Flow-related intracranial aneurysms associated with unfused arterial twigs relevant to different vascular anomalies: embryologic and hemodynamic considerations

Abstract

These unique vascular anomalies, T-MCA and T-NACA, which are caused by heterogeneous maldevelopment of the primitive cerebral vessels, are not benign because of their frequent association with flow-related aneurysms, which are vulnerable to rupture. Microsurgical or endovascular treatments for this type of flow-related aneurysm associated with twigs are mandatory to prevent fatal rebleeding, and more attention has to be given when physicians encounter steno-occlusive MCA lesions in patients with subarachnoid hemorrhage to detect any vulnerable aneurysms associated with twig-like vessels.

Rete middle cerebral artery anomalies: a unifying name, case series, and literature review

“…Shin et al argued that rete MCA anomalies were not an acquired disease because they were identified at a relatively young age (average age 41 years), and patients had neither obvious atherosclerotic degeneration nor leptomeningeal collaterals on cerebral angiography. 26 In a pooled analysis including our cases, patients were not relatively young (average age 51.2 years). Furthermore, the whitish vessel of the rete MCA anomalies found in our operative cases was different from the usual atherosclerotic stenoocclusive vessel.…”

“…Many of these papers were published in Asia, including South Korea and Japan. 2,5,[8][9][10]12,14,16,18,19,21,[24][25][26][27][28][29][30] Therefore, for the clarity of these anomalies, we have coined the term "rete MCA anomaly" to integrate these various names. Rete means a network of blood vessels.…”

“…The pathogenesis of rete MCA is not well known yet. Many authors described rete MCA as a congenital anomaly resulting from a fusion interference of the main trunk of the MCA in the embryonic development stage 1,3,15,22,25,26 ( Fig. 4).…”

Unfused or twig-like middle cerebral artery

“…At last Shin et al [18] reported four cases with flow related six aneurysms in the twig-like segments. The author named one of these cases as twig-like MCA and the other three of them as twig-like networks of an anomalous collateral artery.…”

Anomalies of the Middle Cerebral Artery

“…8) In 2012, Seo et al reported the largest series with 15 cases and named the finding as aplastic or twig-like MCA. 10) Recently, Shin et al reported four cases, 11) and Akkan et al reported six cases. 12) Common angiographical features of these cases were as follows; 1) a steno-occlusive lesion can be seen on the unilateral MCA, 2) plexiform arterial network exists instead of the main MCA trunk, 3) perforators arise from the plexiform arterial network, and 4) cortical branches beyond the occluded MCA trunk have anterograde flow with normal configuration.…”