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O38 Cortical topographical analysis of evoked potentials to elucidate dementia
14s
C o m m u n i c a t i o n s orales/Oral communications
037
038
AN EEG SPECTRUM SUBTRACTION METHOD TO QUANTIFY MU RHYTHM
CORTICAL TOPOGRAPHICALANALYSIS OF EVOKED POTENTIALS TO ELUCIDATE DEMENTIA
A. PE~kk~nen, K. Alhainen, J. Partanen and P.J. Riekkinen University Central Hospital of Kudpio, Kuopio (Finland) Blocking cholinergic projections from nucleus basalis to cortex mimics Alzheimer's disease (AD) in animals. The resulted EEG change is a marked increase of high voltage spindels (HVS). In humans the central mu rhythm is assumed to correspond to HVS activity of animals, although it has not been reported in AD so far. Mu rhythm is difficult to distinguish, because it is small in amplitude and its frequency is within the alpha band. We used the following method in a quantitative study of changes of my rhythm induced by cholinergic treatment. Two consecutive samples of EEG were recorded from each patient: the first one in the relaxed awake state with eyes closed and the second one with the patient continuously clenching and opening of his/her right fist. The bipolar EEG derivations were C4-P4, C3-P3, T6-O2 and T5-OI. An additional channel was used to register eye movements. Both samples consisted four 8-second, artefact free epochs per derivation. FFT was carried out with half-overlapplng technique and Harm windowing. The average EEG spectrum of each sample was compressed into six frequency bands: delta, there, alpha, beta, 20-30 Hz and 30-60 Hz. The absolute and relative amplitudes and powers in each band were calculated. Since mu and alpha rhythms are both in the same frequency band and mu rhythm disappears hy motor activation, we calculated its quantity by subtracting the alpha value during motor activity from the alpha value recorded under resting awake condition. As the right fist was clenehed~ derivation C3-P3 was used in calculation. The frequency bands 20-30 Hz and 30-60 Hz were used to monitor muscle artefact level and its changes between measurements. Our preliminary results show that the quantity of mu rhythm in the baseline recording is of high prognostic value in classifying Alzheimer's patients as responders or nonresponders to cholinergic treatment.
R.D.Sidmmn, D.J.Mmjor, M.R.Ford, G.Ramsey, The University o f Southwestern Louisiana, Lafayette (USA) and the I n s t i t u t e of Living, Hartford (USA) Ear the most p a rt , in evoked p o t e n t i a l studiee examining age-related changes in normal subjects as well as EP features in dementia~ the investigations have primarily related the latencies and amplitudes of certain scalprecorded components in resting and cognitive task condition paradigms to dysfunction. Inferences are made based upon data measured at very few recording channels- for example, the vertex in the case of auditory EPs and the occiput in the case of visual EPs. Unfortunately traditional electrophysiological measures appear to be poor predictors of clinical status in Alzheimer's patients at one year, for example. In this presentation we apply a technique for simulating potential Fields on the cortical surface to auditory and visual evoked responses from normal aging volunteers and patients suffering from dementias. This cortical imaging ~eehnique (CIT) allows the discrimination of EP features that are not apparent in standard topographical maps.
040 039 COMPUTERIZED EEG AND T O P O G R A P H I C A L ANALYSIS OF THE DIAGNOSIS OF DEMENTIA OF THE ALZHEIMER TYPE DEMENTIA OF THE ALZHEIMER TYPE. 5. G u e ~ , C. Derouesn~, D. Ancri, S. Guiliou, M-C. 5ourdel, E. L a n d r e e t M. K h a l a f a t . H6pital S a i n t e - A n n e e t H6pital de la Salp~tri~re. P a r i s - F r a n c e .
EEG c h a n g e s in d e m e n t i a ol the A l z h e i m e r type h a v e been well described w i t h conventional EEG and c o m p u t e r i z e d EEG. For some a u t h o r s the l a t t e r m e t h o d ~xa~ able to d i s c r i m i n a t e a group of d e m e n t e d people and a group of n o r m a l one with an a c c u r a c y of a l m o s t $O %. But the clinical use of such s t a t i s tical analysis is difficult and the question is a l w a y s open of the i n t e r e s t of t h e s e m e t h o d s in the clinical field w i t h d e m e n t i a . We r e p o r t h e r e the results of a c o m p u t e r i z e d 16 channel EEG study of 7g probable d e m e n t e d people s e l e c t e d in a c c o r d a n c e w i t h the NINCDS-ADP, DA work group c r i t e r i a . S t a t i s t i c a l analysis w a s p e r f o r m e d on a PC c o m p u t e r w i t h BMDP s o f t w a r e . T h e r e is a c l e a r c o r r e l a t i o n b e t w e e n EEG c h a n g e s and the deg r e e of the neuropsychological i m p a i r m e n t w i t h o u t any d i f f e r e n c e s w i t h the a g e of the p a t i e n t , the age at onset and duration of the disease. D e m e n t e d people and normals w e r e classified with an a c c u r a c y a l m o s t identical to the one a l r e a d y obs e r v e d by others. But the authors propose to use as c u t - o f f values the l o w e s t values of the s a m p l e of n o r m a l people (8.3 for the m e a n f r e q u e n c y and 1.t; for the alpha to t h e t a ratio). The p e r f o r m a n c e a c h i e v e d with this a u t o m a t e d p r o c e d u r e will be c o m p a r e d to the conventional EEG results, How to use t h e s e m e t h o d s in the diagnosis of d e m e n t i a and "the role of t o p o g r a phical analysis will be then discussed.
