Virtual endoscope-assisted intracranial aneurysm surgery: evaluation of fifty-eight surgical cases.

OBJECTIVE: Better visualization of the intracranial aneurysm may improve surgical outcomes. To this aim, we evaluated the effectiveness of using virtual endoscopy (VE) during intracranial aneurysm surgery. METHODS: Fifty-eight patients with 63 intracranial aneurysms were enrolled in this study. Every patient was examined by digital subtraction angiography (DSA) and a randomly selected twenty-six cases were also examined by computed tomography (CT). CT angiography data were linked via imaging software for reconstruction of VE images. All patients were operated on using standard microsurgical procedures. Among these cases, randomly selected cohorts of twenty-six patients with 28 intracranial aneurysms were operated on also using VE-assisted surgical procedures. The surgical results of both groups were compared to determine the efficacy of the VE-assisted surgical procedure. RESULTS: Aneurysm locations, surgical timing and Hunt-Hess grade distribution were not statistically significant between both groups (p=0.948). However, significantly reduced complication rates and increased post-operative Glasgow outcome scores were observed in the VE group (p<0.05) compared to control. CONCLUSION: Aneurysms and surrounding anatomic structures were well depicted by VE in three dimensions with interactive fly-through views. This method improved our surgical results by improving visualization of the aneurysm and increasing surgical orientation. We report that this method can be very helpful to surgeons during intracranial aneurysm surgery and may reduce post-surgical complications.

Trigeminal and occipital peripheral nerve stimulation for craniofacial pain: a single-institution experience and review of the literature.

OBJECT: Treatment of chronic neuropathic pain in the region of the head and face presents a challenge for pain specialists; patients who do not respond to conventional treatment modalities usually continue to suffer from pain due to the lack of reliable medical and surgical approaches. Peripheral nerve stimulation (PNS) has been used to treat neuropathic pain for many decades, but only recently has it been applied systematically to the craniofacial region. To advance the study of this treatment option, the authors present their initial experience with this approach, summarize published data on the use of PNS in treatment of craniofacial pain, and discuss some technical details of the craniofacial PNS procedure. METHODS: A review of prospectively collected data in 30 patients who underwent PNS surgery for craniofacial pain was performed. The pain location, duration, cause, and previous treatments were analyzed, along with the surgical details, initial and long-term results, complications, and repeated operations. Stimulated nerves in this group included supraorbital (seven patients), infraorbital (six), and occipital (21); in 19 patients more than one nerve was stimulated. Twenty-two patients proceeded with implantation of a permanent system after the trial. Of these, at the time of the latest evaluation (mean follow-up duration 35 months), in two patients the devices had been removed because of pain improvement over time, in three the devices were removed due to loss of effectiveness (two cases) or late infection (one), and the rest are enjoying either complete (15 patients) or partial (two patients) pain relief. Three patients underwent repeated operation due to lead erosion, infection, or migration. CONCLUSIONS: Peripheral nerve stimulation appears to be a safe and effective approach in the treatment of craniofacial neuropathic pain. The growing body of literature supports a wider acceptance of this approach in the field of pain surgery.

Multilocated mature teratoma: a case report and review of the literature.

Mature teratomas are rare inclusion tumors, which have benign behaviors. Different locations of the tumor were reported in the literature. However, multiple tumor locations are extremely rare. An eight year old patient presented with an intraventricularly mature teratoma. During the six year follow up-period, two separately located masses were observed in the chest area and in the right iliac region, and both tumors were histologically diagnosed as mature teratomas. In this study, this unique case of mature teratoma presented with multiple locations in three separate body compartments. Furthermore, intraventricular dissemination with sellar and parasellar extension was observed in the third ventricle.

Stereotactically-guided fourth ventriculo-peritoneal shunting for the isolated fourth ventricle.

The isolated fourth ventricle (IFV) develops in which obstruction to the out flow of cerebrospinal fluid from the choroid plexus of the fourth ventricle occurs rostrally and caudally. IFV has been a rare occurrence and is difficult to treat. We had an occasion to admit a 28-year-old female to our hospital due to hydrocephalus: she also had a history of meningitis a year ago. The patient was initially managed by a lateral ventriculo-peritoneal shunting procedure. Six months after the procedure the patient began to suffer from vomiting, nausea, and diplopia. CT and MRI scans demonstrated an isolated fourth ventricle enlargement; and thus, a fourth ventriculo-peritoneal shunting procedure was performed under stereotactic conditions. The authors present a case of an isolated fourth ventricle after lateral ventriculo-peritoneal shunting for hydrocephalus, which was treated with a stereotactically guided fourth ventriculo-peritoneal shunting procedure. The technique of this procedure is described below.

Structure of viroid replicative intermediates: physico-chemical studies on SP6 transcripts of cloned oligomeric potato spindle tuber viroid.

The structure and structural transitions of transcripts of cloned oligomeric viroid were studied in physico-chemical experiments and stability calculations. Transcripts of (+) and (-) polarity, from unit up to sixfold length, were synthesized from DNA clones of the potato spindle tuber viroid (PSTV) with the SP6 transcription system. Their structural properties were investigated by optical denaturation curves, high performance liquid chromatography (HPLC), electron microscopy, sedimentation-diffusion equilibrium and velocity sedimentation. Secondary structures of the RNAs and theoretical denaturation curves were calculated using an energy optimization program. The secondary structure of lowest free energy for unit length and oligomeric transcripts is a rod-like structure similar to that of the mature circular viroids. When this structure is used as a model for calculations, there is a large degree of agreement between the theoretical and the experimental denaturation curves. At high temperatures, however, (+) strand transcripts exhibited a transition which was more stable than expected from the calculations or than was known from curves of mature viroids. This transition arises from a rearrangement of the central conserved region of viroids to a helical region of 28 stable base pairs either intermolecularly leading to bimolecular complexes, or intramolecularly giving rise to a branched secondary structure. The rearrangement could be detected by electron microscopy, HPLC, and analytical ultracentrifugation. The helical region serves to divide up the oligomeric (+) strand into structural units which may be recognized by cleavage and ligation enzymes which process the oligomeric intermediates to circular mature viroids.

