. The degrees of impairment of other functions such as attention and visuospatial skills are now being evaluated. Psychiatrically, affective disorders seem to be the most common diagnoses, and debate exists about whether these abnormalities are a function of the demyelinating process itself or are a reaction to the disability produced by the disorder.