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  • Author or Editor: Nobuhito Saito x
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Taichi Kin, Hirofumi Nakatomi, Masaaki Shojima, Minoru Tanaka, Kenji Ino, Harushi Mori, Akira Kunimatsu, Hiroshi Oyama and Nobuhito Saito

Object

In this study, the authors used preoperative simulation employing 3D computer graphics (interactive computer graphics) to fuse all imaging data for brainstem cavernous malformations. The authors evaluated whether interactive computer graphics or 2D imaging correlated better with the actual operative field, particularly in identifying a developmental venous anomaly (DVA).

Methods

The study population consisted of 10 patients scheduled for surgical treatment of brainstem cavernous malformations. Data from preoperative imaging (MRI, CT, and 3D rotational angiography) were automatically fused using a normalized mutual information method, and then reconstructed by a hybrid method combining surface rendering and volume rendering methods. With surface rendering, multimodality and multithreshold techniques for 1 tissue were applied. The completed interactive computer graphics were used for simulation of surgical approaches and assumed surgical fields. Preoperative diagnostic rates for a DVA associated with brainstem cavernous malformation were compared between conventional 2D imaging and interactive computer graphics employing receiver operating characteristic (ROC) analysis.

Results

The time required for reconstruction of 3D images was 3–6 hours for interactive computer graphics. Observation in interactive mode required approximately 15 minutes. Detailed anatomical information for operative procedures, from the craniotomy to microsurgical operations, could be visualized and simulated three-dimensionally as 1 computer graphic using interactive computer graphics. Virtual surgical views were consistent with actual operative views. This technique was very useful for examining various surgical approaches. Mean (± SEM) area under the ROC curve for rate of DVA diagnosis was significantly better for interactive computer graphics (1.000 ± 0.000) than for 2D imaging (0.766 ± 0.091; p < 0.001, Mann-Whitney U-test).

Conclusions

The authors report a new method for automatic registration of preoperative imaging data from CT, MRI, and 3D rotational angiography for reconstruction into 1 computer graphic. The diagnostic rate of DVA associated with brainstem cavernous malformation was significantly better using interactive computer graphics than with 2D images. Interactive computer graphics was also useful in helping to plan the surgical access corridor.

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Hirofumi Nakatomi, Jeffrey T. Jacob, Matthew L. Carlson, Shota Tanaka, Minoru Tanaka, Nobuhito Saito, Christine M. Lohse, Colin L. W. Driscoll and Michael J. Link

OBJECTIVE

The management of vestibular schwannoma (VS) remains controversial. One commonly cited advantage of microsurgery over other treatment modalities is that tumor removal provides the greatest chance of long-term cure. However, there are very few publications with long-term follow-up to support this assertion. The purpose of the current study is to report the very long-term risk of recurrence among a large historical cohort of patients who underwent microsurgical resection.

METHODS

The authors retrospectively reviewed the medical records of patients who had undergone primary microsurgical resection of unilateral VS via a retrosigmoid approach performed by a single neurosurgeon-neurotologist team between January 1980 and December 1999. Complete tumor removal was designated gross-total resection (GTR), and anything less than complete removal was designated subtotal resection (STR). The primary end point was radiological recurrence-free survival. Time-to-event analyses were performed to identify factors associated with recurrence.

RESULTS

Four hundred fourteen patients met the study inclusion criteria and were analyzed. Overall, 67 patients experienced recurrence at a median of 6.9 years following resection (IQR 3.9–12.1, range 1.2–22.5 years). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following resection were 93% (95% CI 91–96, 248 patients still at risk), 78% (72–85, 88), 68% (60–77, 47), and 51% (41–64, 22), respectively. The strongest predictor of recurrence was extent of resection, with patients who underwent STR having a nearly 11-fold greater risk of recurrence than the patients treated with GTR (HR 10.55, p < 0.001). Among the 18 patients treated with STR, 15 experienced recurrence at a median of 2.7 years following resection (IQR 1.9–8.9, range 1.2–18.7). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following GTR were 96% (95% CI 93–98, 241 patients still at risk), 82% (77–89, 86), 73% (65–81, 46), and 56% (45–70, 22), respectively. Estimated recurrence-free survival rates at 5, 10, and 15 years following STR were 47% (95% CI 28–78, 7 patients still at risk), 17% (5–55, 2), and 8% (1–52, 1), respectively.

CONCLUSIONS

Long-term surveillance is required following microsurgical resection of VS even after GTR. Subtotal resection alone should not be considered a definitive long-term cure. These data emphasize the importance of long-term follow-up when reporting tumor control outcomes for VS.

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Hirofumi Nakatomi, Hidemi Miyazaki, Minoru Tanaka, Taichi Kin, Masanori Yoshino, Hiroshi Oyama, Masaaki Usui, Hiroshi Moriyama, Hiromi Kojima, Kimitaka Kaga and Nobuhito Saito

OBJECT

Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery.

METHODS

Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone–elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed.

RESULTS

A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade.

CONCLUSIONS

Preservation of function was significantly better for patients who received extended recuperation treatment.