Faculty Bibliography

INTRODUCTION: Postoperative antibiotics (PA) are often administered to patients after instrumented spinal surgery until all drains are removed to prevent surgical site infections (SSI). This practice is discouraged by numerous medical society guidelines, so our institutional Neurosurgery Quality Improvement Committee decided to discontinue use of PA for this population. METHODS: We retrospectively reviewed data for patients who had instrumented spinal surgery at our institution for seven months before and after this policy change and compared the frequency of SSI and development of antibiotic related complications in patients who received PA to those who did not (non-PA). RESULTS: We identified 188 PA patients and 158 non-PA patients. Discontinuation of PA did not result in an increase in frequency of SSI (2% of PA patients vs. 0.6% of non-PA patients, p = .4). Growth of resistant bacteria was not significantly reduced in the non-PA period in comparison to the PA period (2% in the PA period and 1% in the non-PA period). The cost of antibiotics for PA patients was $5,499.62, whereas the cost of antibiotics for the non-PA patients was $0. On a per patient basis, the cost associated with antibiotics and resistant infections was significantly greater for patients who received PA than for those who did not (median of $26.32 with IQR $9.87-$46.06 vs. median of $0 with IQR $0-$0; p < .0001). CONCLUSION: After discontinuing PA for patients who had instrumented spinal procedures, we did not observe an increase in the frequency of SSI. We did, however, note that there was a non-significant decrease in the frequency of growth of resistant organisms. These findings suggest that patients in this population do not need PA, and complications can be reduced if PA are withheld.

Background: Assessment of preoperative imaging is important for operative planning of meningioma resection. A hyperintense rim on T2-weighted (T2W) MRI is frequently thought to represent a CSF cleft between the tumor and the brain, suggesting a clean arachnoid plane. However, brain invasion (loss of arachnoid plane) is often encountered instead. We sought to further characterize this radiographic finding and identify correlates with intraoperative brain invasion and pathology in patients undergoing meningioma resection. Methods: Retrospective review of 42 patients (mean age: 54.2 years, SD: 13.0, 76% female) who underwent meningioma resection between 2013 and 2016 at a single institution. Demographic variables and pathology results were recorded. Radiographic variables on preoperative MRI included presence and size of a hyperintense rim on T2W MRI, a contrast-enhancing rim on fluid-attenuated inversion recovery (FLAIR), and adjacent edema. Operative reports were reviewed for identification of loss of arachnoid plane (brain invasion) noted during surgery. Radiographic findings were then correlated with brain invasion using nonparametric statistics. Results: Of 42 meningiomas resected, there were 29 (69%) WHO Grade I, 12 (29%) WHO Grade II, and 1 (2%) WHO Grade III. Twenty-three tumors (55%) were located at the skull base. On preoperative T2WI, 36 (86%) of meningiomas demonstrated a hyperintense cleft with a mean width of 2.86 mm (SD: 1.66) and 16 had adjacent edema. Twenty-six meningiomas demonstrated a contrast-enhancing rim on FLAIR with a mean width of 2.85 mm (SD: 1.06) and 28 meningiomas exhibited a rim that was both T2 hyperintense and enhancing on FLAIR. Intraoperatively, 24 (57%) of meningiomas were found to have partial or complete loss of an arachnoid plane between the tumor and adjacent brain parenchyma. Both a hyperintense T2 cleft and enhancing FLAIR rim were associated with loss of arachnoid plane (p=0.004 for T2, <0.001 for FLAIR, <0.001 for combined). Conclusion: Preoperative MRI of meningiomas often identifies a T2 hyperintense rim frequently thought to represent a CSF cleft. A correlation with enhancement on FLAIR and intraoperative loss of arachnoid plane suggests this may be a useful marker of brain invasion and could aid in operative planning and risk assessment

