Brainatomy-Demystifying the Temporal Bone, Rule of 3-2-1

BACKGROUND

The temporal bone is difficult to comprehend in three-dimensional (3D) space. We provide a novel 3D mental model of the temporal bone which helps clinicians and surgeons dealing with it in teaching, diagnosing, conservative managements, and preoperative and intraoperative orientation. This study is part of the scientific project Brainatomy.

OBJECTIVE

To analyze and simplify the temporal bone anatomy to enhance its comprehension and long-term retention.

METHODS

The study was conducted at the Neurosurgical Department of the University Hospital of Bochum, Germany. We retrospectively analyzed data sets of 221 adult patients who underwent computed tomography (CT) of the skull (n = 167) and magnetic resonance imaging (MRI) of the brain (n = 54). A total of 142 patients with their respective imaging scans remained in our pool of interest after excluding 79 scans. The raw digital imaging and communications in medicine scans were transformed into 3D objects. Spatial analyses were then conducted, and all collected data were used to create our own 3D model of the temporal bone.

RESULTS

We define the temporal bone as a prism-shaped model and divide it into 6 compartments: apex, neurovascular, mastoid, blank, tympanic, and temporomandibular compartments. The division into compartments has been achieved with the "Rule of 3-2-1." Finally, the 3D model has been used to record a video (Video), using a novel and "easy-to-follow" didactic approach.

CONCLUSION

This simplified 3D model along with the corresponding video (Video) potentially enhances the efficiency of studying temporal none anatomy with a novel "easy-to-follow" approach.

Ovoid Foramen Magnum Shape is Associated with Increased Complications and Decreased Extent of Resection for Anterolateral Foramen Magnum Meningiomas

Background  Antero-laterally located meningiomas of the foramen magnum (FM) pose significant surgical resection challenges. The effect of FM shape on surgical resection of FM meningiomas has not been previously studied. The present study investigates how FM shape effects the extent of tumor resection and complication rates in antero-lateral FM meningiomas. Materials and Methods  This retrospective study included 16 consecutive patients with antero-lateral FM meningiomas operated on by a single surgeon. FMs were classified as ovoid ( n  = 8) and nonovoid ( n  = 8) using radiographic evaluation. Results  Sixteen patients were examined: seven males and nine females (mean age of 58.5, and range of 29 to 81 years). Gross total resection was achieved in 81% of patients, with tumor encased vertebral arteries in 44%. Patient characteristics were similar including age, sex, preoperative tumor volume, relationship of vertebral artery with tumor, preoperative Karnofsky performance score (KPS), symptom duration, and presence of lower cranial nerve symptoms. The ovoid FM group had lower volumetric extents of resection without statistical significance (93 ± 10 vs. 100 ± 0%, p  = 0.069), more intraoperative blood loss (319 ± 75 vs. 219 ± 75 mL, p  = 0.019), more complications per patient (1.9 ± 1.8 vs. 0.3 ± 0.4, p  = 0.039), and poorer postoperative KPS (80 ± 21 vs. 96 ± 5, p  = 0.007). Hypoglossal nerve palsy was more frequent in the ovoid FM group (38 vs. 13%). Conclusion  This is the first study demonstrating that ovoid FMs may pose surgical challenges, poorer operative outcomes, and lower rates of extent of resection. Preoperative radiological investigation including morphometric FM measurement to determine if FMs are ovoid or nonovoid can improve surgical planning and complication avoidance.

The Suprasellar Meningioma Patient-Reported Outcome Survey: a disease-specific patient-reported outcome measure for resection of suprasellar meningioma

OBJECTIVE

Suprasellar meningioma resection via either the transcranial approach (TCA) or the endoscopic endonasal approach (EEA) is an area of controversy and active evaluation. Skull base surgeons increasingly consider patient-reported outcomes (PROs) when choosing an approach. No PRO measure currently exists to assess quality of life for suprasellar meningiomas.

METHODS

Adult patients undergoing suprasellar meningioma resection between 2013 and 2019 via EEA (n = 14) or TCA (n = 14) underwent semistructured interviews. Transcripts were coded using a grounded theory approach to identify themes as the basis for a PRO measure that includes all uniquely reported symptoms. To assess content validity, 32 patients and 15 surgeons used a Likert scale to rate the relevance of items on the resulting questionnaire and the general Patient-Reported Outcomes Measurement Information System-29 (PROMIS29). The mean scores were calculated for all items and compared for TCA versus EEA patient cohorts by using unpaired t-tests. Items on either questionnaire with mean scores ≥ 2.0 from patients were considered meaningful and were aggregated to form the novel Suprasellar Meningioma Patient-Reported Outcome Survey (SMPRO) instrument.

