Capabilities of Dynamic Magnetic Resonance Angiography in Patients With Cerebral Aneurysms in the Postoperative Period

Abstract

Introduction: The leading cause of hemorrhagic stroke is a ruptured cerebral aneurysm (CA), accounting for 70%-85% of nontraumatic subarachnoid hemorrhages. The primary goals of CA treatment are to prevent a rupture, thrombosis, or symptoms of mass effect. The main treatment options for intracranial aneurysms are open clipping, flow-diverter device implantation, resection and stenting of aneurysms. Treated aneurysms should be monitored to assess the stability of the occlusion because more than 20% of surgically treated aneurysms are known to recur. Magnetic resonance angiography (MRA) has recently become increasingly attractive for the follow-up of surgically treated CAs because it is noninvasive, does not require hospitalization, and reduces complications associated with the frequent use of cerebral angiography.Objective: To evaluate capabilities of dynamic MRA in postoperative monitoring of patients with CAs.Materials and methods: The study was conducted at the premises of the Scientific Research Institute – Ochapovsky Regional Clinical Hospital No. 1 (Krasnodar, Russian Federation). In a hospital setting, 38 patients with CAs were examined in the late postoperative period. All the patients underwent magnetic resonance imaging, 3-dimensional time-of-flight (3D-TOF) MRA, and dynamic MRA followed by cerebral angiography. Imaging findings (MRA, dynamic MRA, and cerebral angiography) were evaluated by radiologists, x-ray surgeons, and neurosurgeons. They assessed treated aneurysms according to the Raymond-Roy occlusion classification: complete obliteration (class 1), residual neck (class 2), and residual aneurysm (class 3). Untreated aneurysms in patients with multiple CAs and de novo aneurysms were also assessed, and we looked for other vascular malformations.Results: The study was conducted in the late postoperative period from 6 to 18 months. A total of 38 patients participated in the study; of them 27 were women (age, 32-77 years) and 11 were men (age, 32-65 years). Dynamic MRA detected neck remnants of 4 clipped aneurysms and 2 embolized ones, which was confirmed by cerebral angiography. According to the dynamic MRA results, in case of clipped aneurysms neck remnants were found in the anterior communicating artery (n = 2), internal carotid artery (n = 1), and anterior choroidal artery (n = 1). In case of embolized aneurysms, neck remnants were revealed in the internal carotid artery (n = 1) and basilar artery (n = 1). Dynamic MRA also detected 5 additional aneurysms: 2 internal carotid artery aneurysms, 1 basilar artery aneurysm, 1 anterior cerebral artery aneurysm, and 1 anterior communicating artery aneurysm. These findings coincided with those of cerebral angiography. Based on the results of our study, the sensitivity and specificity of dynamic MRA in detecting CA neck remnants and untreated aneurysms were 100%.Discussion: Dynamic MRA findings are fully consistent with those of cerebral angiography in terms of determining an aneurysm occlusion status during postoperative follow-up. As for evaluation of de novo intracranial aneurysms, dynamic MRA is also superior to noncontrast 3D-TOF MRA in assessment of aneurysm shape and neck detection. Therefore, dynamic MRA can clearly visualize the structure of cerebral vessels mainly due to the effect of blood flow and static tissue contrast, and the principle is mainly the effect of multiphase scanning and accumulation of contrast agent.Conclusions: Dynamic MRA has a number of advantages over cerebral angiography, such as noninvasiveness, high-resolution images of the cerebral arteries, absence of radiation exposure, use of iodinated contrast agent, and absence of artifacts from metal clips or embolic material.