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Takashi Handa, Yoshio Suzuki, Kiyoshi Saito, Kenichiro Sugita and Sunil J. Patel

✓ The case is presented of an isolated intramedullary posterior spinal artery aneurysm at the C-2 level in a 3-year-old girl. Quadriplegia related to probable intramedullary hemorrhage was the presenting symptom. Magnetic resonance imaging revealed findings consistent with an intramedullary vascular lesion, and vertebral angiography confirmed this to be an aneurysm of the posterior spinal artery. No associated vascular abnormalities were noted, and the aneurysm was successfully resected. Previous reports of isolated spinal aneurysms are reviewed.

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Akira Akabane, Kiyoshi Saito, Yoshio Suzuki, Masato Shibuya and Kenichiro Sugita

✓ To evaluate the effects of unroofing the optic canal during retraction of the optic nerve, the authors monitored changes in visual evoked potentials (VEPs) stimulated by a light-emitting diode in the canine model. At rest, an early VEP wave was reliably observed with an amplitude of 8.2 ± 0.6 µV and a latency of 51.5 ± 0.7 msec; this wave was named N50. The intracranial optic nerve was retracted using a weight of 5, 10 or 50 g. The earliest change in VEP noted during retraction was a reduction in N50 wave amplitude. The length of time required until N50 amplitude decreased to 50% of the control group (T50) was 10.7 ± 1.8 minutes with a weight of 5 g, 4.9 ± 0.7 minutes with 10 g, and 2.9 ± 0.4 minutes with 50 g, with statistically significant differences between the groups. Retraction of the optic nerve with all weights finally resulted in the disappearance of the N50 wave. The amplitude of the N50 wave recovered fully to control size when retraction was released immediately after the wave disappeared. The time course of amplitude recovery did not differ significantly between groups. Unroofing the optic canal prolonged the T50 during retraction significantly to 20.7 ± 2.9 minutes with a weight of 5 g, 18.9 ± 4.2 with 10 g, and 9.0 ± 2.4 with 50 g. These results demonstrate that unroofing the optic canal can protect the optic nerve from damage during operations that require optic nerve retraction.

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Masato Shibuya, Masakazu Takayasu, Yoshio Suzuki, Kiyoshi Saito and Kenichiro Sugita

✓ The authors describe the use of a bifrontal basal interhemispheric approach with or without division of the anterior communicating artery (ACoA) for removal of large craniopharyngiomas. This approach is a more basal modification of the anterior interhemispheric approach, allowing preservation of most bridging veins. Since 1988, 22 patients underwent operations using this approach to achieve total or near-total excision of large craniopharyngiomas. Division of the ACoA was performed in 11 of 17 patients with retrochiasmatic tumors with no early or late complications related to division of the artery. There were no operative mortalities. Visual improvement (59%) and preservation of the pituitary stalk (64%) were achieved in a high percentage of patients. Preservation of the pituitary stalk correlated well with postoperative pituitary function. The bifrontal basal interhemispheric approach allowed a bilateral, wider operative field with better orientation and views of important neural structures and perforating arteries without requiring combination with other approaches. When the ACoA limited operative exposure, the artery could be divided safely. The authors discuss indications for, and advantages of, the bifrontal basal interhemispheric approach with or without division of the ACoA in the removal of large craniopharyngiomas.

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Goro Otsuka, Kiyoshi Saito, Tazuka Yoshida, Yoshio Suzuki and Jun Yoshida

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Kiyoshi Saito, Keizo Fukuta, Masakatsu Takahashi, Yukio Seki and Jun Yoshida

✓ The authors report two patients with benign fibroosseous lesions involving the center of the skull base: a 15-year-old boy with repetitive meningitis and pneumocephalus and a 11-year-old boy with nasal obstruction and headache. The clinical diagnoses were ossifying fibroma and aneurysmal bone cyst, respectively. Lesions in both patients extended to the nasal cavity, the sphenoid and posterior ethmoid sinuses, and the skull base, where the planum sphenoidale, the sella turcica, the upper two-thirds of the clivus, and the medial portion of the middle cranial base were involved. The lesions were totally removed using an anterior craniofacial approach. Characteristics of these lesions and the surgical approach are discussed.

