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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, Alex Kotlyar, Vijay Thadani, Barbara C. Jobst, Krzysztof Bujarski, Terrance M. Darcey and David W. Roberts

Object

Intracranial monitoring for epilepsy has been proven to enhance diagnostic accuracy and provide localizing information for surgical treatment of intractable seizures. The authors investigated the usefulness of hippocampal depth electrodes in the era of more advanced imaging techniques.

Methods

Between 1988 and 2010, 100 patients underwent occipitotemporal hippocampal depth electrode (OHDE) implantation as part of invasive seizure monitoring, and their charts were retrospectively reviewed. The authors' technique involved the stereotactically guided (using the Leksell model G frame) implantation of a 12-contact depth electrode directed along the long axis of the hippocampus, through an occipital twist drill hole.

Results

Of the 100 patients (mean age 35.0 years [range 13–58 years], 51% male) who underwent intracranial investigation, 84 underwent resection of the seizure focus. Magnetic resonance imaging revealed mesial temporal sclerosis (MTS) in 27% of patients, showed abnormal findings without MTS in 55% of patients, and showed normal findings in 18% of patients. One patient developed a small asymptomatic occipital hemorrhage around the electrode tract. The use of OHDEs enabled epilepsy resection in 45.7% of patients who eventually underwent standard or selective temporal lobe resection. The hippocampal formation was spared during surgery because data obtained from the depth electrodes showed no or only secondary involvement in 14% of patients with preoperative temporal localization. The use of OHDEs prevented resections in 12% of patients with radiographic evidence of MTS. Eighty-three percent of patients who underwent resection had Engel Class I (68%) or II (15%) outcome at 2 years of follow-up.

Conclusions

The use of OHDEs for intracranial epilepsy monitoring has a favorable risk profile, and in the authors' experience it proved to be a valuable component of intracranial investigation. The use of OHDEs can provide the sole evidence for resection of some epileptogenic foci and can also result in hippocampal sparing or prevent likely unsuccessful resection in other patients.

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Kimon Bekelis, Tarek A. Radwan, Atman Desai, Ziev B. Moses, Vijay M. Thadani, Barbara C. Jobst, Krzysztof A. Bujarski, Terrance M. Darcey and David W. Roberts

Object

Intracranial monitoring for epilepsy has been proven to enhance diagnostic accuracy and provide localizing information for surgical treatment of intractable seizures. The authors investigated their experience with interhemispheric grid electrodes (IHGEs) to assess the hypothesis that they are feasible, safe, and useful.

Methods

Between 1992 and 2010, 50 patients underwent IHGE implantation (curvilinear double-sided 2 × 8 or 3 × 8 grids) as part of arrays for invasive seizure monitoring, and their charts were retrospectively reviewed.

Results

Of the 50 patients who underwent intracranial investigation with IHGEs, 38 eventually underwent resection of the seizure focus. These 38 patients had a mean age of 30.7 years (range 11–58 years), and 63% were males. Complications as a result of IHGE implantation consisted of transient leg weakness in 1 patient. Of all the patients who underwent resective surgery, 21 (55.3%) had medial frontal resections, 9 of whom (43%) had normal MRI results. Localization in all of these cases was possible only because of data from IHGEs, and the extent of resection was tailored based on these data. Of the 17 patients (44.7%) who underwent other cortical resections, IHGEs were helpful in excluding medial seizure onset. Twelve patients did not undergo resection because of nonlocalizable or multifocal disease; in 2 patients localization to the motor cortex precluded resection. Seventy-one percent of patients who underwent resection had Engel Class I outcome at the 2-year follow-up.

Conclusions

The use of IHGEs in intracranial epilepsy monitoring has a favorable risk profile and in the authors' experience proved to be a valuable component of intracranial investigation, providing the sole evidence for resection of some epileptogenic foci.

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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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M. Ross Bullock

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

Object

Motor vehicle accidents (MVAs) are a leading cause of death and disability in young people. Given that a major cause of death from MVAs is traumatic brain injury, and neurosurgeons hold special expertise in this area relative to other members of a trauma team, the authors hypothesized that neurosurgeon population density would be related to reduced mortality from MVAs across US counties.

Methods

The Area Resource File (2009–2010), a national health resource information database, was retrospectively analyzed. The primary outcome variable was the 3-year (2004–2006) average in MVA deaths per million population for each county. The primary independent variable was the density of neurosurgeons per million population in the year 2006. Multiple regression analysis was performed, adjusting for population density of general practitioners, urbanicity of the county, and socioeconomic status of the county.

Results

The median number of annual MVA deaths per million population, in the 3141 counties analyzed, was 226 (interquartile range [IQR] 151–323). The median number of neurosurgeons per million population was 0 (IQR 0–0), while the median number of general practitioners per million population was 274 (IQR 175–410). Using an unadjusted analysis, each increase of 1 neurosurgeon per million population was associated with 1.90 fewer MVA deaths per million population (p < 0.001). On multivariate adjusted analysis, each increase of 1 neurosurgeon per million population was associated with 1.01 fewer MVA deaths per million population (p < 0.001), with a respective decrease in MVA deaths of 0.03 per million population for an increase in 1 general practitioner (p = 0.007). Rural location, persistent poverty, and low educational level were all associated with significant increases in the rate of MVA deaths.

Conclusions

A higher population density of neurosurgeons is associated with a significant reduction in deaths from MVAs, a major cause of death nationally. This suggests that the availability of local neurosurgeons is an important factor in the overall likelihood of survival from an MVA, and therefore indicates the importance of promoting neurosurgical education and practice throughout the country.

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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, Tarek A. Radwan, Atman Desai and David W. Roberts

Object

Frameless stereotactic brain biopsy has become an established procedure in many neurosurgical centers worldwide. Robotic modifications of image-guided frameless stereotaxy hold promise for making these procedures safer, more effective, and more efficient. The authors hypothesized that robotic brain biopsy is a safe, accurate procedure, with a high diagnostic yield and a safety profile comparable to other stereotactic biopsy methods.

Methods

This retrospective study included 41 patients undergoing frameless stereotactic brain biopsy of lesions (mean size 2.9 cm) for diagnostic purposes. All patients underwent image-guided, robotic biopsy in which the SurgiScope system was used in conjunction with scalp fiducial markers and a preoperatively selected target and trajectory. Forty-five procedures, with 50 supratentorial targets selected, were performed.

Results

The mean operative time was 44.6 minutes for the robotic biopsy procedures. This decreased over the second half of the study by 37%, from 54.7 to 34.5 minutes (p < 0.025). The diagnostic yield was 97.8% per procedure, with a second procedure being diagnostic in the single nondiagnostic case. Complications included one transient worsening of a preexisting deficit (2%) and another deficit that was permanent (2%). There were no infections.

Conclusions

Robotic biopsy involving a preselected target and trajectory is safe, accurate, efficient, and comparable to other procedures employing either frame-based stereotaxy or frameless, nonrobotic stereotaxy. It permits biopsy in all patients, including those with small target lesions. Robotic biopsy planning facilitates careful preoperative study and optimization of needle trajectory to avoid sulcal vessels, bridging veins, and ventricular penetration.