RESULTS

Qualitative analyses resulted in 55 candidate items. Relative to patients who underwent the EEA, those who underwent the TCA reported significantly worse future outlook before surgery (p = 0.01), tiredness from medications 2 weeks after surgery (p = 0.001), and word-finding and memory difficulties 3 months after surgery (p = 0.05 and < 0.001, respectively). The items that patients who received a TCA were most concerned about included medication-induced lethargy after surgery (2.9 ± 1.3), blurry vision before surgery (2.7 ± 1.5), and difficulty reading due to blurry vision before surgery (2.7 ± 2.7). Items that patients who received an EEA were most concerned about included blurry vision before surgery (3.5 ± 1.3), difficulty reading due to blurry vision before surgery (2.4 ± 1.3), and problems with smell postsurgery (2.9 ± 1.3). Although surgeons overall overestimated how concerned patients were about questionnaire items (p < 0.0005), the greatest discrepancies between patient and surgeon relevance scores were for blurry vision pre- and postoperatively (p < 0.001 and < 0.001, respectively) and problems with taste postoperatively (p < 0.001). Seventeen meningioma-specific items were considered meaningful, supplementing 8 significant PROMIS29 items to create the novel 25-item SMPRO.

CONCLUSIONS

The authors developed a disease- and approach-specific measure for suprasellar meningiomas to compare quality of life by operative approach. If demonstrated to be reliable and valid in future studies, this instrument may assist patients and providers in choosing a personalized surgical approach.

ABBREVIATIONS

EEA = endoscopic endonasal approach; GTR = gross-total resection; PRO = patient-reported outcome; PROMIS29 = Patient-Reported Outcomes Measurement Information System-29; QOL = quality of life; SMPRO = Suprasellar Meningioma Patient-Reported Outcome Survey; TCA = transcranial approach.

Navigating a Carotico-Clinoid Foramen and an Interclinoidal Bridge in the Endonasal Endoscopic Approach: An Anatomical and Technical Note

Objective  The carotico-clinoid foramen and interclinoid bridge are two anatomical variants of the sellar region. If these anatomical variants go unrecognized and are not managed safely by the surgeon during expanded endoscopic endonasal surgery for a posterior clinoidectomy, a carotid artery injury may occur. We summarize a method to safely navigate in the presence of the carotico-clinoid foramen and interclinoid bridge in an endoscopic endonasal approach. Study Design  The study involves cadaveric dissection and management of the anatomical variants. Setting  The study took place in a cadaveric dissection laboratory. Participants  The object of study is one cadaveric head. Main Outcome Measures  After discovering the two variants in both cavernous sinuses of a cadaveric head, we established a stepwise coping strategy to avoid carotid artery injury while performing an endoscopic endonasal bilateral interdural pituitary transposition, and we report the final view after endoscopic management. Results  Debulking of the middle clinoid process can decrease the obstacle effect, and the pituitary transposition can be performed medial to the ossified carotico-clinoid ligament. Disconnection of the interclinoid bridge is the prerequisite to an effective posterior clinoidectomy, and distinguishing the transition between the sellar diaphragm and the interclinoid bridge is essential. Conclusion  In the presence of both the carotico-clinoid foramen and the interclinoid bridge, a bilateral interdural pituitary transposition can still be performed, although preoperative strategic preparation, full inspection, and stepwise disconnections are of paramount importance in such a scenario to avoid cavernous carotid artery injury.

Meningioma of posterolateral tentorial incisura: a case demonstration of paramedian supracerebellar transtentorial approach

The paramedian supracerebellar transtentorial approach allows unobstructed exposure to the quadrigeminal cistern, tectal plate, pineal region, tentorial incisura, medial basal temporal lobe, and posterior ambient cistern. The authors present a meningioma of the posterolateral tentorial incisura case in a 62-year-old male who presented with a long history of upper-extremity tremors and walking difficulties. MRI revealed supra- and infratentorial tumor extension and hydrocephalus. This approach enabled us to achieve gross-total resection without causing neurovascular injury or any postoperative neurological deficits. For each pathology, the pros and cons of various approaches should be considered based on the anatomy, vasculature, and any surrounding structures.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2138.

