|
KMID : 0378019690120120039
|
|
New Medical Journal
1969 Volume.12 No. 12 p.39 ~ p.54
|
|
|
An Experimental Study on Effects of Vestibule-Ocular Response in Transtentorial Pressure Cone
|
|
|
|
|
Abstract
|
|
|
It is well known that severe symptoms doveloping in the transtentorial pressure cone, secondary to supratentorial space-occupying lesions are caused by descending disturbances in the brain stem function. Among these symptoms the degree of oculomotor dysfunction, dilated pupil or anisocoria, is believed to be the most valid criterion for surgical intervention as determination of prognosis. However, according to many reports, the percentage of pupillary changes in the clinical statistics vary and theories for the pathogenesis are still controversial.
Since the reports of Ethelberg and later Vaernet on the impairment of the vestibulo-ocular reflexes in cases of transtentorial herniation, some of neurologists have become interested in this subject. The author has always believed that there was a correlation between the severity of the transtentorial pressure cone and vestibulo-ocular dysfunction.
The present study was planned to investigate effects of the 3 neuron response evoked by stimulation to the vestibulo-ocular circuit and to correlate this with other symptoms of the transtentorial pressure cone expecting the response to be as an additional valuable indicator for decompressive surgery and prognosis.
Materials and Methods
A total of 65 rabbits with normal caloric test, weighing around 2kg. were used.
These animals were divided into two groups?, 35 for group I experiment and 30. for,.group II experiment,: Each of these animals served as his own control for the study.
Group I experimental study:
The balloon of the intracranial pressure producing apparatus which was divised in this study, was placed subdurally through a threphine,in,the, fronto-central region over the vertex. ´Increment of the intracranial pressure was produced by air added´ to the balloon of the apparatus: Every 15 minutes cold caloric stimulaions, 2-5°C of water 10-20cc, : were applied, and detailed neurological findings, vital signs, biparietal E.E.G. findings were obtained.
Arterial blood pressure was monitored by a femoral artery catheter attached to a Stathahm strain gauge, and respirations were monitored with use of a Bellow type transducer. This data was synchronously recorded on the Grass polygraph and categorized into 4 stages; control base line, dilated pupil caloric positive, dilated pupil caloric negative (change-over stage), and terminal vasoparesis, over a period of 2 hours until the animals showed no cardiac response on E. C. G. The dead animals were subjected to the post mortem examination.
Group II experimental study:
The total of 30 rabbits was again subdivided in 2 groups of 15 rabbits each. The transtentorial pressure cone was created by the same methods as in the group I experiment. In one group of animals, the intracranial pressure was decompressed at the stage of dilated pupil just before the change-over from caloric positive to negative, and the other group right after the stage. The mortality rate was observed in each group over 48 hours postoperatively.
Results and Conclusion
1) The order of developing symptoms in the transtentorial pressure cone is, in general, identical to that of clinical cases. At the stage of change-over from the caloric positive to negative following dilated pupils, the brainstem reflexes; light reflex 86.6% Corneal reflex 86.6% and blink reflex 85.7%, were abolished and followed , by respiratory arrest. Thereafter two thirds of the experimental animals showed a flattened E.E.G. before 0 blooa pressure; and the remaining one third first showed 0 blood pressure and then he flattened E E G before no cardiac response on the E C G
2) As oculomotor dysfunctions, internuclear paralysis was noted in 12.5% of all transtentorial herniated animals which also disappeared at the caloric negative stage.
3) While the mortality rate showed 13.4% in the decompression group at the dilated pupil . with positive caloric response, the another group at the stage immediately following change-over from the positive to negative showed 80%.
4) It is concluded that the vestibulo-ocular response could be used as an additional valuable neurological indicator in the diagnosis of comatosed animals with dilated pupils due to transtentorial pressure cone. However the significance of the response as an indicator might be limited to that period between involvement of the pupilloconstrictor fibers and the paralysis of the somatic nerve fibers to the extraocular muscles.
|
|
|
KEYWORD
|
|
|
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|
|
|