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Masafumi Fukuda, Makoto Oishi, Tetsuya Hiraishi, Manabu Natsumeda and Yukihiko Fujii

Object

The authors retrospectively analyzed various clinicopathological factors to determine which are related to regrowth during a long-term follow-up period in patients who underwent incomplete vestibular schwannoma (VS) resection.

Methods

This study involved 74 patients (25 men and 49 women) in whom a VS was treated surgically via the lateral suboccipital approach, and who had postoperative follow-up periods exceeding 5 years. The mean follow-up was 104.1 months (range 60–241 months), and the mean patient age at surgery was 48.1 years (range 19–75 years). The tumors ranged in size from 0 mm (localized within the internal auditory canal) to 56 mm (28.3 ± 12.2 mm [mean ± SD]).

Results

Gross-total resection (GTR) was performed in 41 (55%) of the 74 patients; subtotal resection ([STR]; 90–99%) in 25 (34%); and partial resection ([PR]; < 90%) in 8 (11%). Regrowth rates in the GTR, STR, and PR groups were 2.4% (1 of 41 cases), 52% (13 of 25), and 62.5% (5 of 8), respectively, and the times to regrowth ranged from 6 to 76 months (median 31.9 months). The regrowth-free survival curves differed significantly between the complete (GTR) and incomplete (STR and PR) resection groups. Eighteen (54.5%) of the 33 patients who underwent incomplete resection showed evidence of regrowth during follow-up. Univariate and multivariate analyses of various factors revealed that both the thickness of the residual tumor, based on MR imaging after surgery, and the MIB-1 index were positively related to residual tumor regrowth. The receiver operating characteristic curves, plotted for both the thickness of the residual tumor and the MIB-1 index, identified the optimal cutoff points for these values as 7.4 mm (sensitivity 83.3%, specificity 86.7%) and 1.6 (sensitivity 83.3%, specificity 66.7%), respectively.

Conclusions

Greater residual tumor thickness, based on MR imaging after the initial surgery, and a higher MIB-1 index are both important factors related to postoperative tumor regrowth in patients who have undergone incomplete VS resection. These patients require frequent neuroimaging investigation during follow-up to assure early detection of tumor regrowth.

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Masafumi Fukuda, Makoto Oishi, Tetsuya Hiraishi, Akihiko Saito and Yukihiko Fujii

Object

The purpose of this study was to determine whether monitoring of pharyngeal motor evoked potentials (PhMEPs) elicited by transcranial electrical stimulation during skull base tumor surgery might be useful for predicting postoperative swallowing deterioration.

Methods

The authors analyzed PhMEPs in 21 patients during 22 surgical procedures for the treatment of skull base tumors. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supramaximal stimuli (220–550 V). Pharyngeal MEPs were recorded from the posterior wall of the pharynx through a modified endotracheal tube. The correlation between the final/baseline PhMEP ratio and postoperative swallowing function was examined.

Results

Postoperative swallowing function was significantly (p < 0.05), although not strongly (r = −0.47), correlated with the final/baseline PhMEP ratio. A PhMEP ratio < 50% was recorded during 4 of 22 procedures; in all 4 of these cases, the patients experienced postoperative deterioration of swallowing function. After 18 procedures, the PhMEP ratios remained > 50%; nevertheless, after 4 (22.2%) of these 18 procedures, patients showed deterioration of swallowing function.

Conclusions

Intraoperative PhMEP monitoring can be useful for predicting swallowing deterioration following skull base surgery, especially in patients with swallowing disturbances that are mainly due to reduction in the motor functions of the pharyngeal muscles.

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Kazuhiko Nishino, Hitoshi Hasegawa, Kenichi Morita, Masafumi Fukuda, Yasushi Ito, Yukihiko Fujii and Mitsuya Sato

OBJECTIVE

Arteriovenous malformations (AVMs) in the cerebellopontine angle cistern (CPAC) are specific lesions that can cause neurovascular compression syndromes as well as intracranial hemorrhage. Although case reports describing the CPAC AVMs, especially those presenting with trigeminal neuralgia (TN), have been accumulating by degrees, the pathophysiology of CPAC AVMs remains obscure. The authors' purpose in the present study was to evaluate the clinical and radiographic features of CPAC AVMs as well as the treatment options.

