Intracerebral hemorrhage due to a rete middle cerebral artery-related rupture of a distal lenticulostriate artery aneurysm: Two case reports

•Distal lenticulostriate artery aneurysms associated with a rete middle cerebral artery can be divided in two categories.•A “proximal type aneurysm” arises from proximal trunk of a middle cerebral artery before branching into twigs.•An “involved type aneurysm” arises from inside the twigs.•Conservative management is feasible as well as endovascular embolization. Intracerebral hemorrhage (ICH) after a rete middle cerebral artery (MCA)-related rupture of a distal lenticulostriate artery (LSA) aneurysm is extremely rare, only five cases have been reported in the previous literature. In this study, we report two cases of a rete MCA-related rupture wherein LSA aneurysms were treated with endovascular and medical therapy. A 69-year-old woman with a right rete MCA developed a right putaminal hematoma due to the rupture of a right dilated LSA aneurysm. As the parent LSA arose proximal to the abnormal arterial network, we first planned endovascular aneurysmal embolization. However, due to penetration of the parental artery with a microwire, we operated on the parental artery occlusion. The aneurysm disappeared after treatment without any ischemic lesion in the right cerebral hemisphere. The second case was a 72-year-old woman with a right putaminal hematoma. As the LSA was thin and arose from the anomaly itself, the patient was treated conservatively without surgical intervention. Angiography performed 14 days after onset demonstrated spontaneous disappearance of the aneurysm. There is no common consensus on treatment strategies for rete MCA-related distal LSA aneurysms. We propose that parental artery occlusion and conservative observation can be treatment options for this rare type of aneurysm.