Macrovascular Decompression of Facial Nerve With Anteromedial Transposition of a Dolichoectatic Vertebral Artery: 3-Dimensional Operative Video.

Most cranial nerve compression syndromes (ie, trigeminal neuralgia and hemifacial spasm) are caused by small arteries impinging on a nerve and are relieved by microvascular decompression. Rarely, cranial nerve compression syndromes can be caused by large artery impingement and can be relieved by macrovascular decompression. When present, this compression often occurs in association with degenerative atherosclerosis in the vertebral arteries (VA) and basilar artery. Conservative treatment is recommended for mild forms, but surgical transposition of the VA away from the root entry zone (REZ) can be considered. This video demonstrates macrovascular decompression of a dolichoectatic VA in a 74-yr-old female with refractory left hemifacial spasm. After obtaining IRB approval, patient consent was sought for the procedure. With the patient in three-quarter-prone position, a far-lateral craniotomy was performed. The dentate ligament was cut to free the VA, and the suprahypoglossal portion of the vagoaccessory triangle was widened. VA compressed the REZ of the facial nerve, but was mobilized anteromedially off the REZ. A muslin sling was wrapped around the VA and its tail brought down to the clival dura, which was punctured with a 19-gauge needle and enlarged with a dissector. The sling was pulled anteromedially to this puncture site and secured to the dura with an aneurysm clip, relieving the REZ of all compression. The patient tolerated the procedure with mild, transient hoarseness and her hemifacial spasm resolved completely. This case demonstrates the macrovascular decompression technique with anteromedial transposition of the vertebrobasilar artery, which can also be used for trigeminal neuralgia.

Minimally Invasive Exposure of the Maxillary Artery at the Anteromedial Infratemporal Fossa.

BACKGROUND: The maxillary artery (MA) has been described as a reliable donor for extracranial-intracranial high-flow bypass. Existing techniques to harvest MA require brain retraction and drilling of the middle fossa (with or without a zygomatic osteotomy), carrying the potential risks of venous bleeding, injury to the branches of the maxillary or mandibular nerves, muscular transection, or temporomandibular junction disorders. OBJECTIVE: To describe a novel technique to expose the MA without bony drilling and with minimal impact to surrounding structures. METHODS: A conventional curvilinear incision was performed in 10 cadaveric specimens, prior to elevating the scalp to expose the zygomatic root and lateral orbital rim. The sphenozygomatic suture was followed to the anterolateral edge of the inferior orbital fissure (IOF) to locate and harvest the pterygoid segment of the MA. Topographic anatomy was assessed using surrounding landmarks and 3D Cartesian coordinates to define the surgical area. The number of visible MA branches and their lengths were recorded. RESULTS: The MA was successfully exposed in all specimens. This approach allowed 6 branches of MA to be exposed. The average length of exposure was 23.3 ± 8.3 mm and the average surgical area was 2.8 ± 0.9 cm2. The IOF was 11.5 ± 4.2 mm from the MA. CONCLUSION: Our technique provides landmarks to identify the distal pterygoid segment of MA as a donor for extracranial-intracranial bypasses without the need for additional craniectomies. Clear anatomical landmarks, including the sphenozygomatic suture, anterolateral edge of IOF, infraorbital artery, and the pterygomaxillary fissure defined a trajectory to efficiently localize the MA with minimal risk to surrounding structures.

Contralateral Approach to Middle Cerebral Artery Aneurysms: An Anatomical-Clinical Analysis to Improve Patient Selection.

BACKGROUND: A contralateral approach to aneurysm clipping in cases of bilateral middle cerebral artery (MCA) aneurysms reduces surgical time and cost. However, there is a lack of evidence for objective patient selection. In this study, we assessed the change in surgical freedom along the contralateral MCA to provide objective evidence for patient selection. METHODS: Sixteen cadaveric specimens were studied. Through a pterional approach, the surgical freedom was calculated moving distally along the contralateral MCA in 5-mm increments. In addition, in a series of 19 MCA aneurysms clipped contralaterally by the senior author, the average length of the MCA from its origin to the aneurysm neck was measured on angiography. RESULTS: In these patients treated via a contralateral approach, the average length of the MCA segment from its origin to the aneurysm neck was 12.4 mm. Starting at the MCA origin, surgical freedom decreased significantly between all adjacent target points except at 5-10 mm from the MCA origin. CONCLUSIONS: After the proximal 5 mm, there is no significant decrease in surgical maneuverability within the proximal 10 mm of MCA when approached contralaterally. When compared to the average length of the MCA from its origin to the aneurysm neck in the clinical series, it can be concluded that the first 10 mm (average, 12.4 mm) of the contralateral MCA may be considered a surgical comfort zone for a contralateral approach. This criterion may be useful for patient selection for a contralateral approach in cases of multiple bilateral intracranial aneurysms.

