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Giuseppe Lanzino and David F. Kallmes

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Harry J. Cloft, Nasser Razack and David F. Kallmes

Object. The aim of this study was to determine the prevalence of cerebral saccular aneurysms in patients with persistent primitive trigeminal artery (PPTA). The prevalence of cerebral saccular aneurysms in patients with PPTA previously has been reported to be 14 to 32%, but this rate range is unreliable because it is based on collections of published case reports rather than a series of patients chosen in an unbiased manner.

Methods. The authors retrospectively evaluated their own series of 34 patients with PPTA to determine the prevalence of cerebral aneurysms in this population. The prevalence of intracranial aneurysms in patients with PPTA was approximately 3% (95% confidence interval 0–9%).

Conclusions. The prevalence of intracranial aneurysms in patients with PPTA is no greater than the prevalence of intracranial aneurysms in the general population.

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Huy M. Do, Mary E. Jensen, William F. Marx and David F. Kallmes

The authors report the clinical symptoms and response to therapy of a series of patients who presented with subacute or chronic back pain due to vertebral osteonecrosis (Kümmell's spondylitis) and who underwent percutaneous vertebroplasty.

The authors performed a retrospective chart review of a series of 95 patients in whom 149 painful, nonneoplastic compression fractures were demonstrated and who were treated with percutaneous transpediculate polymethylmethacrylate (PMMA) vertebroplasty. In six of these patients there was evidence of vertebral osteonecrosis, as evidenced by the presence of an intravertebral vacuum cleft on radiography or by intravertebral fluid on magnetic resonance (MR) imaging. Clinical and radiological findings on presentation were noted. Technical aspects of the vertebroplasty technique were compiled. Response to therapy, defined as qualitative change in pain severity and change in level of activity, was noted immediately following the procedure and at various periods on follow-up reviews.

One man and five women, who ranged in age from 72 to 90 years (mean 81 years), were treated. Each patient had one compression fracture. The fractures were at T-11 (one patient), L-1 (two patients), L-3 (two patients), and L-4 (one patient). The pain pattern was described as severe and localized to the affected vertebra, and sometimes radiated along either flank. Pain duration ranged from 2 to 12 weeks, and the pain was refractory to conservative therapy that consisted of bedrest, analgesics, and external bracing. At the time of treatment, all patients were bedridden because of severe back pain. In all patients either plain radiographic or computerized tomography evidence of intravertebral vacuum cleft or MR imaging evidence of vertebral fluid collection consistent with avascular necrosis of the vertebral body was demonstrated. Four patients underwent bilateral transpediculate vertebroplasty, and two patients underwent unilateral transpediculate vertebroplasty. The fracture cavities were specifically targeted for PMMA injection. Additional fortification of the osteoporotic vertebral body trabeculae was also performed when feasible. "Cavitygrams" or intraosseous venograms with gentle contrast injection were obtained prior to application of cement mixture. In all patients subjective improvement in pain and increased mobility were demonstrated posttreatment. The follow-up period ranged from 4 to 24 hours after treatment. Two patients made additional office visits at 1 and 3 months, respectively.

Patients presenting with vertebral osteonecrosis (Kümmell's spondylitis) often suffer from local paraspinous or referred pain. When performing vertebroplasty on these patients, confirmation of entry into the fracture cavities with contrast-enhanced "cavitygrams" should be performed prior to injection of PMMA cement. The response to vertebroplasty with regard to amelioration of pain and improved mobility is encouraging.

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Robert J. McDonald, Harry J. Cloft and David F. Kallmes

Object

The authors sought to identify the presence of a “July effect,” a transient increase in adverse outcomes during July, among a cohort of spontaneous subarachnoid hemorrhage (SAH) admissions recorded in the National Inpatient Sample (NIS).

