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Toshio Matsushima, Ken Matsushima, Shigeaki Kobayashi, J. Richard Lister and Jacques J. Morcos

Dr. Albert L. Rhoton Jr. was a pioneer of the study of microneurosurgical anatomy. Championing this field over the past half century, he produced more than 500 publications. In this paper, the authors review his body of work, focusing on approximately 160 original articles authored by Rhoton and his microneuroanatomy fellows. The articles are categorized chronologically into 5 stages: 1) dawn of microneurosurgical anatomy, 2) study of basic anatomy for general neurosurgery, 3) study for skull base surgery, 4) study of the internal structures of the brain by fiber dissection, and 5) surgical anatomy dealing with new advanced surgical approaches. Rhoton introduced many new research ideas and surgical techniques and approaches, along with better microsurgery instruments, through studying and teaching microsurgical anatomy, especially during the first stage. The characteristic features of each stage are explained and the transition phases of his projects are reviewed.

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Tetsuya Goto, Kazuhiro Hongo, Yukinari Kakizawa, Hisashi Muraoka, Yosuke Miyairi, Yuichiro Tanaka and Shigeaki Kobayashi

✓ The NeuRobot is a telecontrolled microscopic micromanipulator system designed for neurosurgical procedures. The unit houses a three-dimensional endoscope and three robot arms that the surgeon operates without direct contact with the patient. The authors have successfully performed robotics-assisted neurosurgical procedures by using the NeuRobot in a 54-year-old man who had a recurrent atypical meningioma. Following the usual preparation of craniotomy and opening of the dura mater, a portion of the tumor was removed using the NeuRobot with the aid of microscopic observation. No complication related to the use of the NeuRobot was encountered and the patient's postoperative course was uneventful. Although various kinds of robots have been developed for use in neurosurgery in recent years, a robotic telemanipulation system capable of performing several surgical tasks has not previously been introduced to clinical neurosurgery. This is the first case report in which neurosurgical manipulation by a robotics system is described.

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Tetsuyoshi Horiuchi, Yuichiro Tanaka, Kazuhiro Hongo and Shigeaki Kobayashi

Object. Aneurysmal subarachnoid hemorrhage rarely occurs in young adults. The aim of this work was to clarify the clinical characteristics of ruptured aneurysms in young adults in the third and fourth decades of life and to compare these two age groups.

Methods. The authors retrospectively investigated 2493 patients who underwent surgical repair for ruptured cerebral aneurysms during a 14-year period (1988–2001). There were 25 patients (1%) in the third decade of life and 106 patients (4.3%) in the fourth decade. In general, favorable outcome was achieved in both groups. There were significant differences in the sizes and locations of aneurysms between the two age groups. Among patients in the fourth decade of life, the aneurysm was large and was located more often on the anterior cerebral artery.

Conclusions. In this study the authors summarize the clinical characteristics of a large series of 131 young adult patients with ruptured cerebral aneurysms. Congenital factors as well as hemodynamic stress may contribute to differences in aneurysm size and location between the two age groups.

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Yuichiro Tanaka, Shigeaki Kobayashi, Kazuhiro Hongo, Tsuyoshi Tada, Atsushi Sato and Hiroshi Takasuna

Object. The clinical and neuroimaging characteristics of hydrocephalus associated with vestibular schwannoma were retrospectively analyzed to improve the perioperative management of the circulation of cerebrospinal fluid.