METHODS

This study defined a CPAC AVM as a small AVM predominantly located in the CPAC with minimal extension into the pial surface of the brainstem and closely associated with cranial nerves. All patients with CPAC AVMs treated in the authors' affiliated hospitals over a 16-year period were retrospectively identified. Clinical charts, imaging studies, and treatment options were evaluated.

RESULTS

Ten patients (6 men and 4 women), ranging in age from 56 to 77 years (mean 65.6 years), were diagnosed with CPAC AVMs according to the authors' definition. Six patients presented with hemorrhage, 3 with TN, and the remaining patient developed a hemorrhage subsequent to TN. Seven AVMs were associated with the trigeminal nerve (Group V), and 3 with the facial-vestibulocochlear nerve complex (Group VII–VIII). All patients in Group VII–VIII presented with the hemorrhage instead of hemifacial spasm. Regarding angioarchitecture, the intrinsic pontine arteries provided the blood supply for all CPAC AVMs in Group V. In addition, 5 of 7 AVMs with hemorrhagic episodes accompanied flow-related aneurysms, although no aneurysm was detected in patients with TN alone. With respect to treatment, all patients with hemorrhagic presentation underwent Gamma Knife surgery (GKS), resulting in favorable outcomes except for 1 patient who experienced rebleeding after GKS, which was caused by the repeated rupture of a feeder aneurysm. The AVMs causing TN were managed with surgery, GKS, or a combination, according to the nidus-nerve relationship. All patients eventually obtained pain relief.

CONCLUSIONS

Clinical symptoms caused by CPAC AVMs occur at an older age compared with AVMs in other locations; CPAC AVMs also have distinctive angioarchitectures according to their location in the CPAC. Although GKS is likely to be an effective treatment option for the CPAC AVMs with hemorrhagic presentations, it seems ideal to obliterate the flow-related aneurysms before performing GKS, although this is frequently challenging. For CPAC AVMs with TN, it is important to evaluate the nidus-nerve relationship before treatment, and GKS is especially useful for patients who do not require urgent pain relief.

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Makoto Oishi, Masafumi Fukuda, Tetsuya Hiraishi, Naoki Yajima, Yosuke Sato and Yukihiko Fujii

Object

The purpose of this paper is to report on the authors' advanced presurgical interactive virtual simulation technique using a 3D computer graphics model for microvascular decompression (MVD) surgery.

Methods

The authors performed interactive virtual simulation prior to surgery in 26 patients with trigeminal neuralgia or hemifacial spasm. The 3D computer graphics models for interactive virtual simulation were composed of the brainstem, cerebellum, cranial nerves, vessels, and skull individually created by the image analysis, including segmentation, surface rendering, and data fusion for data collected by 3-T MRI and 64-row multidetector CT systems. Interactive virtual simulation was performed by employing novel computer-aided design software with manipulation of a haptic device to imitate the surgical procedures of bone drilling and retraction of the cerebellum. The findings were compared with intraoperative findings.

Results

In all patients, interactive virtual simulation provided detailed and realistic surgical perspectives, of sufficient quality, representing the lateral suboccipital route. The causes of trigeminal neuralgia or hemifacial spasm determined by observing 3D computer graphics models were concordant with those identified intraoperatively in 25 (96%) of 26 patients, which was a significantly higher rate than the 73% concordance rate (concordance in 19 of 26 patients) obtained by review of 2D images only (p < 0.05). Surgeons evaluated interactive virtual simulation as having “prominent” utility for carrying out the entire surgical procedure in 50% of cases. It was evaluated as moderately useful or “supportive” in the other 50% of cases. There were no cases in which it was evaluated as having no utility. The utilities of interactive virtual simulation were associated with atypical or complex forms of neurovascular compression and structural restrictions in the surgical window. Finally, MVD procedures were performed as simulated in 23 (88%) of the 26 patients .

Conclusions

Our interactive virtual simulation using a 3D computer graphics model provided a realistic environment for performing virtual simulations prior to MVD surgery and enabled us to ascertain complex microsurgical anatomy.

