High Incidence of Initial Loss of Consciousness with Abnormal F-18 FDG and O-15 Water Brain PET in Patients with Chronic Closed Head Injury

Background: The purpose of this study is to evaluate the incidence of loss of consciousness (LOC) with functional abnormalities by brain positron emission tomography (PET) in patients with closed head injury using fluorine-18 labeled fluorodeoxyglucose (F-18 FDG) and O-15 water PET imaging. Methods: 36 sequential patients referred from rehabilitation service without known brain disease who had cognitive complaints months after head injury and had F-18 FDG and O-15 water PET, CT and/or MRI imaging were included. The image findings were compared and correlated with the incidence of initial LOC. Results: Significant difference was found in the association of abnormal imaging findings with LOC between functional (PET) and anatomical (CT or MRI) modalities. There was also significant discrepancy between PET and CT/MRI findings. Of the 28 patients with normal CT or MRI, 10 patients or 36% had abnormal PET findings (p=0.007). However, there was, however, high concordance (92%) between perfusion and metabolic PET images. Conclusion: There are significantly more functional than anatomic abnormalities in chronic closed head injury. PET may help in confirming the diagnosis and subsequent management when CT/MRI is normal. Those with normal PET are less likely to have LOC at the time of initial injury.