Comprehensive Anatomic Assessment of the Pterional, Orbitopterional, and Orbitozygomatic Approaches for Basilar Apex Aneurysm Clipping.

BACKGROUND: The pterional approach, along with its orbitopterional and orbitozygomatic extensions, is among the most common surgical approaches for tackling challenging aneurysms of the basilar artery apex (BAX). There is general consensus that the orbitozygomatic approach provides the best exposure for these lesions. However, there is little objective evidence to support approach selection for surgical treatment of BAX aneurysms. OBJECTIVE: To compare different features regarding surgical treatment of BAX aneurysms between the pterional, orbitopterional, and orbitozygomatic approaches. METHODS: The pterional, orbitopterional, and orbitozygomatic approaches were sequentially completed on 10 cadaveric specimens. The visibility of perforators, lengths of exposure, and safe clipping for major BAX branches, surgical area of exposure, and the surgical freedom for the BAX target were assessed. RESULTS: The orbitopterional approach provided significantly greater values than the pterional approach in all variables, except for exposure of the bilateral P1 posterior cerebral artery (PCA) perforators. When compared to the orbitopterional approach, the orbitozygomatic approach did not provide a statistically significant increase in (1) surgical freedom through the carotid-oculomotor triangle, (2) area of exposure, (3) ipsilateral, and (4) contralateral P1 PCA perforator visibility, and (5) ipsilateral PCA exposure and (6) clipping lengths. CONCLUSION: The orbitopterional approach provides significantly greater surgical exposure to BAX than the pterional approach. The orbitopterional approach is less invasive while providing similar surgical access to the BAX compared to the orbitozygomatic. The results of this study show that the orbitopterional approach may be optimal for the treatment of most BAX aneurysms, particularly to reduce morbidity resulting from the full orbitozygomatic approach.

Analysis of Surgical Freedom Variation Across the Basilar Artery Bifurcation: Towards a Deeper Insight Into Approach Selection for Basilar Apex Aneurysms.

BACKGROUND: The orbitozygomatic approach is generally advocated over the pterional approach for basilar apex aneurysms. However, the impact of the extensions of the pterional approach on the obtained maneuverability over multiple vascular targets (relevant to basilar apex surgery) has not been studied before. OBJECTIVE: To analyze the patterns of surgical freedom change across the basilar bifurcation between the pterional, orbitopterional, and orbitozygomatic approaches. METHODS: Surgical freedom was assessed for 3 vascular targets important in basilar apex aneurysm surgery (ipsilateral and contralateral P1-P2 junctions, and basilar apex), and compared between the pterional, orbitopterional, and orbitozygomatic approaches in 10 cadaveric specimens. RESULTS: Transitioning from the pterional to orbitopterional approach, the surgical freedom increased significantly at all 3 targets (P < .05). However, the gain in surgical freedom declined progressively from the most superficial target (60% for ipsilateral P1-P2 junction) to the deepest target (35% for contralateral P1-P2 junction). Conversely, transitioning from the orbitopterional to the orbitozygomatic approach, the gain in surgical freedom was minimal for the ipsilateral P1-P2 and basilar apex (<4%), but increased dramatically to 19% at the contralateral P1-P2 junction. CONCLUSION: The orbitopterional approach provides a remarkable increase in surgical maneuverability compared to the pterional approach for the basilar apex target and the relevant adjacent arterial targets. However, compared to the orbitopterional, the orbitozygomatic approach adds little maneuverability except for the deepest target (ie, contralateral P1-P2 junction). Therefore, the orbitozygomatic approach may be most efficacious with larger basilar apex aneurysms limiting the control over of the contralateral P1 PCA.