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Shinya Jinguji, Junichi Yoshimura, Kenichi Nishiyama, Hiroshi Aoki, Keisuke Nagasaki, Manabu Natsumeda, Yuichiro Yoneoka, Masafumi Fukuda and Yukihiko Fujii

Object

Radiation monotherapy—prophylactic craniospinal or whole-brain irradiation paired with a radiation boost to the primary tumor—is the standard treatment for intracranial germinomas at the authors' institution. The authors assessed long-term outcomes of patients with germinoma who underwent therapy and identified factors affecting them.

Methods

The authors retrospectively analyzed data obtained in 46 patients (35 males and 11 females, age 5–43 years at diagnosis) who had been treated for intracranial germinomas between 1990 and 2009 at the authors' institution. Thirty patients had germinomas in localized regions and 16 in multiple regions. Thirty-eight patients (83%) underwent radiotherapy alone (craniospinal irradiation in 32 and whole-brain irradiation in 6). Seven patients underwent radiochemotherapy and 1 underwent chemotherapy alone. The mean radiation doses for the whole brain, spine, and primary tumor site were 26.9, 26.6, and 49.8 Gy, respectively. The median follow-up period was 125 months.

Results

The 10-year overall and recurrence-free survival rates were 93.3% and 89.3%, respectively. None of the 38 patients who received radiation monotherapy developed a recurrent lesion, whereas 1 of 7 who underwent radiochemotherapy and the 1 patient who underwent chemotherapy had a recurrent lesion. Of the entire population, 26 patients required hormone replacement therapy, 2 had short stature, and 1 developed a radiation-induced meningioma. Seventeen of the 25 childhood- or adolescent-onset patients were 19 years or older at the latest follow-up visit, 15 of whom graduated from senior high school, and only 2 of whom graduated from college. Of 34 patients who were 19 years or older at the latest visit, 4 were students, 18 worked independently, 4 worked in sheltered workplaces, and 8 were unemployed. Of the 34 patients, 4 got married after the initial treatment, 3 of whom had children. There were 8 patients (17%) with low postoperative Karnofsky Performance Scale (KPS) scores that were significantly associated with impaired neurocognitive functions, severe surgical complications, and neurological impairments. In 10 of the 46 patients, KPS scores at the latest visit were lower than their postoperative KPS scores. These decreases in KPS scores were significantly correlated with a delayed decline in neurocognitive functions in childhood-onset patients and a postoperative impairment of neurocognitive functions in patients with adolescent- or adult-onset germinoma.

Conclusions

No tumor recurrence occurred in germinoma patients treated with the authors' radiation monotherapy, which appears to be effective enough to cure the tumor. Brain damage caused by tumors themselves and surgical complications were found to adversely affect functional outcomes in patients regardless of their age. Although radiotherapy rarely caused late adverse effects in patients with adolescent- or adult-onset, in some childhood-onset lesions, the radiation seems to carry the risk of neurocognitive dysfunctions, which are attributable to late adverse effects. Accordingly, treatments for germinoma patients should be selected according to a patient's age and the extent of the tumor and with particular care to avoid surgical complications.

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Makoto Oishi, Masafumi Fukuda, Naoki Yajima, Kenzo Yoshida, Machiko Takahashi, Tetsuya Hiraishi, Tetsuro Takao, Akihiko Saito and Yukihiko Fujii

Object

In this paper, the authors' goal was to report their novel presurgical simulation method applying interactive virtual simulation (IVS) using 3D computer graphics (CG) data and microscopic observation of color-printed plaster models based on these CG data in surgery for skull base and deep tumors.

Methods

For 25 operations in 23 patients with skull base or deep intracranial tumors (meningiomas, schwannomas, epidermoid tumors, chordomas, and others), the authors carried out presurgical simulation based on 3D CG data created by image analysis for radiological data. Interactive virtual simulation was performed by modifying the 3D CG data to imitate various surgical procedures, such as bone drilling, brain retraction, and tumor removal, with manipulation of a haptic device. The authors also produced color-printed plaster models of modified 3D CG data by a selective laser sintering method and observed them under the operative microscope.

Results

In all patients, IVS provided detailed and realistic surgical perspectives of sufficient quality, thereby allowing surgeons to determine an appropriate and feasible surgical approach. Surgeons agreed that in 44% of the 25 operations IVS showed high utility (as indicated by a rating of “prominent”) in comprehending 3D microsurgical anatomies for which reconstruction using only 2D images was complicated. Microscopic observation of color-printed plaster models in 12 patients provided further utility in confirming realistic surgical anatomies.