Surgical approaches for resection of third ventricle colloid cysts: meta-analysis

Although outcome studies and systematic reviews have been published on the surgical treatment of third ventricle colloid cysts (TVCC), there are no meta-analyses that compare the outcomes for various surgical approaches. This meta-analysis assesses the outcomes and complications for transcortical, transcallosal, and endoscopic surgical approaches used to excise TVCCs. A meta-analysis of surgically excised TVCCs was performed with an assessment of outcome for transcortical, transcallosal, and endoscopic approaches. A random-effects model analyzed the extent of surgical excision. The analysis included reports that compared at least two of these surgical approaches, for a total of 11 studies comprising a population of 301 patients. The transcortical approach was associated with a higher incidence of complete excision compared to the endoscopic approach (OR = 0.137, p = 0.041), with no significant differences observed between transcortical and transcallosal approaches, and between transcallosal and endoscopic approaches. Comparison between endoscopic and pooled microsurgical approaches was also insignificant (OR = 0.22, p = 1). The risk of motor weakness was increased with the transcortical approach compared to the endoscopic approach (OR = 6.10, p = 0.018). There were no significant differences between transcortical and transcallosal approaches regarding newly onset seizures, and no significant mortality differences between all three approaches. This study demonstrates that microsurgical approaches are associated with a greater extent of resection compared to endoscopic approaches; however, best results are likely achieved based on the surgeon's expertise, flexibility, and case review.

Intraoperative application of a new-generation 3D IV-DSA technology in resection of a hemorrhagic cerebellar AVM

Although intravenous digital subtraction angiography (IV-DSA), cone-beam CT, and rotational angiography are well-established technologies, using them in a single system in the hybrid operating room to acquire high-quality noninvasive 3D images is a recent development. This video demonstrates microsurgical excision of a ruptured cerebellar arteriovenous malformation (AVM) in a 66-year-old male followed by intraoperative IV-DSA acquisition using a new-generation system (Artis Icono). IV-DSA confirmed in real time that no residual remained following excision without the need to reposition the patient. To the best of the authors’ knowledge, this is the first surgical video to demonstrate the simplified workflow and application of this technology in neurovascular surgery.

The video can be found here: https://youtu.be/bo5ya9DQQPw

Demonstration of Microsurgical Technique and Nuances for the Obliteration of Complex Intracranial Dural Arteriovenous Fistulas in Three Consecutive Cases: Operative Video

An intracranial dural arteriovenous fistula (DAVF) is an uncommon acquired dural shunt between an artery and a vein without a parenchymal nidus. DAVF occlusion may be achieved using either endovascular or open surgical means. Combining both techniques is also frequently used in clinical practice. In this video, we present 3 patients with Borden type III, complex intracranial DAVFs. The first patient presented with intracranial hemorrhage and underwent a successful microsurgical obliteration of the fistula in the tentorium. Two other patients had DAVFs that were incidentally found. Both underwent embolization procedures, which did not result in complete DAVF obliteration. Both patients then subsequently underwent microsurgical obliteration of these DAVFs. All 3 patients had very good outcomes. In 2 of these cases, we performed indocyanine green video angiography to identify fistulous connections. As demonstrated in this Video 1, microsurgical obliteration of DAVFs is relatively straightforward. This provides a valuable treatment option of some selected DAVFs and should be considered as a primary initial treatment option of complex DAVFs in certain locations. Open surgical obliteration is the best possible, most durable, and most effective therapeutic option when there are failures or shortcomings with endovascular management.

Trigeminal Neuralgia Caused by Vascular Compression from the Petrous Carotid Artery with Bony Erosion and Meckel Cave Encephalocele: Clinical Imaging with Surgical Video

Trigeminal neuralgia (TN) is most commonly caused by neurovascular compression of the superior cerebellar artery. We present the first reported TN case where nerve compression was caused by the petrous internal carotid artery in the vicinity of a Meckel cave (MC) encephalocele. The patient underwent a pterional craniotomy for decompression of the gasserian ganglion and trigeminal nerve branches. All symptoms were resolved post surgery. We surmise that the principal cause of the TN was vascular compression from an exposed petrous internal carotid artery in the presence of an encephalocele. Causation was irrespective of whether the dehiscence in the petrous apex was a congenital defect or associated with destruction from the encephalocele. Based on this observation, we recommend that surgeons carefully consider all possible causes of patient symptoms as they prepare a meticulous dissection plan to avoid damage to surrounding neurovascular structures.

