Endoscope-assisted far lateral craniotomy for resection of posterior fossa neurocysticercosis: illustrative case.

BACKGROUND: Neurocysticercosis is a parasitic infection that commonly affects the ventricles, subarachnoid spaces, and spinal cord of the central nervous system. The authors report an unusual manifestation of purely posterior fossa neurocysticercosis treated with endoscope-assisted open craniotomy for resection. OBSERVATIONS: A 67-year-old male presented with 2 months of progressive dizziness, gait ataxia, headaches, decreased hearing, and memory impairment. Imaging revealed an extra-axial cystic lesion occupying the foramen magnum and left cerebellopontine angle with significant mass effect and evidence of early hydrocephalus. Gross-total resection was accomplished via a left far lateral craniotomy with open endoscopic assistance, and pathological findings were consistent with neurocysticercosis. Postoperatively, he was noted to have a sixth nerve palsy, and adjuvant therapy included albendazole. By 9 months postoperatively, he exhibited complete resolution of an immediate postoperative sixth nerve palsy in addition to all preoperative symptoms. His hydrocephalus resolved and did not require permanent cerebrospinal fluid (CSF) diversion. LESSONS: When combined with traditional skull base approaches, open endoscopic techniques allow for enhanced visualization and resection of complex lesions otherwise inaccessible under the microscope alone. Recognition and obliteration of central nervous system neurocysticercosis can facilitate excellent neurological recovery without the need for CSF diversion.

Anatomy of the Ventricles, Subarachnoid Spaces, and Meninges.

The ventricular system, subarachnoid spaces, and meninges are structures that lend structure, support, and protection to the brain and spinal cord. This article provides a detailed look at the anatomy of the intracranial portions of these structures with a particular focus on neuroimaging methods.

Head and Neck Sarcomas: A Review of Clinical and Imaging Findings Based on the 2013 World Health Organization Classification.

OBJECTIVE: Head and neck sarcomas are a complex, heterogeneous group of tumors that present a diagnostic challenge to radiologists because they have many overlapping imaging features. The purpose of this article is to review the imaging and clinical features and highlight distinguishing features of head and neck sarcomas. CONCLUSION: An understanding of characteristic imaging and clinical features of head and neck sarcomas is important for the radiologist to narrow the differential diagnosis and help guide management.

Suprasellar Ganglioglioma: Expanding the Differential Diagnosis.

This case study describes a young man with symptoms suggestive of the presence of a space-occupying lesion within the cranial cavity. Imaging studies confirmed a lesion in the suprasellar region and surgical intervention to remove the tumor yielded an unexpected diagnosis. Neuroimaging characteristics and histopathology including immunohistochemistry are described. Gangliogliomas are uncommon CNS neoplasms and are most commonly found in the temporal and frontal lobes of young, male adults. They are rarely seen in the suprasellar region and only a handful of cases have been reported to date. The differential diagnoses associated with these suprasellar region lesions can be dependent on the age of the patient and neuroimaging characteristics. The present report highlights the importance of histopathological examination and the need to consider a wide range of diagnostic entities in the differential diagnosis of lesions in this topographic distribution, including rarely encountered tumors such as gangliogliomas.

Gold nanoparticle-initiated free radical oxidations and halogen abstractions.

We report on the use of EPR spectroscopy and spin trapping technique to detect free radical intermediates formed in the presence of gold nanoparticles. Phosphine- and amine-protected gold nanoparticles were found to initiate air oxidation of organic substrates containing active hydrogen atoms, such as amines and phosphine oxides. Nanoparticles protected by stronger bound ligands (e.g., thiols) were inactive in these reactions. We also found that gold nanoparticles are able to abstract a halogen atom from the halogenated compounds, presumably due to the high affinity of gold metal for halogens. Reaction of Au nanoparticles with chloroform showed an unusual inverse isotope effect. The trichloromethyl spin adduct was observed when Au nanoparticles were mixed with CDCl(3) but not with CHCl(3). This unexpected behaviour suggests that C-H bond breaking is not the rate-determining step in Au-initiated hydrogen abstraction.

The effects of chelating agents on radical generation in alkaline peroxide systems, and the relevance to substrate damage.

A spin-trapping EPR technique has been employed to explore the generation of hydroxyl radicals from reactions between a series of first row transition metal ions and aqueous hydrogen peroxide at pH 10, and with a range of chelating agents (EDTA, DTPMP and the readily biodegradable ligands S,S-EDDS and IDS). In the absence of these chelating agents only Cu(II) generates a significant level of hydroxyl radicals; in their presence with Cu(II) EDTA and IDS give similar behaviour whereas EDDS and DTPMP inhibit hydroxyl radical generation. For Fe(II), EDTA, DTPMP and IDS significantly enhance ( radical)OH production under these conditions whereas EDDS does not. Results from model cellulose damage experiments broadly confirm the findings for copper, though experiments with Fe(II) lead to somewhat contrasting results. Our findings are discussed in terms of binding constants and implications for alkaline peroxygen bleaching systems.

