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  • By Author: Lunsford, L. Dade x
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Mark E. Linskey, A. Julio Martinez, Douglas Kondziolka, John C. Flickinger, Ann H. Maitz, Theresa Whiteside and L. Dade Lunsford

the microscope, the two perpendicular tumor implant diameters were measured using sterile electrocardiographic calipers which were then read against a fine-gradation ruler. Measurements were accurate within 0.1 mm. A 0.5-mm length of sterile coiled titanium wire was placed adjacent to the tumor implant beneath the renal capsule for x-ray targeting purposes ( Fig. 1 ). The average tumor diameter was determined by the equation: D = length × width × ½, and the tumor volume from the equation: V = length × width × width × ½. 7 Fig. 1. A: Artist's rendition of

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Brian R. Subach, Douglas Kondziolka, L. Dade Lunsford, David J. Bissonette, John C. Flickinger and Ann H. Maitz

Leksell model G stereotactic headframe was affixed to the patient's head after intravenous administration of mild sedation and infiltration of the scalp with a buffered local anesthetic agent. Target localization was performed using high-resolution contrast-enhanced multiplanar magnetic resonance (MR) imaging. Computerized tomography (CT) scanning was used before 1991. Since 1992, a specific volume-acquisition MR imaging protocol with 1-mm slices has been used to provide detailed graphic information regarding the tumor and adjacent critical structures and to allow

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Brian R. Subach, Douglas Kondziolka, L. Dade Lunsford, David J. Bissonette, John C. Flickinger and Ann H. Maitz

Object

Stereotactically guided radiosurgery is one of the primary treatment modalities for patients with acoustic neuromas (vestibular schwannomas). The goal of radiosurgery is to arrest tumor growth while preserving neurological function. Patients with acoustic neuromas associated with neurofibromatosis Type 2 (NF2) represent a special challenge because of the risk of complete deafness. To better define the tumor control rate and long-term functional outcome, the authors reviewed their 10-year experience in treating these lesions.

Methods

Forty patients underwent stereotactic radiosurgery at the University of Pittsburgh, 35 of them for solitary tumors. The other five underwent staged procedures for bilateral lesions (10 tumors, 45 total). Thirteen patients (with 29% of tumors) had undergone a median of two prior resections. The mean tumor volume at radiosurgery was 4.8 ml and the mean tumor margin dose was 15 Gy (range 12–20 Gy).

The overall tumor control rate was 98%. During the median follow-up period of 36 months, 16 (36%) tumors regressed, 28 (62%) remained unchanged, and one (2%) grew. In the 10 patients for whom more than 5 years of clinical and neuroimaging follow-up results were available (median 92 months), five tumors were smaller and five remained unchanged. Surgical resection was performed in three patients (7%) after radiosurgery; only one showed radiographic evidence of progression. Useful hearing (Gardner-Robertson Class I or II) was preserved in six (43%) of 14 patients and this rate improved to 67% after modifications made in 1992. Normal facial nerve function (House-Brackmann Grade 1) was preserved in 25 (81%) of 31 patients. Normal trigeminal nerve function was preserved in 34 (94%) of 36 patients.

Conclusions

Stereotactically guided radiosurgery is a safe and effective treatment for patients with acoustic tumors in the setting of NF2. The rate of hearing preservation may be better with radiosurgery than with other available techniques.

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L. Dade Lunsford, Douglas Kondziolka, John C. Flickinger, David J. Bissonette, Charles A. Jungreis, Ann H. Maitz, Joseph A. Horton and Robert J. Coffey

physicians and reviewed at our institution. Results Radiation Dosimetry Results of radiation dosimetry planning are presented in Table 4 . The volume of the largest AVM treated was 31.5 cu cm (the diameter for a sphere of equivalent volume is 39.2 mm). In order to maintain a steep fall-off in radiation dose, patients accepted for treatment usually had an AVM measuring less than 35 mm in mean diameter. TABLE 4 Radiosurgery dosimetry planning in 227 patients with arteriovenous malformation Lesion Volume & Coverage Cases No