Effects of Different Therapeutic Radiation Doses on the Development of Neural Tube Defects in Chick Embryos and the Correlation with Bone Morphogenetic Protein 4 and 7 Expression Levels.

AIM: To investigate the effects of different therapeutic radiation doses on the prevalence of neural tube defects (NTDs) in chick embryos and bone morphogenetic protein (BMP) 4 and BMP7 expression levels. MATERIAL AND METHODS: The chick embryos (n=143) were derived from fertile, specific pathogen-free eggs of domestic fowl. The presence of NTDs was analyzed using a stereomicroscope, and BMP4 and BMP7 expression levels were assessed by immunohistochemical staining. The chick embryos were divided into five groups: control (no radiation exposure) (n=23), exposure to thorax computerized tomography (CT) (n=30); exposure to abdominopelvic CT (n=30), exposure to cranium CT (n=30), and exposure to brain perfusion CT (n=30). RESULTS: The prevalence of NTDs and BMP4 and BMP7 expression levels in the different groups were compared. In the cranium CT dose group, both the NTD prevalence (20%, p=0.002) and BMP7 (p=0.031) expression levels were significantly higher than those in the other groups. However, none of the medical doses of irradiation altered BMP4 expression levels (p=0.242). No NTDs were detected in the thorax CT and abdominopelvic CT groups. CONCLUSION: Exposure to irradiation at cranium CT doses may induce the development of NTDs and increase BMP7 expression. Dose radiation exposure using thorax CT and abdominopelvic CT protocols does not appear to induce NTDs.

OCT-Detected Optic Nerve Head Neural Canal Direction, Obliqueness, and Minimum Cross-Sectional Area in Healthy Eyes.

PURPOSE: To assess anterior scleral canal opening (ASCO) offset relative to Bruch's membrane opening (BMO) (ASCO/BMO offset) so as to determine neural canal direction, obliqueness, and minimum cross-sectional area (NCMCA) in 362 healthy eyes. DESIGN: Cross-sectional study. METHODS: After optical coherence tomography optic nerve head and retinal nerve fiber layer thickness (RNFLT) imaging, BMO and ASCO were manually segmented. Planes, centroids, size, and shape were calculated. Neural canal direction was defined by projecting the neural canal axis vector (connecting BMO and ASCO centroids) onto the BMO plane. Neural canal obliqueness was defined by the angle between the neural canal axis and the BMO plane perpendicular vector. NCMCA was defined by projecting BMO and ASCO points onto a neural canal axis perpendicular plane and measuring the area of overlap. The angular distance between superior and inferior peak RNFLT was measured, and correlations between RFNLT, BMO, ASCO, ASCO/BMO offset, and NCMCA were assessed. RESULTS: Mean (SD) NCMCA was significantly smaller than either the BMO or ASCO area (1.33 (0.42), 1.82 (0.38), 2.22 (0.43) mm2, respectively), and most closely correlated to RNFLT (P < .001, R2 = 0.158). Neural canal direction was most commonly superior-nasal (55%). Mean neural canal obliqueness was 39.4° (17.3°). The angular distance between superior and inferior peak RNFLT correlated to neural canal direction (P ≤ .008, R2 = 0.093). CONCLUSIONS: ASCO/BMO offset underlies neural canal direction, obliqueness, and NCMCA. RNFLT is more strongly correlated to NCMCA than to BMO or ASCO, and its peripapillary distribution is influenced by neural canal direction.

The effect of magnetic resonance imaging on neural tube development in an early chicken embryo model.

PURPOSE: We aimed to determine whether varying the magnetic field during magnetic resonance imaging would affect the development of chicken embryos and neural tube defects. METHODS: Following incubation for 24 h, we exposed chicken embryos to varying magnetic fields for 10 min to assess the impact on development. Three magnetic resonance imaging devices were used, and the eggs were divided into four groups: group 1 is exposed to 1 T, group 2 is exposed to 1.5 T, group 3 is exposed to 3 T, and group 4, control group, was not exposed to magnetic field. After MRI exposure, all embryos were again put inside incubator to complete 48 h. "The new technique" was used to open eggs, a stereomicroscope was used for the examination of magnified external morphology, and each embryo was examined according to the Hamburger and Hamilton chicken embryo stages. Embryos who had delayed stages of development are considered growth retarded. Growth retardation criteria do not include small for stage. RESULTS: Compared with embryos not exposed to a magnetic field, there was a statistically significant increase in the incidence of neural tube closure defects and growth retardation in the embryos exposed to magnetic fields (p < 0.05). However, although the incidence of neural tube closure defects was expected to increase as exposure (tesla level) increased, we found a higher rate of defects in the 1.5-T group compared with the 3-T group. By contrast, the highest incidence of growth retardation was in the 3-T group, which was consistent with our expectation that growth retardation would be more likely as tesla level increased. CONCLUSIONS: We therefore conclude that the use of magnetic resonance imaging as a diagnostic tool can result in midline closure defects and growth retardation in chicken embryos. We hypothesize that this may also be true for human embryos exposed to MRI. If a pregnant individual is to take an MRI scan, as for lumbar disc disease or any other any other reason, our results indicate that consideration should be given to an avoidance of MRI during pregnancy.

