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Background Aneurysm formation after stereotactic irradiation of skull base tumors is rare. The formation and rupture of an internal carotid artery (ICA) aneurysm in a patient with skull base Ewing sarcoma/primitive neuroectodermal tumor (PNET), who underwent surgery followed by multiple courses of intensity-modulated radiation therapy (IMRT) and chemotherapy, is described. Case Description A 25-year-old man presented with a sinonasal tumor with intraorbital and intracranial growth. At that time cerebral angiography did not reveal any vascular abnormalities. The lesion was resected subtotally. Histopathologic diagnosis was Ewing sarcoma/PNET. The patient underwent multiple courses of chemotherapy and three courses of IMRT at 3, 28, and 42 months after initial surgery. The total biologically effective dose delivered to the right ICA was 220.2 Gy. Seven months after the third IMRT, the patient experienced profound nasal bleeding that resulted in hypovolemic shock. Angiography revealed a ruptured right C4-C5 aneurysm and irregular stenotic changes of the ICA. Lifesaving endovascular trapping of the right ICA was done. The patient recovered well after surgery but died due to tumor recurrence 6 months later. Conclusion Excessive irradiation of the ICA may occasionally result in aneurysm formation, which should be borne in mind during stereotactic irradiation of malignant skull base tumors.

Background: Radiosurgical management of large cystic metastatic brain tumors represents a significant challenge. Nevertheless, modified dose planning has shown beneficial results in such cases., Method and Results: "Donut's shape" radiosurgical treatment planning is based on the chain-like application of multiple, small-sized isocenters for selective coverage of the contrast-enhancing tumor capsule and minimal irradiation of the central cystic area. Such an approach was used for the management of large cystic intracranial metastases, which were not accompanied by a significant mass effect and did not require immediate volume reduction. Treatment was done using Leksell Gamma Knife model C with automatic positioning system. The majority of treated lesions showed significant shrinkage after radiosurgery and no major complications were met., Conclusion: Large cystic metastatic brain tumors may be successfully treated with gamma knife radiosurgery alone using the proposed "donut's shape" dose planning with coverage of the contrast-enhancing tumor capsule by multiple small-sized isocenters., (© Georg Thieme Verlag KG Stuttgart · New York.)

Introduction: The influence of histopathological grade and MIB-1 index of intracranial meningioma on the results of its radiosurgical management is not clear. The objective of the present retrospective study was to make an evaluation of these factors along with an analysis of other variables associated with progression-free survival after gamma knife radiosurgery (GKR)., Patients and Methods: Thirty-four intracranial meningiomas with known detailed histopathological diagnosis were analyzed. Tumors of WHO histopathological grades I, II, and III were diagnosed in 24, 3, and 7 cases, respectively. The median MIB-1 index was 1.3% (range: 0-31.9%). In 14 cases the MIB-1 index was 3.0% and more. In 26 cases the treatment was done at the time of tumor recurrence. Median volume of the neoplasm at the time of GKR was 4.1 mL (range: 0.4-43.1 mL). Median marginal dose was 12 Gy (range: 8-19 Gy). Median length of follow-up constituted 63 months (range: 19-132 months)., Results: Actuarial progression-free survival at 1, 3, 5, and 10 years constituted 100, 94, 83, and 58%, respectively. Histopathological grade II or III (p<0.0001), MIB-1 index 3% and more (p=0.0004), and non-skull base location (p=0.0026) of the tumor showed negative associations with progression-free survival in multivariate analyses. Actuarial progression-free survival at 5 years after GKR for benign and non-benign meningiomas constituted 100 and 45%, respectively (p<0.0001)., Conclusion: Radiosurgery is a highly effective management option for benign intracranial meningiomas, but growth control of non-benign ones is significantly worse. It requires close neuroradiological follow-up and necessitates the search for modified treatment strategies.

The objective of the present study was an evaluation of the incidence and risk factors for erroneous histopathological diagnosis of low-grade glioma after stereotactic biopsy. Twenty-eight tumors diagnosed as low-grade glioma after stereotactic biopsy and surgically resected thereafter were analyzed. There were 13 astrocytomas, 7 oligodendrogliomas, and 8 mixed gliomas. All neoplasms had a lobar location. Seven tumors had contrast enhancement on MRI. The number of tissue samples obtained during stereotactic biopsy was one in 19 cases, two in 4, and three or more in 5. Complete diagnostic agreement in tumor typing and grading after stereotactic biopsy and surgical resection was attained in 10 cases (36%). Agreement in tumor typing was marked in 16 cases (57%). Erroneous typing was more frequent in tumors with an MIB-1 index of less than 3% (P = 0.0629) and mixed gliomas (P = 0.0801). Overgrading of WHO grade I tumors was marked in 3 cases (11%) and undergrading of WHO grade III gliomas in 8 cases (28%). Tumor undergrading was more frequent in cases with an MIB-1 index of more than 3% (P = 0.0045). The MIB-1 index detected after stereotactic biopsy was nearly always lower compared with those established after surgical resection (P < 0.0001). In conclusion, the histopathological diagnosis of low-grade glioma established after stereotactic biopsy is associated with a substantial risk of inaccuracy. Tumors with low proliferative activity and mixed gliomas are especially susceptible for erroneous tumor typing. Undergrading of high-grade gliomas may be suspected if the MIB-1 index in the tumor specimen constitutes more, than 3%.

