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Atman Desai, Kimon Bekelis, Wenyan Zhao, Perry A. Ball and Kadir Erkmen

Object

Stroke is a leading cause of death and disability. Given that neurologists and neurosurgeons have special expertise in this area, the authors hypothesized that the density of neuroscience providers is associated with reduced mortality rates from stroke across US counties.

Methods

This is a retrospective review of the Area Resource File 2009–2010, a national county-level health information database maintained by the US Department of Health and Human Services. The primary outcome variable was the 3-year (2004–2006) average in cerebrovascular disease deaths per million population for each county. The primary independent variable was the combined density of neurosurgeons and neurologists per million population in the year 2006. Multiple regression analysis was performed, adjusting for density of general practitioners (GPs), urbanicity of the county, and socioeconomic status of the residents of the county.

Results

In the 3141 counties analyzed, the median number of annual stroke deaths was 586 (interquartile range [IQR] 449–754), the median number of neuroscience providers was 0 (IQR 0–26), and the median number of GPs was 274 (IQR 175–410) per million population. On multivariate adjusted analysis, each increase of 1 neuroscience provider was associated with 0.38 fewer deaths from stroke per year (p < 0.001) per million population. Rural location (p < 0.001) and increased density of GPs (p < 0.001) were associated with increases in stroke-related mortality.

Conclusions

Higher density of specialist neuroscience providers is associated with fewer deaths from stroke. This suggests that the availability of specialists is an important factor in survival after stroke, and underlines the importance of promoting specialist education and practice throughout the country.

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Kimon Bekelis, Atman Desai, Wenyan Zhao, Dan Gibson, Daniel Gologorsky, Clifford Eskey and Kadir Erkmen

Object

Computed tomography angiography (CTA) is increasingly used as a screening tool in the investigation of spontaneous intracerebral hemorrhage (ICH). However, CTA carries additional costs and risks, necessitating its judicious use. The authors hypothesized that subsets of patients with nontraumatic, nonsubarachnoid ICH are unlikely to benefit from CTA as part of the diagnostic workup and that particular patient risk factors may be used to increase the yield of CTA in the detection of vascular sources.

Methods

The authors performed a retrospective analysis of 1376 patients admitted to Dartmouth-Hitchcock Medical Center with ICH over an 8-year period. Patients with subarachnoid hemorrhage, hemorrhagic conversion of ischemic infarcts, trauma, and known prior malignancy were excluded from the analysis, resulting in 257 patients for final analysis. Records were reviewed for medical risk factors, hemorrhage location, and correlation of CTA findings with final diagnosis. Multiple logistic regression analysis was used to investigate the combined effects of baseline variables of interest. Model selection was conducted using the stepwise method with p = 0.10 as the significance level for variable entry and p = 0.05 the significance level for variable retention.

Results

Computed tomography angiography studies detected vascular pathology in 34 patients (13.2%). Patient characteristics that were associated with a significantly higher likelihood of identifying a structural vascular lesion as the source of hemorrhage included patient age younger than 65 years (OR = 16.36, p = 0.0039), female sex (OR = 14.9, p = 0.0126), nonsmokers (OR = 103.8, p = 0.0008), patients with intraventricular hemorrhage (OR = 9.42, p = 0.0379), and patients without hypertension (OR = 515.78, p < 0.0001). Patients who were older than 65 years of age, with a history of hypertension, and hemorrhage located in the cerebellum or basal ganglia were never found to have an identified structural source of hemorrhage on CTA.

Conclusions

Patient characteristics and risk factors are important considerations when ordering diagnostic tests in the workup of nonsubarachnoid, nontraumatic spontaneous ICH. Although CTA is an accurate diagnostic examination, it can usually be omitted in the workup of patients with the described characteristics. The use of this algorithm has the potential to increase the yield, and thus the safety and cost effectiveness, of this diagnostic tool.

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Atman Desai, Kimon Bekelis and Kadir Erkmen

Effective surgical obliteration of spinal dural arteriovenous fistulas (DAVFs) traditionally requires laminectomy or hemilaminectomy to allow intradural exposure and occlusion of the draining vein. The authors present successful treatment of a spinal DAVF by using a tubular retractor system to provide minimally invasive exposure at the L5–S1 level adequate for both microsurgical treatment and intraoperative indocyanine green angiography.

