2010 年 33 巻 2 号 p. 165-172
In patients with mild traumatic brain injury (MTBI), higher brain dysfunctions which consist of cognitive impairments such as memory, attention, performance and social behavioral disturbances could be rarely apparent. However, higher brain dysfunctions should be identified by neuropsychological tests and supported by a social welfare for handicapped patients. Acknowledgement of higher brain dysfunctions after MTBI without obvious brain damages on morphological neuroimagings could be a social issue under controversy. An imaging of cortical neuron damages in patients with higher brain dysfunctions after MTBI was studied by functional neuroimaging using 123I-Iomazenil (IMZ) SPECT.
Statistical imaging analyses using 3 dimensional stereotactic surface projections (3D-SSP) for 123I-IMZ SPECT and 123I-IMP SPECT as CBF studies were performed in 11 patients with higher brain dysfunctions after MTBI. In all patients with higher brain dysfunctions defined by neuropsychological tests, cortical neuron damages were observed in bilateral medial frontal lobes, but reduction of CBF in bilateral medial frontal lobes were less obviously showed in 8 patients (apparent in 3 and little in 5). Group comparison of 3D-SSP of 123I-IMZ SPECT between 11 patients and 18 normal controls demonstrated significant selective loss of cortical neuron in bilateral medial frontal gyrus (MFG). Extent of abnormal pixels on each cortical gyrus using stereotactic extraction estimation (SEE) for 3D-SSP of 123I-IMZ SPECT confirmed that 8 patients had abnormal pixel extent >10% in bilateral MFG and 5 patients had abnormal pixel extent >10% in bilateral anterior cingulate gyrus.
In patients with MTBI, higher brain dysfunctions seems to correlate with selective loss of cortical neuron within bilateral MFG which could be caused by Wallerian degeneration as secondary phenomena after diffuse axonal injury within corpus callosum. Statistical imaging analysis using 3D-SSP for 123I-IMZ SPECT could be valuable for diagnosis of higher brain dysfunctions without obvious brain damages on morphological neuroimagings in patients with MTBI.
