Olivia Kola

Bypass surgery for complex middle cerebral artery aneurysms: an algorithmic approach to revascularization

OBJECT Management of complex aneurysms of the middle cerebral artery (MCA) can be challenging. Lesions not amenable to endovascular techniques or direct clipping might require a bypass procedure with aneurysm obliteration. Various bypass techniques are available, but an algorithmic approach to classifying these lesions and determining the optimal bypass strategy has not been developed. The objective of this study was to propose a comprehensive and flexible algorithm based on MCA aneurysm location for selecting the best of multiple bypass options. METHODS Aneurysms of the MCA that required bypass as part of treatment were identified from a large prospectively maintained database of vascular neurosurgeries. According to its location relative to the bifurcation, each aneurysm was classified as a prebifurcation, bifurcation, or postbifurcation aneurysm. RESULTS Between 1998 and 2015, 30 patients were treated for 30 complex MCA aneurysms in 8 (27%) prebifurcation, 5 (17%) bifurcation, and 17 (56%) postbifurcation locations. Bypasses included 8 superficial temporal artery-MCA bypasses, 4 high-flow extracranial-to-intracranial (EC-IC) bypasses, 13 IC-IC bypasses (6 reanastomoses, 3 reimplantations, 3 interpositional grafts, and 1 in situ bypass), and 5 combination bypasses. The bypass strategy for prebifurcation aneurysms was determined by the involvement of lenticulostriate arteries, whereas the bypass strategy for bifurcation aneurysms was determined by rupture status. The location of the MCA aneurysm in the candelabra (Sylvian, insular, or opercular) determined the bypass strategy for postbifurcation aneurysms. No deaths that resulted from surgery were found, bypass patency was 90%, and the condition of 90% of the patients was improved or unchanged at the most recent follow-up. CONCLUSIONS The bypass strategy used for an MCA aneurysm depends on the aneurysm location, lenticulostriate anatomy, and rupture status. A uniform bypass strategy for all MCA aneurysms does not exist, but the algorithm proposed here might guide selection of the optimal EC-IC or IC-IC bypass technique.

Exposure of the External Carotid Artery Through the Posterior Triangle of the Neck: A Novel Approach to Facilitate Bypass Procedures to the Posterior Cerebral Circulation

BACKGROUND The external carotid artery (ECA) is the main high-flow donor for extracranial-intracranial revascularization procedures. However, anatomic restraints limit the availability of ECA in posterior exposures of the craniocervical junction aimed for bypass to distal vertebral artery segments. OBJECTIVE To examine the feasibility and safety of exposure of the ECA through the posterior triangle of the neck. METHODS A preliminary feasibility study on the posterior neck exposure of the ECA was performed in 1 cadaveric head (2 sides) followed by a morphometric study on 9 cadaveric heads (18 sides). Through an extension of the muscular stage of the far-lateral approach, the fascial plane between the posterior belly of the digastric muscle and the capsule of the parotid gland was dissected inferior to the C1. Topographic anatomy of the exposed distal segment of the ECA was defined in detail, including bony landmarks and the facial nerve. RESULTS ECA was found successfully using the proposed technique in all specimens. In 90% of the specimens, ECA was exposed without transgression of the capsule of the parotid gland. The facial nerve was not encountered during the surgical exposures. CONCLUSION ECA can be safely and effectively exposed through the posterior triangle of the neck using the proposed approach. This method can facilitate extracranial-intracranial bypass procedures to V3/V4 vertebral artery. Advantages of this novel approach are shortening the graft length and surgical timing, less invasiveness, and optimizing surgical trajectories for completion of both donor and recipient bypass anastomosis.

Assessment of the Temporopolar Artery as a Donor Artery for Intracranial-Intracranial Bypass to the Middle Cerebral Artery: Anatomic Feasibility Study

BACKGROUND Intracranial-intracranial bypass is a valuable cerebral revascularization option. Despite several advantages, one of the main shortcomings of the intracranial-intracranial bypass is the possibility of ischemic complications of the donor artery. However, when sacrificed, the temporopolar artery (TPA) is not associated with major neurologic deficits. We sought to define the role of TPA as a donor for revascularization of the middle cerebral artery (MCA). METHODS Pterional craniotomy was performed on 14 specimens. The TPA was released from arachnoid trabecula, and the small twigs to the temporal lobe were cut. The feasibility of side-to-side and end-to-side bypass to the farthest arterial targets on insular, opercular, and cortical MCA branches was assessed. The distance of the bypass point was measured in reference to limen insulae. RESULTS A total of 15 TPAs were assessed (1 specimen had 2 TPAs). The average cisternal length of the TPA was 37.3 mm. For side-to-side bypass, the TPA was a poor candidate as an intracranial donor, except for the cortical orbitofrontal artery, which was reached in 87% of cases. However, the end-to-side bypass was successfully completed for most arteries (87%-100%) on the anterior frontal operculum and more than 50% of the cortical or opercular middle and posterior temporal arteries. There was no correlation between the TPAs cisternal length and maximum bypass reach. CONCLUSIONS When of favorable diameter, the TPA is a competent donor for intracranial-intracranial bypass to MCA branches at the anterior insula, and anterior frontal and middle temporal opercula (arteries anterior to the precentral gyrus coronal plane).

Internal Maxillary Artery to Anterior Circulation Bypass with Local Interposition Grafts Using a Minimally Invasive Approach: Surgical Anatomy and Technical Feasibility

BACKGROUND The internal maxillary artery (IMA) is a reliable donor for extracranial-intracranial high-flow bypasses. However, previously described landmarks and techniques to harvest the IMA are complex and confusing and require extensive bone drilling, carrying significant neurovascular risk. The objective of our study was to describe a minimally invasive technique for exposing the IMA and to assess the feasibility of using the IMA as a donor for anterior-circulation recipient vessels using 2 different local interposition vessels. METHODS Via a minimally invasive technique, the IMA was harvested in 10 cadaveric specimens and a pterional craniotomy was performed. Two interposition grafts-the superficial temporal artery (STA) and middle temporal artery-were evaluated individually. Transsylvian exposure of the second segment of middle cerebral artery (M2), the supraclinoid internal carotid artery, and the proximal postcommunicating anterior cerebral artery segment was completed. Relevant vessel calibers and graft lengths were measured for each bypass model. RESULTS The mean caliber of the IMA was 2.7 ± 0.5 mm. Of all 3 recipients, the shortest graft length was seen in the IMA-STA-M2 bypass, measuring 42.0 ± 8.4 mm. There was a good caliber match between the M2 (2.4 ± 0.4 mm) and STA (2.3 ± 0.4 mm) at the anastomotic site. The harvested middle temporal artery was sufficient in length in only 30% cases, with a mean distal caliber of 2.0 ± 0.7 mm. CONCLUSIONS This study confirmed the technical feasibility of IMA as a donor for an extracranial-intracranial bypass to the second segment of the anterior cerebral artery, M2, and the supraclinoid internal carotid artery. However, IMA-STA-M2 was observed to be the most suitable bypass model.