OBJECTIVE: Because the d-2-hydroxyglutarate (D2HG) product of mutant isocitrate dehydrogenase 1 (IDH1mut) is released by tumor cells into the microenvironment and is structurally similar to the excitatory neurotransmitter glutamate, we sought to determine whether IDH1mut increases the risk of seizures in patients with glioma, and whether D2HG increases the electrical activity of neurons. METHODS: Three WHO grade II-IV glioma cohorts from separate institutions (total N = 712) were retrospectively assessed for the presence of preoperative seizures and tumor location, WHO grade, 1p/19q codeletion, and IDH1mut status. Rat cortical neurons were grown on microelectrode arrays, and their electrical activity was measured before and after treatment with exogenous D2HG, in the presence or absence of the selective NMDA antagonist, AP5. RESULTS: Preoperative seizures were observed in 18%-34% of IDH1 wild-type (IDH1wt) patients and in 59%-74% of IDH1mut patients (p < 0.001). Multivariable analysis, including WHO grade, 1p/19q codeletion, and temporal lobe location, showed that IDH1mut was an independent correlate with seizures (odds ratio 2.5, 95% confidence interval 1.6-3.9, p < 0.001). Exogenous D2HG increased the firing rate of cultured rat cortical neurons 4- to 6-fold, but was completely blocked by AP5. CONCLUSIONS: The D2HG product of IDH1mut may increase neuronal activity by mimicking the activity of glutamate on the NMDA receptor, and IDH1mut gliomas are more likely to cause seizures in patients. This has rapid translational implications for the personalized management of tumor-associated epilepsy, as targeted IDH1mut inhibitors may improve antiepileptic therapy in patients with IDH1mut gliomas.

OBJECTIVE The authors sought to determine the effects of eliminating the use of prolonged prophylactic systemic antibiotics (PPSAs) in patients with subdural and subgaleal drains. METHODS Using a retrospective database, the authors collected data for patients over the age of 17 years who had undergone cranial surgery at their institution between December 2013 and July 2014 (PPSAs period) or between December 2014 and July 2015 (non-PPSAs period) and had subdural or subgaleal drains left in place postoperatively. RESULTS One hundred five patients in the PPSAs period and 80 in the non-PPSAs period were identified. The discontinuation of PPSAs did not result in an increase in the frequency of surgical site infection (SSI). The frequency of Clostridium difficile (CDI) and the growth of resistant bacteria were reduced in the non-PPSAs period in comparison with the PPSAs period. In the 8 months after the drain prophylaxis protocol was changed, $93,194.63 were saved in the costs of antibiotics and complications related to antibiotics. CONCLUSIONS After discontinuing PPSAs for patients with subdural or subgaleal drains at their institution, the authors did not observe an increase in the frequency of SSI. They did, however, note a decrease in the frequency of CDI and the growth of resistant organisms. It appears that not only can patients in this population do without PPSAs, but also that complications are avoided when antibiotic use is limited to 24 hours after surgery.

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.

Palliative cervical cordotomy can be performed via percutaneous radiofrequency ablation of the lateral C1-2 spinothalamic tract. This rare procedure can be safe, effective, and advantageous in mitigating medically intractable unilateral extremity pain for selected patients with end-stage cancer. This report reviews the indications, techniques, risks, and potential benefits of cordotomy. We describe our recent experience treating 3 patients with CT-guided C1-2 cordotomy and provide the first characterization of spinal cord diffusion MR imaging changes associated with successful cordotomy.

Introduction Postoperative antibiotics (PA) are often administered to patients after instrumented spinal surgery until all drains are removed to prevent surgical site infections (SSI). This practice is discouraged by numerous medical society guidelines, so our institutional Neurosurgery Quality Improvement Committee decided to discontinue use of PA for this population. Methods We retrospectively reviewed data for patients who had instrumented spinal surgery at our institution for seven months before and after this policy change and compared the frequency of SSI and development of antibiotic related complications in patients who received PA to those who did not (non- PA). Results We identified 188 PA patients and 158 non-PA patients. Discontinuation of PA did not result in an increase in frequency of SSI (2% of PA patients vs. 0.6% of non-PA patients, p=0.4). Growth of resistant bacteria was not significantly reduced in the non-PA period in comparison to the PA period (2% vs. 1%, p=1). The cost of antibiotics for PA patients was $5,499.62, whereas the cost of antibiotics for the non- PA patients was $0. On a per patient basis, the cost associated with antibiotics and resistant infections was significantly greater for patients who received PA than for those who did not (median of $26.32 with IQR $9.87-$46.06 vs. median of $0 with IQR $0-$0; p<0.0001). Conclusions After discontinuing PA for patients who had instrumented spinal procedures, we did not observe an increase in the frequency of SSI. We did, however, note that there was a non-significant decrease in the frequency of growth of resistant organisms. These findings suggest that patients in this population do not need PA, and complications can be reduced if PA are withheld