Download movement of the cerebrospinal fluid in the cerebral and spinal cord

MOVEMENT OF THE CEREBROSPINAL FLUID IN THE CEREBRAL AND SPINAL CORD SPACES
Yu. E. Moskalenko and A. I. Naumenko
Department of Physiology, First Pavlov Medical Institute and the Department of Technical Safety, Ul'ianov Electrotechnical Institute, Leningrad
As far as we know, electroplethysmography is now being applied in the investigation of movements of the cerebrospinal fluid in the cerebral and spinal cord spaces for the first time. Despite
the fact that these periodic movements, the constant flow and ebb of the c.s.f., had already been
discovered in the last century, there is still no uniform opinion on them. While many writers
(Becher, 1922; Ewig and Lullies, 1924; Hurtle, 1927; Alov, 1949) agree that the fluid is in constant fluctuating movement, there is wide divergence of opinion on the nature of the movement.
METHOD
We have previously described a method of low-frequency electroplethysmography which permits recording of changes in the electrical conductivity of the cerebrospinal fluid and blood in
the cavities of the brain and spinal cord (Mostalenko and Naumenko, 1956). This method was
employed in the work now described.
The experiments were made on cats which, under general medinal anaesthesia, were subjected to
the trephining of 4 openings (diameter 5 mm), 2 in the parietal bones at distances of 1-5 cm from
the midline, and 2 in the vertebral column (first cervical and third lumbar vertebrae). Into these
openings Plexiglas obturators, mounting silver electrodes having an area of 18 mm2, were
screwed, and the openings were then sealed with collodion to restore the air-tight condition of
the cerebrospinal spaces (Fig. 1).
Fig. I. Diagram of the position of the electrodes in the acute experiment on the cat.
An alternating current of 10,000 c/s was delivered to the electrodes, and the passing of this current over a considerable period of time did not have any apparent effect on the experimental an-
 Fiziol. zh. SSSR 43: No. 10, 928-933, 1957 [Reprint order no. SEC 143].
imal. The recording of changes in the electrical resistance of the c.s.f. and blood was effected
with specially devised apparatus. The 18 experiments carried out yielded uniform results.
RESULTS AND DISCUSSION
In the examination of the electrical resistance of the organs we encounter 2 kinds of values. First,
the average fixed resistance of the particular organ can be determined. This depends on the properties of the tissues in the organ, the surface area of the electrodes, the interelectrode distance and
the frequency of the current used. In our experiments the average value of the resistance between
the electrodes in the sub-arachnoid space was 680 + 820Ώ. The corresponding resistance in the
cavity of the spinal canal was 850 + 920 Ώ. The variation in resistance in both spaces was 0-5-15 Ώ. These variations in resistance coincide in time with the cardiac contractions and with respiration, and constitute the second characteristic of the electrical resistance in these cavities.
With the blood circulation in the brain and spinal cord being recorded simultaneously, the important point is to determine the changes in resistance, which are brought about, in our opinion,
by change in the quantitative relationship between blood and c.s.f. in the cavities concerned,
since the conductivity of blood is 2-5 times less than that of the c.s.f. It is therefore convenient to
calculate the relative changes in the electrical resistance in the cerebral and spinal cord spaces,
which do not depend on the mean
Fig. 3. Displacements of c.s.f. of the third order caused by asphyxia on the animal.
At 1 min: commencement of asphyxia; at 12 min: end of asphyxia. (1)—cerebral space; (2)—spinal space.

Significance of

and
V
as in Fig. 2.
V
CONCLUSIONS
(1) The results obtained with low-frequency electroplethysmography are evidence of its usefulness for the investigation of the rhythmical movements of the cerebrospinal fluid in the cerebral
and spinal spaces.
(2) The respiratory movements of the c.s.f., being in opposite phase in the cerebral and spinal
spaces, point to both anatomical and physiological "antagonism" between these areas.
(3) In the respiratory movements of the c.s.f. from the cerebral space into the spinal canal an average of about 12-15 per cent of the fluid is involved, and in the waves of the third order, about
30 per cent.
(4) The summated movement of fluid is not regular, as the resultant movement depends on differently phased cardiac and respiratory movements and on waves of the third order. These displacements of fluid reach maximum proportions when the phases coincide, and when they are
antithetical the changes are much reduced.
(5) The movements of cerebrospinal fluid associated with inspiration and expiration are the result of different conditions affecting the outflow of venous blood from the brain and spinal cord
spaces.
Translated by R. Crawford
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