Published online: 2020-12-05 Case Report The Use of Real-Time 3D Intraoperative Ultrasound “Angiography” in Localization and Occlusion Control of a Ruptured Mycotic Aneurysm: A Case Report Grigorios Gkasdaris1,3 Nikolaos Barettas1 1 Department of Neurosurgery, School of Health Sciences, Democritus University of Thrace, Alexandroupolis, Greece 2 Department of Neurosurgery, Universitätsmedizin Göttingen, Goettingen, Germany 3 Department of Clinical Neurosciences, Service of Neurosurgery, Lausanne University Hospital, Lausanne, Switzerland Efthymia Theodoropoulou1 Address for correspondence Ntenis Nerntengian, Department of Neurosurgery, Universitätsmedizin Göttingen, Robert-Koch-Straße 40, 37075 Göttingen, Germany (e-mail: nerdenyan@gmail.com). J Neurol Surg A Abstract Keywords ► mycotic aneurysm ► distal middle cerebral artery ► intraoperative 3D ultrasound ► clipping ► infectious aneurysm received May 31, 2020 accepted after revision August 13, 2020 Background Infectious (mycotic) aneurysms are rare with high mortality and are most commonly found at the distal branches of the middle cerebral artery (MCA). Because aneurysms of the distal MCA are located deep in the Sylvian fissure and are small in size, intraoperative identification and safe clip occlusion of these aneurysms are challenging. Thus, the use of intraoperative imaging and navigation can be beneficial. We describe the use of intraoperative real-time 3D ultrasound “angiography” (3D-iUS) in localizing and occlusion control of a ruptured MCA M3 segment mycotic aneurysm. To our knowledge, its application in the surgery of a ruptured mycotic distal MCA aneurysm is not yet reported. Clinical Presentation A 54-year-old woman with a history of septic thrombophlebitis treated with long-term antibiotic therapy presented with sudden onset of headaches, dysphasia, and seizures. Computed tomography (CT) revealed subarachnoid hemorrhage in the distal portion of the left Sylvian fissure. Digital subtraction angiography (DSA) showed an aneurysm at the peripheral branch of the M3 segment of the MCA with characteristics of an infectious aneurysm. A microsurgical treatment was decided. 3D-iUS scan showed an aneurysm within the Sylvian fissure at a depth of 5 cm. The aneurysm was clipped and a repeated 3D-iUS scan showed total occlusion of the aneurysm and patency of the parent artery. The intraoperative findings were confirmed with a postoperative DSA. Conclusion Our case report shows that real-time 3D-iUS, despite its limitations, is an important tool to locate and ascertain the successful clip occlusion of an aneurysm, especially when intraoperative angiography (IA) and indocyanine green (ICG) videoangiography are not available due to low-income settings. © Georg Thieme Verlag KG Stuttgart · New York DOI https://doi.org/ 10.1055/s-0040-1720988. ISSN 2193-6315. Downloaded by: Imperial College London. Copyrighted material. Ntenis Nerntengian1,2 Theodosios Birbilis1 Nerntengian et al. Introduction Distal middle cerebral artery (MCA) aneurysms account for approximately 2 to 6% of MCA aneurysms.1 Because these aneurysms are small in size, located deep in the Sylvian fissure, and possibly surrounded closely by the adjacent brain parenchyma,2,3 intraoperative localization of these aneurysms is challenging and neuronavigation may prove beneficial. To our knowledge, although the use of threedimensional intraoperative ultrasound (3D-iUS) in the operation of intracranial aneurysms is common, its application in the surgery of a ruptured distal MCA infectious aneurysm is not yet reported. Payer et al reported the use of color-coded duplex sonography to intraoperatively locate a distal MCA aneurysm, but it is not mentioned whether or not the modality was employed to control the occlusion of the aneurysm and whether the aneurysm was infectious or not.4 In our case report, we present a method for localizing a ruptured infectious aneurysm of the peripheral branch of the M3 segment using real-time 3D-iUS. We also describe its employment after clipping of the aneurysm, to determine whether the clip occlusion was fully or partially achieved and to control patency of the parent vessel. Case Presentation A 54-year-old woman with a history of prolonged hospitalization in our intensive care unit with septic thrombophlebitis and consequent long-term antibiotic therapy presented with acute intense headaches, dysphasia, and epileptic seizures. A computed tomography (CT) scan of the brain showed a Fisher grade 2 subarachnoid hemorrhage (►Fig. 1a) in the distal portion of the left Sylvian fissure. Digital subtraction angiography (DSA) revealed an aneurysm at the peripheral branch of the M3 segment of the MCA, in proximity to Wernicke’s area (►Fig. 1b, c) with characteristics of an infectious (mycotic) aneurysm. Because of aneurysm rupture, despite long-term antibiotic therapy, aneurysm morphology, and proximity to eloquent area, we chose microsurgical treatment. A left-sided pterional craniotomy was performed. Given the location of the aneurysm, realtime 3D-iUS “angiography” (3D ultrasound-based neuronavigation system, SonoWand, Mison, Trondheim, Norway) was utilized as a precise, real-time, and minimally invasive method for its localization. Before opening the dura, a scan with a 5-MHz ultrasound probe was performed with 3D Power Doppler. A sterile ultrasound gel pad was placed between the probe and the dura to avoid artifacts caused by air (►Fig. 1d). The scan showed the aneurysm within the Sylvian fissure to be at a depth of 5 cm (►Fig. 1e). The distal Sylvian fissure over the aneurysm was opened. As infectious aneurysms