Radiation Therapy in Acoustic Neuroma

Neuromas or schwannomas of the eighth cranial nerve are benign slow-growing Schwann cell-derived tumors, called acoustic neuromas, or vestibular schwannomas. The incidence is approximately less than 1 per 100,000 persons/ year. Acoustic neuroma has a clinical presentation related to cranial nerve involvement or brainstem and cerebellar compression due to tumor progression. When suspected, clinical diagnosed is confirmed by MRI. The management of vestibular schwannoma is still a quite controversial issue and can include wait and see policy, surgery, and radiotherapy. The treatment choice is based upon the balance between the expected morbidity of the tumor and of the therapy, taking into account also patient\u2019s preference. Medium size (2\u20133 cm) and large tumors (>3 cm) need an active treatment (surgery or radiotherapy), while smaller tumors can undergo observation as an alternative to active treatment.Epidemiology, clinical presentation, diagnosis, and results of the current treatment options including observation, surgery, and radiotherapy will be presented and discussed

Does water stress, nutrient limitation, or H-toxicity explain the differential stature among Heath Forest types in Central Kalimantan, Indonesia?

To investigate the causes of the reduced stature of heath forest compared to lowland evergreen rain forest (LERF), the quantity and quality of small litterfall (LF), the standing crop of litter on the forest floor (LSC), and the annual rates of litter decay were determined over a period of 12 months in three contrasting lowland rain forest types in Central Kalimantan, Indonesia. In addition, a litterbag experiment monitored the mass loss of leaves from three dominant tree species in two heath forests (HF) of contrasting stature. Soil water and shallow groundwater dynamics in the two HFs were monitored as well. LF in the LERF was higher compared to both tall heath forest (THF) and relatively stunted heath forest (SHF), but did not differ between the two HFs. Stand-level nutrient-use efficiencies for nitrogen and phosphorus were greatest for the SHF, followed by the THF and the LERF, respectively. The observed differences in nutrient-use efficiency between the two HFs did not result in different LF totals, LSC or decomposition rates and hence cannot explain the difference in HF stature. Neither could phenolic concentrations in leaf LF, which were very similar for the two HFs. Top-soil moisture levels were consistently higher in the SHF compared to the THF and never reached wilting point in either forest type whereas shallow groundwater levels in the SHF were both closer to the surface and more persistent than in the THF. Thus, severe water stress is not thought to be a factor of importance determining HF stature. Rather, considering the much lower pH of the topsoil in the SHF compared to the THF it is hypothesized that different degrees of H-toxicity to fine roots may ultimately prove responsible for the contrast in HF stature. © 2012 Springer Science+Business Media B.V

Large Vestibular Schwannomas

Single-fraction radiosurgery has demonstrated its efficacy in large and very large series of patients with vestibular schwannomas. However, single-fraction radiosurgery is reserved to small- to medium-sized lesions. The current standard therapeutic dose (12\u201314 Gy) may actually be too high to be tolerated by healthy surrounding nerve structures, such as the brainstem, which are in direct contact with large schwannomas. Furthermore, there is a direct correlation between tumor size and facial nerve damage. Hypofractionated treatments can be adopted in larger lesions when the patient is not a candidate for surgical resection. The lower dose per fraction used in hypofractionated schedules is, in theory, less harmful for the surrounding healthy structures allowing for higher rates of hearing, facial, and trigeminal nerve preservation, especially in such large lesions. Despite the limited experience in the treatment of Koos grade IV vestibular schwannomas, the results appear interesting, with local tumor control at midterm that are not very different from those obtained in smaller tumors. The major complication is represented by a form of subacute hydrocephalus that affects 10\u201315% of patients that become symptomatic in weeks and can be treated without the necessity of tumor resection. Although controversial, a similar approach represents a valid and effective treatment modality at least for elderly patients or for those with severe medical comorbidities, for whom radiosurgery can be a treatment option. Here, we review the role of hypofraction for the treatment of large and very large vestibular schwannomas and provide practical suggestions for its application