(N-Benzyl-bis-N',N''-salicylidene)-cis-1,3,5-triaminocyclohexane copper(II): a novel catalyst for the aerobic oxidation of benzyl alcohol.

Reaction of Cu(BF(4))(2).6H(2)O with the N(3)O(2) donor ligand H(2)L (where H(2)L = N-benzyl-N',N''-di-tert-butyl-disalicyl-triaminocyclohexane) results in the formation of a novel Cu(II)L complex, 1. X-Ray crystallography of it shows the Cu(II) centre coordinated by two phenolate oxygens and two imine nitrogens in a distorted square plane with an elongated bond to the amine nitrogen (2.512 A) in the axial position. EPR spectroscopy gives g values of g(1) = 2.277, g(2) = 2.100, g(3) = 2.025, and A(1) = 15.6 mT which are consistent with the distorted square pyramidal coordination environment determined from the X-ray structure. UV/visible and electrochemical analysis of shows that it undergoes two reversible processes assigned to the successive oxidation of the phenolate oxygens to phenoxyl radicals, the first at E((1/2)) = 0.89 V (DeltaE = 81 mV, vs. Ag/AgCl) and the second at E((1/2)) = 1.13V (DeltaE = 84 mV, vs. Ag/AgCl). Chemical oxidation results in the formation of a species, assigned as [1](+)(.) which is EPR silent due to antiferromagnetic coupling between the Cu(II) centre and the bound phenoxyl radical. The oxidised species catalyses the oxidation of benzyl alcohol to benzaldehyde.

Experimental and computational studies of structure and bonding in parent and reduced forms of the azo dye Orange II.

The structure and bonding of the azo dye Orange II (Acid Orange 7) in parent and reduced forms have been studied using NMR, infrared, Raman, UV-visible, and electron paramagnetic resonance (EPR) spectroscopy, allied with density functional theory (DFT) calculations on three hydrazone models (no sulfonate, anionic sulfonate, and protonated sulfonate) and one azo model (protonated sulfonate). The calculated structures of the three hydrazone models are similar to each other and that of the model without a sulfonate group (Solvent Yellow 14) closely matches its reported crystal structure. The 1H and 13C NMR resonances of Orange II, assigned directly from 1D and 2D experimental data, indicate that it is present as > or = 95% hydrazone in aqueous solution, and as a ca. 70:30 hydrazone:azo mixture in dimethyl sulfoxide at 300 K. Overall, the experimental data from Orange II are matched well by calculations on the hydrazone model with a protonated sulfonate group; the IR, Raman, and UV-visible spectra of Orange II are assigned to specific vibrational modes and electronic transitions calculated for this model. The EPR spectrum obtained on one-electron reduction of Orange II by the 2-hydroxy-2-propyl radical (*CMe2OH) at pH 4 is attributed to the hydrazyl radical produced on protonation of the radical anion. Calculations on reduced forms of the model dyes support this assignment, with electron spin density on the two nitrogen atoms and the naphthyl ring; in addition, they provide estimates of the structures, vibrational spectra, and electronic transitions of the radicals.

Dipole-dipole interactions in spin-labeled au nanoparticles as a measure of interspin distances.

A series of Au nanoparticles modified with a nitroxide-functionalized ligand was prepared with a range of spin-label coverage. The X-band EPR spectra of frozen solutions of these nanoparticles showed coverage-dependent line-broadening due to dipole-dipole interactions between spin labels. We developed a methodology to analyze such spectra in terms of geometrical features of the nanoparticles (e.g., Au core size and the length of the spin-labeled ligand). Our method is based on the assumption that the spectral line shape is determined by the average distance between nearest-neighboring spin labels adsorbed on the Au particle. Geometrical and statistical analysis then relates this distance to the line shape parameter d1/d, which was calibrated using a model system. Application of this methodology to the experimental spectra provided information about the conformation of ligands on the Au surface. We found that, if the spin-labeled ligand is substantially longer than the surrounding protecting layer, it does not adopt a fully stretched conformation but wraps around the particle immediately above the layer of surrounding ligand. Our results also show that the ligands do not adsorb cooperatively on the Au surface.

Mechanistic study of a place-exchange reaction of Au nanoparticles with spin-labeled disulfides.

The mechanism of a place-exchange reaction of ligand-protected Au nanoparticles was investigated using diradical disulfide spin labels. Analysis of reaction mixtures using a combination of GPC and EPR allowed us to determine concentration profile and propose a kinetic model for the reaction. In this model, only one branch of the disulfide ligand is adsorbed on the Au surface during exchange; the other branch forms mixed disulfide with the outgoing ligand. The two branches of the disulfide ligand therefore do not adsorb in adjacent positions on the surface of Au nanoparticles; this was ultimately proven by the powder EPR spectra of frozen exchange reaction mixtures. Our data also suggest the presence of different binding sites with different reactivity in the exchange reaction. The most-active sites are likely to be nanoparticle surface defects.