ERPs follow-up in A l z h e i m e r ' s Patients, comparison with other dementing disease~ Q n o f r j M , B a z z a n o S., F u l g e n t e T., M a l a t e s t a C o l a m a r t i n o P. Department of Neurology, State University Chiefi (CH), Italy.
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ERPs to a u d i t o r y a n d v i s u a l " o d d - b a l l " paradigms were recorded in 32 patients affected by Alzheimer's Disease (AD) (assessed by Neuropsychological evaluation, 3 years clinical f o l l o w - u p , C T - s c a n a n d MRI). ERPs w e r e r e c o r d e d in s e p a r a t e s e s s i o n s repeated every 3-6 m o n t h s , for 18-42 months ERPs were recorded from 19-31 scalp derivations and 4 supplementary electrodes assessed eye-mouvements artifacts At f i r s t m e a s u r e m e n t s normal P3/ERPs were o b s e r v e d in 12 AD p a t i e n t s , d e l a y e d P3 with normal topography in Ii, absent P3/ERPs with abnormal topography in 6, absent ERPs in 3 patients. Serial recordings showed disappearance of P3a component in 8 p a t i e n t s , s l o w i n g of P3b in 6 patients, progressive topographycal alteration of ERPs ( i n t e r p r e t e d as a b s e n c e of N2 -P3a - P 3 b and emergence of posterior SW) in i0 patients. Correlations with Neuropsychologieal Tests showed a linear regression between P3b latency and WAIS memory subscores. P~a absence and topographycal ERP a l t e r a t i o n s w e r e i n s t e a d r e l a t e d w i t h several low s c o r e s of N e u r o p s y c h o l o g i c a l T e s t s assessing mentation and attention. The v a r i o u s p a t t e r n s of ERP a l t e r a t i o n s (P3a-h-SW delay; a b s e n c e of P 3 a - d e l a y e d P3b-SW; a b s e n c e of P3-b, delayed SW) w e r e not unique of AD, as similar alterations were observed in Multi Infarctual Dementia, Progressive Supranuclear Palsy, D e m e n t i a in a d v a n c e d M u l t i p l e S c l e r o s i s .
C o m m u n i c a t i o n s orales/Oral communications
037
038
AN EEG SPECTRUM SUBTRACTION METHOD TO QUANTIFY MU RHYTHM
CORTICAL TOPOGRAPHICALANALYSIS OF EVOKED POTENTIALS TO ELUCIDATE DEMENTIA
A. PE~kk~nen, K. Alhainen, J. Partanen and P.J. Riekkinen University Central Hospital of Kudpio, Kuopio (Finland) Blocking cholinergic projections from nucleus basalis to cortex mimics Alzheimer's disease (AD) in animals. The resulted EEG change is a marked increase of high voltage spindels (HVS). In humans the central mu rhythm is assumed to correspond to HVS activity of animals, although it has not been reported in AD so far. Mu rhythm is difficult to distinguish, because it is small in amplitude and its frequency is within the alpha band. We used the following method in a quantitative study of changes of my rhythm induced by cholinergic treatment. Two consecutive samples of EEG were recorded from each patient: the first one in the relaxed awake state with eyes closed and the second one with the patient continuously clenching and opening of his/her right fist. The bipolar EEG derivations were C4-P4, C3-P3, T6-O2 and T5-OI. An additional channel was used to register eye movements. Both samples consisted four 8-second, artefact free epochs per derivation. FFT was carried out with half-overlapplng technique and Harm windowing. The average EEG spectrum of each sample was compressed into six frequency bands: delta, there, alpha, beta, 20-30 Hz and 30-60 Hz. The absolute and relative amplitudes and powers in each band were calculated. Since mu and alpha rhythms are both in the same frequency band and mu rhythm disappears hy motor activation, we calculated its quantity by subtracting the alpha value during motor activity from the alpha value recorded under resting awake condition. As the right fist was clenehed~ derivation C3-P3 was used in calculation. The frequency bands 20-30 Hz and 30-60 Hz were used to monitor muscle artefact level and its changes between measurements. Our preliminary results show that the quantity of mu rhythm in the baseline recording is of high prognostic value in classifying Alzheimer's patients as responders or nonresponders to cholinergic treatment.
