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)和横向弛豫(T(2))是否预测了急性高山病(AMS)的症状,还是仅指示了AMS表型,而与症状无关。 14个正常受试者分为两组进行研究;在3,800 m的高度进行明确的AMS和无AMS(不包括中级AMS分数)。根据脑脊髓液信号归一化的T(2)加权信号的T(2)指数估算T(2)弛豫。在常氧状态下进行测量,并在持续缺氧2天(AMS组有症状和无AMS组无症状)和缺氧7天(两组无症状)后重复进行。 ADC降低直接预测AMS症状(P <0.05)。无症状受试者的表观弥散系数增加,或者随着适应环境的减轻症状逐渐减轻。这种模式在基底神经节,白质和灰质中相似。 call体表现不同。脾中不存在(或迅速逆转)受限制的扩散,并且在脾中持续存在。在有症状的受试者中,缺氧2天后T(2,index)下降,而在7天后T(2,index)进一步下降。在无症状受试者中,T(2,index)最初在2天后升高,但在7天后降低。 T(2,index)的变化不能预测AMS症状。这些发现表明,限制扩散是大脑能量状态减弱的指标,可直接预测高海拔地区人类的AMS症状。

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