Comparative Analysis of Orbitozygomatic and Subtemporal Approaches to the Basilar Apex: A Cadaveric Study.

BACKGROUND: The subtemporal and orbitozygomatic approaches are the most commonly used surgical approaches for the treatment of basilar artery apex (BAX) aneurysms. Relative advantages and disadvantages are generally reported based on surgeons' experience. This study was performed to provide a detailed comparison between the subtemporal and orbitozygomatic approaches based on cadaveric dissection analysis for the treatment of BAX aneurysms. METHODS: Subtemporal and orbitozygomatic approaches were performed on 5 cadaveric heads (10 sides), and the following variables were assessed and compared between the 2 approaches: 1) number of exposed perforators on P1-posterior cerebral arteries (PCA); 2) lengths of exposure and clipping for bilateral PCA, superior cerebellar arteries (SCA), and basilar trunk; 3) surgical area of exposure; and 4) surgical freedom at the BAX. RESULTS: Number of perforators exposed on P1-PCA was not different between the subtemporal and orbitozygomatic approaches. Exposure and clipping of ipsilateral SCA and PCA were superior using the subtemporal approach, and better for contralateral SCA and PCA using the orbitozygomatic approach, all reaching statistical significance. The orbitozygomatic approach provided greater exposure and clipping length for the proximal basilar trunk. Although the surgical area of exposure was similar between the 2 approaches, the overall surgical freedom was greater in the orbitozygomatic approach. CONCLUSIONS: The orbitozygomatic approach provides a greater number of surgical corridors to the BAX and is superior regarding multiple surgically relevant anatomic parameters. Importantly, control over the basilar trunk and over the contralateral SCA and PCA (blind spots) is superior with the orbitozygomatic approach.

Revascularization of the upper posterior circulation with the anterior temporal artery: an anatomical feasibility study.

OBJECTIVE In various disease processes, including unclippable aneurysms, a bypass to the upper posterior circulation (UPC) including the superior cerebellar artery (SCA) and posterior cerebral artery (PCA) may be needed. Various revascularization options exist, but the role of intracranial (IC) donors has not been scrutinized. The objective of this study was to evaluate the anatomical feasibility of utilizing the anterior temporal artery (ATA) for revascularization of the UPC. METHODS ATA-SCA and ATA-PCA bypasses were performed on 14 cadaver specimens. After performing an orbitozygomatic craniotomy and opening the basal cisterns, the ATA was divided at the M3-M4 junction and mobilized to the crural cistern to complete an end-to-side bypass to the SCA and PCA. The length of the recipient artery between the anastomosis and origin was measured. RESULTS Seventeen ATAs were found. Successful anastomosis was performed in 14 (82%) of the ATAs. The anastomosis point on the PCA was 14.2 mm from its origin on the basilar artery. The SCA anastomosis point was 10.1 mm from its origin. Three ATAs did not reach the UPC region due to a common opercular origin with the middle temporal artery. The ATA-SCA bypass was also applied to the management of an incompletely coiled SCA aneurysm. CONCLUSIONS The ATA is a promising IC donor for UPC revascularization. The ATA is exposed en route to the proximal SCA and PCA through the pterional-orbitozygomatic approach. Also, the end-to-side anastomosis provides an efficient and straightforward bypass without the need to harvest a graft or perform multiple or difficult anastomoses.

Combination Superficial Temporal Artery-Middle Cerebral Artery Bypass and M2-M2 Reanastomosis With Trapping of a Stented Distal Middle Cerebral Artery Aneurysm: 3-Dimensional Operative Video.

