M. Gerosa

Gamma Knife Radiosurgery in the Management of Unusual Grade I/II Primitive Neuroepithelial Tumours of the Brain

Now, Gamma Knife radiosurgery (GKRS) is considered a first choice therapeutic option in a wide setting of malignant and benign intracranial diseases. Particularly, the application of GKRS in pilocytic (GI) and diffuse (GII) astrcytomas, which currently represent the most frequent brain neoplasms in children and young adults, has been often described. In the different series, the reported overall tumor growth control (TGC) varies between 50%-100%, the Overal Survival (OS) is 78.6%-100% with a 5-year local progression free survival (PFS) comprised between 88.9% and 97.4%. The GKRS-related permanent neurologic morbidity is generally less then 5% (0%-7%) (Kano et al., 2009a; Kano et al., 2009b; Boethius et al., 2002; Hadjipanayis et al., 2002a; Hadjipanayis et al., 2002b; Kida et al., 2000; Simonova et al., 2005; Heppner et al., 2005). Therefore, GKRS is considered an effective and safe therapeutic tool in the multidisciplinary treatment of pilocytic and diffuse astrcytomas, as well. Nevertheless, the effectiveness of GKRS is much less known as concerns other unusual Low-Grade Primitive Neuroepithelial Tumors (LGPNTs) of the brain because data regarding the long-term efficacy of GKRS on a large series of patients with such tumors is lacking. The aim of this chapter is to assess the value of GKRS in the management of such cerebral tumors. The interest of this study is founded on several observations: 1) unusual LGPNTs are rare tumours; there are a few series with at least ten reported cases, only (Hasegawa et al., 2002; Kim et al., 2007); 2) these tumors are frequently deep-seated in the brain or located in functional cerebral regions, thus gross total surgical removal may often be highly risky or impossible sometimes; 3) unusual LGPNTs are more frequent in children and young adult patients (Reyns et al., 2006; Yen et al., 2007). Furthermore, the management of residual, recurrent or unresectable tumours represent a challenge for neurosurgeons and neurooncologists due to: 1) histotypes with frequently high radioand chemo-resistance; 2) high risk of permanent delayed brain tissue radiation damage in often very young patients and with long life expectancy. The reason behind the increased

Diffusion-Tensor Imaging Tractography of the Corticospinal Tract for Evaluation of Motor Fiber Tract Radiation Exposure in Gamma Knife® Radiosurgery Treatment Planning

Aims: To assess the feasibility of diffusion-tensor imaging (DTI) fibertractography of the corticospinal tract (CST) performed with 3 T MRI as a tool for Gamma Knife®

Radiosurgical Treatment of Intracranial Meningiomas: Update 2011

Meningiomas account for 16%-25% of all intracranial tumors, and quite often they rank amongst the most frequent neuro-oncological diagnostic subgroups in European or American registries (4, 5, 8, 54) As regards their natural history, (23, 29, 46, 55, 56, 59, 61) the few reported series of conservatively managed symptomatic meningiomas–bearing adequate FUhave documented a consistent progression in approximately one-third of patients, although in a wide spectrum of variability (TABLE 1).

Gamma Knife Radiosurgery in Vestibular Schwannomas: Clinical and Radiological Impact on the Tumor Course

Up to the last decade, therapeutic options for patients with vestibular schwannomas (VS) were limited to total or subtotal excision or expectant serial observation. Stereotactic irradiation, and particularly gamma knife radiosurgery (GKR), have offered an important additional option to the overall management strategy. Clinical results, in terms both of tumor growth control (TGC) and of preserved regional cranial nerve function, have increasingly validated this approach in properly selected indications for either primary or recurrent tumors. Indeed, using current neuroradiological techniques (MRI-CT fusion algorithms) as well as newer radiodosimetry programs and reduced dosages, the reported achievable TGC rate actually exceeds 90% in mid-term follow-up (5 years), whereas the relevance of radio- induced cranial neuropathy has been minimized: facial impairment incidence lower than 3%, with hearing function (Gardner-Robertson [G-R] 1-2) pre- served in over 60% of the patients. Our experience, in a series of 170 treated VS (9.4% NeuroFibromatosis type 2, or NF2) further confirms these data: the group of evaluable cases (112 patients with over 4 years of mean follow-up) shows an overall TGC rate of 93%, with an extremely low incidence of facial impairment (2.7%) and hearing preservation in 66% (G-R 1-2). However, long-term fullow-up results in large series of patients treated by contempo- rary GKR techniques are not yet available: with lowering treatment dosages, surviving tumor cells might sustain a delayed regrowth, eventually decreas- ing TGC rates. To date, GKR may be advocated for small-to-medium-sized VS, with negative cranial nerve staging, absent or minimal hearing deficit, and in several cases with major surgical contraindications or in patients refusing microsurgery. Furthermore, it is worth stressing that particularly for elderly patients with larger schwannomas and for NF2 patients, an integrated program including both GKR and microsurgery should always be considered.

Immunohistochemical demonstration of HLA-DR positive cells in normal and neoplastic brain tissues. I. Preliminary Report

Recent evidence indicates that HLA-DR positive cells of putatively glial origin may be present in normal and neoplastic brain tissues. The nature and function of these cells is under debate. Freshly frozen sections from 9 brain tumor patients were analyzed by immunohistochemical techniques for HLA-DR antigens, using a panel of antisera and monoclonal antibodies, with and without normal human serum pre-incubation; five non-neoplastic brain and cerebellum samples served as control. All normal and tumoral specimens investigated showed a spectrum of HLA-DR positivity. A marked heterogeneity in HLA-DR expression was observed in gliomas: the majority of cells with typical neoplastic morphology were devoid of immunostaining, whereas a smaller amount (10–25%) of predominantly astro-cyte-like elements proved to be HLA-DR positive. In a proportion of these cells, strong reactivity was shown by 2D1 and LC, two different monoclonal antibodies which are considered to be specific for bone-marrow-derived leukocytes and histiocytes. Normal human serum pre-incubation had no significant effect on HLA-DR, GFAP, 2D1 and LC staining; however serum pre-incubation was followed by partial or complete inhibition for OKT6, OKT4 and OKT8 binding.