Clinical Characteristics and Surgical Management of Distal Middle Cerebral Artery Aneurysms

Abstract

This study aimed to evaluate the clinical characteristics and surgical management of distal middle cerebral artery aneurysms (dMCAANs). Of the 2,113 aneurysms treated by direct microsurgery since 2003 (775 ruptured, 1,338 unruptured), 53 (2.5%) were dMCAANs, involving 48 patients (male/female ratio 15:33, mean age 63.1 years). The primary target aneurysms were 27 (26 patients; 5 ruptured) with a mean size of 8.3 mm (range: 3.3-40.0 mm), located at M2:11, M2-3:12, M3:3, and M4:1, with 14 aneurysms showing growth. Five aneurysms measured larger than 12.5 mm, two of which were thrombosed (one completely and one partially). In addition, one 9 mm thrombosed aneurysm and one calcified aneurysm were observed. Secondary aneurysms were treated concomitantly with other aneurysms. This study included 26 lesions in 25 patients with a mean size of 2.9 mm (range: 2-6 mm), located at M2 (n = 19) and M2-3 (n = 7). Of these, 32 patients (66.7%) had multiple aneurysms, with 36 (67.9%) occurring as part of a multiple aneurysm complex. The treatment modalities included clipping (n = 46), trapping with bypass (n = 4), wrapping (n = 2), and excision (n = 1). A complete understanding of the anatomical relationship of the operculum to these structures and a distal-to-proximal approach along the M2 segment from the easily defined M2 origin are essential for the exposure and identification of the parent vessel and aneurysm within the distal Sylvian fissure. Intraoperative indocyanine green fluorescence angiography and navigation were beneficial in identifying the recipient vessel during revascularization and accurately localizing the aneurysm. Of the five ruptured cases, four were associated with intracerebral hematoma and had poor outcomes, while the others had favorable outcomes. dMCAANs exhibit a wide spectrum, ranging from manageable cases with simple clipping to those requiring complex revascularization. Therefore, a flexible surgical strategy, based on imaging and intraoperative findings, is essential.