Distal middle cerebral artery (MCA) aneurysms often have non-saccular morphology and cannot be clipped, requiring revascularization and trapping instead. Combination bypasses are needed when 2 arteries exit the aneurysm, and extracranial-intracranial and intracranial-intracranial bypasses can be used. This video demonstrates a combination bypass used to treat a previously stented distal MCA aneurysm with both a superficial temporal artery (STA)-to-MCA bypass and an M2-to-M2 reanastomosis. This 56-yr-old man presented with distal left-sided MCA aneurysm 2 years earlier and attempted stent-assisted coiling was aborted after the aneurysm was perforated with stenting alone. Follow-up angiography demonstrated progressive aneurysm enlargement, and he was referred for surgery. The patient consented for the procedure and a pterional craniotomy extended posteriorly exposed the distal Sylvian fissure and efferent M4-cortical arteries. After splitting the Sylvian fissure, the "flash fluorescence" technique with indocyanine green (ICG) videoangiography identified an M4 recipient artery from the deeper of 2 exiting branches for STA-MCA bypass.1 The aneurysm was then trapped, and inflow and the more superficial outflow arteries were anastomosed end to end (M2-M2 in-situ bypass). A platelet plug that developed at the reanastomosis site was broken apart with mechanical manipulation, and ICG videoangiography demonstrated patency of both bypasses. The patient recovered without any neurological deficits, and postoperative computed tomography angiography confirmed bypass patency. Combination bypasses are needed when unclippable bifurcation aneurysms require revascularization. Careful intraoperative evaluation of patency of the bypass is imperative and helps identifying and addressing any potential early bypass occlusion.

The Middle Temporal Artery: Surgical Anatomy and Exposure for Cerebral Revascularization.

BACKGROUND: The middle temporal artery (MTA) is the proximal medial branch of the superficial temporal artery (STA), supplying the temporalis muscle along with deep temporal arteries. Its use in vascularized flaps for reconstructive and otologic procedures has been described, yet its potential use in neurosurgery has not been studied. We report a novel technique for exposing the MTA and evaluated its characteristics for extracranial-intracranial cerebrovascular bypass. METHODS: After a curvilinear frontotemporal incision in 10 cadaveric specimens, the STA was dissected from distal to proximal. The horizontal portion of MTA was found posterolateral to the posterior end of the zygomatic root and was followed proximally until its origin and distally until its 2 terminal branches. The total length, visible branches, and caliber of MTA were measured. RESULTS: The mean total harvested length of MTA was 31.7 ± 5.1 mm, with an average proximal caliber of 1.7 ± 0.4 mm, and distal caliber of 1.3 ± 0.5 mm. There were 4-6 terminal MTA branches. The caliber of the proximal STA trunk was 2.5 ± 0.5 mm. The origin of the MTA was visible with a mean distance of 16.9 ± 4.8 mm inferior to the PEZR. The parotid gland was traversed and a communicating auriculotemporal nerve to the temporal branch of the facial nerve crossed MTA in 2 specimens. CONCLUSIONS: MTA can be safely harvested with an anterolateral approach, following its horizontal portion at the level of the zygomatic root, which is constant. The length and caliber of MTA makes it a potential alternative donor vessel or interposition graft for extracranial-intracranial bypass, especially when other donors are unavailable.

The transperiosteal "inside-out" occipital artery harvesting technique.

OBJECTIVE The occipital artery (OA) is a frequently used donor vessel for posterior circulation bypass procedures due to its proximity to the recipient vessels and its optimal caliber, length, and flow rate. However, its tortuous course through multiple layers of suboccipital muscles necessitates layer-by-layer dissection. The authors of this cadaveric study aimed to describe a landmark-based novel anterograde approach to harvest OA in a proximal-to-distal "inside-out" fashion, which avoids multilayer dissection. METHODS Sixteen cadaveric specimens were prepared for surgical simulation, and the OA was harvested using the classic (n = 2) and novel (n = 14) techniques. The specimens were positioned three-quarters prone, with 45° contralateral head rotation. An inverted hockey-stick incision was made from the spinous process of C-2 to the mastoid tip, and the distal part of the OA was divided to lift up a myocutaneous flap, including the nuchal muscles. The OA was identified using the occipital groove (OG), the digastric muscle (DM) and its groove (DG), and the superior oblique muscle (SOM) as key landmarks. The OA was harvested anterogradely from the OG and within the flap until the skin incision was reached (proximal-to-distal technique). In addition, 35 dry skulls were assessed bilaterally (n = 70) to study additional craniometric landmarks to infer the course of the OA in the OG. RESULTS The OA was consistently found running in the OG, which was found between the posterior belly of the DM and the SOM. The mean total length of the mobilized OA was 12.8 ± 1.2 cm, with a diameter of 1.3 ± 0.1 mm at the suboccipital segment and 1.1 ± 0.1 mm at the skin incision. On dry skulls, the occipitomastoid suture (OMS) was found to be medial to the OG in the majority of the cases (68.6%), making it a useful landmark to locate the OG and thus the proximal OA. CONCLUSIONS The anterograde transperiosteal inside-out approach for harvesting the OA is a fast and easy technique. It requires only superficial dissection because the OA is found directly under the periosteum throughout its course, obviating tedious layer-by-layer muscle dissection. This approach avoids critical neurovascular structures like the vertebral artery. The key landmarks needed to localize the OA using this technique include the OMS, OG, DM and DG, and SOM.

