Pathogenesis of the mass effect of cerebral contusions and the role of surgery in its management

Introduction: Despite intensive medical therapy, elevated ICP is uncontrollable in some patients with traumatic cerebral contusion. Surgical excision of the contused brain tissue appears to be the only therapy which provides satisfactory control of ICP in such patients. In the present study, we analyzed clinical and experiment data to determine the mechanism underlying the mass effect of cerebral contusion and the role of surgical excision of the contused brain tissue in ICP control. Methods: We reviewed the clinical data obtained from patients (n = 46) with cerebral contusions who revealed a delayed deterioration pattern in the time courses of their clinical conditions. Patients who developed contusion hemorrhages which were sufficiently large to consider for surgical evacuation (diameter> 3 cm) were excluded. Experimental data were obtained from cerebral contusions produced with the controlled cortical impact injury model of the rat (n = 56). Results: Neurological deterioration in the patients was observed within the initial 12-36 hours in association with an increase in ICP. The time course of neurological deterioration corresponded to progressive increase in mass effect of contusion necrosis as evaluated with MRI, rather than development of contusion hemorrhages or white matter edema. In the experimental animals, it was found that the tissue osmolality of areas of contusion necrosis was markedly elevated during the initial 24 hours. Slow infusion of Gd-DTPA disclosed that enhancement of areas of contusion necrosis and hemorrhages, but not areas of white matter fibers at as early as 12-24 hours post-trauma. In many patients, excellent control of the ICP and recovery in their clinical conditions were quickly achieved by surgical excision of the contused brain tissue. Discussion: The mass effect which develops during the initial 12-36 hours post-trauma may be attributable primarily to an increased tissue osmolality within contusion necrosis. An increase in cerebrovascular permeability may play a synergistic role in producing the mass effect. The beneficial effect of surgical excision of the contused brain tissue may be accounted for by simultaneous elimination of these mechanisms, in addition to an increase in space compensation.