Methods. A retrospective analysis was performed in 236 patients with unilateral vestibular schwannomas. The patients' ages ranged from 17 to 83 years (mean 53.6 ± 13.2 years), and the diameters of the tumors the patients harbored ranged from 5 to 60 mm (mean 30.5 ± 12.7 mm). Hydrocephalus was present before tumor resection in 33 patients (14%) and in six of these patients focal dilation of the sylvian fissures was noted. There was a significant correlation between the incidence of hydrocephalus and tumor size. The incidence of preoperative hydrocephalus among elderly patients (≥ 65 years of age) was 28.6% and that among younger patients (< 65 years of age) was 10.8%. Tumors in elderly patients with hydrocephalus (mean tumor diameter 32.8 ±11.7 mm; 12 patients) were significantly smaller than those in younger patients (mean tumor diameter 41.7 ± 10.9 mm; 21 patients). Among patients with tumors smaller than 30 mm (114 patients), the incidence of hydrocephalus in elderly patients (25%) was 12-fold higher than that in younger patients (2.1%). Six patients with hydrocephalus who had focal dilation of the sylvian fissures were significantly older than 27 patients with hydrocephalus in whom there was no focal dilation. The dilated sylvian fissures collapsed in two patients spontaneously after tumor resection and in the other four patients after shunt placement.

Conclusions. The incidence of associated hydrocephalus is higher in older patients. Communicating hydrocephalus tends to occur in elderly patients. Enlargement of the ventricles with focal dilation of the sylvian fissures should not be misinterpreted as physiological brain atrophy.

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Walid Attia, Tsuyoshi Tada, Kazuhiro Hongo, Hisashi Nagashima, Toshiki Takemae, Yuichiro Tanaka and Shigeaki Kobayashi

Object. The behavior of brain tissue in cases of arteriovenous malformations (AVMs) is a matter of debate. The authors believe that the local microvascular environment in the AVM bed shares the hemodynamic changes influencing that behavior in one way or another. The purpose of this study was to investigate the microvascular pathological features in the immediate perinidal brain tissue.

Methods. This retrospective study was conducted using excised AVM specimens obtained in 35 patients, from which the authors selected 20 specimens that fulfilled the criteria for sufficient brain tissue around the excised nidus. Specimens were stained with hematoxylin and eosin, and the immediate perinidal microvascular environment was examined using light microscopy.

Conclusions. Eighty-five percent of the AVMs studied showed the presence of huge, dilated capillaries, and 65% showed severe congestion of these capillaries. The authors have named these capillaries “giant bed capillaries.” In this study capillary bleeding was shown in AVMs, and a pericapillary space was seen around some vessels. The brain parenchyma containing AVMs with these findings proved to be significantly ischemic.

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Tetsuya Goto, Kazuhiro Hongo, Tomomi Iwashita, Hisashi Nagashima, Susumu Oikawa, Kazuhiko Kyoshima and Shigeaki Kobayashi

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Yukinari Kakizawa, Kazuhiro Hongo, Hisayoshi Takasawa, Yosuke Miyairi, Atsushi Sato, Yuichiro Tanaka and Shigeaki Kobayashi

✓ Three-dimensional (3D) neuroimages are generally considered useful for neurosurgical practice. Nevertheless, neuroimaging modalities such as 3D digital subtraction angiography and 3D computerized tomography angiography are still insufficient because the resulting images fail to delineate neural structures. Complex neurosurgical procedures are mostly performed in the cerebrospinal fluid (CSF) space of the basal cistern, where vessels and neural structures are present along with the lesion. The magnetic resonance (MR) imaging—derived 3D constructive interference in steady-state (CISS) imaging displays the margin between the CSF and neural structures, vessels, and dura mater in detail, in a two-dimensional fashion. The authors know that volume-rendered 3D CISS images would be more useful for surgery than conventional ones. Although the usefulness of “virtual MR image endoscopy” was reported previously, the endoscopic view is different from the operative field because of the perspective being emphasized. Therefore, to simulate surgical views, the authors made 3D neuroimages from a 3D CISS MR sequence by using an advanced computer workstation. After generating volume images, a cutting method was used in the desired plane to visualize the lesion with reference to a multiplanar reformatted image. The authors call these “real” 3D CISS images, and they are more comparable to the operative field. This newly developed method of producing a real 3D CISS image was used in 30 cases and contributed to the understanding of the relationship between a lesion and surrounding structures before attempting neurosurgical procedures, with minimal invasiveness to the patient.

