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Howard A. Riina and Y. Pierre Gobin

The treatment of arteriovenous malformations (AVMs) has evolved over the last 40 years. These complex vascular lesions remain among the most difficult lesions to treat. Successful treatment of AVMs of the brain includes extensive preoperative planning, multimodality treatment options, and modern postoperative surgical care. The advent of new technologies, including interventional neuroradiology and radiosurgery, has expanded the range of malformations that can be treated effectively and has had a significant impact on those individuals who manifest this disease process. The purpose of this paper is to describe the current grading technique used by the authors and to explore the preoperative treatment and planning that leads to successful surgical obliteration of these lesions. Some description of preoperative interventions, including radiosurgery and interventional procedures will be mentioned; however, only in the context of how they impact on the surgical treatment of these lesions. In other articles in this edition of Neurosurgical Focus interventional procedures and radiosurgery as treatment adjuncts and as primary therapies will be discussed in greater detail.

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Editorial

Unruptured aneurysms

Howard A. Riina and Robert F. Spetzler

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Jason M. Schwalb, Howard A. Riina, Brett Skolnick, Jurg L. Jaggi, Tanya Simuni and Gordon H. Baltuch

✓ The treatment of essential tremor with thalamic deep brain stimulation (DBS) is considered to be more effective and to cause less morbidity than treatment with thalamotomy. Nonetheless, implantation of an indwelling electrode, connectors, and a generator is associated with specific types of morbidity. The authors describe three patients who required revision of their DBS systems due to lead breakage. The connector between the DBS electrode and the extension wire, which connects to the subclavicular pulse generator, was originally placed subcutaneously in the cervical region to decrease the risk of erosion through the scalp and to improve cosmesis. Three patients presented with fractured DBS electrodes that were located in the cervical region near the connector, necessitating reoperation with stereotactic retargeting and placement of a new intracranial electrode. At reoperation, the connectors were placed subgaleally over the parietal region.

Management of these cases has led to modifications in the operative procedure designed to improve the durability of DBS systems. The authors recommend that surgeons avoid placing the connection between the DBS electrode and the extension wire in the cervical region because patient movement can cause microfractures in the electrode. Such microfractures require intracranial revision, which may be associated with a higher risk of morbidity than the initial operation. The authors also recommend considering prophylactic relocation of the connectors from the cervical area to the subgaleal parietal region to decrease the risk of future DBS electrode fracture, which would necessitate a more lengthy procedure to revise the intracranial electrode.

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Marc L. Otten, Howard A. Riina, Y. Pierre Gobin and Mark M. Souweidane

✓ The authors report a case of preoperative embolization and resection of a choroid plexus papilloma of the lateral ventricle in a 4-month-old boy. These vascular tumors of the central nervous system present a significant intraoperative bleeding risk. Attempts at preoperative embolization to reduce the bleeding risk have rarely succeeded because of the small and tortuous vessels feeding these tumors in infants. The case presented here supports the feasibility of preoperative embolization as a therapeutic adjunct in infants.

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Matthew B. Potts, Daniel W. Zumofen, Eytan Raz, Peter K. Nelson and Howard A. Riina

Endovascular embolization is typically reserved as an adjuvant therapy in the management of cerebral arteriovenous malformations (AVMs), either for preoperative devascularization or preradiosurgical volume reduction. Curative embolization plays a limited role in AVM treatment but several studies have shown that it is possible, especially with later-generation liquid embolic agents. Given the complexity of AVM anatomy and the recent controversies over the role of any intervention in AVM management, it is critical that the cerebrovascular community better define the indications of each treatment modality to provide quality AVM management. In this review, the authors evaluate the role of curative AVM embolization. Important considerations in the feasibility of curative AVM embolization include whether it can be performed reliably and safely, and whether it is a durable cure. Studies over the past 20 years have begun to define the anatomical factors that are amenable to complete endovascular occlusion, including size, feeding artery anatomy, AVM morphology, and endovascular accessibility. More recent studies have shown that highly selected patients with AVMs can be treated with curative intent, leading to occlusion rates as high as 100% of such prospectively identified lesions with minimal morbidity. Advances in endovascular technology and techniques that support the efficacy and safety of curative embolization are discussed, as is the importance of superselective diagnostic angiography. Finally, the durability of curative embolization is analyzed. Overall, while still unproven, endovascular embolization has the potential to be a safe, effective, and durable curative treatment for select AVMs, broadening the armamentarium with which one can treat this disease.

