Clinical Embryology Neuropore Closure - Research Paper Example

Clinical Neurology Neuropore Closure Organogenesis is the process in which the different cells in the body of vertebrates come together to form organs. In human beings this process takes place within the first three weeks up to 8 weeks, there is no definite time (Wyszynski 18). Neurulation is one of the stages of organogenesis. This is the stage where the neural tube where the spinal cord passes is formed. The whole central nervous system formation in vertebrates starts with neurulation (Fisch 174). It starts when the notochord signal the ectoderm germ layer to form a flat neural plate. The resultant neural plate then, upon release of certain specific growth hormones, curve at the centre until the edges meet to form a tube- the neural tube. This tube is the basis of the central nervous system as all the other organs, for example the brain, will develop from it through differentiation. Neurulation is a multi-stage process and the folding of the neural late takes place at around the 20th day after fertilization of the ova. The folding starts at the middle and proceeds towards the head and towards the tail, that is, cranially and caudally respectively (Wyszynski 23). The resultant opening at the two ends are thus referred to as cranial and caudal neuropores. In human embryos these neuropores need to close if at all the embryo is to develop into a normal foetus. The cranial neuropore is the first to close and it does so on the 25th day of the embryo development whereas caudal neuropore closes two days later. If for any reason any of these neuropore fail to close then the child is born with a defect. The failure of the cranial part, that is the head part, also known as anterior, then a condition known as anencephaly occurs. If it is the caudal, also known as the posterior, that fails to close then a condition known as spina bifida arises. If it fails to close at both ends it causes a more severe condition known as rachischisis (Stiles 118). Anencephaly Physiology Anencephaly is a disorder where the neural tube either fully or wholly fails to close at the anterior end of the neural tube. This process takes place just after the neural tube has completely formed, so it is supposed to take place between the 23rd and the 26th day after fertilization (Fisch 176). Failure to close manifests itself by the conspicuous absence of the major portion of the brain, the scalp and even the skull. This large part of the brain that is missing is known as the telencephalon and it is the one containing the various cerebral spheres. There is still a small part of the brain that forms independently; however, this brain part is exposed as it is usually the skull and the scalp that offers protection. This exposure exposes these babies to a lot of danger (Stiles 121). Signs and Symptoms Signs are what cannot be visually observed whereas symptoms can. The major symptom is that these children do not respond to neither sound nor touch. This is because they lack the cerebrum part of the brain which is responsible for those senses. As such they do not feel pain, and are blind and deaf. Diagnosis The only way to diagnose this condition is through ultrasound examination. This examination is usually conclusive as the baby can be seen with an abnormal shape of the head because the large part of the brain is missing. There is usually no remedy for this since the formation stage that has been affected takes place at the very first days of the pregnancy, probably even before the mother realizes that she is pregnant. Therefore the remedies available are all proactive as opposed to reactive (Mason 42). The most plausible reactive measure that can be taken is abortion. This is dictated by the legislative directions of the location where the mother resides. Causes There is no universally acceptable reason for occurrence of this defect; there are only possible reasons that have been advanced to explain as extensive research is still being carried. The condition is not directly hereditary though some studies show that it may hereditary connections have an outside chance of increasing the odds of the defect occurring. Mothers who are taking drugs for epilepsy or who are diabetic and rely on insulin are highly likely to bear children with this condition. All factors held constant, a child has a 0.1% chance of being born with this condition. Now for these mothers on medication the chances rise to 3% (Fisch 177). Exposure to radiation and toxic substances has also been cited as a possible contributor to these chances. The elements referred to include x-ray, nuclear energy exposure, mercury and lead. The proactive measure being taken is to advice all females that are planning to or are in the risk of getting pregnant to include a 0.4 milligram of folic acid in their diet every day. Those mothers who had had an anencephalic child before are advised to take ten times the amount to reduce the chances. It is not yet known how folic acid reduces the chances but the sure thing is that it works (Mason 38). Prognosis There is no treatment or cure for this condition, the prognosis sadly is death. Even in the rare cases where the foetus survives they do not achieve a conscious existence because the brain part responsible for the same is missing. Most medical practitioners consider relieving the child of the ‘non-existence’ with the consent of the parent and the codes governing their practice in that particular location. There are however a few fetuses who have survived and their cases documented. A good example is of Kaliysha Barrett who has been in that condition for 6 years, the longest for any child to survive. The cerebral cortex is missing but the midbrain keeps her alive and functioning. She is however in an unstable condition of late as her anticipated death looms. Other cases include Nickolas Coke who survived for 3 years and 11 months and Victoria de Cristo who survived for 2 years and a half (Mason 41). Spina Bifida Physiology This is a defect condition that occurs when the posterior end of the neural tube fails to close, either fully or partially. It is a developmental defect that occurs during the early formative stages of the embryo. Some vertebrae columns do not fully form and remain open (Wyszynski 24). If the opening is large enough a sac forms as the spinal cord and some cerebrospinal fluid bulge out of the neural tube. This sac commonly appears at the lumbar and sacral areas and may paralyze the area where it appears leading to disability. There are many levels of seriousness of the defect and this usually depends on the size of the gap and the place where that gap occurs. Signs and Symptoms The most obvious symptom is the protrusion of a sac mostly at the back. Other symptoms include leg weakness and sometimes paralysis, skin irritation at the affected area, and back pain. Other symptoms include abnormal positioning of the cerebellum where it is placed at the upper part of the neck as opposed to at the back of the skull. The persons affected by this condition have poor cognitive ability and struggle academically in reading, writing and overall learning. They also tend to have poor social skills and less confidence and friends (Stiles 124). Causes Just like anencephaly medications for diabetes and epilepsy and anticunvulsions increase the chances of spina bifida. It is not hereditary though environmental factors may trigger the condition that would otherwise be dormant. Obesity and high temperatures have also been cited as a contributing factor. Just like in anencephaly cases, prospective pregnant mothers are advised to take 0.4 milligrams of folic acid every day as it significantly reduces the chances of occurrence (Fisch 180). Diagnosis Ultrasound examination can be used to diagnose the problem. However, in the cases where there is no the condition has no external manifestation, that is occurring internally only, then the ultrasound may not detect the defect. In fact there are many people who have been affected yet they are ignorant of the situation sometimes throughout their lives. An alternative means is a detailed blood screening of the mother’s blood. Treatment There is no cure or treatment for this condition. The best approach is taking proactive measure, for example, by taking doses of folic acid. However, surgery can be undertaken as a corrective step to close the bulge or opening at the back (Mason 50). Prognosis and Chances The prognosis is good. In most cases the life of the person is not in danger though cases of paralysis are common (Fisch 181). The chances are still at 0.1% in the population. Research has also shown that mothers who have had child with this condition have a 2% chance of having another one with spina bifida when they decide to have a child. The condition is also prevalent among white people as opposed to blacks. A good case is that of Jeffrey Tate, a music conductor and John Mellencamp, an American actor, musician, songwriter and painter. There are a lot of examples that can be cited. It just shows that the affected can go on with their lives depending on the extent of the condition and that disability is not inability. Work Cited Fisch, Adam. Neuroanatomy: Draw It to Know It. Oxford: Oxford University Press, 2009. Print Mason, Peggy. Medical Neurobiology. Oxford: Oxford University Press, 2011. Print. Stiles, Joan. The Fundamentals of Brain Development: Integrating Nature and Nurture. Cambridge: Harvard University Press, 2008. Print. Wyszynski, Diego. Neural Tube Defects: From Origin to Treatment. Oxford: Oxford University Press, 2005. Print. Read More