are fragile,3,5 the MCA was clipped for proximal control and to avoid the risk of an intraoperative rupture during surgical manipulations. The aneurysm was then clipped and the temporary clip was removed. After the placement of the final clip, a new ultrasound scan revealed total occlusion of the aneurysm and patency of the parent artery (►Fig. 1f ). The total duration of the scan was Journal of Neurological Surgery—Part A 5 minutes. The intraoperative findings were confirmed with a postoperative DSA (►Fig. 1g, h). The patient showed no postoperative complications and was discharged after 4 weeks with total remission of her symptoms. Discussion Intracranial infectious aneurysms are rare with high mortality. In most of the case, they are located at the distal MCA.6,7 Antibiotic therapy is the cornerstone in the treatment of unruptured infectious aneurysms. In case of a rupture, surgical or endovascular treatment can be applied according to the clinical and radiological findings.5,8–11 Because they are located deep in the Sylvian fissure, small sized, and because of the complex anatomy of the distal MCA, localizing and complete occlusion of these aneurysms, while preserving the patency of the parent artery, are challenging.2,3,12 This makes the role of navigation important in the treatment of these pathologies. Brain shift is known to reduce the accuracy in neuronavigation.13,14 Intracranial lesions can be identified with high sensitivity using the intraoperative ultrasound15 and real-time images can be obtained to overcome brain shift.16 Real-time 3D-iUS expands the surgeons’ view of the vascular anatomy outside of the margins of the visible operative field.17,18 Moreover with the Doppler mode of ultrasound, blood flow in the parent artery can be measured before and after the application of the clip. Although intraoperative angiography (IA) is still the best tool to confirm aneurysm obliteration and patency of the parent artery,19 it is associated with radiation exposure, requires hybrid operating room, and may not be available in all neurosurgical institutes due to its high cost. In comparison to IA, the use of real-time 3D-iUS interferes less with the flow of the operation and thus reduces operation time. Indocyanine green (ICG) videoangiography compatible microscope may also not be attainable in resource-limited settings. The real time 3D-iUS also proved to be useful in intraoperatively identifying and controlling the clip occlusion of pericallosal aneurysms located deep in the interhemispheric fissure. Interpreting a possible stenosis of the parent artery after clipping depends on the surgeon’s experience and skill to take scans in the same region and at the same angle as before clipping so that the results are comparable. Drawbacks such as lower image quality in comparison to 3D-DSA and problems in visualization of possible small aneurysm neck remnants due to clip artifacts17 are amenable to technological developments. Turner et al showed that visualization of intracranial aneurysms using the transcranial power Doppler can be augmented with contrast agents,20 and Podlesek et al suggested that interpretation of the 3D-iUS images can be facilitated by coregistering the ultrasound image data with preoperative rotational DSA image data.17 Ultrasound contrast microbubbles can also be used to enhance the visualization of the vessels. Larger studies comparing the findings of real-time 3D-iUS after clipping of the aneurysm and postoperative DSA should be done to further evaluate the accuracy of this modality. In our study, we used the Downloaded by: Imperial College London. Copyrighted material. Use of 3D-iUS in Ruptured Mycotic Aneurysm Nerntengian et al. Downloaded by: Imperial College London. Copyrighted material. Use of 3D-iUS in Ruptured Mycotic Aneurysm Fig. 1 (a) Computed tomography (CT) scan on admission showing subarachnoid hemorrhage in the distal portion of the Sylvian fissure. (b,c) Preoperative digital subtraction angiography (DSA) showing the aneurysm at the peripheral branch of the M3 segment (yellow arrow). (d) Intraoperative image showing the sterile ultrasound gel pad (black asterisk). (e) Ultrasound image showing the aneurysm (yellow arrow). (f) Ultrasound image after clip application showing total occlusion of the aneurysm with patent parent artery (yellow arrow showing the clip). (g,h) Postoperative DSA without evidence of residual aneurysm (yellow arrow showing the clip). term ultrasound “angiography.” This is because this modality gives a couple of minutes to visualize the vascular anatomy in real time and not because we believe it can replace IA. Conclusion We believe that real-time 3D-iUS (power Doppler), despite its limitations, constitutes a reliable, fast, and inexpensive Journal of Neurological Surgery—Part A Nerntengian et al. solution to intraoperatively locate and ascertain the total occlusion of an aneurysm serving as an invaluable tool in the armamentarium of the vascular neurosurgeon which can even substitute IA and ICG videoangiography when the latter modalities are not available in resource-limited settings. Conflict of Interest None declared. References 1 Joo SP, Kim TS, Choi JW, et al. Characteristics and management of ruptured distal middle cerebral artery aneurysms. Acta Neurochir (Wien) 2007;149(07):661–667 2 Samson DS, Batjer HH, White J, Trammell JT, Eddleman CS. Intracranial Aneurysm Surgery: Basic Principles and Techniques. 1st ed. New York, NY: Thieme; 2012:65–67 3 Tandon PN, Ramamurthi R. Ramamurthi and Tandon’s Textbook of Neurosurgery. 3rd ed. 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