The availability of the intraoperative MRI and real-time neuronavigation has dramatically changed the principles of surgery for gliomas. Current intraoperative computer-aided technologies permit perfect localization of the neoplasm, precise estimation of its volume, and clear definition of its interrelationships with the eloquent brain structures. This allows maximal tumor resection with minimal risk of postoperative disabilities. Under such conditions the medical treatment has become significantly dependent on the quality of the provided information and can be designated as information-guided management. Therefore, appropriate management of the wide spectrum of the intraoperative medical data and its adequate distribution between members of the surgical team for facilitation of the clinical decision-making is very important for attainment of the best possible outcome. Further progress in advanced neurovisualization, robotics, and comprehensive medical information technology has a great potential to increase the safety of the neurosurgical procedures for parenchymal brain tumors in the eloquent brain areas.

Small intratumoral calcifications are often seen within meningioma, but ossification of the whole neoplasm is very rare. The case of an ossified frontosphenoorbital meningioma en plaque is presented. The radiological appearance resembled extensive hyperostosis extending from the anterior clinoid process to the cerebral convexity and falx cerebri. It is possible that, in some cases of meningioma, the identified "hyperostosis" represents partial ossification of the tumor itself.

Optimal management of cavernous sinus hemangiomas remains unclear. Total microsurgical removal of these neoplasms may be extremely difficult due to their rich vascularization. Three cases of cavernous sinus hemangioma treated with low-dose Gamma Knife radiosurgery are presented. Marginal dose varied from 10 to 13 Gy. Treatment planning and radiation dosimetry were done with a goal of conformal and selective coverage of the lesion with 50% prescription isodose line using multiisocenter technique. In all cases significant shrinkage of the neoplasm was marked at 3 months after treatment. Mean volume reduction at 12 months after radiosurgery was 60% (range: 45-75%). In all patients the shrinkage of the neoplasm was accompanied by notable improvement of the preexistent oculomotor nerve palsy. No radiosurgery-related complications were met during follow-up. In conclusion, low-dose Gamma Knife radiosurgery seems to be very effective for management of cavernous sinus hemangiomas, and can be considered as a treatment modality of choice for these lesions.

Metabolic characteristics of intracranial metastases, detected with proton magnetic resonance spectroscopy (1H-MRS) have known associations with clinical predictors of tumor response to radiosurgery. Therefore, it can be suspected that the metabolic profile of the neoplasm by itself might have some prognostic significance for the outcome after irradiation. Twenty-six intracranial metastases, which underwent metabolic evaluation with single-voxel 1H-MRS before gamma knife radiosurgery (GKR) and were followed for at least 3 months after treatment, were selected for retrospective analysis. The tumors most frequently originated from the lungs (9 cases), breast (7 cases), colon and rectum (5 cases). The average volume of the investigated intracranial neoplasm was 5.4+/-2.0 mL. The average marginal irradiation dose was 18.6+/-2.3 Gy. The mean follow-up after GKR constituted 8.0+/-5.5 months. Tumor response to GKR was identified in 13 cases on average 2.2+/-1.8 months after treatment. Local recurrence was marked in 10 cases on average 8.7+/-4.1 months after treatment. None of the investigated 1H-MRS metabolic parameters of intracranial metastases showed a statistically significant association with the outcome after GKR. The negative results of the present study make doubtful the predictive value of metabolic characteristics of intracranial metastases, detected with single-voxel 1H-MRS, for the outcome after radiosurgery.

Radiosurgical treatment of brain tumors is sometimes considered to be free from significant acute complications or adverse effects. A rare case of fatal intratumoral hemorrhage immediately after gamma knife radiosurgery (GKR) for brain metastasis is reported. A 46-year-old woman with lung cancer complicated by systemic dissemination experienced an acute episode of headache, speech disturbances, and right-side hemiparesis. She had no history of arterial hypertension or coagulation disorders. CT and MRI disclosed multiple brain metastases. The largest tumor, which was located in the left frontal lobe and caused a significant mass effect, was removed microsurgically without any complications. GKR for nine residual metastases was done on the fourth postoperative day. The marginal dose, which corresponded to the 50% prescription isodose line, constituted 20 Gy. No complications were noticed during frame fixation, treatment itself, or frame removal. Fifteen minutes after the end of the GKR session the patient acutely fell into a deep coma. Urgent CT disclosed a massive hemorrhage in the left cerebellar hemisphere in the vicinity of the radiosurgically treated lesion. The patient died 4 days later and autopsy confirmed the presence of intratumoral hemorrhage. In conclusion, GKR for metastatic brain tumors should not be considered as a risk-free procedure and, while extremely rare, even fatal complications can occur after treatment.

