Faculty Bibliography

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.

BACKGROUND:Aneurysms associated with brain arteriovenous malformations (AVMs) represent a hemorrhage risk in addition to that of the AVM nidus. In high-risk or unresectable cases, targeted treatment of an aneurysm causing hemorrhage may effectively decrease future hemorrhage risk. The objective of this report is to describe our series of patients with intraventricular AVM-associated aneurysms treated surgically. We highlight technical nuances of the surgical approaches to aneurysms in the lateral and third ventricles. METHODS:A retrospective review was performed of patients in whom an intraventricular aneurysm rupture was responsible for hemorrhage. In each patient, the aneurysm was excluded surgically via an interhemispheric approach, including transcallosal, transchoroidal, or transcingulate corridors. Aneurysm, AVM characteristics, surgical approach, and outcomes were reviewed. RESULTS:Six patients were included in the series. In 5 patients, the disease was located on the left and approached from the right. Aneurysms were located in, or projecting into, the lateral ventricle in 4 patients (transcingulate approach) and in the third ventricle in 2 patients (transchoroidal fissure approach). The aneurysm was clipped in 1 patient and resected in 5 patients. The associated AVM was resected in 2 patients. In all patients, the surgical approach allowed adequate treatment of the aneurysm without new neurologic morbidity. No patients experienced recurrent intraventricular hemorrhage during follow-up. CONCLUSIONS:Ruptured intraventricular aneurysms associated with brain AVMs can be treated surgically to reduce the risk of rebleeding in patients in whom the aneurysms are not accessible to endovascular treatment and in which the AVM nidus may not be safely resected.