Communications affich6es/Posters 65S

P81

EEG POWER, COHERENCE AND PHASE IN ALZHEIMER'S DISEASE G.G. Celesia, ~G. Boleioni, *C. Baggio, M. Brigell and G. Rubboli Dept. of Neurology, Loyola University, Chicago, U.S.A.

~FIDIA Pharmaceuticals, Abano TerTae, Padua, Italy

High resolution power spectra, coherence and phase of EEG were analyzed in 25 Alzheimer's patients and 30 normal subjects. A computer graphic method (G. Bolcioni and C. Baggio: Fidia Biomedical Inf. 2/3, 1-13;1989) permits visualization and quantification of the data via a color coded mosaic pattern array representing the power spectrum of the electrode positions. Color coded matrices represent coherence and phase values between two pairs of electrodes, and simultaneously display 64 electrode combinations. Alsheimer's disease (AD) patients either lacked alpha activity or showed slower alpha frequency compared to normals. Theta and delta peaks were often the predominant rhythm of the more severely affected patients. Intrahemispheric coherence particularly between fronto-occipital regions was reduced in AD patients. The phase opposition obseL'ved in normals between frontal and occipital regions was disrupted in AD subjects. Intrahemispheric coherence was diminished; and the normal high coherence between right and left occipital regions was absent. The EEG analysis was conducted both with linked ear and with Hjorth's source derivation method. The limitations and benefits of the two methods will he discussed. Abnormalities of EEG coherence and phase in AD may reflect topographic inhomogeneities of cortical function.

P82

EVOKED POTENTIALS IN DEMENTIA OF ALZHEIMER TYPE

M=D±de l a Calzada, A. Codina, T. Sa~gal~s, V. Gimeno, F.Pujadas, O.Romero, M.V.Soriano.

Hospital General Valle Hebr6n. Barcelona. Spain

We have studied the Pattern Reversal-Visual Evoked Potentials (PE-VEP), Flash-Visual Evoked Potentials (F-VEP), Brainstem Auditory Evoked Potentials (BAEP), Median Nerve Somatosensorial Evoked Potentials (MN-SSEP) and Somatosensorial P300 in 54 patients, aged between 51 and 81 years and diagnosed as having an Alzheimer Disease. Their results were compared whith those of a 15 healthy subjects control group, matched in age.

We founded a considerable retard of latency begining with the third ~ave of F-VEP and increment of II-IV interval. In 29% of cases the V wave is absent. There is an enlargement of P300 latency (mean:458s) in pathological group and is recorded in previous areas than in control group, it is a~sent in near a half of demented patients.

All patients and control subjects were suhmited to Mini-Mental, Pfeiffer, Wessler and Hachinski tests.

Nonparametric statistical tests evidence significant differences between both groups respect F-VEP and P300 disturbances.

They are'nt significant differences whith regard to PR-VEP.

P83

AGE-RELATED INSTABILITY OF AROUSAL DURING SLEEP ASSESSED THROUGH THE PARAMETERS OF CYCLIC ALTERNATING PATTERN

Libor~o ParrJno, MarJo Giovanni Terzano, Mirel.la Boselli

Sleep Disorders Center, Dept. of Neurology

University of Parma, Italy

The complex arrangement of the phasic events during non-REM

sleep allows to distinguish a double modakity of arousal or-

ganization expressed by two complementary EEG patterns: a ph~

sic modality or Cyclic Alternating Pattern (CAP), consisting

of b~phasic (phase A and phase B)cycles clustered in sequen-

ces and related to a sustained condition of arousal JnstabJ]i

ty; and a tonic modality or non-CAP, in which the prevalence-

of EEG statJonaritJes and the poor amount of phasic events de

fine a state of prolonged stability in sleep depth. The noct-

urnal recordings of 6 sound sleepers aged over 60 years were

matched with those carried out on 5 healthy young ad-

ults aged betweon 20 and 30 years. The enhanced instability

of arousal in elderly subjects found a consistent confirma-

tion Jn the prominent increase of CAP cycles (222 vs.

119) and of CAP Rate. The reduced capacity to build up

synchronized sleep patterns (stages 3 and 4) was associated

with a dJminuished amount of A phases of CAP with synchroni

zed features (52% vs. 77%) and w~th a significant decrease

of "descending" CAP sequences, i.e. occurring c'[ose

to downward stage shifts. In both groups, the length

of phase A overlapped impressively, whereas the duration

of the B phases, corresponding to the inhibitory component

of CAP oscJ]]atJon, was significantly shorter in the

aged sample. The structura] re-arrangement in sleep

reflects the impaired capacity of the elderly brain

to reach deep sleep and to maintain prolonged steady-states

of arousal. The integration of CAP within the classical para-

ters may shed light on the pathophysJologJcal mechanisms of

sleep-related disorders diffused among the aged (insomnia,

breathing disturbances, nocturnal myoc]onus) commonly suppor-

ted by under]yJng conditions of arousa] instability.

P84

CORRELATION BETWEEN BRAIN ELECTRICAL ACTIVITY AND CEREBRAL

BLOOD FLOW IN PATIENTS WITH DEMENTIA OF THE ALZHEIMER TYPE

S. Passero, R. Rocchi, C. Paradiso, N. Battistini

Institute for Nervous and Mental Diseases. University of

Siena. Siena, Italy

The most frequent findings seen in patients with dementia

are EEG slowing and regional cerebral blood flow (rCBF)

reduction, but evaluation of the relationship between

these two phenomena are still lacking. We therefore

estimated relations between rCBF changes and EEG

abnormalities in 18 patients with DAT who undervent

extensive clinical and laboratory investigations including

quantitative EEG mapping and rCBF determination. Cognitive

impairment ranged from mild to severe. None of the patients

had focal cerebral lesions on TC scan and~or NMR scan

esaminations. Fourteen normal subjects served as control

group. EEG electrodes were placed on 16 positions over the

scalp surface, using the international 10-20 system, rCBF

was measured by the Xenon 133 inhalation method in 16

regions over each hemisphere. It was computed as the Initial

Slope Index (ISI) which consists mainly of gray matter flow.

Relative powers in each band, peak frequency in the alpha

band and ratios of powers in different bands were used as

independent (predictor) variables, and the mean rCBF value

of two adjacent regions corresponding to the location of

each EEG electrode was used as dependend variable in

multiple regression analyses. Age was used as covariate

variable. All the rCBF variables were more or less strongly

related to EEG measures, but the relative importance of each

predictors varies depending on the region in question.

Relative power in the theta band, peak frequency in the

alpha band and ratio of powers alpha/theta were the best

predictors of rCBF changes.