Identification of the Distal Dural Ring and Definition of Paraclinoid Aneurysms According to Bony Landmarks on 3-Dimensional Computed Tomography Angiography: A Cadaveric and Radiological Study

BACKGROUND

Determining if paraclinoid aneurysms are intradural or extradural is critical for surgical planning.

OBJECTIVE

To create an easily reproducible diagnostic method based on bony anatomy that precisely locates the distal dural ring (DDR) to determine the position of paraclinoid aneurysms as intradural, transitional, or extradural.

METHODS

Bilateral anatomic dissections of 10 cadaveric heads (20 sides) were performed to evaluate DDR anatomy. We observed a plane that reflects the position of the DDR passes through 4 bony landmarks: 1) The anterior clinoid-internal carotid artery intersection, 2) the optic strut, 3) the optico-carotid elevation, and 4) the base of the posterior clinoid process. This landmark-based plane can thus define the location of the DDR using 3-dimensional computed tomography angiography (CTA). This was confirmed in 27 surgical patients with intradural/transitional aneurysms and 7 patients with extradural aneurysms confirmed with magnetic resonance imaging (MRI). The DDR plane method easily classified aneurysm locations as intradural (above the DDR plane), extradural (below the DDR plane), or transitional (the DDR plane crosses the aneurysm). The aneurysm's location was subsequently confirmed intraoperatively or with MRI.

RESULTS

The DDR plane method determined if paraclinoid aneurysms were intradural, transitional, or extradural in all 34 cases examined. The visibility of the anatomic features that define the DDR plane was also verified in 82% to 89% of CTA images from 100 patients.

CONCLUSION

The DDR plane method provides a useful diagnostic tool to evaluate the position of the DDR and determine the anatomic location of paraclinoid aneurysms.

Surgical Strategies for Cerebral Revascularization in Patients with Limited Bypass Conduit Options and Unexpected Intraoperative Difficulties

BACKGROUND

Cerebral bypass procedures are complex and require substantial experience and skills and thorough preoperative planning. Cerebrovascular surgeons face increasingly complex bypass cases because most routine cases are managed by endovascular means, and because increasing numbers of patients have complex medical problems that affect available and suitable bypass conduit options. We report the cases of several patients undergoing cerebral bypass with limited bypass conduit alternatives, in whom there were unexpected intraoperative difficulties requiring complex solutions.

METHODS

The neurological surgery department database was reviewed to identify patients who had undergone cerebral bypass procedures during a 13-year period in whom there were limited available bypass conduits, and in whom unexpected intraoperative difficulties were encountered during cerebral bypass.

RESULTS

Patient outcomes and graft patency were evaluated for 13 patients including 6 with ischemia, 3 with giant aneurysms, 2 with mycotic aneurysms, 1 with dissecting aneurysm, and 1 with gunshot-induced pseudoaneurysm. Median duration of follow-up was 43 months. In 12 of 13 patients, bypass graft/grafts were patent on the last computed tomography angiogram. In 1 patient, a prophylactic bypass procedure, the graft was not filling, probably because of lack of demand. Two patients died during follow-up of unrelated causes.

CONCLUSIONS

Cerebrovascular surgeons should be versatile in dealing with patients with complex bypass. When there are limited available conduit options, we find that collaboration with other surgical specialties (e.g., plastics and vascular) is helpful. In patients in whom extreme intraoperative difficulties are expected, thorough preoperative planning with multiple backup plans should be exercised, as described in this report.

Intraoperative Shortening of Aneurysm Clips: Revisiting an Old Technique in a New Era

BACKGROUND

It can sometimes be challenging to find a suitable clip to treat an unusual aneurysm, or when the surrounding anatomy is unusual, especially in resource-limited environments. We describe a method to modify aneurysm clips based on the method originated by Sugita et al in 1985. Herein clip modification (Clip-Mod) is used to treat anatomically difficult anterior communicating artery aneurysms.