The use of endoscopes for surgery of the cerebellopontine angle tumors is steadily obtaining widespread acceptance. The objective of the present study was a laboratory and clinical evaluation of the safety of the endoscope-controlled microneurosurgical removal of the intrameatal vestibular schwannomas through a retrosigmoid approach. The anatomical investigation was done on formalin-fixed cadaver heads and dry temporal bones. Clinical series included 33 consecutive patients (23 women and 10 men; mean age 50 +/- 15 years). A bayonet-style rigid endoscope with 70 degrees angle of view and 4 mm outer diameter was found to be optimal for observation of the internal auditory canal. Its insertion in the cerebellopontine cistern should be preferably done under control through an operating microscope. Endoscope-controlled manipulations necessitate the use of a special holder system, which provides a stable position of the device and allows bimanual manipulations by the surgeon. A thermographic evaluation did not reveal a significant increase of the local temperature due to use of the endoscope. Use of the endoscope permitted removal of the neoplasm from the most lateral part of the internal auditory canal and identification of the nerve of tumor origin. In total, 28 tumors underwent total removal, and anatomical preservation of the facial nerve was attained in 31 cases. Damage of the facial nerve by the endoscope was met once. In 8 out of 16 patients, who showed serviceable hearing before surgery, this was preserved after tumor removal. In conclusion, endoscope-controlled removal of the intrameatal vestibular schwannomas seems to be a technically feasible, effective and safe procedure. Nevertheless, good equipment and special training are absolutely necessary for attainment of optimal results.

Malignant transformation of benign neoplasm after radiosurgery is usually diagnosed based on the initial presence of benign tumor, its exposure to ionizing radiation, elapsed time from radiation exposure to malignant progression, and different histological characteristics or growth rate of the regrowing tumor comparing with those originally treated. Three presented cases fulfilled these diagnostic criteria; however, it seems that progression of the tumors (schwannoma, meningioma, chordoma) resulted from the natural course of the disease, rather than represented side effects of gamma knife radiosurgery. Evaluation of the proliferative potential of the benign neoplasm before radiosurgical treatment either directly, if tumor sampling is available, or indirectly, by calculation of the tumor growth rate and/or analysis of the data of the metabolic imaging (PET, MRS) is important for identification of "aggressive" subtypes, precise prediction of prognosis, and confirmation of the radiation-induced malignant transformation in cases of tumor regrowth.

Comparative analysis of the diagnostic accuracy of FDG PET, single-voxel, and multi-voxel proton MRS for differentiation between radiation-induced necrosis and tumor recurrence was done in 9 patients with brain metastases treated by gamma knife radiosurgery. In all cases enlargement of the lesion and increase of the perilesional edema were demonstrated by MRI on average 10.6+/-2.6 months after initial treatment. Radiation-induced necrosis was identified in 5 patients (histologically in 2, clinically in 3). In one of these a false positive result of FDG PET was observed, whereas data of proton MRS were always correct. The diagnosis of tumor recurrence was established in 4 patients (histologically in 3, clinically in 1). Among these both FDG PET and single-voxel proton MRS showed false negative results (each method twice), whereas multi-voxel proton MRS always permitted us to establish the correct diagnosis. The present study demonstrates the higher diagnostic accuracy of multi-voxel proton MRS, in comparison with single-voxel proton MRS and FDG PET, for the differentiation of the radiation-induced necrosis and tumor recurrence. Its use is especially important in mixed lesions with co-existence of both post-irradiation changes and viable neoplasm. Monitoring of the treatment response by serial multi-voxel proton MRS seems to be reasonable during follow-up of patients with brain metastases after radiosurgery.

There is usually concern that ventricular enlargement is necessary for safe neuroendoscopic procedures. However, newly developed models of neurofiberscopes with a small outer diameter can be effectively used even in patients without ventriculomegaly. We present the case of a successful neurofiberscopic biopsy of a third ventricle anaplastic astrocytoma in a previously shunted patient without hydrocephalus. Subsequent gamma knife radiosurgery led to complete disappearance of the tumor. It seems that presence of collapsed ventricles, and even symptoms consistent with the slit ventricle syndrome, should not be considered as contraindications for neurofiberscopic surgery when brain compliance is sufficiently preserved. The latter should be considered as the key point of safe endoscopic manipulations. The combination of the neuroendoscopy and stereotactic radiosurgery provides wide possibilities for minimally invasive management of selected intracranial tumors.