p84 correlation between brain electrical activity and cerebral blood flow in patients with dementia...
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Communications affich6es/Posters 65S
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.
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.
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.
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.