青少年接受脑肿瘤的颅脑放疗治疗时，患有脑血管并发症的风险增加。放射线诱发的动脉branchiogenic moyamoya综合症（MMS）是其众所周知的并发症。我们报道了一个8岁男孩的病例，他有髓母细胞瘤的病史，接受手术切除并进行术后辅助肿瘤治疗。六年后，他出现小脑/室管膜下出血。他接受了急诊外侧脑室引流（EVD）插入术，随后进行了后颅骨下颅后开颅手术。在开放硬脑膜时，我们注意到右侧小脑半球表面有一条异常血管，并未干扰。术中未发现明显异常。脑血管造影证实，在此EC-IC搭桥中，右侧枕动脉（OA）与后下脑动脉（PICA）外颅内侧部位存在搭桥，该EC-IC搭桥供应了PICA远端领域。一条假定的血流动脉瘤从PICA远端的搭桥处起源，被鉴定为出血的原因。我们强调了该患者群中头颅内出血的罕见原因。接受放射治疗的儿童可能具有极其敏感的脑血管，需要密切关注并评估自发出血后的血管病理性并发症的情况。© 2023作者，独家授权给施普林格-自然出版集团旗下的施普林格-德国公司。

Paediatric patients receiving cranial irradiation therapy for brain tumours are at increased risk of cerebrovascular complications. Radiation-induced moyamoya syndrome (MMS) is a well-recognised complication of this. We present a case of an 8-year-old boy with a history of medulloblastoma, who underwent surgical excision followed by post-operative adjuvant oncological treatment. Six years later, he developed cerebellar/intraventricular haemorrhage. He underwent an emergency external ventricular drain (EVD) insertion followed by posterior fossa suboccipital craniotomy. On dural opening, an abnormal vessel was visualised on the surface of the right cerebellar hemisphere, which was not disturbed. No obvious abnormalities were identified intra-operatively. Cerebral catheter angiography confirmed the presence of a right-sided occipital artery (OA) to posterior inferior cerebellar artery (PICA) extracranial to intracranial (EC-IC) bypass with a zone of the distal PICA territory supplied by this EC-IC bypass. A presumed flow aneurysm originated from the bypass in the distal PICA, identified as cause for the haemorrhage. We highlight a rare cause for intracranial haemorrhage in this cohort of patients. Children who have undergone radiotherapy may have exquisitely sensitive cerebral vasculature and need careful vigilance and evaluation for vasculopathic complications following spontaneous haemorrhage.© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.