A Case of Partially Thrombosed Dissecting Giant Aneurysm in the Distal Middle Cerebral Artery Treated by Endovascular Parent Artery Occlusion

Partially thrombosed and dissecting giant peripheral aneurysms present significant challenges for treatment with both direct surgical and endovascular approaches. We report a case of partially thrombosed, dissecting giant aneurysm in the peripheral segment of the middle cerebral artery treated with straightforward endovascular parent artery occlusion without saccular packing. A 30-year-old male presented with sudden loss of consciousness and subarachnoid hemorrhage and was transferred to our hospital. On admission, his level of consciousness was assessed as Japan Coma Scale 100 and Glasgow Coma Scale 8 (E1V2M5), with severe paralysis of the right upper and lower limbs. Computed tomography and magnetic resonance imaging demonstrated a partially thrombosed middle cerebral artery aneurysm with a maximum diameter of 31 mm at the M2 non-branching segment of the left middle cerebral artery mid-trunk. Cerebral angiography indicated potential collateral circulation, no retrograde opacification of the aneurysm, and absence of perforating branches near the lesion, so we selected endovascular parent artery occlusion that targeted only the proximal portion of the aneurysm. Postoperative care focused on managing intracranial pressure and overall systemic management. The patient recovered without significant infarction and was discharged home with a modified Rankin Scale score of 1 4 months after the onset. In general, peripheral aneurysms are less likely to cause perforator infarcts, and larger aneurysms are more tolerant of parent artery occlusion. Therefore, simple endovascular parent artery occlusion targeting only the proximal portion of the aneurysm offers both anatomical and pathophysiological advantages and provides a viable option when direct surgery is challenging.