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Joseph Yuan-Mou Yang, Richard Beare, Marc L. Seal, A. Simon Harvey, Vicki A. Anderson and Wirginia J. Maixner

OBJECTIVE

Characterization of intraoperative white matter tract (WMT) shift has the potential to compensate for neuronavigation inaccuracies using preoperative brain imaging. This study aimed to quantify and characterize intraoperative WMT shift from the global hemispheric to the regional tract-based scale and to investigate the impact of intraoperative factors (IOFs).

METHODS

High angular resolution diffusion imaging (HARDI) diffusion-weighted data were acquired over 5 consecutive perioperative time points (MR1 to MR5) in 16 epilepsy patients (8 male; mean age 9.8 years, range 3.8–15.8 years) using diagnostic and intraoperative 3-T MRI scanners. MR1 was the preoperative planning scan. MR2 was the first intraoperative scan acquired with the patient's head fixed in the surgical position. MR3 was the second intraoperative scan acquired following craniotomy and durotomy, prior to lesion resection. MR4 was the last intraoperative scan acquired following lesion resection, prior to wound closure. MR5 was a postoperative scan acquired at the 3-month follow-up visit. Ten association WMT/WMT segments and 1 projection WMT were generated via a probabilistic tractography algorithm from each MRI scan. Image registration was performed through pairwise MRI alignments using the skull segmentation. The MR1 and MR2 pairing represented the first surgical stage. The MR2 and MR3 pairing represented the second surgical stage. The MR3 and MR4 (or MR5) pairing represented the third surgical stage. The WMT shift was quantified by measuring displacements between a pair of WMT centerlines. Linear mixed-effects regression analyses were carried out for 6 IOFs: head rotation, craniotomy size, durotomy size, resected lesion volume, presence of brain edema, and CSF loss via ventricular penetration.

RESULTS

The average WMT shift in the operative hemisphere was 2.37 mm (range 1.92–3.03 mm) during the first surgical stage, 2.19 mm (range 1.90–3.65 mm) during the second surgical stage, and 2.92 mm (range 2.19–4.32 mm) during the third surgical stage. Greater WMT shift occurred in the operative than the nonoperative hemisphere, in the WMTs adjacent to the surgical lesion rather than those remote to it, and in the superficial rather than the deep segment of the pyramidal tract. Durotomy size and resection size were significant, independent IOFs affecting WMT shift. The presence of brain edema was a marginally significant IOF. Craniotomy size, degree of head rotation, and ventricular penetration were not significant IOFs affecting WMT shift.

CONCLUSIONS

WMT shift occurs noticeably in tracts adjacent to the surgical lesions, and those motor tracts superficially placed in the operative hemisphere. Intraoperative probabilistic HARDI tractography following craniotomy, durotomy, and lesion resection may compensate for intraoperative WMT shift and improve neuronavigation accuracy.

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Richard J. Harvey, João F. Nogueira Jr., Rodney J. Schlosser, Sunil J. Patel, Eduardo Vellutini and Aldo C. Stamm

Object

The authors describe the utility of and outcomes after endoscopic transnasal craniotomy and skull reconstruction in the management of skull base pathologies.

Methods

The authors conducted a observational study of patients undergoing totally endoscopic, transnasal, transdural surgery. The patients included in the study underwent treatment over a 12-month period at 2 tertiary medical centers. The pathological entity, region of the ventral skull base resected, and size of the dural defect were recorded. Approach-related complications were documented, as well as CSF leaks, infections, bleeding-related complications, and any minor complications.

Results

Thirty consecutive patients were assessed during the study period. The patients had a mean age of 45.5 ± 20.2 years and a mean follow-up period of 182.4 ± 97.5 days. The dural defects reconstructed were as large as 5.5 cm (mean 2.49 ± 1.36 cm). One patient (3.3%) had a CSF leak that was managed endoscopically. Two patients had epistaxis that required further care, but there were no complications related to intracranial infections or bleeding. Some minor sinonasal complications occurred.

Conclusions

Skull base endoscopic reconstructive techniques have significantly advanced in the past decade. The use of pedicled mucosal flaps in the reconstruction of large dural defects resulting from an endoscopic transnasal craniotomy permits a robust repair. The CSF leak rate in this study is comparable to that achieved in open approaches. The ability to manage the skull base defects successfully with this approach greatly increases the utility of transnasal endoscopic surgery.

