Study On Structure Of Middle And Distal Filum Terminale In Human Fetuses

Background and objectiveTethered cord syndrome (TCS), a common and severe congenital disease in children, defined as the disposal of incontinence, lower limb deformities and sensory motor dysfunction caused by ischemia and hypoxia attributed to fixation and drag of spinal meningocele, thick and short filum terminale (FT), rigid osteocartilaginous median septum, as well as adhesion, oppression of lipoma and dermoid cyst on conus medullaris. Its incidence is relatively high (1-3‰), often concomitant with spinal cord dysplasia and nerve defects. Currently the surgical treatment of TCS is mainly disconnecting FT to relieve the dragging of low-set conus. With the deep recognizing of TCS, TCS which the conus is at the normal location is becoming more and more important, and the end of the spinal cord is above the L2, it is also named tight filum terminal syndrome: FT have pathological changes, which result in the dragging to conus, then the conus is ischemic and hypoxia, which result in some symptoms of nervous lesion. The clinical manifestation is similar with TCS. The diagnose is difficult by MRI examination. It is the most easily kind of misdiagnosising and missed diagnosis. It is necessary to research the FT deeply for discussing the more allround diagnosis criteria.FT is always described as a fibra-haemal union body, because of the growing disproportion between spine and spinal cord. FT extend from conus to coccygeal bone, so it is divided into two parts: within and out of the dura. Yamada researched the pathophysiology of TFTS deeply, and manufacture animal experiment model that FT drag conus. They also observed the bloodstream disorder and ischemic and hypoxia of the dragged conus, which result in the dysbolism of the nerve cell in lumbosacral area. The neurologic impairment happens aggravatingly. Thus, they consider that the dragging to the conus is the key of TCS, even if the conus is in the normal location, the slight dragging also result in that metabolism changes and the conus is damaged. Then nerve functional disturbance happens like the TFTS. Thus, the FT is becoming more and more important in TCS. But, the composition and structure of the normal FT is not illuminated completely in Human Fetuses. The study on the FT in all kinds of organism is growing gradually at home and abroad. But the study on structure of the FT in Human fetus has not been reported.This experiment investigate the composition and ultrastructure of the FT in Human fetus by the scanning electron microscope and light microscope for exploring the relation between the FT and the pathogenetic of TCS and offering rationale and reference for the diagnostic criteria in pathobiology and the therapia methods of TCS.Materials and methods15 new birth died fetuses (5 males, 10 females) were collected in the department of Obstetrics and Gynecology in the third Affiliated Hospital of Zhengzhou University. Fetuses with nervous system disease and defect were excluded. Measuring the crown-rump length of the fetuses and the length and diameter of FT. Due to the proximal FT is similar with the structure of spinal cord and the proximal FT is mainly cell component, the middle and distal FT is mainly puff connective tissue, which were described in different kinds of species. We get only the middle and distal FT. Rinsed repeatedly with 0.1mol/L phosphate buffer solution of Ph7.4.Then 9 cases were fixed with 4%paraform, stained with HE and specific stain.6 cases were fixed with 2.5% glutaraldehyde in 4℃for the study of scanning electron microscope.Results1.General observationThe range of crown-rump length of the fetuses is from161 mm to 330 mm. The average length of FT is 45.5 mm. The average diameter of the starting point of FT is 1.24 mm and and The average diameter of the middle point of FT is 0.35 mm. The end of the conus medullaris is above L₂.The appearance of FT is slightly whiteness which is similar with cauda equine in naked eye.2.Morphous and element in light microscopeThe middle and distal FT is loose connective tissue that is composed of bulk fibers and parce micrangiums in HE.FT are pkged by Meninx. There are red mottling fiber bundles and small amounts parce micrangiums and red cells in transection. There are central canal and redundant ependymal epithelium cells. Pink fiber bundles is trabs and circuity appearance. There are thick and pink fibers and more slender fibers in each other, and there are significant differences in fiber bundles gaps. There are two existence forms about elastic fiber in three specific stains: they mainly reside in collagen fibers dispersally, some distribute in collagen fibers intensively. Intricate and black fineness reticular fibers connect the collagen fibers bundles.3.Ultrastructure in scanning electron microscopeA complex and tridimensional fineness structure is evidenced in scanning electron microscope. The periph meninx is folded. The bulk of the FT is composed of 1μm to 5μm thick spring like longitudinal bundles of collagen separated by 5μm to 30μm layer intervals and 1μm to 5μm intervals in the layer, although a small quantity of capillaries and other elements may be present. A delicate (0.13μm) meshwork of collagen transversal fibers connects these bundles and fibers in every bundle in high power electron microscope. Collagen bundles can also be found between layers and bundles.Conlusions1. The middle and distal FT is three diamensions stereochemical structure composed of collagen fibers,elastric fibers,reticular fibers and blood capillary in human fetuses.2. Collagen fibers,elastric fibers,reticular fibers and folded meninx of the middle and distal FT hint elasticity physiologic function in human fetuses. 3. The changes of structure and composition of the middle and distal FT make its elasticity decreasing and dragging the conus in human fetuses.