Assessment of the endoscopic endonasal approach to the basilar apex region for aneurysm clipping.

OBJECTIVEThe expanded endoscopic endonasal approach (EEA) has shown promising results in treatment of midline skull base lesions. Several case reports exist on the utilization of the EEA for treatment of aneurysms. However, a comparison of this approach with the classic transcranial orbitozygomatic approach to the basilar apex (BAX) region is missing.The present study summarizes the results of a series of cadaveric surgical simulations for assessment of the EEA to the BAX region for aneurysm clipping and its comparison with the transcranial orbitozygomatic approach as one of the most common approaches used to treat BAX aneurysms.METHODSFifteen cadaveric specimens underwent bilateral orbitozygomatic craniotomies as well as an EEA (first without a pituitary transposition [PT] and then with a PT) to expose the BAX. The following variables were measured, recorded, and compared between the orbitozygomatic approach and the EEA: 1) number of perforating arteries counted on bilateral posterior cerebral arteries (PCAs); 2) exposure and clipping lengths of the PCAs, superior cerebellar arteries (SCAs), and proximal basilar artery; and 3) surgical area of exposure in the BAX region.RESULTSExcept for the proximal basilar artery exposure and clipping, the orbitozygomatic approach provided statistically significantly greater values for vascular exposure and control in the BAX region (i.e., exposure and clipping of ipsilateral and contralateral SCAs and PCAs). The EEA with PT was significantly better in exposing and clipping bilateral PCAs compared to EEA without a PT, but not in terms of other measured variables. The surgical area of exposure and PCA perforator counts were not significantly different between the 3 approaches. The EEA provided better exposure and control if the BAX was located ≥ 4 mm inferior to the dorsum sellae.CONCLUSIONSFor BAX aneurysms located in the retrosellar area, PT is usually required to obtain improved exposure and control for the bilateral PCAs. However, the transcranial approach is generally superior to both endoscopic approaches for accessing the BAX region. Considering the superior exposure of the proximal basilar artery obtained with the EEA, it could be a viable option when surgical treatment is considered for a low-lying BAX or mid-basilar trunk aneurysms (≥ 4 mm inferior to dorsum sellae).

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.

Anterior clinoidectomy using an extradural and intradural 2-step hybrid technique.

In Brief: The authors found a practical intraoperative landmark to localize the optic strut during anterior clinoidectomy and used it as the basis for performing anterior clinoidectomy in two steps: extradural phase and intradural phase. This anatomically based technique can increase the safety of anterior clinoidectomy by providing easily identifiable landmarks and reducing intradural bone drilling, which could put the adjacent neurovauscular structures at risk.

Anterior Temporal Artery-to-Anterior Cerebral Artery Bypass: Anatomic Feasibility of a Novel Intracranial-Intracranial Revascularization Technique.

BACKGROUND: Complex aneurysms of the anterior cerebral artery (ACA) may require a bypass procedure as part of their surgical management. Most current bypass paradigms recommend technically demanding side-to-side anastomosis of pericallosal arteries or use of interposition grafts, which involve longer ischemia times. The purpose of this study is to assess the feasibility of an anterior temporal artery (ATA) to ACA end-to-side bypass. METHODS: Fourteen cadaveric specimens (17 ATAs) were prepared for surgical simulation. The cisternal course of the ATA was freed from perforating branches and arachnoid. The M3-M4 junction of the ATA was cut, and the artery was mobilized to the interhemispheric fissure. The feasibility of ATA bypass to the precommunicating and postcommunicating ACA was assessed in relation to the cisternal length and branching pattern of the middle cerebral artery. RESULTS: Successful anastomosis was feasible in 14 ATAs (82%). Three ATAs did not reach the ACA. These ATAs were branching distally and originated from the M3 (opercular) middle cerebral artery. In specimens where bypass was not feasible, the average cisternal length of the ATA was significantly shorter than the rest. CONCLUSIONS: ATA-ACA bypass is anatomically feasible and may be a useful alternative to other revascularization techniques in selected patients. It is technically simpler than A3-A3 in situ bypass. ATA-ACA bypass can be performed through the same pterional exposure used for the ACA aneurysms, sparing the patient an additional interhemispheric approach, required for the A3-A3 anastomosis.

