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Achal S. Achrol, Raphael Guzman, Marco Lee and Gary K. Steinberg

Moyamoya disease is an uncommon cerebrovascular condition characterized by progressive stenosis of the bilateral internal carotid arteries with compensatory formation of an abnormal network of perforating blood vessels providing collateral circulation.

The etiology and pathogenesis of moyamoya disease remain unclear. Evidence from histological studies, proteomics, and endothelial progenitor cell analyses suggests new theories underlying the cause of vascular anomalies, including moyamoya disease.

Familial moyamoya disease has been noted in as many as 15% of patients, indicating an autosomal dominant inheritance pattern with incomplete penetrance. Genetic analyses in familial moyamoya disease and genome-wide association studies represent promising strategies for elucidating the pathophysiology of this condition.

In this review, the authors discuss recent studies that have investigated possible mechanisms underlying the etiology of moyamoya disease, including stem cell involvement and genetic factors. They also discuss future research directions that promise not only to offer new insights into the origin of moyamoya disease but to enhance our understanding of new vessel formation in the CNS as it relates to stroke, vascular anomalies, and tumor growth.

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Anand Veeravagu, Marco Lee, Bowen Jiang and Steven D. Chang

The treatment of craniopharyngiomas is composed of an intricate balance of multiple modalities. Resection and radiotherapy have been combined to synergistically control tumor growth while preventing undue harm to crucial neurovascular structures. Although a craniopharyngioma is a benign lesion pathologically, it may induce severe neurological injury due to its location and rate of growth. More recently, the advent of targeted, fractionated radiotherapy has allowed for more aggressive tumor control while reducing the necessity for large resections. Initial studies have demonstrated significant tumor control in patients who are treated with resection combined with radiation therapy, versus surgery alone, with a lower rate of treatment-associated neurological deficits. In this review, a detailed account of the current studies evaluating the role of stereotactic radiosurgery in the management of craniopharyngiomas is presented. The authors also provide a short account of their experience to aid in defining the role of CyberKnife radiosurgery.

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Ramiro Del Valle, Marco Zenteno, José Jaramillo, Angel Lee and Salvador De Anda

Object

The cumulative experience worldwide indicates complete radiosurgical obliteration rates of brain arteriovenous malformations (AVMs) ranging from 35 to 90%. The purpose of this study was to propose a strategy to increase the obliteration rate for AVMs through the dynamic definition of the key target volume (KTV).

Methods

A prospective series of patients harboring an AVM was assessed using digital subtraction angiography in which a digital counter was used to measure the several stages of the frame-by-frame circulation time. All the patients were analyzed using dynamic measurement planning to define the KTV, corresponding to the volume of the shunt with the least vascular resistance and the earliest venous drainage. All patients underwent catheter-based angiography, a subgroup was additionally assessed by means of a superselective catheterization, and among these a further subgroup received embolization. The shunts were also categorized according to their angioarchitectural type: fistulous, plexiform, or mixed. The authors applied the radiosurgery-based grading system (RBGS) as well to find a correlation with the obliteration rate.

Results

This series includes 44 patients treated by radiosurgery; global angiography was performed for all patients, including dynamic measurement planning. Eighty-four percent of them underwent superselective catheterization, and 50% of the total population underwent embolization. In the embolized arm of the study, the pretreatment volume was up to 120 ml. In patients with a single treatment, the mean volume was 8.5 ml, and the median volume was 6.95 ± 4.56 ml (mean ± standard deviation), with a KTV of up to 15 ml. For prospectively staged radiosurgery, the mean KTV was 28 ml. The marginal radiation dose was 18–22 Gy, with a mean of dose 20 Gy. The mean RBGS score was 1.70. The overall obliteration rate was 91%, including the repeated radiosurgery group (4 patients), in which 100% showed complete obliteration. The overall permanent deficit was 2 of 44 patients, 1 in each group.

Conclusions

Dynamic definition of the KTV might increase the obliteration rate, even in complex AVMs, allowing the treatment of smaller volumes off the recruitment vessels (pseudonidus). By using this technique, the authors avoided double-blind treatment, where the neurosurgeon does not know precisely which type of lesion he or she is irradiating and the interventionalist does not know why and what he or she is embolizing.