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Daniel L. Barrow

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Robert F. Spetzler, Paul W. Detwiler, Howard A. Riina and Randall W. Porter

The literature on spinal vascular malformations contains a great deal of confusing terminology. Some of the nomenclature is inconsistent with the lesions described. Based on the experience of the senior author (R.F.S.) in the treatment of more than 130 spinal cord vascular lesions and based on a thorough review of the relevant literature, the authors propose a modified classification system for spinal cord vascular lesions.

Lesions are divided into three primary or broad categories: neoplasms, aneurysms, and arteriovenous lesions. Neoplastic vascular lesions include hemangioblastomas and cavernous malformations, both of which occur sporadically and familially. The second category consists of spinal aneurysms, which are rare. The third category, spinal cord arteriovenous lesions, is divided into arteriovenous fistulas and arteriovenous malformations (AVMs). Arteriovenous fistulas are subdivided into those that are extradural and those that are intradural, with intradural lesions categorized as either dorsal or ventral. Arteriovenous malformations are subdivided into extradural-intradural and intradural malformations. Intradural lesions are further divided into intramedullary, intramedullary-extramedullary, and conus medullaris, a new category of AVM.

This modified classification system for vascular lesions of the spinal cord, based on pathophysiology, neuroimaging features, intraoperative observations, and neuroanatomy, offers several advantages. First, it includes all surgical vascular lesions that affect the spinal cord. Second, it guides treatment by classifying lesions based on location and pathophysiology. Finally, it eliminates the confusion produced by the multitude of unrelated nomenclatural terms found in the literature.

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Rajeev D. Sen, Carolina Gesteira Benjamin, Howard A. Riina and Donato Pacione

The authors report on an 81-year-old woman with a pathologic hangman's fracture secondary to a complex arteriovenous fistula (AVF). The patient presented with severe, unremitting neck pain and was found to have fractures bilaterally through the pars interarticularis of C-2 with significant anterior subluxation of C-2 over C-3 along with widening of the left transverse foramen. Due to an abnormally appearing left vertebral artery (VA) on CT angiography, the patient underwent conventional angiography, which revealed a complex AVF stemming from the left VA at the level of C-2 with dilated posterior cervical veins and a large venous varix. Given the radiographic evidence of bone remodeling and the chronicity of the AVF, it is believed that the C-2 vertebra was weakened over time by the pulsatile and compressive force of the vascular malformation eventually leading to fracture with minimal stress. Coil embolization of the AVF was performed followed by surgical fixation of C-1 to C-4. This case highlights the importance of investigating an underlying disease process in patients who present with significant spinal fractures in the absence of trauma.

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David Wells-Roth, Alessandra Biondi, Vallabh Janardhan, Kyle Chapple, Y. Pierre Gobin and Howard A. Riina

Wide-necked aneurysms remain difficult to treat by either open microneurosurgical or endovascular procedures. Recent advances in the latter technology, including intracranial stents and bioactive coils, now allow an endovascular treatment option for cases in which this was not previously available. In this report the authors describe the new developments in endovascular technologies that make the treatment of wide-necked aneurysms possible. This includes discussion of intracranial stents and bioactive coils designed to promote obliteration of the aneurysm lumen. In addition, methods for coil insertion in wide-necked aneurysms are described, including balloon remodeling and various stent placement procedures. Wide-necked aneurysms previously thought to be untreatable by endovascular means can now be obliterated, thanks to new devices specifically designed for intracranial use.