Unjoined primary and secondary neural tubes: junctional neural tube defect, a new form of spinal dysraphism caused by disturbance of junctional neurulation.

INTRODUCTION: Primary and secondary neurulation are the two known processes that form the central neuraxis of vertebrates. Human phenotypes of neural tube defects (NTDs) mostly fall into two corresponding categories consistent with the two types of developmental sequence: primary NTD features an open skin defect, an exposed, unclosed neural plate (hence an open neural tube defect, or ONTD), and an unformed or poorly formed secondary neural tube, and secondary NTD with no skin abnormality (hence a closed NTD) and a malformed conus caudal to a well-developed primary neural tube. METHODS AND RESULTS: We encountered three cases of a previously unrecorded form of spinal dysraphism in which the primary and secondary neural tubes are individually formed but are physically separated far apart and functionally disconnected from each other. One patient was operated on, in whom both the lumbosacral spinal cord from primary neurulation and the conus from secondary neurulation are each anatomically complete and endowed with functioning segmental motor roots tested by intraoperative triggered electromyography and direct spinal cord stimulation. The remarkable feature is that the two neural tubes are unjoined except by a functionally inert, probably non-neural band. CONCLUSION: The developmental error of this peculiar malformation probably occurs during the critical transition between the end of primary and the beginning of secondary neurulation, in a stage aptly called junctional neurulation. We describe the current knowledge concerning junctional neurulation and speculate on the embryogenesis of this new class of spinal dysraphism, which we call junctional neural tube defect.

Detection of preperimetric glaucoma using Bruch membrane opening, neural canal and posterior pole asymmetry analysis of optical coherence tomography.

We analysed retinal nerve fibre layer (RNFL) defects in eyes with normal circumpapillary RNFL (cpRNFL) thickness using posterior pole asymmetry analysis (PPAA) and investigated the parameters of Bruch membrane opening (BMO) and neural canals using enhanced depth imaging spectral domain optical coherence tomography (EDI-SDOCT). A total of 112 preperimetric glaucomatous eyes of 92 patients were examined to obtain cpRNFL thickness using SD-OCT. Posterior pole asymmetry analysis (PPAA) and central cross-sectional images of the optic nerve head (ONH) were obtained using EDI-SDOCT. Minimal and horizontal distances between the BMO and ONH surfaces (BMOM, BMOH) and the terminal of retinal pigment epithelium (RPE) and ONH surfaces (RPEM, RPEH) were measured. The distribution of the absolute black cells in PPAA was more concentrated in eyes with "U"-shaped neural canals (p < 0.0001). The area under the receiver operating characteristic curve of the ratio of RPEM to RPEH (RPE-R, 0.771 ± 0.08) was significantly larger than the ratio of BMOM to BMOH (BMO-R, 0.719 ± 0.009) for PPAA results. A U-shaped neural canal, lower ratio of RPEM to RPEH, and lower ratio of BMOM to BMOH were considered early indicators of RNFL defects in preperimetric glaucomatous eyes with normal cpRNFL.

[Significance of location of mandibular canal by 3-dimensional CT in the mandibular angle osteotomy].

OBJECTIVE: To decrease the incidence of inferior alveolar neurovascular bundle injury through location of mandibular canal by 3-dimensional (3-D) CT. METHODS: 30 female cases with prominent mandibular angle underwent 3-D CT before operation. The 3-D images were used to measure the distances between upper points of lower teeth to the inferior border of the canal. Then the osteotomy was designed according to the canal position to avoid the inferior alveolar neurovascular bundle injury. The canal protection was observed intraoperatively and postoperatively. RESULTS: The mandibular canal was protected very well in all 30 cases without any injury to the inferior alveolar neurovascular bundle. CONCLUSIONS: The 3-D CT can accurately locate the mandibular canal to guide the design of the mandibular angle osteotomy for patients with prominent mandibular angle.