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Gerhard Pendl

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Gerhard M. Friehs, Oskar Schröttner and Gerhard Pendl

✓ The lateral spinothalamic tract, located in the anterolateral quadrant of the white matter of the spinal cord, is one of the most important structures in transmitting pain within the central nervous system. It has been known for almost a century that destruction of fibers in this tract results in analgesia contralateral to the lesion. The effectiveness and clinical importance of interruption of the lateral spinothalamic tract has been proven in many studies. Today cordotomies are still a useful neurosurgical treatment modality, especially when pain can no longer be sufficiently controlled by analgesic drugs. Although analgesia on the contralateral side is the desired effect, one must also expect to cause disturbance in temperature sensation when performing a cordotomy.

The authors' observations showed that after a cordotomy the dermatome level of analgesia can be variable within certain limits, which is in accordance with the literature. Surprisingly, however, the loss of temperature sensation may differ significantly from the loss of pain sensation. It was also found to be possible to perform a successful cordotomy without altering the sensation of temperature at all. This indicates that pain and temperature sensations may be conducted via separate pathways. Possible mechanisms underlying this phenomenon are discussed.

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Gerald Langmann, Gerhard Pendl, Klaus Müllner, K. H. Feichtinger and Georg Papaefthymiouaf

Object. The authors compared the results of gamma knife radiosurgery in patients with uveal melanoma who underwent high-dose (treated from 1992–1995) and low-dose irradiation (treated from 1996–2002).

Methods. Thirty-one patients with uveal melanomas were treated with a mean margin dose of 52.1 Gy (high dose) and 33 with a mean dose of 41.5 Gy (low dose), and results were compared between groups. The technical procedure was the same in each group except for radiation dose.

In the low-dose group, complete tumor regression (scar formation) occurred in 12% and in the high-dose group in 26%. Partial regression (reduction of the tumor prominence between 50 and 80%) occurred in 81% of the low-dose group and in 58% of the high-dose group.

Neovascular glaucoma as a severe complication developed in 9% of the low-dose group and in 48% of the high-dose group.

Conclusions. Reduction of the margin dose from 52.1 to 41.5 Gy appears to achieve the same rate of tumor regression but is associated with a lower rate of severe side effects such as neovascular glaucoma. The follow-up period in the lowdose group, however, was much shorter.

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Klaus A. Leber, Jutta Berglöff and Gerhard Pendl

As the number of patients treated with stereotactic radiosurgery increases, it becomes particularly important to define with precision adverse effects on distinct structures of the nervous system.

Object. This study was designed to assess the dose—response tolerance of the visual pathways and cranial nerves after exposure of the cavernous sinus to radiation.

Methods. A total of 66 sites in the visual system and 210 cranial nerves of the middle cranial fossa were investigated in 50 patients who had undergone gamma knife treatment for benign skull base tumors. The mean follow-up period was 40 months (range 24–60 months). Follow-up examinations consisted of neurological, neuroradiological, and neuroophthalmological evaluations.

The actuarial incidence of optic neuropathy was zero for patients who received a radiation dose of less than 10 Gy, 26.7% for patients receiving a dose in the range of 10 to less than 15 Gy, and 77.8% for those who received doses of 15 Gy or more (p < 0.0001). Previously impaired vision improved in 25.8% and was unchanged in 51.5% of patients. No sign of neuropathy was seen in patients whose cranial nerves of the cavernous sinus received radiation doses of between 5 and 30 Gy. Because tumor control appeared to have been achieved in 98% of the patients, the deterioration in visual function cannot be attributed to tumor progression.

Conclusions. The structures of the visual pathways (the optic nerve, chiasm, and tract) exhibit a much higher sensitivity to single-fraction radiation than other cranial nerves, and their particular dose—response characteristics can be defined. In contrast, the oculomotor and trigeminal nerves have a much higher dose tolerance.

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Gerhard Pendl, Frank Unger, Georg Papaefthymiou and Sandro Eustacchio

Object. Large brain lesions are considered unamenable to gamma knife treatment because of possible adverse effects. The proximity of eloquent brain to a target location, including some arteriovenous malformations (AVMs), still poses a challenge to the neurosurgeon. Because meningiomas and AVMs often show a slow or absent growth rate, partial radiosurgical treatment in cases with risk of unacceptable surgery-related morbidity is an alternative. The authors evaluated the results of staged treatment.

Methods. Since April 1992, 12 patients suffering from large benign tumors (meningiomas) and seven with AVMs considered inoperable underwent gamma knife radiosurgery in staged procedures. All patients with tumors underwent primary open surgery for partial removal of recurrent growth and subsequent radiosurgical treatment. Four men and eight women ranging in age from 26 to 73 years harbored tumors that ranged in volume from 19 to 90 cm3. Marginal dose ranged from 10 to 25 Gy prescribed in the 30 to 50% isodose. The time interval between the radiosurgical treatments varied from 1 to 8 months. Follow up ranged from 5 and 89 months. Three female and four male patients (age range 10–48 years) had undergone previous AVM embolization and were treated with margin doses of 18 to 22 Gy in the 40 to 50% isodose. The volume range of these AVMs was 11 to 25 cm3. The time interval between radiosurgical treatments ranged from 5 to 36 months. The mean follow up was 22.6 months.

