Abstract
According to recent reports, the prognosis of diffuse brain injury with prolonged coma = diffuse axonal injury (DAI), as defined by Gennarelli, is often good in young cases. A total of 102 DAI cases were divided into two age groups. Group A, aged 29 or younger, and Group B aged 30 or older were studied in terms of neurologic symptoms. neuro-imaging and long term outcome in order to elucidate factors which might be related to a good outcome in younger cases. The long term outocome was evaluated in terms of activity of daily life (ADL) after 12 months or more following injury. Overall, recovery was significantly better in Group A than in Group B. As regards the level of severity of injury, the percentage of cases in Group B increased in proportion to the injury severity grade as determined by clinical symptoms upon admission. Computed tomography (CT) and magnetic resonance imaging (MRI) were evaluated according to the scoring systems we established. CT results indicated that Group B tended to have more serious cases with higher scores and, concurrently , the prognosis in Group B cases with higher scores was poor. By contrast, recovery to ADLS I and II was achieved in 94.9% of Group A cases with lower scores. At the same time, similar recovery to ADLS I and II was observed in some cases with higher CT scores, and 85.7% of such cases were in Group A. In our sequential observation of the MRI scores, the score decreased with the passage of time, the decline being more rapid in Group A than Group B. When the MRI score was evaluated in combination with the CT score, prognosis was good in both groups when the scores remained low, but when one or the other scores were high, recovery to ADL II or more was observed only in Group A. The findings of the ^<123>I-IMP single photon emission computed tomography (SPECT) were semiquantitatively analyzed by means of the delta count percent (D-Co%) of a circumferential profile curve. We observed the D-Co% over a period of time, and it was noted to decrease with time in Group A, but it tended to remain high in many Group B cases. Recovery to ADL II or more was achieved in almost all cases of both groups in which the D-Co% and in which the CT scores remained low, while 75% of those cases having recovered to ADL II or better despite the presence of a high D-Co% or CT score were in Group A. When those cases with demonstrated ventricular dilatation on the basis of the cerebroventricular index (CVI) as calculated from a CT scan in the chronic stage at six months or more after injury were categorized as the dilated group and others as a normal group, almost all Groups B cases were in the dilated group, while the Group A cases were nearly equally divided into the dilated group and normal group. In the dilated group with extensive neural injuries, 81% of Group A were restored to ADLs I and II, but all Group B cases remained on ADL III or less. These findings implied that good prognosis in younger DAI cases as compared with the controls could be attributed to a lower incidence of brain shearing injuries due to acceleration, a superior recovery mechanism owing to collateral sprouting, and inclusion of such cases as those that may present a transient neuro-dysfunction due to cerebral edema and others despite the presence of few neural injuries.
