Mariko Nagai

Tokyo Women's Medical University, Tokyo, Tokyo-to, Japan

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Publications (3)8.98 Total impact

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    ABSTRACT: The objective of the present study was the evaluation of outcome in 130 patients with essential trigeminal neuralgia, who were treated using Leksell Gamma Knife model C with automatic positioning system and followed at least 24 months thereafter. Radiosurgery was guided by fused thin-sliced magnetic resonance (MR) and "bone window" computed tomographic (CT) images. In all cases, retrogasserian part of the trigeminal nerve at the level of trigeminal incisura was selected as a target, and one 4-mm collimator was used for delivery of the maximum irradiation dose of 90 Gy. The coordinates of the isocenter were adjusted for positioning of the nerve in the center of 80% isodose area, and were corrected in each individual case with regard to presence of distortion artifacts on MR images. Initial relief of the typical paroxysmal facial pain was marked in 127 patients (98%) within a median interval of 3 weeks after treatment. However, in 23 patients the pain re-appeared later on. Overall, at the time of the last follow-up 112 patients (86%) were pain-free, including 86 who remained both pain- and medication-free after initial radiosurgery. In 31 cases (24%), treatment was complicated by facial hypesthesia and/or paresthesia. In conclusion, radiosurgery of essential trigeminal neuralgia results in a high rate of initial pain relief, but pain recurrences and associated complications are not uncommon. The outcome may be influenced by various technical nuances; therefore, treatment should be preferably done in specialized clinical centers with sufficient expertise in the management of this disorder.
    No preview · Article · Jun 2011 · Neurosurgical Review
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    ABSTRACT: Abducent nerve schwannomas are extremely rare. The authors recently performed Gamma Knife surgery (GKS) in 4 patients with such tumors and describe their experiences with these cases. The patients consisted of 3 women and 1 man whose ages varied from 31 to 60 years (mean 46 years). Two patients had no symptoms, 1 complained of slight visual disturbances, and the other 1 had abducent nerve palsy. Neurofibromatosis was not diagnosed in any case. All 4 tumors were located in the cavernous sinus: 2 of these tumors within the borders of the sinus, 1 tumor extending into the orbit, and 1 tumor extending into the prepontine cistern. The volume of the neoplasms varied from 1.7 to 4.9 cm(3) (mean 3.0 cm(3)). No patient underwent tumor resection. Treatment was delivered with the aid of a Leksell Gamma Knife model C unit and the automatic positioning system. The dose directed to the tumor margin was 12 Gy in all cases. The dose directed to the anterior visual pathways was kept below 10 Gy and that to the brainstem below 14 Gy. The length of follow-up varied between 7 and 43 months (mean 27 months). There were no acute complications or side effects. Imaging studies showed temporary enlargement of all tumors during the 1st posttreatment year, but thereafter, there was a trend toward reduction in volume. None of the neoplasms displayed regrowth. In the 3 patients who did not have abducent nerve palsy before GKS, it appeared, at least temporarily, after the procedure. Purely intracavernous neoplasms in general followed uneventful posttreatment courses, but dumbbell-shaped tumors were associated with significant morbidity. The cisternocavernous schwannoma underwent cystic degeneration 2 years after GKS, and the patient developed diplopia. After GKS, the patient treated for an orbitocavernous schwannoma experienced a significant deterioration in vision, temporary blindness in 1 eye, and late development of permanent abducent nerve palsy, which were seemingly caused by compression of neurovascular structures within the anulus of Zinn during a temporary increase in the lesion's volume after irradiation. Gamma Knife surgery controls the growth of abducent nerve schwannomas and may be effectively used to manage intracavernous neoplasms. Caution, however, should be used in cases of dumbbell-shaped tumors, particularly those extending through the superior orbital fissure.
    No preview · Article · Dec 2010 · Journal of Neurosurgery
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    ABSTRACT: The objective of the present retrospective study was evaluation of results of "robotic microradiosurgery" of pituitary adenomas invading the cavernous sinus. Eighty-nine patients with such tumors underwent management using Leksell Gamma Knife model C with automatic positioning system. There were 77 residual and 12 recurrent neoplasms. The applied radiosurgical treatment plan was based on the use of multiple isocenters, mainly of smaller size, which were positioned compactly within the border of the lesion with resultant improved dose homogeneity, increased average dose within the target, and sharp dose fall outside the treated volume. The marginal dose varied from 12 to 25 Gy (mean, 18.2 Gy) in non-functional pituitary adenomas (43 cases), and from 12 to 35 Gy (mean, 25.2 Gy) in hormone-secreting ones (46 cases). The length of follow-up after treatment ranged from 24 to 76 months (mean, 36 months). Control of the tumor growth was attained in 86 cases (97%), whereas actual shrinkage of the lesion was marked in 57 cases (64%). In 18 out of 46 secreting neoplasms (39%), normalization of the excess of the pituitary hormone production was noted after radiosurgery. Treatment-associated morbidity was limited to transitory cranial nerve palsy in two patients (2%). No patient with either non-functional or hormone secreting tumor exhibited new pituitary hormone deficit after treatment. In conclusion, highly precise microanatomy-based Gamma Knife robotic microradiosurgery provides an opportunity for effective management of pituitary adenomas invading the cavernous sinus with preservation of the adjacent functionally important neuronal structures.
    Full-text · Article · Jun 2010 · Journal of Neuro-Oncology