Conclusions

The authors' presurgical simulation method applying advanced 3D imaging and modeling techniques provided a realistic environment for practicing microsurgical procedures virtually and enabled the authors to ascertain complex microsurgical anatomy, to determine the optimal surgical strategies, and also to efficiently educate neurosurgical trainees, especially during surgery for skull base and deep tumors.

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Surgical treatment of lumbar ossification of the posterior longitudinal ligament

Report of two cases and description of surgical technique

Mutsuhiro Tamura, Masafumi Machida, Daisuke Aikawa, Kentaro Fukuda, Hitoshi Kono, Yoshio Suda, Masanobu Shioda, Masashi Saito and Masaaki Yamagishi

✓ The authors report two cases of patients with lumbar ossification of the posterior longitudinal ligament (OPLL). One patient underwent surgery via the single posterior approach, and the other patient underwent combined anterior—posterior surgery. The authors consider the anterior approach for excision of the ossified lesion to be the most reasonable for treatment of lumbar OPLL. It is extremely important, however, to select the surgical procedure according to the individual patient's condition.

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Hiroatsu Murakami, Tadashi Kawaguchi, Masafumi Fukuda, Yasushi Ito, Hitoshi Hasegawa and Ryuichi Tanaka

✓ The lateral spread response (LSR) is used in the electrophysiological diagnosis of a hemifacial spasm or for monitoring during microvascular decompression. The authors used LSRs for intraoperative monitoring during endovascular surgery in a rare case of vertebral artery (VA) aneurysm that caused intractable hemifacial spasm.

A 49-year-old woman presented with a right hemifacial spasm that had persisted for 9 months. No other clinical symptom was observed. Vertebral artery angiography revealed a saccular aneurysm of the right VA. Magnetic resonance (MR) imaging demonstrated that the aneurysm was compressing the root exit zone of the right facial nerve. Endovascular treatment of the VA aneurysm was performed while monitoring the patient's LSRs. During occlusion of the VA at sites distal and proximal to the aneurysm, the LSRs temporarily disappeared and then reappeared with a higher amplitude than those measured preceding their disappearance. The hemifacial spasm alleviated gradually and disappeared completely 6 months after treatment. The LSRs changed in parallel with the improvement in the patient's hemifacial spasms and eventually disappeared. No recurrence of symptoms has been noticed as of 18 months postoperatively.

This is the first report of the use of LSR monitoring during endovascular surgery for an intracranial aneurysm that causes hemifacial spasm. Intraoperative and postoperative changes in the LSRs provided useful information regarding the pathophysiology of hemifacial spasm.

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Junichi Yoshimura, Yoshihiro Tsukamoto, Masakazu Sano, Hitoshi Hasegawa, Kazuhiko Nishino, Akihiko Saito, Masafumi Fukuda, Kouichirou Okamoto and Yukihiko Fujii

The authors report a rare case of a huge hypervascular tentorial cavernous angioma treated with preoperative endovascular embolization, followed by successful gross-total removal. A 15-year-old girl presented with scintillation, diplopia, and papilledema. Computed tomography and MRI studies revealed a huge irregularly shaped tumor located in the right occipital and suboccipital regions. The tumor, which had both intra- and extradural components, showed marked enhancement and invasion of the overlying occipital bone. Angiography revealed marked tumor stain, with blood supply mainly from a large branch of the left posterior meningeal artery. Therefore, this lesion was diagnosed as a tentorium-based extraaxial tumor. For differential diagnosis, meningioma, hemangiopericytoma, and malignant skull tumor were considered. Tumor feeders were endovascularly embolized with particles of polyvinyl alcohol. On the following day, the tumor was safely gross totally removed with minimum blood loss. Histopathological examination confirmed the diagnosis of cavernous angioma. To date, there have been no reports of tentorium-based cavernous angiomas endovascularly embolized preoperatively. A tentorial cavernous angioma is most likely to show massive intraoperative bleeding. Therefore, preoperative embolization appears to be quite useful for safe maximum resection. Hence, the authors assert that the differential diagnosis of tentorium-based tumors should include tentorial cavernous angioma, for which preoperative endovascular embolization should be considered.