123I-iomazenil SPECT can detect specific impairment of neuronal integrity in traumatic brain injury with diffuse axonal injury.

Introduction: Objective assessment of the neuronal abnormalities in cases of traumatic brain injury (TBI) with diffuse axonal injury (DAI) is crucial to understanding the underlying pathology, as well as from the point of view of facilitating socioeconomic support for these patients. Neuronal integrity can be evaluated by benzodiazepine binding using ¹²³I-iomazenil (IMZ) SPECT. The purpose of this study was to investigate the extent of neuronal damage in cases of TBI with DAI using ¹²³I-IMZ SPECT and MRI.

Methods: We compared the findings in 31 patients with TBI without any major focal brain lesions and 25 age-matched normal controls. Subjects underwent ¹²³I-IMZ SPECT and MRI, and also assessment by cognitive function tests. The partial volume effect of ¹²³I-IMZ SPECT was corrected using MRI. Regional benzodiazepine binding and brain atrophy in TBI were assessed based on the volume of interest and voxel-based analysis.

Results: In the patients with TBI, decreased binding of IMZ was detected in the medial frontal/orbitofrontal cortex, posterior cingulate gyrus, cuneus, precuneus, and superior region of the cerebellum. The decreased IMZ binding in the cuneus and precuneus was associated with cognitive decline after the injury. In the patients with TBI, brain atrophy was detected in the frontal lobe, anterior temporal and parietal cortex, corpus callosum, and posterior part of the cerebellum. ROC analysis of ¹²³I-IMZ SPECT for the detection of neuronal injury showed a high diagnostic ability of IMZ binding for TBI in the cingulate gyrus, medial regions of the frontal, parietal, and occipital lobes, and superior region of the cerebellum.

Conclusions: In patients with TBI in whom the major pathology was DAI, decreased binding of IMZ, that is, decreased neuronal integrity, was detected in the medial frontal or orbitofrontal cortex, posterior cingulate gyrus, cuneus, precuneus, and superior region of the cerebellum. Decrease in IMZ binding in the cuneus and precuneus was associated with cognitive decline after the injury. On the other hand, brain atrophy in the patients with TBI was detected in the frontal lobe, anterior temporal and parietal cortex, corpus callosum, and posterior part of the cerebellum. ¹²³I-IMZ SPECT with PVC provides reliable diagnostic information and relevant insights into the pathology and mechanism of injury in cases of TBI.

• Download figure
• Open in new tab
• Download powerpoint