Experimential Brain Stem Compression

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.

Two Cases of Cerebellar Infarction

Occlusion of vertebro-basilar artery and its branches can produce massive cerebellar lesion with edematous swelling from ischemia and accompanying hemorrhage. Recognition of this massive cerebellar lesion is essential, because it compresses the brain stem and rapidly leads to coma and death unless immediate surgical decompression of posterior fossa is performed. However, surgery might not be beneficial if the arterial occlusion had simultaneously produced and extensive infarction in the brain stem. The clinical and radiological findings are important in determining the optimum therapy and indication for decompressive surgery. CT scan was the most useful diagnostic test. Prompt and correct diagnosis of this illness is required to ensure adequate therapy. We are presenting two cases of cerebellar infarction, which have quite different clinical pictures and courses. One case has progressive headache for 2 months, which was misdiagnosed as tumorous condition and suboccipital craniectomy was performed but died due to brain swelling. The other one has acute course with compression of brain stem 24hr after onset of sudden headache and suboccipital decompressive surgery was performed and the patient recovered successfully.