Matthew E. Welz

Photoacoustic Imaging for Maximizing Glioma Resection

Increased extent of resection for both lowand high-grade gliomas has been shown to improve progression-free and overall survival. An extent of resection >98% or a contrast-enhancing residual tumor volume of <2 cm has been shown to significantly increase survival for patients with glioblastoma multiforme. Similarly, residual tumor volume of <15 cm improves survival for patients with low-grade gliomas. Current modalities used to maximize resection are 5-aminolevulinic acid (5-ALA) fluorescence and intraoperative magnetic resonance imaging (MRI). 5-ALA-fluorescence-guided resections have been shown to increase the rate of gross total resection and increase 6-month progression survival in high-grade gliomas but require the use of the 5-ALA dye, which can cause skin photosensitivity during and after surgery. The use of intraoperative MRI allows increased resection volumes comparable with those achieved using 5-ALA florescence but requires expensive infrastructure investments and is time consuming. Further modalities are certainly welcome toward realizing the goal of maximal tumor removal while minimizing additional time, cost, and procedure sequela. Photoacoustic imaging (PAI) is an experimental imaging modality that allows interrogation of matter at the molecular level. Derivatives of the technique include photoacoustic tomography (PAT) and multiphoton photoacoustic spectroscopy (MPS). These modalities use a laser to excite molecules (for instance, photon activation), which subsequently undergo characteristic nonradiative decay, producing ultrasonic waves dependent on the molecules excited. The key advantage of PAI over other imaging modalities is the ability to detect chemical species with cellular level accuracy. The technique has been used to localize brain activity in mice in vivo by measuring hemodynamic changes due to metabolic activity and is beginning to find clinical application in breast imaging. High-resolution vascular imaging in mice and humans using PAT has also been achieved. The potential of PAI to investigate brain tissue intraoperatively with cellular-level resolution could allow surgeons to detect low concentrations of malignant cells not visible via other modalities, resulting in more precise and extensive resections of gliomas, as well as differentiate between white and gray matter. Confocal microscopy in conjunction with dyes like 5-ALA is also capable of high-resolution imaging and identification of histologic features but requires contrast agents, whereas PAI does not. In a recent issue of Biomedical Optics, Dahal and Cullum investigated the ability of MPS to distinguish between healthy and malignant brain tissue in vitro. Twelve matched pairs of

Synthetic Replica for Training in Microsurgical Anastomosis: An Important Frontier in Neurosurgical Education

Medical education has evolved through the years, moving away from the Halstedian apprenticeship model. The medical governing bodies involved in medical graduate education have established a set of rulings and recommendations focused on improving patient safety and curbing resident fatigue including limiting work hours to 80 h a week. In addition to duty hour regulations, decreasing volumes and dilution of surgical cases among an increasing number of tertiary care centers have raised concern about the ability of residents to achieve appropriate levels of competency by the time of graduation. Therefore, simulation has seen an increased role in education in the last decade.

Complication Avoidance and Management Research

Complication avoidance is a major consideration with any surgical procedure, and evaluation of complications relies on clear definitions. However, defining what constitutes a complication can be difficult, as perspectives on errors of commission or omission often vary between providers and patients. Here, we present a concise analysis of complications related to neurovascular surgery (defined as any procedural care of patients with neurovascular diseases) and provide a framework for approaching research efforts. This is done by considering opportunities in disease screening and patient selection, perioperative morbidity reduction, and follow-up. In addition, the concept of complication avoidance through surgical simulation is briefly dealt with. This chapter is intended to serve as an initial reference point for the young neurovascular specialist for developing and elaborating on the concept of complication avoidance through various techniques of research.

New generation Hydrogel Endovascular Aneurysm Treatment Trial (HEAT): a study protocol for a multicenter randomized controlled trial

PurposeAneurysm recanalization constitutes a limitation in the endovascular treatment of intracranial aneurysms using conventional bare platinum coils. The development of platinum coils coupled with hydrogel polymers aimed at decreasing the rates of recurrence by way of enhanced coil packing density and biological healing within the aneurysm. While enhanced occlusion and durability has been shown for the first generation hydrogel coils, their use was limited by technical challenges. Less data is available regarding the second-generation hydrogel coils which have been designed to perform like bare platinum coils.MethodsThe new generation Hydrogel Endovascular Aneurysm Treatment Trial (HEAT) is a multicenter, randomized controlled trial that compares the health outcomes of the second-generation HydroCoil Embolic System with bare platinum coils in the endovascular intracranial aneurysms. The primary endpoint is aneurysm recurrence, defined as any progression on the Raymond aneurysm scale, over a 24-month follow-up period. Secondary endpoints include packing density, functional independence, procedural adverse events, mortality rate, initial complete occlusion, aneurysm retreatment, hemorrhage from treated aneurysm, and any aneurysm recurrence.ResultsPatient recruitment initiated in June 2011 and ended in January 2016 in 46 centers. Six hundred eligible patients diagnosed with an intracranial aneurysm, ruptured or unruptured were randomly assigned to one of the two treatment arms.ConclusionThe HEAT trial compares the durability, imaging, and clinical outcomes of the second-generation hydrogel versus bare platinum coils in the endovascular treatment of ruptured or unruptured intracranial aneurysms. The results of this trial may further inform current endovascular treatment guidelines based on observed long-term outcomes.

Awake Surgery for Brain Vascular Malformations and Moyamoya Disease

OBJECTIVEnAlthough a significant amount of experience has accumulated for awake procedures for brain tumor, epilepsy, and carotid surgery, its utility for intracranial neurovascular indications remains largely undefined. Awake surgery for select neurovascular cases offers the advantage of precise brain mapping and robust neurologic monitoring during surgery for lesions in eloquent areas, avoidance of potential hemodynamic instability, and possible faster recovery. It also opens the window for perilesional epileptogenic tissue resection with potentially less risk for iatrogenic injury.nnnMETHODSnInstitutional review board approval was obtained for a retrospective review of awake surgeries for intracranial neurovascular indications over the past 36 months from a prospectively maintained quality database. We reviewed patients clinical indications, clinical and imaging parameters, and postoperative outcomes.nnnRESULTSnEight consecutive patients underwent 9 intracranial neurovascular awake procedures conducted by the senior author. A standardized sedated-awake-sedated protocol was used in all 8 patients. For the 2 patients with arteriovenous malformations and the 3 patients with cavernoma, awake brain surface and white matter mapping was performed before and during microsurgical resection. Axa0neurological examination was obtained periodically throughout all 5 procedures. There were no intraoperative orxa0perioperative complications. Hypotension was avoided during the 2 Moyamoya revascularization procedures in the patient with a history of labile blood pressure. Postoperative imaging confirmed complete arteriovenous malformation and cavernoma resections. No new neurologic deficits or new-onset seizures were noted on 3-month follow-up.nnnCONCLUSIONSnAwake surgery appears to be safe for select patients with intracranial neurovascular pathologies. Potential advantages include greater safety, shorter length of stay, and reduced cost.

Bioresorbable Intracranial Sensors: A New Frontier for Neurosurgeons

The management of brain, spinal cord, and peripheral nerve disorders and injury may benefit from more robust continuous monitoring. Implantation of biosensors is limited by the risk of infection and the need for a second procedure to extract the sensor. Bioresorbable sensors are electronic sensors that can run the required functional course in the body but eliminate via absorption over a reasonable period of time. If properly designed, bioresorbable sensors promise to overcome the limitations of current sensors and reduce the threshold for continuous monitoring.