Hemodynamic differences determining rupture and non-rupture in middle cerebral aneurysms after growth.

BACKGROUND AND PURPOSE: Intracranial aneurysm growth is a significant risk factor for rupture; however, a few aneurysms remain unruptured for long periods, even after growth. Here, we identified hemodynamic features associated with aneurysmal rupture after growth. MATERIALS AND METHODS: We analyzed nine middle cerebral artery aneurysms that grew during the follow-up period using computational fluid dynamics analysis. Growth patterns of the middle cerebral artery aneurysms were divided into homothetic growth (Type 1), de novo bleb formation (Type 2), and bleb enlargement (Type 3). Hemodynamic parameters of the four ruptured aneurysms after growth were compared with those of the five unruptured aneurysms. RESULTS: Among nine aneurysms (78%), seven were Type 1, one was Type 2, and one was Type 3. Three (43%) Type 1 aneurysms ruptured after growth. Maximum oscillatory shear index after aneurysmal growth was significantly higher in ruptured Type 1 cases than in unruptured Type 1 cases (ruptured vs. unruptured: 0.455 ± 0.007 vs. 0.319 ± 0.042, p = 0.003). In Type 1 cases, a newly emerged high-oscillatory shear index area was frequently associated with rupture, indicating a rupture point. Aneurysm growth was observed in the direction of the high-pressure difference area before enlargement. In Types 2 and 3 aneurysms, the maximum oscillatory shear index decreased slightly, however, the pressure difference values remain unchanged. In Type 3 aneruysm, the maximum OSI and PD values remained unchanged. CONCLUSIONS: This study suggests that hemodynamic variations and growth pattern changes are crucial in rupture risk determination using computational fluid dynamics analysis. High-pressure difference areas may predict aneurysm enlargement direction. Additionally, high maximum oscillatory shear index values after enlargement in cases with homothetic growth patterns were potential rupture risk factors.

[Microvascular Decompression to Treat Abducens Nerve Paralysis Caused by Compression of the Anterior Inferior Cerebellar Artery:A Case Report].

Microvascular decompression(MVD)is an effective treatment for hemifacial spasm and trigeminal neuralgia. However, there are few reports regarding its use with abducens nerve palsy. Here, we report the case of a 77-year-old male who presented with diplopia and was admitted to our facility for right abducens nerve palsy. MRI constructive interference in steady-state(CISS)showed that the right anterior inferior cerebellar artery(AICA)was curved in a posterior-superior direction at the beginning of the region of origin, causing compression of the root exit zone of the right abducens nerve. In addition, MRI showed an unruptured fusiform aneurysm(5.3mm×7.1mm)of the vertebral artery(VA)involving the posterior inferior cerebellar artery(PICA). However it was not related to abducens nerve paralysis. The aneurysm was successfully treated with an occipital artery-posterior inferior cerebellar artery(OA-PICA)bypass and clipping of the proximal VA and PICA origin. The position of the offending artery was moved using a Teflon® felt fibrin glue and the retrosigmoid transcondylar fossa approach. The patient recovered from abducens nerve paralysis with no new neurological deficit. We emphasize the importance of choosing an appropriate approach as this increases the possibility of treating abducens nerve paralysis in a timely manner.