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| DIMENSION |
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The EEG alpha component with 3-Hz bandwidth generates smooth concentric
equipotential contours on the scalp as shown in Fig.2 because the electric
generators in the cortical surface is uniform and the generators in facing
walls of sulci cancel each other. In an AD patient, on the other hand,
synapse-neuronal activity (SNA) is no longer uniform and equipotential
contours on the scalp are distorted with several separated loops. A mathematical
expression of smoothness of the scalp potentials has been introduced. In
an AD patient the smoothness looks sometimes as in the normal and intermittently
takes a lower value (unstable). Therefore, we introduced two parameters
Da for mean smoothness over a given time interval and Ds for standard deviation of fluctuating smoothness around the mean value.
We investigated usefulness of these parameters in discriminating AD from
the normal at Department of Psychiatry, Musashi Hospital, NCNP for about
60 AD patients and age-matched 60 normal volunteers. The results of these
120 subjects were found to stay within a fan-beam area in Fig.3; as AD
progresses the mean smoothness decreases and its instability increases,
hence the state (Da, Ds) moves towards left up.
The fan-beam area is divided in three regions according
to diagnoses: the normal region characterizes normal subjects with 10%
of AD patients; the impaired region characterized AD patients with 10%
of normal subjects. The sub-normal region includes normal subjects as well
as AD patients and no decision can be made if a subject is normal or AD.
In this case DIMENSION examination is repeated again two or three months
later. If the state shifts toward the left, he/she is possibly demented
in the early stage.
Ref: T. Musha, T. Asada, F. Yamashita, T. Kinoshita, H. Matsuda, M. Uno, Z. Chen and W.R. Shankle, "A new EEG method for estimating cortical neuronal impairment that is sensitive to early stage Alzheimer's disease," Clinical Neurophysiology, 113 (2002) 1052-1058.
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| Recording of 21ch EEG |
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The EEG recording is very simple. One puts on a helmet with 21 electrodes,
tips of which are covered by materials wet with saline solution. Electric
contacts with the head skin will be stabilized in a few minutes. The 21ch
EEG signals are recorded for 3~5 min in a rest state with closed eyes.
The data (2.5 MB) is sent to our server via INTERNET, and after a few minutes
the Brain Activity Graph is downloaded. The total recording time is about
10 min. |
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| Monitoring Brain Rehabilitation Efficacy |
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DIMENSION is so sensitive to SNA that it can detect a change of the brain
activity after a single rehabilitation treatment. Fig.5 shows SNA as a
function of markers (Da, Ds) before and after a single 2-hour art therapy. Open circles refer to persons
diagnosed as AD, and their improvements of SNAs were clearly observed.
This improvement, however, is temporary. After a week SNA returned back
near the original points. After repeating the art therapy every week in
6 months more than 80% of the patients their SNA moved up near the sub-normal
region; continuation of the therapy kept these people in the improved state.
Dark circles refer to persons who were would-be normal. The majority of
them is in the normal region but some were originally in the impaired region.
They were also activated in SNA after the art therapy. The insert in this
figure shows a scene where AD patients are at the art therapy and one has
21 electrodes, which are covered with a bandana.
Ref.: S. Kimura, T. Musha, K. Kaneko, K. Nishida, K. Sekine, M. Oh, T. Ohshiro,
"Sensitive Estimation of the Effectiveness of Clinical Art on Demented
Patients by Means of DIMENSION," ADPD, 2003, Seville. |
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| Long Term Monitoring of the AD Treatment |
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DIMENSION is also useful in monitoring the process of the treatment of
dementia for a long period of time as shown in Fig.6. The horizontal axis
indicates time in weeks and the vertical axis is Da, where the green belt shows the sub-normal region. The Da value is measured about every two months. Patients were treated by medication
with ARICET as well as by the occupational therapy and music therapy at
Kurashiki-Heisei Hospital. Most of them were initially in the impaired
region and gradually improved towards the normal region. With the aid of
DIMENSION one can compare efficacies of various types of rehabilitation,
and select the best one for each patient. |
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| Prediction of Prognosis |
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| DIMENSION can make a reliable prognosis of AD patients. This is shown in
Fig.7A~C. The vertical axis of Fig.7A and 7B indicate the HDS-R (Hasegawa
Dementia Scale Revised) score which is equivalent to the MMSE score. A
refers to the initial states of 13 patients at St. Marianna University,
School of Medicine Hospital, and Fig.7B refers to their states after 6
months. In either case no correlation with statistical significance is
found between the HDS-R score and Da. The vertical axis in Fig.7C is the rate of change in HAD-R in 6 months,
where we can see a positive correlation with statistical significance between
this rate and the Da value which was observed in the initial stag. It should be noticed that
the sub-normal region bounded by two parallel broken lines separates the
positive and negative rates of change in the HDS-R score. This fact suggests
the following. Even if the HDS-R score takes a high value it is probable
that his/her AD will progress when Da takes a value in the impaired region. In other words, the Da value is more predictive than the HDS-R score or probably the MMSE score
about the future of the disease. |
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