Frameless stereotactic navigation for intraoperative localization of infectious intracranial aneurysm

Co-registration of Imaging Modalities (MRI, CT and PET) to Perform Frameless Stereotaxic Robotic Injections in the Common Marmoset

The common marmoset has emerged as a popular model in neuroscience research, in part due to its reproductive efficiency, genetic and neuroanatomical similarities to humans and the successful generation of transgenic lines. Stereotaxic procedures in marmosets are guided by 2D stereotaxic atlases, which are constructed with a limited number of animals and fail to account for inter-individual variability in skull and brain size. Here, we developed a frameless imaging-guided stereotaxic system that improves upon traditional approaches by using subject-specific registration of computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) data to identify a surgical target, namely the putamen, in two marmosets. The skull surface was laser-scanned to create a point cloud that was registered to the 3D reconstruction of the skull from CT. Reconstruction of the skull, as well as of the brain from MR images, was crucial for surgical planning. Localisation and injection into the putamen was done using a 6-axis robotic arm controlled by a surgical navigation software (Brainsight™). Integration of subject-specific registration and frameless stereotaxic navigation allowed target localisation specific to each animal. Injection of alpha-synuclein fibrils into the putamen triggered progressive neurodegeneration of the nigro-striatal system, a key feature of Parkinson's disease. Four months post-surgery, a PET scan found evidence of nigro-striatal denervation, supporting accurate targeting of the putamen during co-registration and subsequent surgery. Our results suggest that this approach, coupled with frameless stereotaxic neuronavigation, is accurate in localising surgical targets and can be used to assess endpoints for longitudinal studies.

Technical note: the use of frameless stereotactic guidance in the treatment of peripheral intracranial aneurysms

Frameless stereotactic guidance (FSG) has previously been reported to have advantages over intraoperative computed tomography (CT) and frame-based imaging guidance methods in the targeting of intracranial lesions. We report our experience using FSG to minimize brain dissection during microsurgical repair of peripheral aneurysms. We used FSG as a surgical adjunct in the management of 91 peripheral aneurysms. It was used to localise and avoid larger bridging veins, enabling us to minimise unnecessary brain dissection by coming directly down on the aneurysm dome in unruptured lesions or targeting the parent artery just proximal to the aneurysm in ruptured cases. We treated 72 aneurysms located on the distal ACA (79%), 7 on the PCA (7.7%), 6 on the MCA distal to the MCA bifurcation (6.6%), and 6 on the SCA (6.6%). There were no complications related to FSG use. However, we noted a tendency to create an overly limited corridor to the aneurysm, which did not allow sufficient proximal or distal control of the parent artery. In these cases, we had to widen our exposure by further opening the interhemispheric fissure to obtain more proximal control once the aneurysm was reached. Subsequently, we learned to avoid this problem by creating a slightly wider corridor during the initial exposure. Using FSG as a surgical adjunct for peripheral intracranial aneurysms allowed us to safely limit craniotomy size and brain dissection while more confidently exposing these unusually situated lesions, facilitating aneurysm clipping in our series.

Systematic Review of Endovascular, Surgical, and Conservative Options for Infectious Intracranial Aneurysms and Cardiac Considerations

INTRODUCTION

With rising rates of intravenous drug use, Infectious Intracranial aneurysms (IIAs) are a relevant topic for investigation. We performed a systematic review to better understand current practice patterns and limits of current published literature.

METHOD

131 publications with a total of 499 patients (665 aneurysms) were included. Of the 499 patients, 83 were single case reports, and 20.5% of the total had multiple aneurysms. 35.8% of all aneurysms were ruptured. Of those reporting treatment, options included conservative antibiotic therapy (30.0%), open surgical intervention (31.1%), and endovascular occlusion (31.8%). Chronologically, publication of IIAs has increased. Usage of endovascular therapies has grown, while conservative and surgical management have declined in the literature. Overall, 56.2% of aneurysms for which conservative therapy was initiated eventually either underwent intervention or death of patient occurred.

