OBJECTThe 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).METHODSThirty-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.CONCLUSIONSReduction 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 low-dose group, however, was much shorter.

Der Mikrochirurgie des Akustikusneurinoms (Vestibularisschwannoms [20]) ist es vor allem nach Einführung des Operationsmikroskops möglich geworden, in kundiger Hand die gefürchtete Komplikation einer Fazialisläsion zu vermeiden. Bei kleinen Neurinomen gelingt es auch, das Hörvermögen oder auch ein Resthörvermögen zu erhalten [4,17,21,22,27,28,29]. Trotzdem ist die offene Operation des Akustikusneurinoms infolge der schwierigen Lokalisation auch für den geübten Operateur immer noch eine technische Herausforderung und für den Patienten eine Belastung, vor allem bei schlechtem internem Status. Aus diesem Grunde wird bei kleinen Akustikusneurinomen gelegentlich beobachtet, ob sie überhaupt ein Wachstum zeigen, mit dem Risiko, dass das Resthörvermögen gänzlich schwindet.

The effect of radiosurgical treatment of skull base meningiomas in 197 patients with a follow-up of at least 2 years was evaluated. Ninety-two of these patients had combined surgical and radiosurgical treatment, while Gamma Knife Radiosurgery (GKRS) was performed as primary treatment in 105 patients. Follow-up was available in 164 patients with intervals of 25-97 months (median 55 months) after GKRS. The imaging controls revealed decreased tumour size in 84 patients (51%), stable tumour volume in 76 ca ses (47%) and increased tumour size in 4 cases (2%). Neurological examinations showed improved neurological status in 58 cases (35%), stable clinical status in 100 patients (61%) and slight worsening in 6 cases (4%). Due to excellent tumour control rate, good clinical outcome and a low complication rate GKRS represents not only an attractive additional treatment option for basal meningiomas, but may even replace microsurgery in selected cases.

OBJECTIVE: Drug-resistant epilepsy associated with hypothalamic hamartomas (HHs) can be cured by microsurgical resection of the lesions. Morbidity and mortality rates for microsurgery in this area are significant. Gamma knife surgery (GKS) is less invasive and seems to be well adapted for this indication. METHODS: To evaluate the safety and efficacy of GKS to treat this uncommon pathological condition, we organized a multicenter retrospective study. Ten patients were treated in seven different centers. The follow-up periods were more than 12 months for eight patients, with a median follow-up period of 28 months (mean, 35 mo; range, 12-71 mo). All patients had severe drug-resistant epilepsy, including frequent gelastic and generalized tonic or tonicoclonic attacks. The median age was 13.5 years (range, 1-32 yr; mean, 14 yr) at the time of GKS. Three patients experienced precocious puberty. All patients had sessile HHs. The median marginal dose was 15.25 Gy (range, 12-20 Gy). Two patients were treated two times (at 19 and 49 mo) because of insufficient efficacy. RESULTS: All patients exhibited improvement. Four patients were seizure-free, one experienced rare nocturnal seizures, one experienced some rare partial seizures but no more generalized attacks, and two exhibited only improvement, with reductions in the frequency of seizures but persistence of some rare generalized seizures. Two patients, now seizure-free, were considered to exhibit insufficient improvement after the first GKS procedure and were treated a second time. A clear correlation between efficacy and dose was observed in this series. The marginal dose was more than 17 Gy for all patients in the successful group and less than 13 Gy for all patients in the improved group. No side effects were reported, except for poikilothermia in one patient. Behavior was clearly improved for two patients (with only slight improvements in their epilepsy). Complete coverage of the HHs did not seem to be mandatory, because the dosimetry spared a significant part of the lesions for two patients in the successful group. CONCLUSION: We report the first series demonstrating that GKS can be a safe and effective treatment for epilepsy related to HHs. We advocate marginal doses greater than or equal to 17 Gy and partial dose-planning when necessary, for avoidance of critical surrounding structures.

OBJECTIVE:Corpus callosotomy is a surgical option for medically uncontrolled generalized epilepsy in appropriate patients. Because numerous complications related to open callosotomy are still reported, we performed radiosurgical corpus callosotomy with the gamma knife.METHODS:Between October 1992 and June 1995, three patients underwent stereotactic radiosurgery to ablate the anterior third of the corpus callosum. The patients had intractable epilepsy: two had Lennox-Gastaut syndrome, and one had multifocal epilepsy with atonic, tonicoclonic, and atypical absence seizures. The history of seizures ranged from 20 to 37 years' duration. Stereotactic radiosurgery was performed with a cobalt-60 gamma knife using a 4-mm collimator, targeted to the rostrum, genu, and anterior third of body of the corpus callosum. Two patients were treated once with 150 and 160 Gy at maximum, respectively, and one patient was treated in two stages with 50 Gy and then 170 Gy at maximum.RESULTS:The severity and frequency of seizures were significantly reduced in all three patients. The types of seizures associated with the most improved outcome were atonic and generalized tonicoclonic seizures. The mean follow-up period was 38 months. Hospitalization required for this procedure was 3 days. No complications related to irradiation were recorded except transient headache in one patient.CONCLUSION:The outcomes suggest that radiosurgical corpus callosotomy may be a promising alternative treatment to open callosotomy.

