Faculty Bibliography

A man in his 50s presented 1 month after an automobile accident with worsening headaches and an enlarging chronic left subdural haematoma (SDH). He underwent left middle meningeal artery (MMA) embolisation. Due to tortuosity at its origin, we were unable to catheterise the MMA distally. Only proximal coil occlusion at the origin was performed. Follow-up interval head CT showed an increase in the size of the SDH with new haemorrhage, worsening mass effect and midline shift. However, he remained neurologically intact. Contralateral embolisation of the right MMA was performed with a liquid embolic agent. His headaches improved, and a follow-up head CT 3 months later showed near-complete resolution of the SDH.

OBJECTIVE:The extradural anterior petrosectomy is a widely used skull base approach to the upper petroclival region, basilar trunk, and ventral pons. However, there is significant procedure-related morbidity and a complete petrosectomy is required, as the intradural structures are not in view at the time of drilling. We describe an intradural anterior petrosectomy for aneurysms of the basilar trunk and anterior inferior cerebellar artery with intraoperative photographs and artwork to illustrate the approach. METHODS:A temporal craniotomy is made at the root of the zygoma and middle fossa floor. After opening dura, the trochlear nerve is identified at the tentorial edge. The tentorium is incised posterior to the trochlear nerve and the incision is carried forward across the cisternal segment of the trigeminal nerve toward V3 and the superior petrosal sinus. The petrous apex is identified and drilled lateral and posterior to V3 with a diamond bur. Intraoperative navigation is useful to confirm its location. Once posterior fossa dura is identified, the superior petrosal sinus may be safely cauterized and divided, connecting the tentorial incision with an incision in the posterior fossa dura, and exposing the upper basilar trunk and its branches. Additional bone is removed only as needed. RESULTS:Two patients underwent successful treatment of a basilar trunk perforator and anterior inferior cerebellar artery aneurysm with a subtemporal approach and tailored intradural petrosectomy. CONCLUSIONS:The intradural anterior petrosectomy allows limited drilling of the petrous apex and provides sufficient exposure of upper basilar artery aneurysms.

BACKGROUND:Brainstem cavernous malformations with symptomatic hemorrhage have a poor natural history. Those without a pial or ependymal presentation are often observed given the morbidity of resection. Surgical removal is considered only in patients with accessible lesions that have repeated symptomatic hemorrhagic. OBJECTIVE:To describe a novel supracerebellar infratentorial infratrochlear trans-quadrangular lobule approach to safely resect lesions in the upper pons. METHODS:We use a hybrid paramedian/lateral suboccipital craniotomy in the gravity-dependent supine position. Opening the cerebellomesencephalic fissure over the tentorial surface of the cerebellum brings the trochlear nerve, branches of the superior cerebellar artery, and the quadrangular lobule of the cerebellum into view. Removal of small a portion of the quadrangular lobule defines an entry point on the superomedial aspect of the middle cerebellar peduncle, and a surgical trajectory aimed superior to inferior. RESULTS:A total of 6 patients underwent this approach. All presented with symptomatic hemorrhage and all cavernous malformations were completely resected. Five patients were improved or unchanged with modified Rankin scale scores of 1 or 2. CONCLUSION/CONCLUSIONS:The trans-quadrangular lobule approach allows safe resection of upper pontine cavernous malformations along a superior to inferior trajectory.

Brain arteriovenous malformations are an important cause of intracerebral hemorrhage in the young. Ruptured AVM's are often treated, as the risk of rebleeding is high. The treatment of incidentally discovered, unruptured AVMs is controversial as the morbidity and mortality of treatment may exceed that of the AVM's natural history. Management is multimodal and includes observation with follow up, as well as microsurgical resection, endovascular embolization, and stereotactic radiosurgery. Multidisciplinary teams are important in evaluating patients for treatment. The goal of treatment is complete AVM obliteration while preserving neurologic function.

Cerebral revascularization utilizing a variety of bypass techniques can provide either flow augmentation or flow replacement in the treatment of a range of intracranial pathologies, including moyamoya disease, intracranial atherosclerotic disease, and complex aneurysms that are not amenable to endovascular or simple surgical techniques. Though once routine, the publication of high-quality prospective evidence, along with the development of flow-diverting stents, has limited the indications for extracranial-to-intracranial (EC-IC) bypass. Nevertheless, advances in imaging, assessment of cerebral hemodynamics, and surgical technique have changed the risk-benefit calculus for EC-IC bypass. New variations of revascularization surgery involving multiple anastomoses, flow preserving solutions, IC-IC constructs, and posterior circulation bypasses have been pioneered for otherwise difficult to treat pathology including giant aneurysms, dolichoectasia, and medically refractory intracranial atherosclerosis. This review provides a practical update on recent advances in adult intracranial bypass surgery.

