The loss of neuronal integrity may be one of the causes of cognitive disturbances in the patients with brain traumatic injury and normal FLAIR and T2-weighted MRI

Abstract Objective : Traumatic brain injury causes cognitive disturbances in many cases. Some patients have moderate–severe brain dysfunction despite slight or no abnormality in MRI. The purpose of this study is to investigate whether the loss of neuronal integrity exists in the patients with traumatic brain injury using C-11 flumazenil PET (FMZ-PET) without MRI abnormality. Method : This study included 11 patients with traumatic brain injury and posttraumatic cognitive disturbances. All of the studies were examined at least 6 months later after injury. The dynamic flumazenil PET was studied in all patients. The binding potential of flumazenil (BP) was calculated by reference method. Axial T1WI, T2WI and FLAIR images were obtained with 1.5-T scanner. Coronal images were added in some cases. The BP images were visually interpreted by at least two experienced nuclear physicians by consensus. The lesions were determined as positive if a definite localized area of decreased distribution with respect to the surrounding normal tissue was present except for physiological distribution. Results : All of the patients had normal T1, T2 and FLAIR MRI. Nine patients had memory impairment. The low uptakes of BP images were shown in seven patients (63%). The low uptakes of BP were shown in the medial temporal lobe, the lateral temporal lobe, the temporal base and the frontal lobe in five, one, one and two patients, respectively. There were no patients that had low uptake in the cerebellum. Six of the nine patients who had memory impairment showed low uptakes in BP in the temporal lobe. Conclusion : These results indicated that the loss of the neuronal integrity, which was not able to be detected with MRI, was one of the causes of the cognitive disturbances in patients with traumatic brain injury.