Abstracts

RATIONALE: Individuals with Alzheimer[ssquote]s disease (AD) have an increased risk for seizures or epilepsy. While tonic clonic and myoclonic seizures are identifiable in this group, complex partial seizures can be difficult to identify. Reactive seizures and other disorders may complicate the diagnosis. The objective of this study was to determine the utility of the EEG in identifying epileptiform activity or seizures in AD subjects suspected of having seizures.
METHODS: We reviewed the records of patients from the Epilepsy and Dementia Centers of Medical College of Pennsylvania Hospital to identify subjects with a diagnosis of dementia and who had an EEG between January 2000 and December 2001. Seventy six patients met the selection criteria. Of these, only patients with probable AD according to National Institute of Neurological and Communicative Disorders and Stroke/AD and Related Disorders Association criteria, were selected for the study. Subjects with strokes, structural lesions, epilepsy preceeding dementia, and with reversible causes of dementia were excluded. Of the original 76 patients, only 11 remained after applying these exclusion criteria, and formed the study cohort.
Subjects were classified as: epilepsy, single seizure, possible seizure, or unlikely seizure.
EEG findings were divided into : normal, focal slowing, generalized slowing, focal spikes or sharp waves.
Subjects were divided into 3 groups depending on their Mini Mental State Examination (MMSE) scores : 20-30, 10-19, and less than 10.
RESULTS: The age range of the cohort was 60 to 91 years(mean 73.4 years). Six of the subjects were female.
EEGs were obtained in 5 subjects as part of the routine workup of dementia, and in 6 subjects to exclude seizures. 7 subjects had at least one EEG, 2 subjects had 2, one subject had 5, and one had a total of 6 EEGs.
Of the eleven subjects, none were found to have epilepsy, one had a definite seizure (9.1%), one had a probable seizure (9.1%), and nine subjects were classified as unlikely to have had seizures (81.8%).
Six of the 11subjects had normal EEGs (54.5%). 5 had generalized slowing (45.4%), 3 had focal slowing (27.2%), 2 had focal sharp waves (18.1%), and none had focal spikes.
Four subjects (36.3%) had MMSE scores between 20-30, 5 (45.4%) had MMSE scores between 10-19, and 2 (18.1%) had MMSE scores less than 10.
The EEG was normal in all subjects with MMSE scores greater than 20. Of the 5 with MMSE scores 10-19, 2 (40%) had normal EEGs, 3 (60%) had focal and generalized slowing, and 2 (40%) also had sharp waves. The 2 subjects with sharp waves were those classified earlier as having definite and probable seizure respectively. Both subjects with MMSE scores less than 10 had generalized slowing.
CONCLUSIONS: Since we rigorously excluded patients with structural lesions and strokes, including lacunar infarcts, in order to study individuals with pure AD, our cohort sample size was relatively small. In our study, the incidence of epileptiform abnormalities in EEGs of patients with Alzheimers dementia was 18%. This incidence is higher than the incidence of epileptiform abnormalities seen in the general or in the geriatric population. This study also suggests that there may be a correlation between lower MMSE scores and slowing on the EEG. Our study shows that EEG is a useful tool in the evaluation of patients with Alzheimer[ssquote]s dementia.