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Endodermal cysts of the central neuraxis are benign, non-neoplastic epithelium-lined cysts arising from endodermal tissue that have been displaced early in fetal life. Intracranial endodermal cysts are rare and usually located in the posterior fossa. The present study involves a 36-year-old man with a typical epithelial cyst in the posterior fossa. Microscopically, the cyst has a simple columnar epithelium with mucus-producing cells, containing an area composed of dysplastic epithelium with evidence of an intraepithelial carcinoma. The atypical cells have a high proliferative fraction demonstrated by Ki-67 immunostain. Based on these findings, the authors view this case as evidence of a malignant transformation of a classic endodermal cyst. The clinicopathologic features and a review of the literature are discussed.

The structural, electronic, and magnetic properties of several different terminations of the BaFe2As2(001) surface are investigated by means of first-principles calculations. Analysis of the surface stability as a function of the chemical potentials reveals that the three possible terminations (As, full and half Ba coverage) can all be stabilized in different chemical-potential ranges. We determine the most stable structure in each case and study its magnetic and electronic properties. A study of the scanning tunnel microscope maps and work functions provides helpful insights for the interpretation of the still debated experimental findings.

BACKGROUND Although the use of intervertebral fusion after anterior microdiscectomy in cervical disc disease remains controversial, a new surgical device is proposed for use in intervertebral fusion instead of bone graft. METHODS This retrospective study at the Department of Neurosurgery, Cardarelli Hospital, Naples, from January 1993 to December 1998, compares the results of surgery on 58 patients with anterior microdiscectomy and intervertebral bone graft fusion (Group A) (ADIBG) with a group of 52 patients who underwent anterior microdiscectomy and intervertebral titanium cage fusion (Group B) (ADITC) in cervical radiculopathy and spondylotic myelopathy. In both groups a “radical discectomy” was performed under the operating microscope. In group A, interbody fusion was performed with autologous tricortical bone graft. In group B, a new type of titanium device (Novus CT-Ti) was used (Sofamor Danek Group). RESULTS There was no collapse or extrusion of the device and no complications at the donor site (the bone fragments used to fill the cage were taken from osteophytes or vertebral body fragments). The use of this device provides immediate stabilization, reduces or eliminates pain, promotes bone fusion between the vertebrae adjacent to the cage by allowing bone growth through the cage, reestablishes and maintains the intervertebral space, reduces the average hospitalization time, and allows a quicker return to work. CONCLUSIONS Patients who underwent ADITC did well and benefited from the surgery. Those who underwent ADITC did better than those who underwent ADIBG in regard to function, relief from pain, and complications. Early and good stability of the cervical spine seems to be the main advantage of using titanium cages.

Solid MgB$_2$ has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first non-trivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB$_2$ in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on s and p states, thereby stabilizing the observed superconducting phase., 12 pages, 3 figures, revised version

The use of the endoscope (fiberscope) to assist the microsurgical clipping of cerebral aneurysm was first reported by Fischer and Mustafa in 1994. The rigid endoscope has been increasingly used during aneurysm surgery in which structures around the aneurysm can be detected with high quality imaging. Our 3 years of its use now allows us to assess the endoscope's efficacy and limits in standard surgery with a pterional approach in aneurysms of the anterior circulation. The endoscope can carry out a supportive role in planning surgical manoeuvres and in verifying whether clipping has been performed correctly or not. In our view, among the aneurysms of the anterior circulation, the endoscope is particularly useful in those of the internal carotid and the anterior communicating arteries. In many cases of these aneurysms the posterior communicating artery, choroidal artery or one of the distal cerebral arteries is hidden behind the aneurysm dome. Dome retraction is often required in order to see these vascular structures with the microscope. Thus an endoscope with a 30 degrees view angle becomes very useful. The concealed areas are identified without retraction, which prevents the possibility of the aneurysm being ruptured and also reduces the use of temporary clipping. From its early use as a supportive measure that is sometimes useful in surgery for "easy" aneurysms, the endoscope has now become almost indispensable for the "difficult" aneurysms, including the large and giant ones before and after clipping. Thus, the endoscope should be kept ready for use in the operating theatre for any eventuality.We assess the advantages and disadvantages of the use of the endoscope in the microsurgical treatment of intracranial aneurysms.During our 3 years of experience, 52 patients with 48 ruptured and 10 unruptured aneurysms of the anterior circulation (including 6 cases of two-fold aneurysms) underwent clipping with endoscope support through a pterional approach. All ruptured aneurysms produced a Hunt and Hess Grade I or II subarachnoid haemorrhage. The endoscope was inserted before and after clipping in order to observe the conditions surrounding the aneurysm and to receive immediate confirmation that clipping had been performed correctly.In all cases general anatomy visualization was provided by the endoscope, and the correct clip positioning and vessel conditions were easily checked. In 4 cases the endoscope showed that the clip had been positioned incorrectly. Additional clipping was performed in these cases: in 2 cases the clip was re-applied correctly and in another case a clip was added. Only the fourth patient with a large communicating artery died (1.9%) of cerebral infarction. This was due to post-clipping stenosis of one distal cerebral artery in which it was not possible to re-position the clip correctly because of the presence of arteriosclerotic calcific plaque near the aneurysm neck. In 3 cases there was an intraoperative ruptured aneurysm dome that was not caused by the endoscope insertion. No further complications were caused by the endoscope.In certain cases endoscopic-assisted microsurgery is an exceptional aid to the surgeon and must become part of the operating theatre equipment and kept on hand ready for use. The endoscope is, in our opinion, particularly useful in certain aneurysm localisations (internal carotid artery-anterior communicating artery [ICA-ACOMA]).