High-performance liquid chromatography of DNA restriction fragments.

High-performance liquid chromatography on Nucleogen-DEAE 4000-10 has been applied to several problems of the isolation of DNA restriction fragments. Large amounts of DNA fragments of high purity are necessary for biophysical studies and for molecular hybridization in basic research, as well as in medical diagnosis. The influence of various parameters, such as buffer, pH, eluting salt, gradient slope, flow-rate and the addition of urea on the resolution of fragments by high-performance liquid chromatography were studied on an analytical scale, and the optimal conditions were then used for the large-scale preparation of milligram amounts. The best resolution of fragments between 25 and 1500 base pairs was obtained with a linear gradient from 500 mM to 1200 mM sodium chloride in 6 M urea -30 mM sodium phosphate (pH 6.0). Quantitative data are given for the purity and recovery of the sample, and the capacity and lifetime of the column. The following applications of high-performance liquid chromatography of restriction fragments are described: preparation of 2 mg of fragments, separation of 1 mg of DNA insert from 7 mg of its plasmid vector, and analysis of DNA-RNA hybrids.

Dynamics and interactions of viroids.

Viroids are single stranded circular RNA molecules of 120,000 daltons which are pathogens of certain higher plants and replicate autonomously in the host cell. Virusoids are similar to viroids in respect to size and circularity but do replicate only as a part of a larger plant virus. The structure and structural transitions have been investigated by thermodynamic, kinetic and hydrodynamic methods and have been compared to results from calculations of the most favorable native structures and the denaturation process. The algorithm of Zuker et al. was modified for the application to circular nucleic acids. For viroids the calculations confirm our earlier theoretical and experimental results about the extended native structure and the highly cooperative transition into a branched structure. Virusoids, although described in the literature as viroid-like, show less base pairing, branching in the native secondary structure, and only low cooperativity during denaturation. They resemble more closely the properties of random sequences with length, G:C content, and circularity as in viroids but sequences generated by a computer. The comparison of viroids, virusoids and circular RNA of random sequences underlines the uniqueness of viroid structure. The interactions of viroids with dye and oligonucleotide-ligands and with RNA-polymerase II from wheat germ, which enzyme replicates viroids in vitro, has been studied in order to correlate viroid structure and its ability for specific interactions. Specificity of the interactions may be interpreted on the basis of the neighbourhood of double stranded and single stranded regions. In the host cell viroids are localized in the cell nucleus; they may be detected as free nucleic acids and in high molecular weight complexes together with other RNA and proteins.

Large-scale purification of viroid RNA using Cs2SO4 gradient centrifugation and high-performance liquid chromatography.

A procedure for the purification of viroid RNA from tomato plants is described which yields up to a milligram of viroid RNA of gel electrophoretic homogeneity within 2 days. This technique is at least three times as fast as previous methods and is generally applicable to other RNA species. Plant material was homogenized and phenol extracted. In a Cs2SO4 density gradient, viroid RNA together with low-molecular-weight RNA, was separated from large single-stranded RNA, DNA, polysaccharides, polyphenols, and other compounds. The separation is based on the differences in the buoyant density and on the selective precipitation of large single-stranded RNA in Cs2SO4. Further purification of viroid RNA was achieved by HPLC over a weak anion exchanger linked to silica gel of optimized pore size. The elution was carried out by a salt gradient with complete exclusion of divalent metal ions. The procedures were applied to whole plants, leaves, stems, roots, cells, and protoplasts. The yields of nucleic acids at the different steps of purification are given for leaves, stems, and roots.

Mechanism of the interaction between ribosomal protein S1 and oligonucleotides.

The interaction of the ribosomal protein S1 from E. coli MRE 600 with oligonucleotides was studied by hydrodynamic, spectrophotometric, and kinetic methods. UV-difference spectra which are induced by the complex formation could be separated into a hyperchromic contribution originating from the nucleic acid moiety and a hypochromic contribution from the protein. Systematic determination of binding and rate constants was carried out by the temperature-jump relaxation technique. From the quantitative evaluation of the relaxation times and the relaxation amplitudes, the following conclusions could be drawn: The stoichiometry of the complex formation is one mole S1 per one mole oligonucleotide. The binding constant K, the recombination rate constant kR, and the dissociation rate constant kD, respectively, were measured at different temperatures. The values at 10 degrees C are K = 2 x 10(6) M-1, kR = 1.3 x 10(8) M-1S-1, kD = 65 s-1 for A(pA) 12 and K = 7.5 x 10(5) M-1, kR = 6.8 x 10(7) M-1S-1, kD = 90 S-1 for U(pU) 12. Discrepancies with data reported elsewhere are discussed. The stacking-unstacking equilibrium of the free oligonucleotide is frozen if the oligonucleotide is bound to the protein. The conformational change of the oligonucleotide does not occur in the form of a preequilibrium, but is induced after the primary binding step.