Methods

The discharge status, admission month, patient demographics, treatment parameters, and hospital characteristics among spontaneous SAH admissions were extracted from the 2001–2008 NIS. Multivariate regression was used to determine whether an unfavorable discharge status and/or in-hospital mortality significantly increased in summer months in a pattern suggestive of a July effect. Additional models were generated to assess the impact of hospital teaching status on these outcomes.

Results

Among 57,663,486 hospital admissions from the 2001–2008 NIS, 52,879 cases of spontaneous SAH (ICD-9-CM 430) were treated at teaching (36,914 cases [70%]) and nonteaching (15,965 cases [30%]) facilities. Regression models failed to reveal a July effect for in-hospital mortality (χ2 = 0.75, p = 1.000) or unfavorable discharges (χ2 = 1.69, p = 0.999) among monthly SAH admissions, although they did suggest a significant reduction in these outcomes (in-hospital mortality, OR = 0.89, p < 0.001; unfavorable discharges, OR = 0.88, p < 0.001) among teaching hospitals as compared with nonteaching hospitals after adjustment for disparities in demographic, treatment, and hospital characteristics.

Conclusions

The discharge disposition among SAH admissions within the NIS was not suggestive of a July effect but did reveal that teaching institutions have significantly lower rates of adverse outcomes when compared with nonteaching hospitals. Note, however, that the origins of this difference related to teaching status remain unclear.

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Harry J. Cloft, David F. Kallmes, Michelle H. Kallmes, Jonas H. Goldstein, Mary E. Jensen and Jacques E. Dion

Object. The aim of this study was to determine the prevalence of cerebral saccular aneurysms in patients with carotid artery and/or vertebral artery (VA) fibromuscular dysplasia (FMD).

Methods. A metaanalysis was performed using data from 17 previously reported series of patients with internal carotid artery (ICA) and/or VA FMD that included information on the prevalence of cerebral aneurysms. In addition, the authors retrospectively evaluated their own series of 117 patients with ICA and/or VA FMD to determine the prevalence of cerebral aneurysms. The metaanalysis of the 17 earlier series, which included 498 patients, showed a 7.6 ± 2.5% prevalence of incidental, asymptomatic aneurysms in patients with ICA and/or VA FMD. In the authors' series of patients with FMD, 6.3 ± 4.9% of patients harbored an incidental, asymptomatic aneurysm. When the authors' series was combined with those included in the metaanalysis, the prevalence was found to be 7.3 ± 2.2%. The prevalence of aneurysms in the general population would have to be greater than 5.6% for there to be no statistically significant difference (chi-square test, p < 0.05) when compared with this 7.3% prevalence in patients with FMD.

Conclusions. The prevalence of intracranial aneurysms in patients with cervical ICA and/or VA FMD is approximately 7%, which is not nearly as high as the 21 to 51% prevalence that has been previously reported.

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Ross C. Puffer, David J. Daniels, David F. Kallmes, Harry J. Cloft and Giuseppe Lanzino

Object

The authors conducted a study to review their experience with tentorial dural arteriovenous fistulas (DAVFs) treated with transarterial endovascular embolization in which Onyx was used.

Methods

The authors reviewed prospectively collected data in 9 patients with tentorial DAVFs treated with Onyx embolization between 2008 and 2011. Information reviewed included clinical presentation, angiographic features, treatment, and clinical and radiologically documented outcome. Clinical follow-up was available in every patient. Radiological follow-up studies were available in 8 of 9 patients (mean follow-up 4.6 months).

Results

Six of 9 patients had complete angiographic obliteration (in 5 this was confirmed by a follow-up angiogram obtained 3–6 months later), and 2 patients had near-complete obliteration (faint filling of the venous drainage in the late venous phase). One patient had partial obliteration and required surgical disconnection. In all patients with complete obliteration, transarterial embolization was performed through the posterior branch of the middle meningeal artery. There were no procedural complications, and no morbidity or mortality resulted from Onyx embolization.

