Abstract
Extracellular glutamate concentration was measured continuously to detect ischemia of compressed brain tissue after evacuation for acute subdural hematoma. In case 1, the extracellular glutamate concentration was still normal in the compressed brain tissue on the side of the injury when the measurement was commenced. The glutamate levels on the opposite side and intracranial pressure were also still normal at the same time point. The glutamate levels on the injury side began to rise later, from 2 hours after the measurement was commenced. The intracranial pressure increased to 20 mmHg by 2 hours from the elevation of the glutamate levels on the side of the injury, in parallel with the elevation on the opposite side. Brain CT showed no new traumatic lesions and showed brain edema in the compressed brain tissue on the injury side. Cerebrospinal drainage and diuretics were administrated. As observed in case 1, the extracellular glutamate concentration in case 2 was already elevated on the injury side when the measurement was commenced. Yet in this case, the glutamate levels returned to normal within 3 hours. The glutamate levels on the opposite side and intracranial pressure also remained normal. Microdialysis monitoring is useful to detect ischemia of compressed brain tissue after evacuation for acute subdural hematoma. We need to further study the usefulness of extracellular glutamate concentration measurement by microdialysis in patients in the same clinical setting.
