Figure 1 CT at 24 hours

(A, B) Diffuse hyperattenuation in the subarachnoid space with relative sparing of the left lateral fissure.

Figure 2 CT at 48 hours

(A, B) Interval clearance of the hyperattenuation in the subarachnoid space.

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     A 50-year-old woman underwent therapeutic hypothermia after a witnessed cardiac arrest and cardiaccatheterization. A 24-hour head CT (figure 1) showed diffuse hyperattenuation in the subarachnoid space and was reported as subarachnoid hemorrhage. Repeat CT at 48 hours (figure 2) showed significant clearing of the “subarachnoid hemorrhage.”

DISCUSSION ：

      Cerebrocirculatory arrest and reperfusion causes injury that breaks down the blood–brain barrier.1 In patients undergoing contrast imaging, there may be active extravasation of contrast into the subarachnoid space. Hypothermia alters contrast viscosity, decreases glomerular filtration, and subsequently decreases elimination of the contrast.2 It is important to recognize such mimickers of subarachnoid hemorrhage in the era of hypothermia.

                                                  Neurology. 2014 Feb 4;82(5):e44-5

     女性，50岁，在心跳骤停和心导管术后进行低温治疗，24小时后行头颅CT检查提示蛛网膜下腔弥漫高信号，放射科诊断为蛛网膜下腔出血（图1）。48小时后复查头颅CT可见“蛛网膜下腔出血”明显吸收（图2）。

     脑循环中断后再灌注可以破坏血脑屏障，当病人进行增强造影时，造影剂可渗漏至蛛网膜下腔。低温可改变造影剂的粘度系数，降低肾小球滤过率，导致造影剂清除延迟。在低温治疗时需要与蛛网膜下腔出血相鉴别。

评论：

    在头颅CT上看到蛛网膜下腔有高信号并不一定就是蛛血，也可能是积脓、造影剂渗漏，后者正如此病例所显示的一样，几乎无法与蛛血鉴别。因此，有必要再次强调临床信息解读分析的重要性。

    当然，如果在甄别上还是比较纠结怎么办？此时应该祭起神内科检查的法宝-------腰椎穿刺，可一锤定音！由此可见，即使在现代，对蛛血诊断的金标准依然是腰穿，头颅CT有时还是不可靠哦！

补记：

    记得前几年在工作中碰到过一例类似病人，在放完心脏支架后24小时突发昏迷，急诊头颅CT脑沟裂内弥漫高密度影铸型，和SAH很相似，在询问得知有介入造影治疗史后，考虑为对比剂清除延迟，后来腰穿排除了SAH，几天后复查CT表现正常。