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Min Lang, Danilo Silva, Lu Dai, Varun R. Kshettry, Troy D. Woodard, Raj Sindwani and Pablo F. Recinos

OBJECTIVE

Preoperatively determining the extent of parasellar invasion of pituitary macroadenomas is useful for surgical planning and patient counseling. Here, the authors compared constructive interference in steady state (CISS), a T2-weighted gradient-echo MRI sequence, to volume-interpolated breath-hold examination (VIBE), a T1-weighted gradient-echo MRI sequence, for evaluation of cavernous sinus invasion (CSI) by pituitary macroadenomas.

METHODS

VIBE and CISS images of 98 patients with pituitary macroadenoma were retrospectively analyzed and graded using the modified Knosp classification. The Knosp grades were correlated to surgical findings of CSI, which were determined intraoperatively using 0° and 30° endoscopes. The predictive accuracies for CSI according to the Knosp grades derived from the CISS and VIBE images were compared using receiver operating characteristic (ROC) curves. Postoperative MRI was used to evaluate the gross-total resection (GTR) rates.

RESULTS

The CSI rate by pituitary macroadenomas was 27.6% (27 of 98 cases). Of 196 assessments (left and right sides of 98 macroadenomas), 45 (23.0%) had different Knosp grades when scored using VIBE versus CISS images. For the VIBE images, 0% of Knosp grade 0, 4.5% of grade 1, 23.8% of grade 2, 42.1% of grade 3A, 100% of grade 3B, and 83.3% of grade 4 macroadenomas were found to have CSI intraoperatively. For the CISS images, 0% of Knosp grade 0, 2.1% of grade 1, 31.3% of grade 2, 56.3% of grade 3A, 100% of grade 3B, and 100% of grade 4 macroadenomas were found to have CSI intraoperatively. Two pituitary macroadenomas were classified as grade 4 on VIBE sequences but grades 3A and 2 on CISS sequences; CSI was not observed intraoperatively in both cases. The GTR rate was 64.3% and 60.0% for high-grade (3A, 3B, and 4) macroadenomas classified using VIBE and CISS sequences, respectively. The areas under the ROC curves were 0.94 and 0.97 for VIBE- and CISS-derived Knosp grades (p = 0.007), respectively.

CONCLUSIONS

Knosp grades determined using CISS sequence images are better correlated with intraoperative CSI than those determined using VIBE sequence images. CISS sequences may be valuable for the preoperative assessment of pituitary macroadenomas.

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James K. C. Liu, Varun R. Kshettry, Pablo F. Recinos, Kambiz Kamian, Richard P. Schlenk and Edward C. Benzel

Surgical education has been forced to evolve from the principles of its initial inception, in part due to external pressures brought about through changes in modern health care. Despite these pressures that can limit the surgical training experience, training programs are being held to higher standards of education to demonstrate and document trainee competency through core competencies and milestones. One of the methods used to augment the surgical training experience and to demonstrate trainee proficiency in technical skills is through a surgical skills laboratory. The authors have established a surgical skills laboratory by acquiring equipment and funding from nondepartmental resources, through institutional and private educational grants, along with product donations from industry. A separate educational curriculum for junior- and senior-level residents was devised and incorporated into the neurosurgical residency curriculum. The initial dissection curriculum focused on cranial approaches, with spine and peripheral nerve approaches added in subsequent years. The dissections were scheduled to maximize the use of cadaveric specimens, experimenting with techniques to best preserve the tissue for repeated uses. A survey of residents who participated in at least 1 year of the curriculum indicated that participation in the surgical skills laboratory translated into improved understanding of anatomical relationships and the development of technical skills that can be applied in the operating room. In addition to supplementing the technical training of surgical residents, a surgical skills laboratory with a dissection curriculum may be able to help provide uniformity of education across different neurosurgical training programs, as well as provide a tool to assess the progression of skills in surgical trainees.