Seizures in Alzheimer Disease: Clinical and Epidemiological Data

Abstract

Epilepsy and AD are common neurologic disorders for which increasing age is a common and well-established risk factor (1, 2). The potential relation between these two disorders has been supported by experimental and clinical data. From a clinical aspect, patients with AD have an increased risk of developing seizures and epilepsy; thus AD may be an important cause of epilepsy in the elderly. AD and other neurodegenerative conditions represent the presumed etiology for 10% of new onset epilepsy in patients older than 65 (3).The diagnosis of seizures in patients with AD is not always easy because the manifestation of partial seizures might be hard to recognize and distinguish from other behaviors common in these patients. This may lead to underestimation of the real frequency of seizures in AD. At the same time, the possibility that "funny" or "unusual" behaviors of demented patients are considered seizures, particularly by nonepileptologists, may lead to overestimation of seizure rates.We briefly review and comment on studies reporting on the risk of seizures in AD, the possible factors modifying this risk, the role of EEG in the diagnosis of epilepsy and its limitations, the efficacy of antiepileptic drugs and the relationship between seizures and interictal epileptiform activity and AD course. Risk of Seizures in ADCompared with healthy individuals of the same age, patients with sporadic AD have a 6-to 10-fold increased risk of developing clinical seizures during the course of their illness (4-6). There are many prospective and retrospective studies reporting great variability in the lifetime prevalence of seizures in patients with AD, with rates ranging from 1.5 to 64 percent (5-17). However, it is difficult to accurately assess the real prevalence of seizures in AD because of methodological problems in published epidemiologic and observational studies. The studies in which there is pathologic confirmation of AD have small numbers of subjects, with considerable variability in disease duration and severity. Some prospective and retrospective studies have included other forms of dementia and patients with additional symptomatic causes of epilepsy, such stroke or hemorrhage. Two recent prospective cohort studies with large numbers of patients with long follow-up and carefully characterized evaluations estimate the overall incidence of seizures in AD at approximately 1 per 200 person-years of observation, suggesting relatively lower frequencies than other studies (17, 18).There are studies in the elderly reporting recurrence risk after the first seizure as high as 80%, probably because the epilepsy in the elderly population is mainly associated with an underlying structural lesion (15). In AD patients, many of the studies do not distinguish the presence of a single unprovoked seizure from recurrent seizures, namely, epilepsy. To our knowledge, there are no large studies reporting the risk of recurrence of seizures after the first unprovoked seizure in AD, except for few case series that include a small number of Se...

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