R.D.Sidmmn, D.J.Mmjor, M.R.Ford, G.Ramsey, The University o f Southwestern Louisiana, Lafayette (USA) and the I n s t i t u t e of Living, Hartford (USA) Ear the most p a rt , in evoked p o t e n t i a l studiee examining age-related changes in normal subjects as well as EP features in dementia~ the investigations have primarily related the latencies and amplitudes of certain scalprecorded components in resting and cognitive task condition paradigms to dysfunction. Inferences are made based upon data measured at very few recording channels- for example, the vertex in the case of auditory EPs and the occiput in the case of visual EPs. Unfortunately traditional electrophysiological measures appear to be poor predictors of clinical status in Alzheimer's patients at one year, for example. In this presentation we apply a technique for simulating potential Fields on the cortical surface to auditory and visual evoked responses from normal aging volunteers and patients suffering from dementias. This cortical imaging ~eehnique (CIT) allows the discrimination of EP features that are not apparent in standard topographical maps.
040 039 COMPUTERIZED EEG AND T O P O G R A P H I C A L ANALYSIS OF THE DIAGNOSIS OF DEMENTIA OF THE ALZHEIMER TYPE DEMENTIA OF THE ALZHEIMER TYPE. 5. G u e ~ , C. Derouesn~, D. Ancri, S. Guiliou, M-C. 5ourdel, E. L a n d r e e t M. K h a l a f a t . H6pital S a i n t e - A n n e e t H6pital de la Salp~tri~re. P a r i s - F r a n c e .
EEG c h a n g e s in d e m e n t i a ol the A l z h e i m e r type h a v e been well described w i t h conventional EEG and c o m p u t e r i z e d EEG. For some a u t h o r s the l a t t e r m e t h o d ~xa~ able to d i s c r i m i n a t e a group of d e m e n t e d people and a group of n o r m a l one with an a c c u r a c y of a l m o s t $O %. But the clinical use of such s t a t i s tical analysis is difficult and the question is a l w a y s open of the i n t e r e s t of t h e s e m e t h o d s in the clinical field w i t h d e m e n t i a . We r e p o r t h e r e the results of a c o m p u t e r i z e d 16 channel EEG study of 7g probable d e m e n t e d people s e l e c t e d in a c c o r d a n c e w i t h the NINCDS-ADP, DA work group c r i t e r i a . S t a t i s t i c a l analysis w a s p e r f o r m e d on a PC c o m p u t e r w i t h BMDP s o f t w a r e . T h e r e is a c l e a r c o r r e l a t i o n b e t w e e n EEG c h a n g e s and the deg r e e of the neuropsychological i m p a i r m e n t w i t h o u t any d i f f e r e n c e s w i t h the a g e of the p a t i e n t , the age at onset and duration of the disease. D e m e n t e d people and normals w e r e classified with an a c c u r a c y a l m o s t identical to the one a l r e a d y obs e r v e d by others. But the authors propose to use as c u t - o f f values the l o w e s t values of the s a m p l e of n o r m a l people (8.3 for the m e a n f r e q u e n c y and 1.t; for the alpha to t h e t a ratio). The p e r f o r m a n c e a c h i e v e d with this a u t o m a t e d p r o c e d u r e will be c o m p a r e d to the conventional EEG results, How to use t h e s e m e t h o d s in the diagnosis of d e m e n t i a and "the role of t o p o g r a phical analysis will be then discussed.
ERPs follow-up in A l z h e i m e r ' s Patients, comparison with other dementing disease~ Q n o f r j M , B a z z a n o S., F u l g e n t e T., M a l a t e s t a C o l a m a r t i n o P. Department of Neurology, State University Chiefi (CH), Italy.
and G
, of
ERPs to a u d i t o r y a n d v i s u a l " o d d - b a l l " paradigms were recorded in 32 patients affected by Alzheimer's Disease (AD) (assessed by Neuropsychological evaluation, 3 years clinical f o l l o w - u p , C T - s c a n a n d MRI). ERPs w e r e r e c o r d e d in s e p a r a t e s e s s i o n s repeated every 3-6 m o n t h s , for 18-42 months ERPs were recorded from 19-31 scalp derivations and 4 supplementary electrodes assessed eye-mouvements artifacts At f i r s t m e a s u r e m e n t s normal P3/ERPs were o b s e r v e d in 12 AD p a t i e n t s , d e l a y e d P3 with normal topography in Ii, absent P3/ERPs with abnormal topography in 6, absent ERPs in 3 patients. Serial recordings showed disappearance of P3a component in 8 p a t i e n t s , s l o w i n g of P3b in 6 patients, progressive topographycal alteration of ERPs ( i n t e r p r e t e d as a b s e n c e of N2 -P3a - P 3 b and emergence of posterior SW) in i0 patients. Correlations with Neuropsychologieal Tests showed a linear regression between P3b latency and WAIS memory subscores. P~a absence and topographycal ERP a l t e r a t i o n s w e r e i n s t e a d r e l a t e d w i t h several low s c o r e s of N e u r o p s y c h o l o g i c a l T e s t s assessing mentation and attention. The v a r i o u s p a t t e r n s of ERP a l t e r a t i o n s (P3a-h-SW delay; a b s e n c e of P 3 a - d e l a y e d P3b-SW; a b s e n c e of P3-b, delayed SW) w e r e not unique of AD, as similar alterations were observed in Multi Infarctual Dementia, Progressive Supranuclear Palsy, D e m e n t i a in a d v a n c e d M u l t i p l e S c l e r o s i s .