Dementia Epilepsy

Abstract

A recent review suggested that dementia of severe degree affected between 3 and 5% of the population over the age of 65 years, with a similar percentage having milder disease [1]. All studies agree that Alzheimer’s disease (including senile dementia of Alzheimer type) together with multi-infarct dementia account for at least three-quarters of cases [1]. Attempts have been made to define specific criteria for the diagnosis of Alzheimer’s disease, influenced no doubt by the knowledge that some 20% of cases, diagnosed in life, are found to have other conditions at autopsy [2]. The clinical diagnosis of multi-infarct dementia is facilitated by the use of a system which scores a number of factors thought to be associated with an underlying ischaemic pathogenesis. The system has been verified by autopsy study [3]. Clinical features of particular importance in the diagnosis of multi-infarct dementia include abrupt onset of disability, a stepwise deterioration, a history of stroke and focal signs or symptoms. Patients with subcortical arteriosclerotic encephalopathy have a similar history and findings, though often with a more slowly evolving history [4]. Neither Alzheimer’s disease nor multi-infarct dementia are reversible. Perhaps as a consequence, much has been written of the other disorders which either reproduce the features of dementia, but are triggered by psychopathological mechanisms, or are, at least theoretically, amenable to surgical or medical intervention. Reversibility is a subjective concept, and whilst authors have suggested that up to 30% of patients fall into this category [5], their appraisal and, critically, the quality of their follow-up require close scrutiny. A frequently quoted study analysed the results of the investigation of 106 patients admitted with a putative diagnosis of pre-senile dementia [6]. The diagnosis remained uncertain in seven, was confirmed in 84, and was excluded in 15 patients. The last group contained patients with depression, hysteria, mania and drug toxicity. No metabolic causes were discovered among the 84 confirmed cases, but eight proved to have mass lesions, and five normal-pressure hydrocephalus. None of the patients with normal-pressure hydrocephalus benefited from surgery, whilst only two of the mass lesions were benign. If the term reversibility is applied rigorously, therefore, 2.4% of the 84 cases benefited from therapeutic intervention. A divide between the theoretical and practical limits of reversibility is only too apparent from a study of the literature. At times, the discovery of hypothyroidism, drug intoxication or subdurai haematoma has led to the assumption that the sole basis for the patient’s dementia has been discovered with the expectation that the condition can be eliminated by appropriate treatment. In a careful study of 107 patients with a presumptive diagnosis of dementia, 15 were thought to have reversible factors [7]. In practice, three recovered. Of patients identified as having hypothyroidism, drug intoxication or subdural haematoma, three-quarters, two-thirds and half respectively showed a subsequent progressive mental deterioration suggesting the presence of Alzheimer’s disease [7]. The same study, incidentally, emphasized that treatment of concomitant disorders, for example cardiac failure, might improve the mental status of individuals despite the fact that the underlying pathology of their dementia was thought to be Alzheimer’s disease. It has been suggested that those patients with a potentially reversible dementia are more likely to have a shorter history, be less severely affected, to have had exposure to more drugs and more often give a history of sudden deterioration than those with Alzheimer’s disease [7].