Operative Indication of Large Decompressive Craniectomy for Cerebral Contusion with Subdural Hematoma

The usefulness of large decompressive craniectomy in cases of severe contusion with thin subdural hematoma has been reported by Ransohoff et al. The beneficial effects of this procedure, however, still remained obscure from the standpoints that its mechanism and limits within which effectiveness can reasonably be expected were not clear. The present study was designed to obtain an index of the limits for effective decompressive craniectomy mainly in terms of intracranial pressure, cerebral blood flow, electroencephalogram, and far field acoustic response from both animal experiments and clinical investigations. Experimental results indicated that decompressive craniectomy was useless if the intracranial pressure was more than 60 mmHg and the vasomotor index (the ratio of intracranial pressure and systemic arterial pressure) was more than 0.5 with reduced perfusion pressure, impaired venous return, and if there was an 80-90% decrease in cerebral blood flow. It was also shown that such conditions coincided with the absence of far field acoustic response as an expression of the brainstem function. In clinical studies of 60 cases of severe brain contusion with thin subdural hematoma following large decompressive craniectomy, intracranial pressure, cerebral blood flow, angiogram, CT scan and far field acoustic responses were retrospectively checked in both the survival and dead groups. It was found that effective results by this procedure was difficult to obtain whenever the II-VII was in far field acoustic response was absent, the vasomotor index was more than 0.5 and when non-filling angiograms were observed. Thus, indication for large decompressive craniectomy for the treatment of severe brain contusion with thin subdural hematoma is established based on the analysis of these results.