[Study of local shiftings of the brain stem in increased intracranial pressure by a supratentorial balloon].

The study of the mechanism of pressure transmission is important for the treatment of rapid deterioration of a patient's condition with increased intracranial pressure (ICP) from a space taking lesion in neurosurgical practice. The aim of this experiment is to clarify the mechanism of pressure transmission during supratentorial balloon inflation, by continuously monitoring local shiftings of the brain using strain gauge sensors. Mongrel dogs and macaca fuscatas were fixed in stereotaxic head frames with light anesthesia. Brain shiftings were evaluated by sensors discriminating two dimensional directions, sagittal and coronal planes, at the cerebrum. Brain stem shift was measured as displacement from the midline at the midbrain and ventro-dorsal shifting in the pons. ICP was raised by inflation of a supratentorial balloon located in the frontal lobe in one group or the temporal lobe in other group. As parameters detecting the changes in the functions of the brain stem, systemic blood pressure (SAP), respiration and pupil size were simultaneously monitored. Shifting of the brain stem occurred in four staged in both groups. During a minimum increment of ICP shifts to the antiballoon side were observed at the occipital lobe and the midbrain. The pons showed no shift in stage I. During the further inflation of the balloon stage II, the pons started to shift to the ventral side. In this stage the temporal lobe, in addition to the occipital lobe, shifted to the antiballoon side. There was a tendency for stage II to last longer for the frontal balloon than for the temporal balloon.(ABSTRACT TRUNCATED AT 250 WORDS)