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Ahmet Arac, Vanessa Blanchard, Marco Lee and Gary K. Steinberg

Object

Decompressive surgery can be life saving after malignant cerebral infarction. However, severe residual disability occurs in a significant number of surviving patients. Most discussion about the benefits of surgery is based on studies performed in patients who are ≤ 60 years of age. Less is known about the benefits of the procedure in the elderly population. The authors undertook a review of the literature on decompressive craniectomy for malignant cerebral infarction and compared the mortality and outcome data published in patients older and younger than 60 years of age. The authors discuss their analysis, with specific reference to the limitations of the studies analyzed, the outcome measures used, and the special considerations required when discussing stroke recovery in the elderly.

Methods

Studies on decompressive craniectomy for malignant middle cerebral artery infarction reported in the English literature were analyzed. A cutoff point for age of > 60 or ≤ 60 years was set, and the study population was segregated. No studies specifically analyzed patients > 60 years old. A total of 19 studies was identified, 10 of which included patients who were > 60 years of age. A comparison between the 2 age groups was made within the 10 studies and also among all the patients in the 19 studies. Mortality rates and outcome scores were assessed for each study, and a Barthel Index (BI) score of < 60 or a modified Rankin Scale (mRS) score of > 3 was considered to represent a poor outcome. Rates were compared using the Fisher exact test, and p values < 0.05 were considered statistically significant.

Results

Nineteen studies were found, which included 273 patients undergoing decompressive craniectomy for malignant cerebral infarcts. Ten of these studies included 73 patients (26.7%) who were > 60 years of age. The mean follow-up times ranged from 5.75 to 12.3 months in the > 60-years group and 4.2 to 28 months in the ≤ 60-years group. The mortality rate was significantly higher, at 51.3% in the > 60-years group (37 of 72 patients) compared with 20.8% (41 of 197 patients) in the ≤ 60-years group (p < 0.0001). Similarly, patients who survived in the > 60-years group had significantly higher rates of poor outcomes, at 81.8% (27 of 33), compared with 33.1% (47 of 142) in the ≤ 60-year-old group (p < 0.0001). The BI was the most commonly used primary outcome measure (15 out of 19 studies), followed by the mRS score, which was used in 4 studies.

Conclusions

The mortality rate and functional outcome, as measured by the BI and mRS, were significantly worse in patients > 60 years of age following decompressive craniectomy for malignant infarction. Age is an important factor to consider in patient selection for surgery. However, cautious interpretation of the results is required because the outcome scores that were used only measure physical disability, whereas other factors, including psychosocial, financial, and caregiver burden, should be considered in addition to age alone.

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Lee M. Burkholder, David A. Houlden, Rajiv Midha, Erin Weiss and Marco Vennettilli

✓ Peripheral nerve graft repair after severe brachial plexus injury is futile if there is degeneration of motor fibers in the proximal nerve stump to which the graft must be attached. Traditional intraoperative neurophysiological assessment methods like nerve action potential (NAP) and somatosensory evoked potential (SSEP) monitoring have been used to evaluate proximal nerve stump integrity, but these methods do not allow evaluation of the integrity of motor fibers back to the anterior horn cell. Consequently, the authors used transcranial electrical stimulation and recorded neurogenic motor evoked potentials (MEPs) directly from the brachial plexus in a patient undergoing surgical repair of a complete upper brachial plexus injury (Erb palsy) to assess the functional continuity of motor fibers. In addition, selected elements of the brachial plexus were directly stimulated, and NAPs were recorded. Finally, SSEPs were recorded from the scalp after stimulation of selected elements of the brachial plexus. Neurogenic MEPs were present from the medial cord of the brachial plexus, but not the middle or upper trunk; NAPs were present from the lateral and posterior cords after middle trunk stimulation, but absent after upper trunk stimulation; and SSEPs were present after medial cord stimulation but absent after stimulation of the upper and middle trunks. For the first time, neurogenic MEPs were coupled with NAPs and SSEPs to evaluate successfully the functional status of motor fibers back to the anterior horn cell for accurate localization of the lesion sites.