RESULTS

The issue of cardiac valve surgery in relationship to aneurysm therapy was discussed in 20.8% (80 patients) of all 384 infectious endocarditis patients; of which 15.0% (12) underwent valve surgery before aneurysm treatment and 85.0 patients (68)% underwent valve surgery after aneurysm treatment. For 51 of the patients where valve surgery followed aneurysm management, the corresponding aneurysm treatment modality could be determined; 58.8% (30) of whom were managed endovascularly. 32.7% (26) of all cases reporting cardiac surgery details underwent cardiac surgery during their admission with the IIA.

CONCLUSIONS

Overall, increasing trend of endovascular management of IIAs is evident, and a strong temporal preference exhibited by providers to perform cardiac surgery subsequently to IIA management.

Selective Targeted Cerebral Revascularization via Microscope Integrated Indocyanine Green Videoangiography Technology

Protective or flow replacement bypass surgery has an important role in the management of complex middle cerebral artery (MCA) aneurysms. Protective bypass is useful when prolonged temporary arterial occlusion is needed for clip reconstruction. Flow replacement bypass is instead important when aneurysmal trapping is the treatment of choice in order to supply permanent collateral blood flow to the brain distal to the "trapped" vessel. In both cases, the identification of the correct recipient artery is an essential surgical step. When a superficial (cortical) artery is chosen as recipient, it indeed has to represent a distal branch of the involved (temporarily or permanently occluded) vessel.Here we describe a technique for selective-targeted revascularization based on the use of indocyanine green video angiography (ICG-VA), a microscope-integrated intraoperative tool nowadays known to provide real-time assessment of the cerebral circulation with distinct visualization of arterial, capillary and venous angiographic phases. The technique is founded on the analysis of differences in the timing of filling of M4 vessels seen on serial ICG-VAs. It enables reliable identification of the cortical recipient and eliminates the risk of erroneous revascularization of non-involved territories. The surgical decision-making of two patients treated for complex MCA aneurysms with selective-targeted bypass is presented.

Selective-targeted extra-intracranial bypass surgery in complex middle cerebral artery aneurysms: correctly identifying the recipient artery using indocyanine green videoangiography

BACKGROUND

Treatment of complex middle cerebral artery (MCA) aneurysms often requires vessel sacrifice or prolonged temporary occlusion with extra- to intracranial (EC-IC) bypass to preserve perfusion. A crucial surgical step is the identification of the bypass recipient artery matching the distal territory of the involved vessel.

OBJECTIVE

To report about the feasibility and efficiency of an indocyanine green videoangiography (ICG-VA) assisted technique for identification of cortical recipient vessels to perform selective-targeted EC-IC bypass.

METHODS

The proposed technique is based on the analysis of differences in the timing of filling of M4 vessels seen on serial ICG-VAs. A delayed fluorescence can be visualized either primarily on a baseline ICG-VA or secondarily on an ICG-VA performed during temporary occlusion of the involved MCA branch. M4 branches presenting delayed fluorescence represent suitable bypass recipient arteries. We report 7 consecutive patients treated for complex MCA aneurysms with selective-targeted EC-IC bypass.

RESULTS

Application of the proposed technique permitted the correct identification of recipient arteries (cortical branches of the involved MCA segment) in all patients. The cortex distal to the occlusion filled concomitantly on ICG-VA at the end of surgery. All patients underwent successful treatment of the aneurysm, including a cortical bypass. There were no ischemic complications, and a favorable clinical outcome was achieved in all patients (modified Rankin Scale at follow-up ≤ modified Rankin Scale preoperative).

CONCLUSION

The proposed ICG-VA-based technique enables reliable and accurate identification of the cortical recipient artery and eliminates the risk of erroneous revascularization of noninvolved territories.

Superselective indocyanine green angiography for selective revascularization in the management of peripheral cerebral aneurysms

This report describes the management of a fusiform peripheral middle cerebral artery aneurysm by endovascular parent artery occlusion under bypass protection. Localization of the recipient cortical artery was accomplished after craniotomy by superselective injection of diluted ICG dye via a microcatheter positioned proximal to the aneurysm. This report demonstrates that superselective ICG angiography can be a beneficial alternative technique to identify the best anastomosis site intraoperatively.