Internal Maxillary Artery to Upper Posterior Circulation Bypass Using a Superficial Temporal Artery Graft: Surgical Anatomy and Feasibility Assessment.

BACKGROUND: Revascularization of the upper posterior circulation (UPC), including the superior cerebellar artery (SCA) and posterior cerebral artery (PCA), may be necessary as part of the surgical treatment of complex UPC aneurysms or vertebrobasilar insufficiency. The existing bypass options have relative advantages and disadvantages. However, the use of a superficial temporal artery graft (STAg) in a bypass from the internal maxillary artery (IMA) to the UPC has not been previously assessed. We studied the surgical anatomy and assessed the technical feasibility of the IMA-STAg-UPC bypass. METHODS: Fourteen cadaver heads were studied. The STAg was harvested proximally from about 15 mm below the zygomatic arch. The IMA was exposed through the lateral triangle of the middle fossa. The IMA-STAg-UPC bypass was completed using a subtemporal approach. RESULTS: The bypass was successfully performed in all specimens. The average length of the STAg from the donor to the recipient was 46.4 mm for the s2 SCA, and 49.5 mm for the P2 PCA. The average distal diameter of the STAg was 2.3 mm. More than 83% of STAgs had a diameter of ≥2 mm distally. At the point of anastomosis, the average diameter of the SCA was 1.9 mm, and the average diameter of the PCA was 3.0 mm. CONCLUSIONS: The proposed bypass is anatomically feasible and provides a suitable caliber match between the bypass components. Our results provide the anatomic basis for clinical assessment of the bypass in tackling complex lesions of the vertebrobasilar system requiring revascularization.

Microsurgical Bypass Training Rat Model: Part 2-Anastomosis Configurations.

BACKGROUND: Mastery of microsurgical anastomosis is key to achieving good outcomes in cerebrovascular bypass procedures. Animal models (especially rodents) provide an optimal preclinical bypass training platform. However, the existing models for practicing different anastomosis configurations have several limitations. OBJECTIVE: We sought to optimize the use of the rat's abdominal aorta and common iliac arteries (CIA) for practicing the 3 main anastomosis configurations commonly used in cerebrovascular surgery. METHODS: Thirteen male Sprague-Dawley rats underwent inhalant anesthesia. The abdominal aorta and the CIAs were exposed. The distances between the major branches of the aorta were measured to find the optimal location for an end-to-end anastomosis. Also, the feasibility of performing side-to-side and end-to-side anastomoses between the CIAs was assessed. RESULTS: All bypass configurations could be performed between the left renal artery and the CIA bifurcation. The longest segments of the aorta without major branches were 1) between the left renal and left iliolumbar arteries (16.9 mm ± 4.6), and 2) between the right iliolumbar artery and the aortic bifurcation (9.7 mm ± 4.7). The CIAs could be juxtaposed for an average length of 7.6 mm ± 1.3, for a side-to-side anastomosis. The left CIA could be successfully reimplanted on to the right CIA at an average distance of 9.1 mm ± 1.6 from the aortic bifurcation. CONCLUSIONS: Our results show that rat's abdominal aorta and CIAs may be effectively used for all the anastomosis configurations used in cerebral revascularization procedures. We also provide technical nuances and anatomic descriptions to plan for practicing each bypass configuration.

Preserving the Facial Nerve During Orbitozygomatic Craniotomy: Surgical Anatomy Assessment and Stepwise Illustration.