Neurological follow-up examinations showed clinical improvement in 11 patients (58%), whereas five (26%) remained unchanged. Among tumor patients no deterioration or further tumor growth was observed. Tumor necrosis demonstrated noticed in five patients (26%). One patient with an AVM suffered from seizures and hemiparesis. Follow-up magnetic resonance imaging of the residual nidus disclosed no rebleeding.

Conclusions. For selected patients with large benign lesions staged gamma knife radiosurgery could be an alternative, as evidenced by the authors' series in which there was no mortality and low incidence morbidity.

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Klaus Haselsberger, Herbert Radner, Walter Gössler, Claudia Schlagenhaufen and Gerhard Pendl

✓ Because of the short range of the highly energetic particles helium-4 and lithium-7 that results from neutron-induced disintegration of boron-10, the efficacy of Boron Neutron Capture Therapy (BNCT) is heavily dependent on 10B-microlocation. Despite the crucial importance of boron-10, there is little specific information with regard to the agent currently used for inducing BNCT, namely Na2B12H11SH. In the present study, a subcellular 10B-location was investigated in tumor tissue obtained from seven patients with glioblastoma World Health Organization Grade IV. These patients received Na2B12H11SH at doses used in therapeutic trials (75 mg/kg body weight in five patients, and 150 mg/kg body weight in two patients, respectively). In three cases, boron-10 was identified in glioblastoma cells by laser microprobe mass analysis. In these tumors, boron-10 was found only in the nuclei of neoplastic cells but not in other cell compartments. These preliminary results suggest a predominant association of Na2B12H11SH with the nuclei of malignant glioma cells and thus support the value of Na2B12H11SH as a suitable boron carrier for BNCT.

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Gerald Langmann, Gerhard Pendl, Klaus-Müllner, Georg Papaefthymiou and Helmuth Guss

Object. The authors report their experience using gamma knife radiosurgery (GKS) to treat uveal melanomas.

Methods. Between 1992 and 1998, 60 patients were treated with GKS at a prescription dose between 45 Gy and 80 Gy. The mean diameter of the tumor base was 12.2 mm (range 3–22 mm). The mean height of the tumor prominence was 6.7 mm (range 3–12 mm). The eye was immobilized.

The follow-up period ranged from 16 to 94 months. Tumor regression was achieved in 56 (93%) of 60 patients. There were four recurrences followed by enucleation. The severe side effect of neovascular glaucoma developed in 21 (35%) patients in a high-dose group with larger tumors and in proximity to the ciliary body. A reduction in the prescription dose to 40 Gy or less and excluding treatment to tumors near the ciliary body decreased the rate of glaucoma without affecting the rate of tumor control.

Conclusions. Gamma knife radiosurgery at a prescription dose of 45 Gy or more can achieve tumor regression in 85% of the uveal melanomas treated. Neovascular glaucoma can develop in patients when using this dose in tumors near the ciliary body. It is advised that such tumors be avoided and that the prescription dose be reduced to 40 Gy.

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Gerhard M. Friehs, Joseph Legat, Zhen Zheng, Gerhard Pendl and Georg C. Noren

In order to determine the effectiveness of gamma knife (GK) radiosurgery in patients with malignant melanoma metastases, the authors conducted a prospective multicenter study. :Forty-five patients with a total of 96 lesions were treated and followed to measure survival time, tumor control rate, and Karnofsky Performance Scale (KPS) score. The mean survival time was 8.7 months (median 4.2 months), and tumor control was achieved in 86% of lesions. When obtained, the median preoperative KPS of 80 was maintained at a median of 80 post-GK treatment.

The authors found GK treatment for metastases of malignant melanoma to be highly effective in controlling tumor growth. Survival rates obtained after GK treatment were found to be superior to historically obtained data concerning external beam radiotherapy follow up. Radiosurgery with the GK can therefore be considered a good primary treatment option for metastatic brain disease of malignant melanoma.

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Bernhard Sutter, Adam Arthur, Jeffrey Laurent, James Chadduck, Gerhard Friehs, Georg Clarici and Gerhard Pendl

Surgical treatment of intrameduallary spinal cord metastases (ISCM) has become increasingly effective in recent years. The advent of new imaging techniques combined with an enhanced understanding of the natural history of these tumors has improved the effectiveness of the available treatment options. The authors present three new cases of ISCM successfully treated with surgery. A review of 129 cases found in the literature is also discussed. Characteristic symptomology and presentation are reviewed with an eye toward improving diagnostic methodology. The natural history of ISCM is divided into three phases. Surgical intervention should be used early in phase 2.

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Klaus A. Leber, Gerhard Pendl, Sonja Kogler, Fritz Kammerhuber and Franz Ebner