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Melanie G. Hayden, Marco Lee, Raphael Guzman and Gary K. Steinberg

Among the relatively few surgeons to be awarded the Nobel Prize was Alexis Carrel, a French surgeon and pioneer in revascularization surgery at the turn of the 20th century. The authors trace the humble beginnings of cerebral revascularization surgery through to the major developments that helped shape the modern practice of cerebral bypass surgery. They discuss the cornerstone studies in the development of this technique, including the Extracranial/Intracranial Bypass Study initiated in 1977. Recent innovations, including modern techniques to monitor cerebral blood flow, microanastomosis techniques, and ongoing trials that play an important role in the evolution of this field are also evaluated.

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Ahmet Arac, Marco Lee, Gary K. Steinberg, Mary Marcellus and Michael P. Marks

Multiple pathophysiological mechanisms have been proposed for the increased intracranial pressure observed in idiopathic intracranial hypertension (IIH). The condition is well characterized, with intractable headaches, visual obscurations, and papilledema as dominant features, mainly affecting obese women. With the advent of MR venography and increased use of cerebral angiography, there has been recent emphasis on the significant number of patients with IIH found to have associated nonthrombotic dural venous sinus stenosis. This has led to a renewed interest in endovascular stenting as a treatment for IIH. However, the assumption that venous stenosis leads to a high pressure gradient that decreases CSF resorption through arachnoid villi requires further evidence. In this paper, the authors analyze the published results to date of dural venous sinus stenting in patients with IIH. They also present a case from their institution for illustration. The pathophysiological mechanism in IIH requires further elucidation, but venous sinus stenosis with subsequent intracranial hypertension appears to be an important mechanism in at least a subgroup of patients with IIH. Among these patients, 78% had complete relief or improvement of their main presenting symptoms after endovascular stenting. Resolution or improvement in papilledema was seen in 85.1% of patients. Endovascular stenting should be considered whenever venous sinus stenosis is diagnosed in patients with IIH.

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Anand Veeravagu, Raphael Guzman, Chirag G. Patil, Lewis C. Hou, Marco Lee and Gary K. Steinberg

✓Neurosurgical interventions for moyamoya disease (MMD) in pediatric patients include direct, indirect, and combined revascularization procedures. Each technique has shown efficacy in the treatment of pediatric MMD; however, no single study has demonstrated the superiority of one technique over another. In this review, the authors explore the various studies focused on the use of these techniques for MMD in the pediatric population. They summarize the results of each study to clearly depict the clinical outcomes achieved at each institution that had utilized direct, indirect, or combined techniques. In certain studies, multiple techniques were used, and the clinical or radiological outcomes were compared accordingly.

Direct techniques have been shown to aid a reduction in perioperative strokes and provide immediate revascularization to ischemic areas; however, these procedures are technically challenging, and not all pediatric patients are appropriate candidates. Indirect techniques have also shown efficacy in the pediatric population but may require a longer period for revascularization to occur and perfusion deficits to be reversed. The authors concluded that the clinical efficacy of one technique over another is still unclear, as most studies have had small populations and the same outcome measures have not been applied. Authors who compared direct and indirect techniques noted approximately equal clinical outcomes with differences in radiological findings. Additional, larger studies are needed to determine the advantages and disadvantages of the different techniques for the pediatric age group.

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Willem Jan Van Rooij, Jo P. Peluso, Menno Sluzewski and Guus N. Beute

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Marco Zenteno, Jorge Santos-Franco, Vladimir Rodríguez-Parra, Jorge Balderrama, Yolanda Aburto-Murrieta, Susana Vega-Montesinos and Ángel Lee

Object

So-called direct carotid-cavernous fistulas (CCFs) are commonly treated by detachable balloons or coils to occlude the shunt while sparing the carotid artery. Liquid embolic agents have been rarely used, and in particular, to the authors' knowledge, the use of Onyx as the sole agent has never been reported in an indexed publication.

Methods

The authors describe a case series of 5 patients with posttraumatic CCF in whom embolization with Onyx was prospectively used as the sole strategy of management.

Results

Complete occlusion was obtained at the end of the procedure in 4 cases, and the lesion in the remaining patient subsequently occluded at the 6-month follow-up evaluation.

Conclusions

As endovascular techniques for treatment of direct CCFs continue to evolve, this novel approach with Onyx as the sole embolic material seems promising in treating these lesions.