Experimential Brain Stem Compression

ABSTRACT

Patterns of brain-stem compression and secondary brain-stem evoked postentials were investigated to correlate with expanding mass volume and location in mass-induced supratentorial brain compression in cats in which the subjects were divided into four experimental group i.e., frontal, temporal, parietal, and occipital brain-compressed groups. Postmortem insepection of the brain-stem showed either unilateral or bilateral dorsal herniation of the brain in frontal and temporal brain-compressed groups and dorsolateral herniation in parietal and occipital brain-compressed groups, respectively. Microscopic examination revealed that the secondary brain-stem hemorrhages were mostly caused by venous bleeding secondary to venous congestion, the bleeding being more severe in occipital brain-compressed group. As the intracranial pressure was raised by expansion of a supratentorial balloon, the late components of the BSEP were suppressed first, followed by the suppression of the early components. In BSEP recording a significant change was observed in Vth wave with prolongation of latency and decrease in amplitude. This finding suggests that the midbrain is the most vulnerable to compression ischemia. In parietal group, the Vth wave started to be prolonged at 0.4ml of balloon expansion and totally disappeared at 1.8ml of expansion.