A microcosting study of microsurgery, LINAC radiosurgery, and gamma knife radiosurgery in meningioma patients

The aim of the present study is to determine and compare initial treatment costs of microsurgery, linear accelerator (LINAC) radiosurgery, and gamma knife radiosurgery in meningioma patients. Additionally, the follow-up costs in the first year after initial treatment were assessed. Cost analyses were performed at two neurosurgical departments in The Netherlands from the healthcare providers’ perspective. A total of 59 patients were included, of whom 18 underwent microsurgery, 15 underwent LINAC radiosurgery, and 26 underwent gamma knife radiosurgery. A standardized microcosting methodology was employed to ensure that the identified cost differences would reflect only actual cost differences. Initial treatment costs, using equipment costs per fraction, were €12,288 for microsurgery, €1,547 for LINAC radiosurgery, and €2,412 for gamma knife radiosurgery. Higher initial treatment costs for microsurgery were predominantly due to inpatient stay (€5,321) and indirect costs (€4,350). LINAC and gamma knife radiosurgery were equally expensive when equipment was valued per treatment (€2,198 and €2,412, respectively). Follow-up costs were slightly, but not significantly, higher for microsurgery compared with LINAC and gamma knife radiosurgery. Even though initial treatment costs were over five times higher for microsurgery compared with both radiosurgical treatments, our study gives indications that the relative cost difference may decrease when follow-up costs occurring during the first year after initial treatment are incorporated. This reinforces the need to consider follow-up costs after initial treatment when examining the relative costs of alternative treatments

Is there a space–time continuum in olfaction?

The coding of olfactory stimuli across a wide range of organisms may rely on fundamentally similar mechanisms in which a complement of specific odorant receptors on olfactory sensory neurons respond differentially to airborne chemicals to initiate the process by which specific odors are perceived. The question that we address in this review is the role of specific neurons in mediating this sensory system—an identity code—relative to the role that temporally specific responses across many neurons play in producing an olfactory perception—a temporal code. While information coded in specific neurons may be converted into a temporal code, it is also possible that temporal codes exist in the absence of response specificity for any particular neuron or subset of neurons. We review the data supporting these ideas, and we discuss the research perspectives that could help to reveal the mechanisms by which odorants become perceptions

Survival and prognostic factors in patients with brain metastases from malignant melanoma

AIM: We wanted to determine the factors influencing survival in a retrospective review of patients with melanoma brain metastases to permit more specific recommendations regarding therapy. PATIENTS AND METHODS: We reviewed the data of 100 patients treated at the Department of Dermatology and Radiation Oncology, University of Zurich, and the Klinik im Park, Zurich. Information on potential prognostic factors (age, sex, location of the primary tumor, Clark level, Breslow index, histological type, number of brain metastases, stage at initial diagnosis, location of brain metastases, and therapy) was collected from the medical records of 100 patients treated between 1966 and 2002. Univariate and multivariate analyses were performed to identify significant prognostic factors. RESULTS: The overall median survival time was 4.8 months, with 6-month, 1-year and 2-year survival percentages of 36, 14 and 5%, respectively. Univariate analysis indicated that survival correlated significantly with radiotherapy (partial and whole brain), surgery, stereotactic radiosurgery, chemotherapy, Clark level and Breslow index. Treatment with temozolomide (p = 0.052) and number of brain metastases (p = 0.07) failed to be statistically significant. Multivariate analysis confirmed radiotherapy (partial and whole brain), surgery, stereotactic radiosurgery, chemotherapy and the location of brain metastases as independent and significant prognostic factors of survival. The remaining factors did not reach statistical significance in multivariate analysis. CONCLUSION: Radiotherapy, chemotherapy and especially surgery and stereotactic radiosurgery seem to significantly prolong survival, as shown by multivariate analysis. Treatment with temozolomide will possibly play an important role in the future management of patients with brain metastases from cutaneous melanoma, but further prospective studies to verify this assumption are urgently needed

Contribution of a calcium-activated non-specific conductance to NMDA receptor-mediated synaptic potentials in granule cells of the frog olfactory bulb

We studied granule cells (GCs) in the intact frog olfactory bulb (OB) by combining whole-cell recordings and functional two-photon Ca2+ imaging in an in vitro nose-brain preparation. GCs are local interneurones that shape OB output via distributed dendrodendritic inhibition of OB projection neurones, the mitral-tufted cells (MTCs). In contrast to MTCs, GCs exhibited a Ca2+-activated non-specific cation conductance (ICAN) that could be evoked through strong synaptic stimulation or suprathreshold current injection. Photolysis of the caged Ca2+ chelator o-nitrophenol-EGTA resulted in activation of an inward current with a reversal potential within the range -20 to +10 mV. ICAN in GCs was suppressed by the intracellular Ca2+ chelator BAPTA (0.5–5.0 mM), but not by EGTA (up to 5 mM). The current persisted in whole-cell recordings for up to 1.5 h post-breakthrough, was observed during perforated-patch recordings and was independent of ionotropic glutamate and GABAA receptor activity. In current-clamp mode, GC responses to synaptic stimulation consisted of an initial AMPA-mediated conductance followed by a late-phase APV-sensitive plateau (100–500 ms). BAPTA-mediated suppression of ICAN resulted in a selective reduction of the late component of the evoked synaptic potential, consistent with a positive feedback relationship between NMDA receptor (NMDAR) current and ICAN. ICAN requires Ca2+ influx either through voltage-gated Ca2+ channels or possibly NMDARs, both of which have a high threshold for activation in GCs, predicting a functional role for this current in the selective enhancement of strong synaptic inputs to GCs

Odor Representations in the Rat Olfactory Bulb Change Smoothly with Morphing Stimuli

Many species of mammals are very good at categorizing odors. One model for how this is achieved involves the formation of “attractor” states in the olfactory processing pathway, which converge to stable representations for the odor. We analyzed the responses of rat olfactory bulb mitral/tufted (M/T) cells using stimuli “morphing” from one odor to another through intermediate mixtures. We then developed a phenomenological model for the representation of odors and mixtures by M/T cells and show that >80% of odorant responses to different concentrations and mixtures can be expressed in terms of smoothly summing responses to air and the two pure odorants. Furthermore, the model successfully predicts M/T cell responses to odor mixtures when respiration dependence is eliminated. Thus, odor mixtures are represented in the bulb through summation of components, rather than distinct attractor states. We suggest that our olfactory coding model captures many aspects of single and mixed odor representation in M/T cells