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Albert P. Wong, Rishi R. Lall, Nader S. Dahdaleh, Cort D. Lawton, Zachary A. Smith, Ricky H. Wong, Michael J. Harvey, Sandi Lam, Tyler R. Koski and Richard G. Fessler

OBJECT

Patients with symptomatic intradural-extramedullary (ID-EM) tumors may be successfully treated with resection of the lesion and decompression of associated neural structures. Studies of patients undergoing open resection of these tumors have reported high rates of gross-total resection (GTR) with minimal long-term neurological deficit. Case reports and small case series have suggested that these patients may be successfully treated with minimally invasive surgery (MIS). These studies have been limited by small patient populations. Moreover, there are no studies directly comparing perioperative outcomes between patients treated with open resection and MIS. The objective of this study was to compare perioperative outcomes in patients with ID-EM tumors treated using open resection or MIS.

METHODS

A retrospective review was performed using data collected from 45 consecutive patients treated by open resection or MIS for ID-EM spine tumors. These patients were treated over a 9-year period between April 2003 and October 2012 at Northwestern University and the University of Chicago. Statistical analysis was performed to compare perioperative outcomes between the two groups.

RESULTS

Of the 45 patients in the study, 27 were treated with the MIS approach and 18 were treated with the open approach. Operative time was similar between the two groups: 256.3 minutes in the MIS group versus 241.1 minutes in the open group (p = 0.55). Estimated blood loss was significantly lower in the MIS group (133.7 ml) compared with the open group (558.8 ml) (p < 0.01). A GTR was achieved in 94.4% of the open cases and 92.6% of the MIS cases (p = 0.81).

The mean hospital stay was significantly shorter in the MIS group (3.9 days) compared with the open group (6.1 days) (p < 0.01). There was no significant difference between the complication rates (p = 0.32) and reoperation rates (p = 0.33) between the two groups. Multivariate analysis demonstrated an increased rate of complications in cervical spine tumors (OR 15, p = 0.05).

CONCLUSIONS

Thoracolumbar ID-EM tumors may be safely and effectively treated with either the open approach or an MIS approach, with an equivalent rate of GTR, perioperative complication rate, and operative time. Patients treated with an MIS approach may benefit from a decrease in operative blood loss and shorter hospital stays.

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Thomas J. Semrad, Robert O'Donnell, Ted Wun, Helen Chew, Danielle Harvey, Hong Zhou and Richard H. White

Object

The authors sought to define the incidence of symptomatic venous thromboembolism (VTE) in patients harboring malignant gliomas.

Methods

The authors conducted a retrospective analysis of data obtained in all cases of malignant glioma diagnosed in California during a 6-year period; the occurrence of a VTE was identified using linked hospital discharge data. The Cox proportional hazard model was used to analyze the association of specific risk factors with the development of a VTE or death within 2 years of the cancer diagnosis.

Among 9489 cases, the 2-year cumulative incidence of VTE was 7.5% (715 cases), with a rate of 16.1 events per 100 person-years during the first 6 months. Three hundred ninety-one (55%) of these 715 cases were diagnosed within 61 days of major neurosurgery. Risk factors for VTE included older age (hazard ratio [HR] 2.6, confidence interval [CI] 2.0–3.4 for age range 65–74 years compared with ≤ 45 years), glioblastoma multiforme histology (HR 1.7, CI 1.4–2.1), three or more chronic comorbidities (HR 3.5, CI 2.8–4.3 [compared with no comorbidity]), and neurosurgery within 61 days (HR 1.7, CI 1.3–2.3). Patients in whom a VTE was present were at higher risk of dying within 2 years (HR 1.3, CI 1.2–1.4). In a nested case–control analysis of all VTE cases, there was no association between insertion of a vena cava filter and the risk of a recurrent VTE.

Conclusions

In patients harboring a glioma there was a very high incidence of symptomatic VTEs, particularly within 2 months of neurosurgery. The development of a VTE was associated with a 30% increase in the risk of death within 2 years. Further studies are needed to determine if risk stratification and the use of medical prophylaxis after neurosurgery improves outcomes.