METHODS

The Department of Neurological Surgery database was reviewed to find aneurysm patients treated using modified aneurysm clips. Clip-Mod was performed during surgery by shortening the tines of titanium aneurysm clips by abrasion applied from the side of a standard 3-mm surgical diamond drill bit under constant irrigation. Note that the thickness of the tines and the clip spring were not modified or contacted by the drill.

RESULTS

Four cases used modified aneurysm clips, from 648 total clip-treated aneurysms (0.6%) by 2 surgeons over a 14-year period. Three patients presented with subarachnoid hemorrhages that were determined to be due to anterior communicating artery aneurysms. One patient presented with an incidental unruptured anterior communicating artery aneurysm. All 4 patients were treated with 3-mm titanium clips shortened intraoperatively to 1- to 2-mm lengths, to achieve aneurysm obliteration without stenosing parent or perforating vessels.

CONCLUSIONS

All 4 patients have done well clinically with no reoccurrences after 2-6 years' follow-up, which included angiographic evaluation. The use of this "Clip-Mod" technique thus appears useful for anterior communicating artery aneurysms. Clip-Mod could also be considered for treating other aneurysms when the "perfect" length clip is not available.

Gross Total Resection of a Grade IV Astrocytoma Adjacent to the Precentral Gyrus With Nonawake Motor Mapping and Motor-Evoked Potential Monitoring: 3-Dimensional Operative Video

Surgical treatment of the gliomas located in or adjacent to the eloquent areas poses significant challenge to neurosurgeons. The main goal of the surgery is to achieve maximal safe resection while preserving the neurological function. This might be possible with utilizing pre- and intraoperative adjuncts such as functional magnetic resonance imaging (MRI), image guidance, mapping of the function of interest, intraoperative MRI, and neurophysiological monitoring. In this video, we demonstrate the utilization of nonawake mapping and motor-evoked potential (MEP) monitoring for the resection of a right-sided posterior superior frontal gyrus grade IV astrocytoma adjacent to the primary motor cortex. The patient is a 69-yr-old woman presented with multiple episodes of simple partial seizures involving her left leg and spreading to the left arm. MRI and functional MRI examinations showed a heterogeneously enhancing mass with peritumoral edema adjacent to the primary motor cortex. Because the patient did not want to undergo an awake craniotomy, a decision was made to perform the resection of the tumor with nonawake motor mapping and continuous MEP monitoring. Nonawake motor mapping and MEP monitoring enabled us to perform gross total resection. Because it has been shown that supratotal resection may provide improved survival outcome,1,2 we extended the white matter resection beyond the contrast enhancing area in noneloquent parts of the tumor. Surgical steps in dealing with vascular anatomy as well as utilizing intraoperative adjuncts such as motor mapping and MEP monitoring to enhance the extent of resection while preserving the function are demonstrated in this 3-dimensional surgical video.  The patient consented to publication of her operative video.

Spontaneous Subarachnoid Hemorrhage From a Pure Pial Arterial Malformation in the Lateral Cerebellomedullary Junction: Clinical Images with a Surgical Video

Pure pial arterial malformations (PAMs) are poorly understood owing to the limited number of reported cases. Because PAMs have been thought to have a benign natural history, they have generally been managed conservatively, unlike arteriovenous malformations or arteriovenous fistulas. In the present report, we have described a spontaneous subarachnoid hemorrhage from the rupture of a PAM at the cerebellomedullary junction. This hemorrhage was surgically treated using clip trapping.

Hydrocephalus Following Giant Transosseous Vertex Meningioma Resection

Introduction  Meningiomas are among the most common primary intracranial tumors. While well-described, there is limited information on the outcomes and consequences following treatment of giant-sized vertex-based meningiomas. These meningiomas have specific risks and potential complications due to their size, location, and involvement with extracalvarial soft tissue and dural sinuses. Herein, we present four giant-sized vertex transosseous meningioma cases with involvement and occlusion of the sagittal sinus, that postoperatively developed external hydrocephalus and ultimately required shunting. Methods  A retrospective chart review identified patients with large vertex meningiomas that were: (1) large (>6 cm) with hemispheric (no skull base) location, (2) involvement of the superior sagittal sinus resulting in complete sinus occlusion, (3) involvement of dura resulting in a large duraplasty area, (4) transosseous involvement requiring a 5 cm or larger craniectomy for resection of invaded calvarial bone. Results  Tumors were resected in all four cases, with all patients subsequently developing external hydrocephalus which required shunting within 2 weeks to 6 months postsurgery. Conclusion  We believe this may be the first report of the development of hydrocephalus following surgical resection of these large lesions. Based on our observations, we propose that a combination of superior sagittal sinus occlusion and changes in brain elasticity and compliance affect the brain's CSF absorptive capacity, which ultimately lead to hydrocephalus development. We suggest that neurosurgeons be aware that postoperative hydrocephalus can quickly develop following treatment of giant-sized vertex-based meningiomas, and that correction of hydrocephalus with shunting can readily be achieved.

