Previous frequency estimates of cognitive dysfunction in multiple sclerosis have ranged from 54 to 65 percent. These studies may overestimate the frequency in the general MS population, since the patients in these studies were recruited from clinic populations. In the present study, we administered a comprehensive neuropsychological test battery to 100 community-based MS patients and 100 demographically matched healthy controls. Of 31 cognitive test indices examined, 48 MS patients and five controls were impaired on four or more test indices, yielding an overall frequency rate of 43% for the MS group. The pattern of cognitive decline was not uniform: MS patients were more frequently impaired on measures of recent memory, sustained attention, verbal fluency, conceptual reasoning, and visuospatial perception, and less frequently impaired on measures of language and immediate and remote memory. We developed a brief (20-minute) screening battery empirically by selecting the four most sensitive test indices from the comprehensive battery. The brief battery yielded a sensitivity value of 71% and a specificity value of 94% in discriminating cognitively intact from impaired MS patients, as defined by the comprehensive battery. Cognitive impairment was not significantly associated with illness duration, depression, disease course, or medication usage, but was significantly (albeit weakly) correlated with physical disability.

We designed a study to assess the specific contribution of cognitive dysfunction to multiple sclerosis patients' problems in daily living. Based on the results of a comprehensive neuropsychological test battery, we classified 100 MS patients as either cognitively intact (N = 52) or cognitively impaired (N = 48). In addition to a neurologic examination, MS patients completed questionnaires on mood and social functioning, underwent a comprehensive in-home occupational therapy evaluation, and were rated by a close relative or friend regarding specific personality characteristics. While there were no significant differences between the two groups on measures of physical disability and illness duration, patients in the cognitively impaired group were less likely to be working, engaged in fewer social and avocational activities, reported more sexual dysfunction, experienced greater difficulty in performing routine household tasks, and exhibited more psychopathology than cognitively intact patients. These findings suggest that cognitive dysfunction is a major factor in determining the quality of life of patients with MS.

Memory disturbance is common in patients with multiple sclerosis (MS), as previously demonstrated on clinical memory tests of explicit learning using effortful retrieval paradigms. To better understand the mechanisms underlying memory failure, we compared the performance of 46 MS patients and 47 demographically matched normal controls on experimental tests of working memory, semantic encoding, and implicit memory. On the working memory task, MS patients demonstrated an exaggerated word length effect, which indicates a deficit in the control process of articulatory rehearsal. In contrast, MS patients demonstrated a normal buildup and release from proactive inhibition, which suggests intact semantic encoding. Finally, on priming and procedural memory tasks, MS patients performed without difficulty. The MS patients' test performance was not correlated with illness duration or course, severity of physical disability, or psychoactive medication use.Memory impairment is the most common form of cognitive dysfunction observed in patients with multiple sclerosis (MS). From 40% to 60% of MS patients perform below expectations on learning and memory

Article abstract-Previous research has suggested that cerebral lesions observed on magnetic resonance imaging (MRI) of MS patients are clinically "silent." We examined the validity of this assertion by correlating neuropsychological test performance with MRI findings in 53 MS patients. We used a semiautomated quantitation system to measure three MRI variables: total lesion area (TLA), ventricular-brain ratio (VBR) Magnetic resonance imaging (MRI) is extremely sensitive for the detection of focal areas of demyelination in patients with MS.lv2 The clinical significance of these lesions remains unclear. Their correlation with neurologic symptoms and degree of disability has been uniformly disappointing,3-6 prompting the view that MS lesions occur in brain regions that are clinically "silent." Others7v8 have recommended the use of neuropsychological testing to evaluate the possible relationship between cerebral demyelination and cognitive dysfunction.Two studiesgJO attempted to relate cognitive dysfunction to lesions identified by MRI. Franklin et a19 examined 60 patients with chronic progressive MS and found a significant correlation (r = 0.35) between an overall brain lesion score and a summary score derived from a brief cognitive screening battery. Huber et all0 administered a brief battery of neuropsychological tests to 30 MS patients, nine of whom were classified as "demented," 11 moderately cognitively impaired, and 12 minimally impaired. These investigators observed no significant group differences on three MRI indexes: total lesion score, cerebral atrophy, and severity of periventricular involvement. On the fourth index, atrophy of the corpus callosum, the "demented" patients had significantly higher ratings than the moderate and minimal cognitive impairment groups. These two studies found significant correlations between MRI variables and cognitive testing, yet the strength of the correlations was modest. Three methodologic factors may have contributed to their limited success in obtaining meaningful correlations. First, both studies relied on rating scales to measure the size of lesions from MRIs. Rating scales by definition are subjective and prone to human error. In addition, rating scales provide a more restricted range of data values than quantitative systems that measure lesions in area units; this restricted range may seriously limit the size of obtained correlations. Second, both studies used brief cognitive screening examinations. MS does not produce a uniform decline of all cognitive skills7J1; although these brief batteries covered a number of cognitive functions, they may have missed salient cognitive deficits. A more comprehensive neuropsychological examination may be more successful in measuring those cognitive functions that are influenced by MS-related cerebral pathology. Finally, cognitive test performance is affected by education and age.12 Thus, relatively uneducated or older patients may be classified as impaired on testing when they are functioning close to their premorbid level. Conver...

Thirty-seven patients with multiple sclerosis (MS) were compared to 26 normal controls of equivalent age, education, and verbal intelligence on measures of verbal learning and memory (Digit Span and Supraspan, Brown-Peterson Distractor Task, Selective Reminding Test, Story Recall, and Free Verbal Recall) and verbal fluency (Letter and Animal Fluency). The MS patients exhibited deficits on measures of secondary (long-term) memory and verbal fluency, but performed normally on measures of primary (short-term) memory, recognition memory, and rate of forgetting from secondary memory. These results suggest that the memory disturbance in MS results primarily from an imparied ability to access information from secondary memory, while encoding and storage capacity is intact. Degree of memory impairment was unrelated to length of illness, severity of disability, or self-reported depression.