Characterization of Traumatic Brain Injury Using Imaging and Physiological Parameters: A Pilot Study

The study was a cross-sectional study aimed to obtain preliminary data to characterize traumatic brain injuries (TBIs) of Operation Iraqi Freedom/Operation Endurance Freedom (OIF/OEF) in a cohort of insular veterans using perfusion and molecular imaging, and physiologic parameters.

The size and location of TBI lesions of 6 veterans were evaluated by quantifying cerebral perfusion and metabolism using Tc99m ethyl-cysteinate dimer SPECT/CT and fluorine-18 fluorodeoxyglucos PET/CT, respectively. Somatosensory evoked potentials were collected, and quality of life was measured by assessing functional status, activities of daily living, and depression levels. The study population included OIF/OEF returning soldiers diagnosed with mild/moderate TBI.

Six subjects were enrolled in the study and 4 completed all assessments. The data showed that higher trauma severity might be accompanied by lower levels of independence. Perfusion and metabolic findings were detected in the presence of negative CT. Imaging abnormalities were frequently localized in the frontal lobe. An increased number of perfusion defects compared to metabolic defects were observed.

SPECT/CT and PET/CT might have an added value in the diagnosis of patients with mild/moderate TBI. However, a larger study is required to develop new predictive TBI model systems that include functional and molecular nuclear medicine neuroimaging, and physiologic parameters, in the TBI diagnostic algorithm for veterans with probable TBI. The mismatch between perfusion and metabolism might be suggesting the possibility of up-regulation of cerebral glucose transporters/receptors to compensate for diminished perfusion. It can also imply an important role of impaired vasomotor response or endothelial dysfunction in the etiology of TBI. However, remaining functional neurons and neighboring damaged tissue would still likely be overexcited during reorganization for several months post-injury, potentially explaining the increased metabolic uptake in areas of decreased perfusion.