Delayed Splenial Artery Pseudoaneurysm After Angiographically Negative Intracerebral Hemorrhage: A Case Report.

Intracranial pseudoaneurysms are rare vascular lesions and are associated with a high risk of rupture. Most reported cases are related to trauma or iatrogenic injury, whereas their association with non-traumatic intracerebral hemorrhage remains unclear. Here, we present a case of a 77-year-old female with essential thrombocythemia who presented with acute memory disturbance and headache. Computed tomography revealed an intracerebral hemorrhage in the left cingulate isthmus extending to the parietal lobe. Initial magnetic resonance imaging and digital subtraction angiography failed to identify the source of bleeding. Approximately one month later, during endovascular treatment for an incidental unruptured basilar tip aneurysm, repeat angiography revealed a pseudoaneurysm corresponding to the prior hemorrhagic site. Selective angiography demonstrated that the pseudoaneurysm originated from the splenial artery (posterior pericallosal artery). The pseudoaneurysm was successfully treated with n-butyl cyanoacrylate embolization with parent artery occlusion, followed by stent-assisted coil embolization of the basilar tip aneurysm. The patient was discharged without neurological deficits, and no recurrence was observed on six-month follow-up magnetic resonance imaging. This case highlights the potential for delayed formation of a pseudoaneurysm after non-traumatic intracerebral hemorrhage, particularly in atypical locations and possibly in patients with underlying platelet disorders. Repeat angiographic evaluation should be considered when the initial study fails to identify the bleeding source.