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Yuichiro Tanaka, Kazuhiro Hongo, Tsuyoshi Tada, Keiichi Sakai, Yukinari Kakizawa and Shigeaki Kobayashi

Object. Surgical cure can be achieved in pituitary adenomas when they are completely removed. It is controversial whether postoperative radiation therapy should be given to prevent recurrence, and whether an early reoperation should be performed for residual adenomas, because we have little information about the natural history of postoperative residual adenomas.

Methods. The residual tumor volume was serially measured in 40 nonfunctioning pituitary adenomas (NFPAs) and the tumor volume doubling time (TVDT) was calculated. Correlations between the patients' age, tumor volume, log TVDT, and MIB-1 index were examined. Other factors including the patient's sex, cavernous sinus (CS) invasion by the tumor, or presence of an intratumoral cyst were analyzed to assess their influence on the TVDT. Values are expressed as the means ± standard deviations.

Thirty-eight adenomas increased in volume and two decreased during a follow-up period ranging from 4 to 141 months (mean 52.5 months). Exponentially linear tumor growth was observed in the 38 growing adenomas regardless of the residual tumor volume, with the TVDT ranging from 506 to 5378 days (mean 1836 days). The patients' age was 57.1 ± 15.7 years (range 15–79 years), the tumor volume at the beginning of the magnetic resonance imaging observation period was 2.5 ± 2.2 cm3 (range 0.07–14.5 cm3), and the MIB-1 index was 0.73 ± 0.68% (range 0.1–2.9%). There was a correlation between the log TVDT and patient age (R = 0.73), an inverse correlation between the log TVDT and MIB-1 index (r = −0.49), and an inverse correlation between the MIB-1 index and patient age (r = −0.61). A significant difference (p = 0.0001) was noted between the TVDT (1106 days) in the 19 patients younger than 61 years of age and the TVDT (2566 days) in the 19 patients who were 61 years of age or older. There was also a significant difference (p = 0.0002) between the age (50.8 ± 15.3 years) of the patients with rapidly growing tumors (TVDT < 1836 days, 24 patients) and the age (69.1 ± 7.6 years) of the patients with slowly growing tumors (TVDT > 1836 days, 14 patients). Other factors including the patients' sex, CS invasion, and intratumoral cyst formation did not affect the TVDT of residual NFPAs.

Conclusions. The tumor growth rate of residual NFPAs is strongly influenced by the patient's age. The TVDT in elderly patients is much longer than that previously reported. Treatment strategies that take into consideration the natural history of residual adenomas should be established especially in the elderly population.

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Tetsuya Goto, Kazuhiro Hongo, Jun-ichi Koyama and Shigeaki Kobayashi

Object. Robotic surgery can be used as a novel technology in ultramicrosurgery. A microscopic-manipulator (micromanipulator) system, which has a rigid neuroendoscope and three guiding manipulators, was developed in Japan for less invasive telerobotic neurosurgery. To apply this system in a clinical setting, it is necessary to confirm that it is capable of performing various surgical procedures including cutting, coagulation, and bleeding control. The authors chose the potassium titanyl phosphate (KTP) laser for such procedures. The aim of this paper was to evaluate the feasibility of this system mounted with the KTP laser.

Methods. A prototypical micromanipulator system was tested in rats. Two kinds of in vivo experiments were performed using the KTP laser: coagulation and biopsy. The coagulated lesions were precisely aligned and their maximum depths were proportional to the energy applied during the coagulation experiment. The diagnosable specimens were obtained during the biopsy experiment. The micromanipulator system was able to perform all surgical procedures accurately. There was no complication relating to the use of the micromanipulator system such as brain injury or uncontrollable bleeding.

Conclusions. The results from this study proved that this system works precisely and safely and will become a new neurosurgical tool in managing lesions that are difficult to treat using conventional microsurgery or neuroendoscopic surgery.

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