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• Vol.42 No.6
• CLINICA NEUROL, 42: 512−518, 2002
• Vol.42 No.6 contents

Original Article

Cerebral circulation and metabolism in the patients with higher brain dysfunction caused by chronic minor traumatic brain injury: a study by the positron emission tomography in twenty subjects with normal MRI findings

Hidehiro Kabasawa, M.D.^1)*, Tetsuo Ogawa, M.D.¹⁾, Akihiko Iida, M.D.²⁾ and Michitaka Matsubara, M.D.³⁾

¹⁾Department of Rehabilitation, Nagoya City Rehabilitation and Sports Center
²⁾Department of Radiology, Nagoya City Rehabilitation and Sports Center
³⁾Department of Neurology, Nagoya City Rehabilitation and Sports Center
^*Address for correspondence: Foundation Nagoya City Rehabilitation and Sports Center, 1-2, Mikanyama, Yatomi-cho, Mizuho-ku, Nagoya 467-8622, Japan

Many individuals are affected on their higher brain functions, such as intelligence, memory, and attention, even after minor traumatic brain injury (MTBI). Although higher brain dysfunction is based on impairment of the cerebral circulation and metabolism, the precise relationship between them remains unknown. This study was undertaken to investigate the relationship between the cerebral circulation or cerebral metabolism and higher brain dysfunction.

Twenty subjects with higher brain dysfunction caused by chronic MTBI were studied. They had no abnormal MRI findings. The full-scale intelligence quotient (FIQ) were quantitatively evaluated by the Wechsler Adult Intelligence Scale-Revised (WAIS-R), and the subjects were classified into the normal group and the impaired group. Concurrent with the evaluation of FIQ, positron emission tomography (PET) was performed by the steady state method with ¹⁵O gases inhalation. Regional cerebral blood flow (rCBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO₂) were calculated in the bilateral frontal, parietal, temporal, and occipital lobe. First, of all twenty subjects, we investigated rCBF, OEF and CMRO₂ in all regions. Then we compared rCBF, OEF, and CMRO₂ between the normal group and the impaired group based on FIQ score. We also studied the change of FIQ score of 13 subjects 9.3 months after the first evaluation. In addition, we investigated the change of rCBF, OEF and CMRO₂ along with the improvement of FIQ score.

Although rCBF and OEF of all subjects were within the normal range in all regions, CMRO₂ of more than half of subjects was under the lower normal limit in all regions except in the right occipital lobe, showing the presence of "relative luxury perfusion". Comparison of rCBF, OEF and CMRO₂ between normal group and impaired group revealed that CMRO₂ of the impaired group was significantly lower than that of the normal group in the bilateral frontal, temporal, and occipital lobe. After 9.3 months, FIQ scores of 13 subjects were significantly increased. CMRO₂ was significantly increased in the bilateral frontal and temporal lobe, as well as in the right occipital lobe, along with the improvement of FIQ score.

It was concluded that higher brain dysfunction caused by chronic MTBI was related to malfuntion of neuronal networks based on the generalized decrease of brain oxygen metabolism in all brain regions. Damage to neuronal networks in the bilateral frontal and temporal lobe appeared to play the most important role in higher brain dysfunction.

(CLINICA NEUROL, 42: 512−518, 2002)
key words: minor traumatic brain injury, higher brain dysfunction, PET, WAIS-R, relative luxury perfusion

(Received: 6-Mar-02)