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Eiji Tachibana, Kiyoshi Saito, Keizo Fukuta and Jun Yoshida

Object. This study was undertaken to investigate the healing process and to delineate factors important for the survival of free fascial grafts used for dural repair.

Methods. A dural defect was created in guinea pigs and then reconstructed using either a free fascial graft or an expanded polytetrafluoroethylene (ePTFE) sheet. The fascial graft was covered directly by subcutaneous tissue (Group I) or by a silicone sheet to prevent tissue ingrowth from the subcutaneous tissue (Group II). The ePTFE sheet was covered with a silicone sheet (Group III). One or 2 weeks postoperatively, the strength of the dural repair was evaluated by determining the pressure at which cerebrospinal fluid (CSF) leaked through the wound margins. The dural repair was also histologically examined. In addition, using a rat model, specimens obtained from similar reconstruction sites were immunohistochemically stained with antibodies against basic fibroblast growth factor (bFGF), epidermal growth factor, or transforming growth factor—β.

The pressures at which CSF leaked after 1 and 2 weeks, respectively, were 50 ± 14 mm Hg and 126 ± 20 mm Hg in Group I, 70 ± 16 mm Hg and 101 ± 38 mm Hg in Group II, and 0 mm Hg and 8 ± 8 mm Hg in Group III. Failure of repairs made in Group III occurred at significantly lower pressures when compared with Groups I and II. In Groups I and II, a thick fibrous tissue formed around the fascial graft. This tissue tightly adhered to adjacent dura mater. The fibrous tissue displayed a positive reaction for the presence of bFGF. In Group III, only a thin fibrous membrane surrounded the ePTFE sheet.

Conclusions. Fascial grafts tolerated extraordinary intracranial pressures at 1 week postoperatively. Free fascial grafts can heal with durable fibrous tissue without the presence of a blood supply from an overlying vascularized flap.

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Goro Otsuka, Kiyoshi Saito, Tetsuya Nagatani and Jun Yoshida

Object. Neurofibromatosis Type 2 (NF2) is an intractable disorder predisposing to multiple, recurrent tumors of the central nervous system (CNS). To clarify the survival rate and characteristics that predict poor survival, we retrospectively reviewed clinical data in cases of NF2.

Methods. From among 283 patients with neurofibromatosis who had been registered in a nationwide study in Japan between 1986 and 1987, 74 patients with bilateral vestibular schwannomas were analyzed. The mean duration of follow up after diagnosis was 121 months (range 2–287 months). Results of a Kaplan—Meier product-limit analysis indicated that overall 5-, 10-, and 20-year patient survival rates following diagnosis of NF2 were 85, 67, and 38%, respectively. Early onset of the initial symptom significantly compromised survival; 5-, 10-, and 20-year survival rates in patients with symptom onset at an age younger than 25 years were 80, 60, and 28%, respectively, whereas in patients with symptom onset at an age of 25 years or older the rates were 100, 87, and 62%, respectively. Patients with small vestibular schwannomas at diagnosis (< 2 cm in diameter) had better rates of survival. Other variables such as sex, additional tumors in the CNS, or dermal abnormalities did not significantly affect survival.

Conclusions. This first report of long-term follow-up results concerning the survival of patients with NF2 indicates an adverse effect of early symptom onset.

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Yukimi Nakane, Atsushi Natsume, Toshihiko Wakabayashi, Sachie Oi, Motokazu Ito, Suguru Inao, Kiyoshi Saito and Jun Yoshida

Object

Analysis of meningiomas supports the suggestion that loss of heterozygosity (LOH) of chromosome arm 1p plays an important role in malignancy. The aim of this study was to identify genes related to meningioma progression from the benign state to the atypical and anaplastic states by examining 1p LOH and the promoter methylation of RASSF1A and p73.

