An a3-Anterior Inferior Cerebellar Artery to p3-Posterior Inferior Cerebellar Artery Bypass With Thrombectomy and Trapping of an Anterior Inferior Cerebellar Artery Aneurysm: 3-Dimensional Operative Video

In situ bypasses to the anterior inferior cerebellar artery (AICA) are unusual because, with only one artery in the cerebellopontine angle (CPA), no natural intracranial donors parallel its course. In rare cases, the posterior inferior cerebellar artery (PICA) may have the tortuosity or redundancy to be mobilized to the AICA to serve as a donor. This video demonstrates this p3 PICA-to-a3 AICA in situ side-to-side bypass. A 75-yr-old woman presented with ataxia and hemiparesis from a large thrombotic right AICA aneurysm compressing the brainstem. Strategy consisted of bypass, trapping, and brainstem decompression. Written informed consent for surgery was obtained from the patient. A hockey-stick incision was made to harvest the occipital artery as a backup donor, but its diminutive caliber precluded its use. The bypass was performed through an extended retrosigmoid craniotomy. The aneurysm was trapped completely and thrombectomized to relieve the pontine mass effect. Indocyanine green videoangiography confirmed patency of the bypass, retrograde filling of the AICA to supply pontine perforators, and no residual aneurysmal filling. This unusual in situ bypass is possible when redundancy of the AICA and PICA allow their approximation in the CPA. The anastomosis is performed lateral to the lower cranial nerves in a relatively open and superficial plane. The extended retrosigmoid approach provides adequate exposure for both the bypass and aneurysm trapping. In situ AICA-PICA bypass enables anterograde and retrograde AICA revascularization with side-to-side anastomosis. The occipital artery-to-AICA bypass and the V3 vertebral artery-to-AICA interpositional bypass are alternatives when intracranial anatomy is unfavorable for this in situ bypass.1–6 Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Tailored Communicating Bypass for the Management of Complex Anterior Communicating Artery Aneurysms: “Flow-Counteraction” In Situ Bypass and Interposition Bypass Using Contralateral A2 Orifice as Donor Site

BACKGROUND The use of bypass surgery for anterior communicating artery (ACOM) aneurysms is technically challenging. Communicating bypass (COMB), such as pericallosal artery side-to-side anastomosis, is the most frequently used and anatomically directed reconstruction option. However, in many complex cases, this technique may not afford a sufficient blood supply or necessitate sacrificing the ACOM and the eloquent perforators arising from it. OBJECTIVE To evaluate tailored COMB and propose a practical algorithm for the management of complex ACOM aneurysms. METHODS For 1 patient with an aneurysm incorporating the entire ACOM, conventional in Situ A3-A3 bypass was performed as the sole treatment in order to create competing flow for aneurysm obliteration, sparing the sacrifice of eloquent perforators. In situations in which A2s were asymmetric in the other case, the contralateral A2 orifice was selected as the donor site to provide adequate blood flow by employing a short segment of the interposition graft. RESULTS The aneurysm was not visualized in patients with in Situ A3-A3 bypass because of the “flow-counteraction” strategy. The second patient, who underwent implementation of the contralateral A2 orifice for ipsilateral A3 interposition bypass, demonstrated sufficient bypass patency and complete obliteration of the aneurysm. CONCLUSION The feasibility of conventional COMB combined with complete trapping may only be constrained to selected ideal cases for the treatment of complex ACOM aneurysms. Innovative modifications should be designed in order to create individualized strategies for each patient because of the complexity of hemodynamics and the vascular architecture. Flow-counteraction in Situ bypass and interposition bypass using the contralateral A2 orifice as the donor site are 2 novel modalities for optimizing the advantages and broadening the applications of COMB for the treatment of complex ACOM aneurysms.

Anterior Inferior Cerebellar Artery Bypasses: The 7-Bypass Framework Applied to Ischemia and Aneurysms in the Cerebellopontine Angle

BACKGROUND Aneurysms of the anterior inferior cerebellar artery (AICA) are rare. Primary clip reconstruction of these lesions is a challenge because of the limited surgical exposure and frequent nonsaccular aneurysm morphology. Endovascular treatment options exist, but outcomes are equivalent to those for open surgery. Historically, AICA aneurysms not amenable to clipping or primary coiling have been treated with parent vessel sacrifice. OBJECTIVE To determine whether an AICA revascularization strategy would afford for the safe treatment of AICA aneurysms and other posterior circulation pathologies without compromising perfusion of the AICA territories. METHODS We describe a series of AICA bypasses to treat 4 AICA aneurysms and 3 vertebral artery/AICA occlusions. RESULTS We used 7 types of bypasses to revascularize the AICA territory. Bypass types included extracranial-to-intracranial (EC-IC) bypass without an interpositional graft, EC-IC with an interpositional graft, in situ bypass, reanastomosis, reimplantation, intracranial-to-intracranial bypass with interpositional graft, and combination bypasses. In particular, we performed the following 7 bypasses: OA-a3 AICA, OA-RAG-a3 AICA, p3 PICA-a3 AICA, a2 AICA reanastomosis, V4 VA-a3 AICA, V3 VA-SVG-a3 AICA, and a combined OA-a3 AICA bypass and p3 PICA reanastomosis. AICA revascularization allows for the safe treatment of AICA aneurysms and other posterior circulation pathologies without compromising perfusion of the AICA territories. CONCLUSION All 7 AICA bypasses are feasible for application to AICA aneurysms and ischemic disease. Our experience with the 7-bypass framework demonstrates the utility of the framework as a decision-making tool and the breadth of bypass innovation possible in this anatomically challenging region.

Surgical Clipping for Complex Middle Cerebral Artery Aneurysm: Decision-Making Tree With Tailored Bypass Strategy

INTRODUCTION Bypass surgery is important as an effective strategy for complex middle cerebral artery (MCA) aneurysms. Various bypass techniques were reported, but some of them were challenging and difficult to understand. The aim of this report was to propose our simple and flexible method for selecting ideal bypass option and its outcome. METHODS The strategy of bypass surgery is modified by a consideration of the anatomical situation as follows: Is it possible to make a flow our route? Is the amount of bypass flow sufficient? How is the location of lateral lenticulostriate artery (LSA)? Is the preservation of M2 branches possible? Modality of bypass surgery consists of (1) standard superficial temporal artery (STA)-middle cerebral artery (MCA) bypass (single/double, M3/4), (2) STA-proximal MCA (single/double, M1/2), (3) high flow bypass, (4) in-situ bypass (MCA-MCA parallels), and (4) interposition bypass. Operative strategy is selected based on our decision making tree. RESULTS Between 2015 and 2018, we experienced 280 cases (70 ruptured, 210 unruptured) of direct surgery for cerebral aneurysms. Of these cases, the MCA aneurysm accounted for 40% (112 cases). Among these, revascularization was required in 10 cases of complex anatomy. Strategy of bypass surgery included the following: STA-proximal MCA (M1) single bypass: 1 case, STA-proximal MCA (M2) single bypass: 3 cases, STA-proximal MCA (M2) double bypass: 3 cases, STA-distal MCA (M3-4): 1 case, and MCA-MCA in situ bypass: 2 cases (include combination bypass). Patency of bypass was 96% and neurological worsening that caused by surgery was 20% with no operative mortality. CONCLUSION Our decision-making tree with tailored bypass strategy is reasonable and will help select an optimal strategy for the complex MCA aneurysm surgery.