Microsurgical Revascularization for Thrombosed Middle Cerebral Artery Dissecting Aneurysms: Classification Scheme and Surgical Strategies

Objective: Thrombosed dissecting aneurysms represent highly challenging lesions in neurosurgery. Among these, thrombosed middle cerebral artery (MCA) dissecting aneurysms are clinically rare and exceptionally difficult to manage. Their defining feature is the extensive organized thrombus within the aneurysmal lumen and the subsequent progressive mass effect, which presents a significant dilemma for traditional endovascular treatment and microsurgical clipping to balance safety and efficacy. To address this, the authors summarize the clinical experience of a single senior surgeon at our center to establish a classification scheme for thrombosed MCA dissecting aneurysms to provide a clinical reference. Methods: Over a 10-year period, 12 patients with thrombosed MCA dissecting aneurysms underwent microsurgical revascularization. These lesions were classified into 4 types: stenotic type (n=2, 16.7%), dolichoectatic type (n=5, 41.7%), saccular mass type (n=3, 25.0%), and composite type (n=2, 16.7%). Results: Among the 12 patients, 5 underwent aneurysm excision combined with interposition bypass grafting [4 using a radial artery graft (RAG) and 1 using a superficial temporal artery (STA)]. Six patients underwent extracranial-to-intracranial bypass (2 through EC-radial artery graft-M1 bypass and 4 through STA-MCA bypass, including one double-barrel STA bypass). One patient underwent aneurysm excision combined with wrapping reconstruction. Postoperative angiography demonstrated complete aneurysm obliteration in 10 cases (83.3%) and shrinkage in 2 cases (16.7%); all bypass grafts remained patent. The mean postoperative follow-up period was 48.4 months (range: 6–87 mo). Eleven patients experienced no complications or showed an improved modified Rankin Scale score, while one patient developed hemiplegia due to perforator vessel injury. No postoperative mortalities occurred. Conclusions: Although thrombosed MCA dissecting aneurysms are rare, microsurgical revascularization represents a safe and effective treatment strategy offering favorable long-term outcomes. The classification scheme and surgical strategies proposed in this study provide a valuable clinical reference for these complex lesions.