Formation and reaction of O=MnV species in the oxidation of phenolic substrates with H2O2 catalysed by the dinuclear manganese(IV) 1,4,7-trimethyl-1,4,7-triazacyclononane complex [MnIV2(mu-O)3(TMTACN)2](PF6)2.

The oxidation of phenolic substrates with H2O2 catalysed by [MnIV2(mu-O)3(TMTACN)2](PF6)2 1, (TMTACN, 1,4,7-trimethyl-1,4,7-triazacyclononane) has been investigated by use of ESI mass spectrometry. The role of the phenols as one-electron reductants and as co-ligands in the stabilisation and reaction of an intermediate O=MnV species has been analysed and the presence of a variety of manganese species in solution has been explained. Our results lead to a proposed mechanism for the catalytic oxidation of phenols in this system.

Spin-labelled Au nanoparticles.

A series of Au nanoparticles functionalised with nitroxide spin labels has been prepared and studied by EPR spectroscopy. Samples with low coverage of the spin label were used to investigate the dynamics of the surface-attached labels at different distances from the Au surface. The rotational correlation times of spin labels vary from 10(-10) s to more than 3 x 10(-9) s, depending on the chain length of the label and the surrounding ligand. The samples with higher coverage of the spin label show an increasing contribution of the exchange interaction between nitroxides adsorbed in a close proximity to each other on the same nanoparticle. Quantitative analysis of the EPR spectra of these samples suggests the presence of non-equivalent binding sites on the surface of Au nanoparticles. Additionally, EPR signals of isolated radical pairs were observed at intermediate coverage.

Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution.

A kinetic and mechanistic study is reported of the oxidation of a number of azonaphthol dyes with hydrogen peroxide in aqueous solution, catalysed by some mono and dinuclear manganese(IV) complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN). The results of UV-Vis investigations, augmented by EPR and ESI-MS studies, are described for a series of experiments in which concentrations, pH and ionic strength have been varied. The reactions are characterised by an induction period followed by a relatively rapid oxidation. For the dinuclear manganese complex 2, these are consistent with an initial perhydrolysis of the manganese complex involving both the dye anion and HO2-, to give mononuclear manganese species and the operation of a catalytic cycle incorporating MnIIIL(OH)3, O = MnVL(OH)2 and MnIVL(OH)3 (L = Me3TACN) (cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of MnIVL(OH)3. With the mononuclear manganese complex MnIVL(OMe)3, there is a short lag-phase attributed to perhydrolysis by HO2- followed by the same catalytic cycle.

EPR and modelling studies of hydrogen-abstraction reactions relevant to polyolefin cross-linking and grafting chemistry.

EPR spectroscopy has been employed to study directly the selectivity of hydrogen-atom abstraction by some alkoxyl radicals from a variety of linear and branched alkanes, as well as linear alkenes, chosen as models for low molecular-weight polyolefin cross-linking systems. In situ thermal and photolytic approaches, as well as spin-trapping, have been employed to provide information relating to an accessible temperature range of 233-453 K. in part to mimic conditions relevant to melt processing of polyolefins. Rate constants (in the range 3 x 10(3)-3.7 x 10(5) dm3 mol-1 s-1 per hydrogen) have been determined for C-H abstraction at room temperature. Radical selectivity is largely governed by enthalpic effects (modelled via bond dissociation energy calculations and kinetic analysis). Direct evidence has been obtained for lack of reactivity, as a result of unfavourable steric interactions, for the secondary and tertiary C-H bonds in 2,4-dimethylpentane and 2,4,6-trimethylheptane, models for polypropylene. This has been rationalized via free-energy calculations using DFT.

Observation of protein-derived (BSA) oxygen-centered radicals by EPR spin-trapping techniques.

Electron paramagnetic resonance (EPR) spin-trapping experiments, employing the novel spin-trap DEPMPO, provide evidence for the formation of protein-peroxyl radicals from the reaction of bovine serum albumin (BSA) or lysozyme with HO. in the presence of O2. Spin-trapping leads to the detection of anisotropic spectra of partially immobilized protein-peroxyl spin-adducts; positive identification is based on a novel spectrum simulation approach (through which broadened anisotropic spectra are simulated and compared with experiment) and by comparison of results with those obtained when MeO2. is trapped and the adduct frozen in a solid matrix.

EPR study of a place-exchange reaction on Au nanoparticles: two branches of a disulfide molecule do not adsorb adjacent to each other.

An EPR study of a place-exchange reaction of a diradical disulfide with butanethiol-protected Au nanoparticles showed that the two branches of the disulfide molecule do not adsorb adjacent to each other on the Au surface. The most likely mechanism includes adsorption of only one branch of the disulfide molecule in the exchange process. The exchange reaction was found to be zeroth-order with respect to the diradical, indicative of a dissociative "SN1"-type mechanism.