This article includes discussion of the neurobehavioral aspects of multiple sclerosis and cognitive and neuropsychiatric features of multiple sclerosis. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Multiple sclerosis is a chronic autoimmune, inflammatory neurologic disease that leads to varying degrees of myelin and axonal injury and destruction in the central nervous system. Although the course of multiple sclerosis is varied and unpredictable, most people with multiple sclerosis initially experience reversible neurologic deficits that are followed by progressive deterioration over time. In addition to debilitating motor symptoms, neurologic deficits such as spasticity and ataxia may accompany changes in cognitive and psychiatric status.
Cognitive impairment is common in multiple sclerosis, with prevalence rates ranging from 45% to 65% at both the earlier and later stages of the disease. Although cognitive decline is more common in the progressive form of multiple sclerosis, evidence suggests that cognitive impairment is a central feature of multiple sclerosis regardless of phenotype. Cognitive impairment in multiple sclerosis affects most cognitive domains, but processing speed, visual learning, and short-term memory deficits (ie, ability to repeat immediately following presentation of verbal information) are most common. Cognitive slowing has been observed to be significantly associated with brain volume loss and global gray matter atrophy (22) and evidence suggests that cognitive decline in multiple sclerosis leads to functional impairments in instrumental activities of daily living. In terms of psychiatric features, mood disorders dominate the clinical picture, with up to 80% of people with multiple sclerosis endorsing some level of depressive symptomatology.
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• Cognitive impairment is a common feature of multiple sclerosis and often leads to declines in the ability to initiate and carry out instrumental activities of daily living.
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• Cognitive impairment may develop at any time during the course of the disease regardless of the presence or absence of neurologic disability.
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• Although cognitive decline is more common in the progressive form of multiple sclerosis, evidence suggests that cognitive impairment is a central feature of multiple sclerosis regardless of phenotype.
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• Cognitive impairment in multiple sclerosis affects most cognitive domains, but processing speed, visual learning, and short-term memory deficits are most common.
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• Neuropsychiatric symptoms are common in multiple sclerosis, with lifetime prevalence rates of depression approaching 50%.
Historical note and terminology
Jean-Martin Charcot is widely recognized as the first person to provide a comprehensive description of multiple sclerosis. However, clinical reports detailing a cluster of symptoms suggestive of multiple sclerosis predate Charcot’s 1868 lectures. For example, Dr. Friedrich von Frerichs initially described cognitive sequelae of multiple sclerosis in 1849 (32). By the 1920s, estimates of cognitive changes in multiple sclerosis began to emerge but these estimates varied widely—from as low as 2% to as high as over 70% (09; 21). By the 1980s and 1990s, neuropsychological evaluations into the cognitive profiles of people with multiple sclerosis were beginning to gain a wider audience thanks to the efforts of Steven M Rao and the development of the Brief Repeatable Battery of Neuropsychological Tests in Multiple Sclerosis (34; Rao and Cognitive Function Study Group N 1990; 35; 36).
In contrast to the limited early attention given to cognitive changes associated with multiple sclerosis, psychiatric symptoms were implicated in some of the very first descriptions of the disease. In fact, Charcot referenced psychiatric symptoms such as euphoria, mania, and depression in his first clinicopathological description of what would ultimately be known as multiple sclerosis (43). Similar to cognition, however, it was not until much later (ie, 1950s) that rigorous and systematic empirical investigations into the neuropsychiatric correlates of multiple sclerosis began to be conducted (41).