This work aims at understanding the large reduction of superconducting critical temperature T/sub c/ observed in YSr/sub 2/Cu/sub 3/O/sub 6+x/ as compared to its YBa/sub 2/Cu/sub 3/O/sub 6+x/ counterpart ( Delta T/sub c/=- 30 K). We report on a combined study of structural and electronic properties of RESr/sub 2/Cu/sub 3/O/sub 6+x/ (RE=Y, Yb) polycrystalline samples. Neutron diffraction data and Cu NQR spectra show that, contrary to REBa/sub 2/Cu/sub 3/O/sub 6+x/ RESr/sub 2/Cu/sub 3/O/sub 6+x/ is locally tetragonal and no CuO chains are formed. This arises from the random occupancy of oxygen along the a-or b-direction in the basal planes. Ab-initio calculations of the electronic structure using the full-potential linearized-augmented-plane-wave method (FLAPW) in the local density approximation (LDA) suggest that the CuO chains are not formed because of the large elastic strain associated with the orthorhombic distortion produced by the chain formation. In addition, by using ! a square root (2a) * square root (2a) supercell simulating the absence of chains, we find that oxygen disorder greatly alters the band structure near the Fermi level. Our analysis indicates that this alteration leads to a reduction of hole transfer from the CuO chains to the CuO/sub 2/ planes, which accounts for the reduction of T/sub c/ experimentally observed.

The increase of Tc with x in Al1-xMgxB2 is controlled by the Fermi level tuning at a "shape resonance" (i.e., the 2D-3D cross-over, at x = 0.66, of the topology of the Fermi surface of ? holes in the superlattice of boron mono-layers intercalated by Al1-xMgx ions) and by the tensile "micro-strain" in the boron sub-lattice (due to the lattice misfit between the boron and the intercalated layers). The softening of the E2g phonon frequency with increasing boron tensile micro-strain ? in the range 3% < ? < 6% shows the increasing electron-lattice interaction. The linear scaling, for 0.66 < x < 1, of Tc vs. the Fermi temperature TF of the ? holes shows a constant coupling strength with kF?0 = 90 (where kF is the Fermi wave vector and ?o is the Pippard coherence length) that points toward a vibronic pairing mechanism.

An innovative instrumentation and stabilization system was used for the treatment of unstable thoracolumbar fractures. The new osteosynthesis apparatus employs pedicle screw fixation, plate application, and a mechanical device for dynamic reduction in stable posterior fixation. Sixteen patients were treated with this operative technique that included a decompressive laminectomy, an arthropedunculectomy, and the removal of vertebral canal bone fragments. In most patients, three vertebral bodies, rather than four or five, were immobilized. All patients were studied pre- and postoperatively with plain radiographs and computed tomography. Pre- and postoperative examinations demonstrated no alteration in neurological status. All patients, however, with incomplete lesions showed improvement in neurological function at a mean follow-up period of 12 months. The authors' experience suggests that the new system offers ease and versatility of application, restoration of vertebral alignment through mechanical reduction, and enhanced spinal stability. The new system, moreover, enables the reduction of lateral dislocation.