Dementia in multiple sclerosis: is it Alzheimer's or a new entity?

Abstract

Multiple Sclerosis (MS) is a chronic autoimmune multifocal inflammatory demyelinating disease with secondary neurodegeneration affecting predominantly females between 20-40 years. The clinical course over years is very variable. Milder cognitive dysfunctions in various conditions are very frequent in acute stage and in the further courses of the disease. Dementia is reported as a rare condition in MS. Rodriguez et al found in 1994 an incidence of 3,7 %. Over a period of 10 years we have investigated in our outpatient MS center the cognitive state of more than 400 MS patients for dementia according to the DSM IV classification and its correlation to MS. The main neuropsychological instrument was the Minimental Status Examination (MMSE). The Expanded Disability Status Scale (EDSS) of our patients ranged from 0 (no signs, no disability) to 9 (bed ridden, helpless). In our data we classified 3 subtypes of dementia in MS (DMS). In DMS type 1 the cognitive decline is one of the main symptoms and develops early in the disease without marked motor symptoms. The DMS type 2 is associated with an malignant or chronic progressive course of MS itself. Therefore DMS type 2 developed in association with marked motor impairement later in the clinical course. In DMS type 1 and 2 a marked demyelination of the white matter and/or cortical involvement with brain atrophy, demonstrated by magnetic resonanz imaging is present. DMS type 3 is associated with older age with or without major motor disability. In these cases we found no clear correlation between the course and severity of MS and the dementia syndrome itself. In ptients with MS the development of dementia is very heterogenous. DMS type 1 and 2 are directly associated with the progression of the chronic autoimmune disease and the involvement of cortical and/or white matter structures. In DMS type 3 cases a comorbid condition with Alzheimer Dementia is discussed. It seems as DMS is not as rare as described in literature. Further epidemiologic studies are necessary to evaluate the incidence of DMS in a greater population