Methods

The authors studied 40 surgical specimens (22 WHO Grade I, 11 Grade II, and seven Grade III) obtained in 37 patients with meningioma. The LOH at 1p36 was analyzed using microsatellite markers, and promoter methylation of p73 and RASSF1A was analyzed using methylation-specific polymerase chain reaction.

Results

No 1p LOH was detected in the Grade I tumors, whereas it was detected in more than 80% of the Grade II and III tumors. Methylation of the p73 promoter was observed in 81.8 and 71.4% of the Grade II and III tumors, respectively, but it was not observed in any of the Grade I tumors; methylation of the RASSF1A promoter was observed in 18.2, 63.6, and 42.9% of the Grade I, II, and III tumors, respectively. Interestingly, 1p LOH and p73 promoter hyper-methylation were detected in the malignantly transformed tumors but not in the lower-grade primary ones.

Conclusions

Based on the hypothesis that meningiomas cumulatively acquire genetic alterations and thus progress from the benign to the atypical and anaplastic states, genetic alterations in the methylation status of p73 or RASSF1A along with 1p LOH may result in the malignant transformation of a meningioma. This type of genetic fingerprint may play both diagnostic and therapeutic roles.

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Takeshi Okada, Kiyoshi Saito, Masakatsu Takahashi, Yasuhisa Hasegawa, Yasushi Fujimoto, Akihiro Terada, Yuzuru Kamei and Jun Yoshida

Object

The aim of this study was to describe a method for resecting malignant tumors originating in the external auditory canal or middle ear and requiring en bloc resection of the petrous bone.

Methods

Between 1995 and 2005, the authors performed en bloc petrosectomy for 18 malignant tumors in 9 male and 9 female patients, ranging in age from 15 to 74 years. Fourteen tumors originated in the external ear, 2 in the middle ear, and 2 in the parotid gland. The pathological entities included 15 squamous cell carcinomas, 2 adenoid cystic carcinomas, and 1 rhabdomyosarcoma. Through an L-shaped temporosuboccipital craniotomy, a medial osteotomy was created through the inner ear for tumors without extension into the inner ear (14 cases) and through the tip of the petrous bone for tumors reaching the inner ear (4 cases). Temporal dura mater in 3 patients and the base of the temporal lobe in 2 patients were included in the en bloc resection.

Results

Surgical complications occurred in 5 patients (28%) with no deaths. During a mean follow-up period of 45 months, 3 patients died of tumor recurrence. Overall, 2- and 5-year survival rates were 86 and 78%, respectively. Two of three patients with dural extension and 1 of 2 with brain invasion remain alive. Two of four patients with tumor extension into the inner ear died.

Conclusions

En bloc petrosectomy is recommended for malignant tumors of the ear. It is safe and effective for lesions limited to the middle ear and may be the procedure of choice for tumors reaching the inner ear and those with dural or brain invasion.

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Eiji Ito, Kiyoshi Saito, Tetsuya Nagatani, Masaaki Teranishi, Yuzuru Kamei, Shunjiro Yagi, Takashi Kawabe, Norihiro Niimi and Jun Yoshida

Lymphangioma localized to the bones of the skull base is rare. The authors report herein the case of a 5-year-old boy who presented with lymphangioma of the bone, localized to the skull base and leading to cerebrospinal fluid (CSF) rhinorrhea with meningitis. Neuroimaging demonstrated lytic destruction with a cyst in the right middle skull base. The patient was successfully treated with resection of the tumor and prevention of CSF leakage. Histopathological examination revealed a lymphangioma. An enlarging lymphangioma can lead to bone destruction. A differential diagnosis of a lytic lesion for a cyst at the skull base is important for proper case management.