Diffusion magnetic resonance imaging (MRI) provides a sensitive indicator of cerebral hypoxia. We investigated if apparent diffusion coefficient (ADC) and transverse relaxation (T(2)) predict symptoms of acute mountain sickness (AMS), or merely indicate the AMS phenotype irrespective of symptoms. Fourteen normal subjects were studied in two groups; unambiguous AMS and no-AMS at 3,800 m altitude (intermediate AMS scores were excluded). T(2) relaxation was estimated from a T(2) index of T(2)-weighted signal normalized by cerebrospinal fluid signal. Measurements were made in normoxia and repeated after 2 days sustained hypoxia (AMS group symptomatic and no-AMS group asymptomatic) and after 7 days hypoxia (both groups asymptomatic). Decreased ADC directly predicted AMS symptoms (P<0.05). Apparent diffusion coefficient increased in asymptomatic subjects, or as symptoms abated with acclimatization. This pattern was similar in basal ganglia, white matter, and gray matter. Corpus callosum behaved differently; restricted diffusion was absent (or rapidly reversed) in the splenium, and was sustained in the genu. In symptomatic subjects, T(2,index) decreased after 2 days hypoxia and further decreased after 7 days. In asymptomatic subjects, T(2,index) initially increased after 2 days, but decreased after 7 days. T(2,index) changes were not predictive of AMS symptoms. These findings indicate that restricted diffusion, an indicator of diminished cerebral energy status, directly predicts symptoms of AMS in humans at altitude.

译文

扩散磁共振成像 (MRI) 提供了脑缺氧的敏感指标。我们调查了表观扩散系数 (ADC) 和横向松弛 (T(2)) 是否可以预测急性高山病 (AMS) 的症状,或者仅指示AMS表型而与症状无关。研究了两组中的14名正常受试者; 3,800  m高度的明确AMS和no-AMS (排除中间AMS得分)。T(2) 松弛是根据脑脊液信号归一化的T(2) 加权信号的T(2) 指数估算的。在常氧下进行测量,并在持续缺氧2天 (有症状的AMS组和无症状的no-AMS组) 和缺氧7天 (两组均无症状) 后重复进行。ADC降低直接预测AMS症状 (P<0.05)。在无症状的受试者中,表观扩散系数增加,或者随着症状的适应而减轻。这种模式在基底神经节,白质和灰质中相似。Call体的行为不同; 脾脏中不存在 (或迅速逆转) 受限的扩散,并在基因组中持续存在。在有症状的受试者中,缺氧2 d后T(2,指数) 降低,7 d后进一步降低。在无症状的受试者中,T(2,指数) 在2天后最初增加,但在7天后降低。T(2,指数) 变化不能预测AMS症状。这些发现表明,受限的扩散是大脑能量状态降低的指标,直接预测了人类在海拔地区的AMS症状。

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