S-I-9. Indications and Limits of an Extensive External Decompoession

Intracranial hypertension was hnduced by an extradural balloon in cats and ischemic lesions were examined by intra-aortic perfusion of colloidal carbon.After decompression at the stage of anisocoria,restoration of circulation was fairly good.At the stage of dilated fixed pupils ischemic areas reducrd to a considerable extent after decompression.However,nearly 50 per cent of cases had circulatory dosturbance with petechial hemorrhages in the upper brain stem.Photic evoked potentialsin visual cortex,upper brain stem and peripheralfacial nerve were recorded to clarify the cerebral function under discussion.At the stage of dilated pupils evoked potentials in the upper grain stem and the facial nerve were greatly suppressrd or almost disappeared and in animals in which evoked potentials in these regions recovered after decompression,recovery of clinical signs and circulatory disturbance in the upper brain stem was satisfactory.On the other hand,those in which evoked potentials in the visual cortex had restored but not in the upper brain stem and the facial nerve,showed only temporary recovery in vital signs.