「精神障害（うつ）」と「高次脳機能障害」の脳形態画像・機能画像所見を比較する試み—MRI・SPECTを用いた頭部外傷後の症例における検討

Characteristics of Statistical Imaging Analysis in Morphological and Functional Brain Imaging of Neuropsychological Impairments and Nonorganic Mental Disorder after Traumatic Head Injury

要旨　目的：頭部外傷後の器質性の高次脳機能障害と非器質性の精神障害の統計画像解析所見の特徴を明らかにすることを試みる．方法：頭部外傷後の，うつ群6例，高次脳機能障害群6例，そして，健常対照群6例を対象として，全症例にTc-ECD SPECTとMRI 3D volumetryを施行し，結果を統計画像解析した上で，3群間でStatistical Parametric Mapping（SPM）比較した（2 sample t-test, uncorrected p＜0.01）．結果：対照群と比し，うつ群と高次脳機能障害群で共通して，前部帯状回などの内側前方領域に，有意なTc-ECD低集積と灰白質容積減少を認めた．この所見は，うつ群より高次脳機能障害群に有意に強かった．高次脳機能障害群では，これら機能異常所見と形態異常所見の両者が，より深部の領域に広がったが，うつ群では，機能異常所見のみが背外側領域に向かい広がりを見せた．結論：本研究により，頭部外傷後の高次脳機能障害と非器質性の精神障害の形態・機能画像所見上の新たな特徴が示唆され，今後の研究的・臨床的アプローチ開発の新たな作業仮説が示された．

Abstract　Objective : The objective of the present study was to clarify the differences in statistical imaging analysis of functional and morphologic imaging between neuropsychological impairments (NPI) and nonorganic mental disorder (MD) after traumatic head injury. Methods : Six depressive patients after head injury without abnormal findings on conventional MRI (MD group), six nondepressive patients with NPI after diffuse axonal injury (NPI group), and six healthy subjects with a history of head injury (control group) were enrolled in this study. For all subjects, ^99mTc-ethylcysteinate dimmer (Tc-ECD) SPECT and MRI 3D volumetry were performed. Imaging data were analyzed using statistical parametric mapping, and then, the analyzed data were compared among the three groups (2 sample t test, uncorrected p＜0.01). Results : Compared to the Control group, significant low Tc-ECD uptake and regional grey matter volume reduction were noticed bilaterally in the anterior medial brain aspects such as the anterior cingulate cortex in both the MD group and the NPI group. These findings were significantly greater in the NPI group than in the MD group. Moreover, these functional and morphologic abnormalities were also spread to more medial and deep aspects such as the posterior limbic and the brain stem in the NPI group. Conversely, in the MD group without morphologic abnormalities, only functional abnormalities spread above the common lesions to the dorsolateral brain aspects such as the superior frontal lobe. Conclusion : Our results revealed some characteristics of statistical imaging analysis in functional and morphologic imaging of MD and NPI patients after head injury. These findings seem to be novel and can serve as useful information for future investigation of neural correlates with both NPI and MD after head injury.