Electron crystallography as a complement to X-ray powder diffraction techniques

ISSN:1433-7266ISSN:2194-4946ISSN:0044-2968ISSN:2196-710

Combining precession electron diffraction data with X-ray powder diffraction data to facilitate structure solution

Information derived from precession electron diffraction (PED) patterns can be used to advantage in combination with high-resolution X-ray powder diffraction data to solve crystal structures that resist solution from X-ray data alone. PED data have been exploited in two different ways for this purpose: (1) to identify weak reflections and (2) to estimate the phases of the reflections in the projection. The former is used to improve the partitioning of the reflection intensities within an overlap group and the latter to provide some starting phases for structure determination. The information was incorporated into a powder charge-flipping algorithm for structure solution. The approaches were first developed using data for the moderately complex zeolite ZSM-5, and then tested on TNU-9, one of the two most complex zeolites known. In both cases, including PED data from just a few projections facilitated structure solution significantly.ISSN:0021-8898ISSN:1600-576

Dystonic movement disorders and spinal degenerative disease

The occurrence of degenerative spinal disease subsequent to dystonic movement disorders has been neglected and has received more attention only recently. Spinal surgery is challenging with regard to continuous mechanical stress when treatment of the underlying movement disorder is insufficient. To characterize better the particular features of degenerative spinal disease in patients with dystonia and to analyze operative strategies, we reviewed the available published data. Epidemiologic studies reveal that degenerative spinal disorders in patients with dystonia and choreoathetosis occur much earlier than in the physiological aging process. Dystonic movement disorders more often affect the spine at higher cervical levels (C(2-5)), in contrast to spinal degeneration with age which manifests more frequently at the middle and lower cervical spine (C(5-7)). Degenerative changes of the cervical spine are more likely to occur on the side where the chin is rotated or tilted to. Various operative approaches for treatment of spinal pathologies have been advocated in patients with dystonic movement disorders. The available data do not allow making firm statements regarding the superiority of one approach over the other. Posterior approaches were first used for decompression, but additional anterior fusion became necessary in many instances. Anterior approaches with or without instrumented fusion yielded more favorable results, but drawbacks are pseudarthrosis and adjacent-level disease. Parallel to the development of posterior fusion techniques, circumferential surgery was suggested to provide a maximum degree of cord decompression and a higher fusion rate. Perioperative local injections of botulinum toxin were used initially to enhance patient comfort with halo immobilization, but they are also applied in patients without external fixation nowadays. Treatment algorithms directed at the underlying movement disorder itself, taking advantage of new techniques of functional neurosurgery, combined with spinal surgery have recently been introduced and show promising results

Laser-guided lumbar medial branch kryorhizotomy

The authors describe a modification of the medial branch kryorhizotomy technique for the treatment of lumbar facet joint syndrome using a fluoroscopy-based laser-guided method. A total of 32 patients suffering from lumbar facet joint syndrome confirmed by positive medial nerve block underwent conventional or laser-guided kryorhizotomy. The procedural time (20.6 +/- 1.0 vs 16.3 +/- 0.9 minutes, p 0.05). No difference in the outcome was observed between the 2 groups of patients (visual analog scale score 3.5 +/- 0.2 vs 3.3 +/- 0.3, p > 0.05). This improved minimally invasive surgical technique offers advantages to conventional fluoroscopy-based kryorhizotomy

A modified “far-lateral” approach for safe resection of retroodontoid dural cysts

Cystic mass lesions at the ventral craniocervical junction have been described only rarely in the past, however, they have received more attention with improved imaging modalities in recent years. These lesions have been approached by various operative procedures. A modified “far-lateral” approach combined with a C1 hemilaminectomy without fusion was used to safely remove the cyst and decompress the cervical medulla in a 72-year-old woman with cervicooccipital pain and paresthesia in both arms. Following surgery, complete resolution of symptoms was achieved, and no recurrence at 1 year follow-up was detected. A modified “far-lateral” approach offers several advantages when compared with other operation techniques