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Frederick A. Boop, Azedine Medhkour, John Honeycutt, Charles James, W. Bruce Cherny and Christopher Duntsch

✓ The authors report on the development of an anterior cerebral artery pseudoaneurysm that hemorrhaged after monopolar coagulation for a ventricular catheter lodged in the interhemispheric fissure. After observing this complication, the authors developed a simple bench test that can be performed by any neurosurgeon to determine the safest coagulation parameters for any given diathermy unit. A modified grounding pad was placed in a beaker of a protein solution consisting of egg whites. Ventricular catheters were then placed in the solution, and a monopolar diathermy current was applied to a metal stylet at various wattages and for different durations of time. Inducing coagulation at 40 W with a diathermy unit produced flames emanating from around the pores of the catheter tip. Flash flames were also observed at 35 W, forming a coagulum of egg white for a distance of up to 1 cm from the catheter tip. All heat was dissipated through the holes of the first 16 mm of the catheter. At 20 W the flame was minimal and coagulation appeared adequate, whereas at 15 W only bubbles were seen around the tip together with suboptimal coagulum formation.

This technique is a simple and effective means of determining the optimal setting for monopolar diathermy and can be used to figure the optimal catheter coagulation wattage for a given diathermy unit. Considering the results of this study, the authors have lowered the current for coagulation in ventricular catheters to 20 W.

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Amar S. Shah, Peter T. Sylvester, Alexander T. Yahanda, Ananth K. Vellimana, Gavin P. Dunn, John Evans, Keith M. Rich, Joshua L. Dowling, Eric C. Leuthardt, Ralph G. Dacey, Albert H. Kim, Robert L. Grubb, Gregory J. Zipfel, Mark Oswood, Randy L. Jensen, Garnette R. Sutherland, Daniel P. Cahill, Steven R. Abram, John Honeycutt, Mitesh Shah, Yu Tao and Michael R. Chicoine

OBJECTIVE

Intraoperative MRI (iMRI) is used in the surgical treatment of glioblastoma, with uncertain effects on outcomes. The authors evaluated the impact of iMRI on extent of resection (EOR) and overall survival (OS) while controlling for other known and suspected predictors.

METHODS

A multicenter retrospective cohort of 640 adult patients with newly diagnosed supratentorial glioblastoma who underwent resection was evaluated. iMRI was performed in 332/640 cases (51.9%). Reviews of MRI features and tumor volumetric analysis were performed on a subsample of cases (n = 286; 110 non-iMRI, 176 iMRI) from a single institution.

RESULTS

The median age was 60.0 years (mean 58.5 years, range 20.5–86.3 years). The median OS was 17.0 months (95% CI 15.6–18.4 months). Gross-total resection (GTR) was achieved in 403/640 cases (63.0%). Kaplan-Meier analysis of 286 cases with volumetric analysis for EOR (grouped into 100%, 95%–99%, 80%–94%, and 50%–79%) showed longer OS for 100% EOR compared to all other groups (p < 0.01). Additional resection after iMRI was performed in 104/122 cases (85.2%) with initial subtotal resection (STR), leading to a 6.3% mean increase in EOR and a 2.2-cm3 mean decrease in tumor volume. For iMRI cases with volumetric analysis, the GTR rate increased from 54/176 (30.7%) on iMRI to 126/176 (71.5%) postoperatively. The EOR was significantly higher in the iMRI group for intended GTR and STR groups (p = 0.02 and p < 0.01, respectively). Predictors of GTR on multivariate logistic regression included iMRI use and intended GTR. Predictors of shorter OS on multivariate Cox regression included older age, STR, isocitrate dehydrogenase 1 (IDH1) wild type, no O 6-methylguanine DNA methyltransferase (MGMT) methylation, and no Stupp therapy. iMRI was a significant predictor of OS on univariate (HR 0.82, 95% CI 0.69–0.98; p = 0.03) but not multivariate analyses. Use of iMRI was not associated with an increased rate of new permanent neurological deficits.

CONCLUSIONS

GTR increased OS for patients with newly diagnosed glioblastoma after adjusting for other prognostic factors. iMRI increased EOR and GTR rate and was a significant predictor of GTR on multivariate analysis; however, iMRI was not an independent predictor of OS. Additional supporting evidence is needed to determine the clinical benefit of iMRI in the management of glioblastoma.