《急诊每日一题》蛛网膜下腔出血与脑核磁共振2021年2月

Question 问题：

Studies have demonstrated the utility of MRI for detection of subarachnoid hemorrhage after an initial false-negative NCCT.  Yet，why do guidelines still recommend LP for cases of suspicious SAH, even after negative MRI? 

研究显示在首次假阴性平扫CT后可以做MRI诊断蛛网膜下腔出血（SAH）。但是，为什么即使MRI阴性，指南还是建议对疑似SAH病例做腰穿？

 Answer 答案：

Because MRI is ineffective at detecting perimesencephalic SAH, a spontaneous bleed of presumed venous etiology at the level of the brainstem, which accounts for 8-10% of all SAH. Overall, PMSAH has an excellent prognosis。

因为MRI对脑干水平可能的静脉自发性出血，即占全部SAH5-10%的中脑周围SAH（PMSAH）阳性率低。总体上，PMSAH预后是相当好的。

参考文献：

Emerg Radiol, epub, 2/13/21