Despite a variety of treatment options for brain arteriovenous malformations (bAVMs), many lesions remain challenging to treat and present significant ongoing risk for hemorrhage. In Vitro investigations have recently led to a greater understanding of the formation, growth, and rupture of bAVMs. This has, in turn, led to the development of therapeutic targets for medications for bAVMs, some of which have begun testing in clinical trials in humans. These include bevacizumab, targeting the vascular endothelial growth factor driven angiogenic pathway; thalidomide or lenalidomide, targeting blood-brain barrier impairment; and doxycycline, targeting matrix metalloproteinase overexpression. A variety of other medications appear promising but either requires adaptation from other disease states or development from early bench studies into the clinical realm. This review aims to provide an overview of the current state of development of medications targeting bAVMs and to highlight their likely applications in the future.

Odontoid fractures are common cervical spine fractures and lead to atlantoaxial instability depending on their type. Fractures through the base of the odontoid neck are considered for surgery. While the management of these fractures is controversial and may include external immobilization or posterior fusion, an odontoid screw offers the advantages of directly crossing the fracture site while preserving motion at C1-2. Although intraoperative navigation is routinely utilized in spine surgery, there are few reports of navigated anterior odontoid screw placement. In this report, we describe the safe and accurate placement of two anterior odontoid screws using the O-arm navigation system in an octogenarian with a type II odontoid fracture. Details of the technical approach are also provided. The follow-up imaging at three months confirmed the healing of the fracture. Intraoperative navigation using the O-arm system allows for safe and accurate placement of two odontoid screws.

BACKGROUND:The extent of obliteration of ruptured intracranial aneurysms treated with coil embolization has been correlated with the risk of rerupture. However, many practitioners consider that a small neck remnant is unlikely to result in significant risk after coiling. OBJECTIVE:To report our recent experience with ruptured anterior cerebral artery aneurysms treated with endovascular coiling, which recurred or reruptured, requiring microsurgical clipping for subsequent treatment. METHODS:Retrospective review of patients with intracranial aneurysms treated at our institution since August 2018. Patient and aneurysm characteristics, initial and subsequent treatment approaches, and outcomes were reviewed. RESULTS:Six patients were included. Out of those 6 patients, 5 patients had anterior communicating artery aneurysms, and 1 patient had a pericallosal aneurysm. All initially presented with subarachnoid hemorrhage (SAH) and were treated with coiling. Recurrence occurred at a median of 7.5 mo. In 2 cases, retreatment was initially performed with repeat endovascular coiling, but further recurrence was observed. Rerupture from the residual or recurrent aneurysm occurred in 3 cases. In 2 cases, the aneurysm dome recurred; in 1 case, rerupture occurred from the neck. All 6 patients underwent treatment with microsurgical clipping. Follow-up catheter angiography demonstrated a complete occlusion of the aneurysm in all cases with the preservation of the parent vessel. CONCLUSION/CONCLUSIONS:Anterior cerebral artery aneurysms may recur after endovascular treatment, and even small neck remnants present a risk of rerupture after an initial SAH. Complete treatment requires a complete exclusion of the aneurysm from the circulation. Even in cases that have been previously coiled, microsurgical clipping can represent a safe and effective treatment option.

BACKGROUND AND PURPOSE:Extracranial-to-intracranial (EC-IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC-IC bypass. METHODS:Three consecutive patients undergoing EC-IC bypass for carotid occlusion were evaluated pre- and postoperatively using CVR testing with pre- and poststimulus 4D flow-MRI for assessment of the bypass graft and intracranial vasculature. RESULTS:Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC-IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10-80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels. CONCLUSION:Four-dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra- and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC-IC bypass.

BACKGROUND:The superficial temporal artery-middle cerebral artery (STA-MCA) bypass augments blood flow in patients with cerebral ischemia or replaces flow in patients with complex aneurysms or skull base tumors requiring vessel sacrifice. METHOD:We provide a description of the STA-MCA bypass with figures and video to illustrate the procedure. CONCLUSION:The STA-MCA end-to-side anastomosis is a foundational skill for the cerebrovascular surgeon and a building block for more complex bypasses.