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Kimon Bekelis, Symeon Missios, Atman Desai, Clifford Eskey and Kadir Erkmen

Object

Microsurgical resection of arteriovenous malformations (AVMs) is facilitated by real-time image guidance that demonstrates the precise size and location of the AVM nidus. Magnetic resonance images have routinely been used for intraoperative navigation, but there is no single MRI sequence that can provide all the details needed for characterization of the AVM. Additional information detailing the specific location of the feeding arteries and draining veins would be valuable during surgery, and this detail may be provided by fusing MR images and MR angiography (MRA) sequences. The current study describes the use of a technique that fuses contrast-enhanced MR images and 3D time-of-flight MR angiograms for intraoperative navigation in AVM resection.

Methods

All patients undergoing microsurgical resection of AVMs at the Dartmouth Cerebrovascular Surgery Program were evaluated from the surgical database. Between 2009 and 2011, 15 patients underwent surgery in which this contrast-enhanced MRI and MRA fusion technique was used, and these patient form the population of the present study.

Results

Image fusion was successful in all 15 cases. The additional data manipulation required to fuse the image sets was performed on the morning of surgery with minimal added setup time. The navigation system accurately identified feeding arteries and draining veins during resection in all cases. There was minimal imaging-related artifact produced by embolic materials in AVMs that had been preoperatively embolized. Complete AVM obliteration was demonstrated on intraoperative angiography in all cases.

Conclusions

Precise anatomical localization, as well as the ability to differentiate between arteries and veins during AVM microsurgery, is feasible with the aforementioned MRI/MRA fusion technique. The technique provides important information that is beneficial to preoperative planning, intraoperative navigation, and successful AVM resection.

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Kimon Bekelis, Pablo A. Valdés, Kadir Erkmen, Frederic Leblond, Anthony Kim, Brian C. Wilson, Brent T. Harris, Keith D. Paulsen and David W. Roberts

Object

Complete resection of skull base meningiomas provides patients with the best chance for a cure; however, surgery is frequently difficult given the proximity of lesions to vital structures, such as cranial nerves, major vessels, and venous sinuses. Accurate discrimination between tumor and normal tissue is crucial for optimal tumor resection. Qualitative assessment of protoporphyrin IX (PpIX) fluorescence following the exogenous administration of 5-aminolevulinic acid (ALA) has demonstrated utility in malignant glioma resection but limited use in meningiomas. Here the authors demonstrate the use of ALA-induced PpIX fluorescence guidance in resecting a skull base meningioma and elaborate on the advantages and disadvantages provided by both quantitative and qualitative fluorescence methodologies in skull base meningioma resection.

Methods

A 52-year-old patient with a sphenoid wing WHO Grade I meningioma underwent tumor resection as part of an institutional review board–approved prospective study of fluorescence-guided resection. A surgical microscope modified for fluorescence imaging was used for the qualitative assessment of visible fluorescence, and an intraoperative probe for in situ fluorescence detection was utilized for quantitative measurements of PpIX. The authors assessed the detection capabilities of both the qualitative and quantitative fluorescence approaches.

Results

The patient harboring a sphenoid wing meningioma with intraorbital extension underwent radical resection of the tumor with both visibly and nonvisibly fluorescent regions. The patient underwent a complete resection without any complications. Some areas of the tumor demonstrated visible fluorescence. The quantitative probe detected neoplastic tissue better than the qualitative modified surgical microscope. The intraoperative probe was particularly useful in areas that did not reveal visible fluorescence, and tissue from these areas was confirmed as tumor following histopathological analysis.

Conclusions

Fluorescence-guided resection may be a useful adjunct in the resection of skull base meningiomas. The use of a quantitative intraoperative probe to detect PpIX concentration allows more accurate determination of neoplastic tissue in meningiomas than visible fluorescence and is readily applicable in areas, such as the skull base, where complete resection is critical but difficult because of the vital structures surrounding the pathology.