Loss of neuronal integrity: a cause of hypometabolism in patients with traumatic brain injury without MRI abnormality in the chronic stage.
OBJECTIVE
Traumatic brain injury (TBI) causes brain dysfunction in many patients. However, some patients have severe brain dysfunction but display no abnormalities on magnetic resonance imaging (MRI). There have been some reports of hypometabolism even in such patients. The purpose of this study was to investigate the relationship between metabolic abnormality and loss of neuronal integrity in TBI patients with some symptoms but without MRI abnormalities.


METHODS
The study population comprised ten patients with TBI and ten normal volunteers. All of the patients were examined at least 1 year after the injury. ( 15)O-labelled gas PET and [(11)C]flumazenil (FMZ) positron emission tomography (PET) were carried out. The cerebral metabolic rate of oxygen (CMRO(2)) and binding potential (BP) images of FMZ were calculated. Axial T2WI, T2*WI and FLAIR images were obtained. Coronal images were added in some cases.


RESULTS
All of the patients had normal MRI findings, and all showed areas with abnormally low CMRO(2). Low uptake on BP images was observed in six patients (60%). No lesions that showed low uptake on BP images were without low CMRO(2). On the other hand, there were 14 lesions with low CMRO(2) but without BP abnormalities.


CONCLUSIONS
These results indicate that there are metabolic abnormalities in TBI patients with some symptoms after brain injury but without abnormalities on MRI. Some of the hypometabolic lesions showed low BP, indicating a loss of neuronal integrity. Thus, FMZ PET may have potential to distinguish hypometabolism caused by neuronal loss from that caused by other factors.
Department of Nuclear Medicine, Hokkaido University School of Medicine, North 15th, West 7th, Kitaku Sapporo 060-8638, Japan. tshiga@med.hokudai.ac.jp
Tohru
T
Shiga
Katsunori
K
Ikoma
Chietsugu
C
Katoh
Hirotaka
H
Isoyama
Tetsuaki
T
Matsuyama
Yuji
Y
Kuge
Hiroyuki
H
Kageyama
Tomoya
T
Kohno
Satoshi
S
Terae
Nagara
N
Tamaki
D000328:Adult; D000368:Aged; D001928:Brain Diseases, Metabolic / Q000000981:diagnostic imaging* / Q000473:pathology*; D001930:Brain Injuries / Q000000981:diagnostic imaging* / Q000473:pathology*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000000981:diagnostic imaging* / Q000473:pathology*; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity