2019 年 47 巻 6 号 p. 423-427
Background: Although neuroimaging technology has rapidly advanced over the recent decades, the initial evaluations for an idiopathic subarachnoid hemorrhage (SAH) cannot detect the bleeding source in 15%-20% of cases, and some assessments produce false-negative results. Thus, it is generally recommended that SAH with unknown etiology should be re-evaluated 2 weeks after symptom onset to identify the cryptogenic vascular lesion. Here, we present a case of a dissecting distal superior cerebellar artery (SCA) aneurysm that was detected 4 months after SAH onset.
Case presentation: A 42-year-old female presented with sudden-onset headache and was diagnosed with SAH on computed tomography (CT). Initial evaluation, including angiography, could not identify the bleeding source. Subsequently, several magnetic resonance imaging (MRI) evaluations also failed to detect the bleeding source. An MRI performed 4 months later showed aneurysmal dilatation of the left distal SCA, thought to be the bleeding source. This lesion was successfully treated using endovascular coil embolization.
Conclusion: In cases of SAH with unknown etiology, frequent re-evaluation for a vascular lesion is indicated to avoid delayed re-bleeding. As MRI can non-invasively detect a wide variety of lesions, it may be suitable for repeat evaluation of SAH with unknown etiology.