Delayed Onset Abducens Nerve Palsy following Uncomplicated Large Cystic Vestibular Schwannoma Resection: Case Report

Although delayed facial palsy after vestibular schwannoma (VS) surgery is a poorly understood but a well-known phenomenon, other delayed cranial nerve palsies in the cerebellopontine angle have not been reported after VS surgery. In this report, we describe a 54-year-old woman with a large cystic VS who experienced double vision and a new delayed onset right abducens nerve (AbN) palsy, 3 weeks after gross total resection of VS via a translabyrinthine approach. To the best of our knowledge, this is the first report describing delayed isolated AbN palsy after uncomplicated VS surgery. Magnetic resonance imaging findings and the management of this complication following VS surgery are discussed in this case report.

Minimizing Retraction by Pia-Arachnoidal 10-0 Sutures in Intrasulcal Dissection

BACKGROUND

In contemporary microneurosurgery reducing retraction-induced injury to the brain is essential. Self-retaining retractor systems are commonly used to improve visualization and decrease the repetitive microtrauma, but sometimes self-retaining retractor systems can be cumbersome and the force applied can cause focal ischemia or contusions. This may increase the morbidity and mortality. Here, we describe a technique of retraction using 10-0 sutures in the arachnoid.

OBJECTIVE

To evaluate the imaging and clinical results in patients where 10-0 suture retraction was used to aid the surgical procedure.

METHODS

Adjacent cortex was retracted by placing 10-0 nylon suture in the arachnoid of the bank or banks of the sulcus. The suture was secured to the adjacent dural edge by using aneurysm clips, allowing for easy adjustability of the amount of retraction. We retrospectively analyzed the neurological outcome, signal changes in postoperative imaging, and ease of performing surgery in 31 patients with various intracranial lesions including intracranial aneurysms, intra- and extra-axial tumors, and cerebral ischemia requiring arterial bypass.

RESULTS

Clinically, there were no injuries, vascular events, or neurological deficits referable to the relevant cortex. Postoperative imaging did not show changes consistent with ischemia or contusion due to the retraction. This technique improved the visualization and illumination of the surgical field in all cases.

CONCLUSION

Retraction of the arachnoid can be used safely in cases where trans-sulcal dissection is required. This technique may improve initial visualization and decrease the need for dynamic or static retraction.

Revascularization for Cerebral Ischemia, Step-by-Step Demonstration of Bonnet Bypass: 3-Dimensional Operative Video

The superficial temporal artery (STA) to the middle cerebral artery (MCA) bypass is the most common bypass type for revascularization to treat cerebral ischemia. If the ipsilateral STA is not available for anastomosis, various options for bypass conduits can be exercised. When the entire ipsilateral external carotid and its branches are not available, the contralateral STA may be used as a donor artery through an interposition graft. This technique is known as a "bonnet bypass." In this video, we demonstrate the utilization of a bonnet bypass in a 48-yr-old man with protein S deficiency, and right carotid artery occlusion with recurrent strokes and transient ischemic attacks (TIA). After exhausting nonsurgical options by treating with 2 antiplatelet drugs and supportive lifestyle changes, the patient continued to experience TIAs and watershed strokes in the right hemisphere. Angiography showed that the right anterior artery and the MCA were filled through the Circle of Willis, but the ipsilateral STA and entire external and common carotid arteries were not patent for potential use as a bypass donor. Since the ipsilateral bypass options were not available, we elected to perform a bypass from the contralateral STA trunk to the ipsilateral M2 with a saphenous vein interposition graft, for a so-called bonnet bypass. The patient did well after surgery and has remained symptom-free for 19 mo post bypass. The surgical technique and each step in performing this bonnet bypass are demonstrated in this 3-dimensional video. The patient consented to the publication of his operative video.