OBJECTIVE: We used a paramedian, infratentorial-supracerebellar, transcollicular approach to resect 11 intrinsic tectal lesions, including 8 tumors and 3 hematomas, in 11 patients. The route of access to the lesions was designed to minimize the anatomic and functional damage to the surrounding structures. METHODS: Access was through one superior colliculus in each of seven patients, through one inferior colliculus in each of two patients, and through the superior and inferior colliculi of one side in each of two patients. RESULTS: Of the eight tumors, three were totally resected, four were nearly totally resected, and one was partially resected. The preoperative ocular symptoms did not change in six of these eight patients and worsened in two, and the neurological deficits, except ocular symptoms, improved in two. All three hematomas were completely removed, along with abnormal blood vessels in the wall of the hematoma cavity; all three of these patients experienced neurological improvement. CONCLUSION: We conclude that the paramedian, infratentorial-supracerebellar, transcollicular approach permits safe removal of intrinsic tectal lesions. Resection of the superior or inferior colliculus or both on one side seems to be neurologically well tolerated.

Surgery of midline lesions is difficult in many cases and often only partial removal is possible. Between May 1992 and April 1997, 81 patients with midline lesions were treated radiosurgically. The lesions were located in the hypothalamic region (25), thalamus (20), third ventricle (2), quadrigeminal plate (9), pons (13), fourth ventricle (4), pineal region (4) and other locations (4). Forty-eight patients were male and 33 were female. Histologically, there were 56 benign cases (13 arteriovenous malformations, 11 low grade gliomas, 20 craniopharyngiomas, 5 meningiomas, 3 hamartomas, 4 miscellaneous) and 25 malignant cases (10 metastases, 10 high grade gliomas, 2 medulloblastomas, 3 miscellaneous). Clinical and radiological follow-up was obtained in 71 patients (88%). In all patients the treatment was well tolerated. Radiographic response could be achieved in 39 of 68 tumor patients (57%). A complete obliteration was seen in 6 arteriovenous malformations (60%) 2 years after radiosurgery. A second radio-surgical procedure was necessary in 2 patients because of incomplete obliteration after 3 years. According to our experience, we can conclude that radiosurgery appears to be effective as adjuvant treatment of midline lesions.

Neurosurgical training in Austria is characterized by individual concepts of the 3 medical school departments as well as 6 departments at community hospitals. Thus, the situation in Austria is comparable with many European countries [2]. In addition in Austria, neurosurgery as an individual and distinct speciality evolved at the various sites at different times with different background.

Purpose/Ob~eet~'ve:It is thought that focally increased dose resulLs in improved survival in selected patients with malignant glioma, and many patients receive radiosurgery as part of their therapy.However, the association between selection and outcome is poorly understood.We performed a retrospective multi-institutional analysis to determine factors associated with better or worse survival and complications.The 9 participating Gamma Knife facilities provided a broad range of selection criteria and clinical and technical data that could be related to outcome. Materials & Methods:A total of 202 tumors were treated in 189 patients (176 patients with unifocal tumor; 13 patients with bifocal tumors treated on the same day), with 30% of patients treated for primary tumor and 70~ for recurrent tumor.Pathological diagnoses included glioblastoma (51%), anaplastic astrocytoma (23%), astrocytoma (23%), and pilocytic astrocytoma (3%).Median (range) characteristics were: age 47 years (2-84 years), KPS 90 (40-100), minimum tumor dose 16 Gy (5-37.5 Gy), prescription isodose percent 50% (20-90%), number of isocenters per tumor 5 (1-15), and median treatment volume 64 cc (0.3-96.0 cc).Brachytherapy selection criteria were satisfied in 65% of patients.The primary endpoints of the study were survival and complications.Median follow-up of surviving patients was 65 weeks after radiosurgery (maximum 341 weeks). Results:Acute complications were seen in 9% of evalualed patients, chronic complications in 17% of evaluated patients followed at least one year, and chronic steroid dependency in 36% of evaluated patients followed at least one year.Long-term KPS was found to improve or remain stable in approximately half of surviving patients.No factors were identified that were significantly associated with risk of chronic complications.Risk of acute complications and chronic corticosteroid dependency were associated with older patient age.Multivariate analysis showed that significantly improved survival was associated with 5 variables: lower pathologic grade, younger age, increased Karnofsky performance status (KPS), smaller tumor volume, and unifocal tumor.A hazard ratio model that is independent of the technical details of radiosurgery suggests that variations in reported survival following radiosurgery may be explained in part by differences in distributions of these variables.Survival from the date of radiosurgery was not found to be significantly related to technical parameters associated with radiosurgery (dose, isocenters, prescription percent, inhomogeneity), extent of pre-radiosurgery surgery, or whether typical brachytherapy selection criteria were satisfied. Conclusion:Patients with a poor constellation of 5 clinical variables are unlikely to obtain significant benefit from radiosurgery; patients with a favorable constellation may obtain a benefit similar to that of brachythcrapy.These 5 variables should be incorporated in the design of future studies.

A review of a series of 56 patients with a giant intracranial aneurysm showed that 28 presented with signs related to the mass effect and 19 with subarachnoid hemorrhage (SAH). Additional clinical signs observed were seizures, ischemia, and endocrinological disturbances. Fourty-five aneurysms involved the carotid artery territory and eleven the vertebrobasilar system. On computed tomography (CT) images partially thrombosed aneurysms (23 cases) showed 1) a marginal or central “target” appearance on contrast enhanced scans corresponding to the non-thrombosed lumen as demonstrated by angiography, 2) capsular enhancement in 16 cases and 3) calcifications in 9. SAH occured in 13 and 6 cases of non-thrombosed and partially thrombosed aneurysms, respectively. Magnetic resonance imaging (MRI) in 6 cases showed several layers of thrombosis in 4 cases and a small signal void close to the parent artery. In one case of a non-thrombosed aneuroysm, thrombosis was mimicked by flow artifacts of MRI.