OBJECTIVE: Surgical safety and efficiency during an orbitozygomatic (OZ) osteotomy rely on thorough knowledge of the surgical anatomy of the facial nerve. Although the anatomy of the facial nerve and its relation to the pterional craniotomy are described, a thorough assessment of facial nerve preservation techniques during the OZ approach and its variations is lacking. We assessed the surgical anatomy of the facial nerve related to the OZ approach and provided a thorough stepwise description on how to preserve it. METHODS: The OZ approach was performed bilaterally in 15 cadaveric heads. The interfascial and subfascial techniques were performed to study their nuances in preserving the facial nerve. We compared the 2 techniques and provided a thorough description on how to preserve the facial nerve during each step of the OZ approach. RESULTS: At the zygomatic arch, the facial nerve was found between the galea and the superficial temporal fascia. A cut in the fascia at the posterior end of the zygomatic arch did not cross any facial nerve branches. The subfascial technique was simpler, more efficient, and provided more structural protection of the facial nerve branches than the interfascial technique. CONCLUSIONS: The frontal division of the facial nerve is related directly to dissection over the zygomatic bone and may be injured during fascial dissection or osteotomies. Both interfascial and subfascial techniques are feasible to use during the OZ craniotomy and provide ample exposure of the OZ unit. Regarding the preservation of the facial nerve branches, we favor the subfascial method.

Microsurgical Clipping of an Unruptured Carotid Cave Aneurysm: 3-Dimensional Operative Video.

Most aneurysms originating from the clinoidal segment of the internal carotid artery (ICA) are nowadays managed conservatively, treated endovascularly with coiling (with or without stenting) or flow diverters. However, microsurgical clip occlusion remains an alternative. This video demonstrates clip occlusion of an unruptured right carotid cave aneurysm measuring 7 mm in a 39-year-old woman. The patient opted for surgery because of concerns about prolonged antiplatelet use associated with endovascular therapy. After patient consent, a standard pterional craniotomy was performed followed by extradural anterior clinoidectomy. After dural opening and sylvian fissure split, a clinoidal flap was opened to enter the extradural space around the clinoidal segment. The dural ring was dissected circumferentially, freeing the medial wall of the ICA down to the sellar region and mobilizing the ICA out of its canal of the clinoidal segment. With the aneurysm neck in view, the aneurysm was clipped with a 45° angled fenestrated clip over the ICA. Indocyanine green angiography confirmed no further filling of the aneurysm and patency of the ICA. Complete aneurysm occlusion was confirmed with postoperative angiography, and the patient had no neurologic deficits (Video 1). This case demonstrates the importance of anterior clinoidectomy and thorough distal dural ring dissection for effective clipping of carotid cave aneurysms. Control of venous bleeding from the cavernous sinus with fibrin glue injection simplifies the dissection, which should minimize manipulation of the optic nerve. Knowledge of this anatomy and proficiency with these techniques is important in an era of declining open aneurysm cases.

Microsurgical Bypass Training Rat Model, Part 1: Technical Nuances of Exposure of the Aorta and Iliac Arteries.

BACKGROUND: Animal models using rodents are frequently used for practicing microvascular anastomosis-an essential technique in cerebrovascular surgery. However, safely and efficiently exposing rat's target vessels is technically difficult. Such difficulty may lead to excessive hemorrhage and shorten animal survival. This limits the ability to perform multiple anastomoses on a single animal and may increase the overall training time and costs. We report our model for microsurgical bypass training in rodents in 2 consecutive articles. In part 1, we describe the technical nuances for a safe and efficient exposure of the rat abdominal aorta and common iliac arteries (CIAs) for bypass. METHODS: Over a 2-year period, 50 Sprague-Dawley rats underwent inhalant anesthesia for practicing microvascular anastomosis on the abdominal aorta and CIAs. Lessons learned regarding the technical nuances of vessel exposure were recorded. RESULTS: Several technical nuances were important for avoiding intraoperative bleeding and preventing animal demise while preparing an adequate length of vessels for bypass. The most relevant technical nuances include (1) generous subcutaneous dissection; (2) use of cotton swabs for the blunt dissection of the retroperitoneal fat; (3) combination of sharp and blunt dissection to isolate the aorta and iliac arteries from the accompanying veins; (4) proper control of the posterior branches of the aorta; and (5) efficient division and mobilization of the left renal pedicle. CONCLUSIONS: Applying the aforementioned technical nuances enables safe and efficient preparation of the rat abdominal aorta and CIAs for microvascular 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 TPA's 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).