Conclusions

Transarterial Onyx embolization is a valid, effective, and safe alternative to surgical disconnection in many patients with tentorial DAVFs. The presence of an adequate posterior branch of the middle meningeal artery is critical to achieve a microcatheter position distal enough to increase the likelihood of complete obliteration.

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David F. Kallmes, Waleed Brinjikji and Alejandro A. Rabinstein

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Tord D. Alden, Gerald R. Hankins, Elisa J. Beres, David F. Kallmes and Gregory A. Helm

Gene therapy has many potential applications in neurosurgery. One application involves bone morphogenetic protein-2 (BMP-2), a low-molecular-weight glycoprotein that induces bone formation in vivo. Numerous studies have demonstrated that the BMP-2 protein can enhance spinal fusion. This study was undertaken to determine whether direct injection of an adenoviral construct containing the BMP-2 gene can be used for spinal fusion. Twelve athymic nude rats were used in this study. Recombinant, replication-defective type-5 adenovirus with a universal promoter and BMP-2 gene (Ad-BMP-2) was used. A second adenovirus constructed with a universal promoter and ß-galactosidase (ß-gal) gene (Ad-ß-gal) was used as a control. Seven and one-half microliters of virus was injected percutaneously and paraspinally at the lumbosacral junction in three groups (four animals each): 1) Ad-BMP-2 bilaterally, 2) Ad-BMP-2 on the right, Ad-ß-gal on the left, and 3) Ad-ß-gal bilaterally. Computerized tomography (CT) scans of the lumbosacral spine were obtained at 3, 5, and 12 weeks. At 12 weeks, the animals were killed for histological inspection. Ectopic bone formation was seen both on three-dimensional CT reconstruction and histologically in all rats at sites treated with Ad-BMP-2. Histological analysis revealed bone at different stages of maturity adjacent to the spinous processes, laminae, and transverse processes. This study clearly demonstrated that it is possible to produce in vivo endochondral bone formation by using direct adenoviral construct injection into the paraspinal musculature, which suggests that gene therapy may be useful for spinal fusion in the future.

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Jennifer S. McDonald, Michelle J. Clarke, Gregory A. Helm and David F. Kallmes

Object

The presence of a “July effect,” where the influx of new residents and fellows at teaching hospitals every July may negatively affect patient care and outcomes, is widely debated. The authors used the Nationwide Inpatient Sample (NIS) to identify all cases of spinal surgery and examine outcomes among patients who underwent surgery in July compared with those who underwent surgery in other months.

Methods

Spinal surgery hospitalizations from 2001 to 2008 were identified in the NIS by extracting relevant ICD-9 codes. Rates of in-hospital mortality, discharge to a long-term care facility, and postoperative complications were compared between admission months and between teaching and nonteaching hospitals using the Wilcoxon rank-sum test, Fisher exact test, and multivariate regression analysis.

Results

Compared with patients admitted in other months, patients who were admitted to teaching hospitals in July for spinal surgery showed a similar likelihood of in-hospital mortality (OR 0.94 [95% CI 0.78–1.11], p = 0.46), reaction to implanted device/instrumentation (OR 0.88 [95% CI 0.77–1.02], p = 0.09), and postoperative wound dehiscence (OR 1.12 [95% CI 0.94–1.33], p = 0.25). A significantly higher likelihood of discharge to a long-term care facility (OR 1.03 [95% CI 1.00–1.07], p = 0.0467) and postoperative infection (OR 1.11 [95% CI 1.05–1.17], p = 0.0341) was observed in teaching hospitals in July compared with other months; however, incidence rates were similar regardless of admission month. Higher-risk patients (Charlson score ≥ 2) admitted to teaching hospitals in July had a similar likelihood of all outcomes regardless of admission month.

Conclusions

This study of nationwide hospitalizations demonstrates that the influx of new residents and fellows in July has a negligible effect on periprocedural outcomes following spinal surgery.