Misplaced Pages

#199800

76-602: While the oldest formations in Adrar Bous date to the Precambrian period (~4600 – 541.0 ± 1.0 Ma), much of the ring-dike formation originated during the early Silurian period (443.8 ± 1.5 – 419.2 ± 3.2 Ma), likely due to the melting of the Saharan ice caps at that time. The massif is composed primarily of granite , and is host to a number of workable rocks: jasper , quartzite , chalcedony , and others. Surrounding

152-708: A supereon , but this is also an informal term, not defined by the ICS in its chronostratigraphic guide. Eozoic (from eo- "earliest") was a synonym for pre-Cambrian , or more specifically Archean . A specific date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks (Archean Eon) from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia . Probable fossils 100 million years older have been found in

228-414: A blood test or amniocentesis finds a high level of alpha-fetoprotein (AFP), there is a higher risk of spina bifida. Ultrasound examination may also detect the problem. Medical imaging can confirm the diagnosis after birth. Spina bifida is a type of neural tube defect related to but distinct from other types such as anencephaly and encephalocele . Most cases of spina bifida can be prevented if

304-537: A higher dose of 4–5 mg/day. However, the daily requirement of folate and the recommended folate blood levels to prevent neural tube defects are not well established. Tests are not 100% perfect, so even though screening results present negative, there is still a slight chance that spina bifida is present. Spina bifida can usually be detected during the second trimester of pregnancy by fetal ultrasound . Increased levels of maternal serum alpha-fetoprotein (MSAFP) should be followed up by two tests – an ultrasound of

380-403: A history of the condition. Spina bifida occurs when local regions of the neural tube fail to fuse or there is failure in formation of the vertebral neural arches. Neural arch formation occurs in the first month of embryonic development (often before the mother knows she is pregnant). Some forms are known to occur with primary conditions that cause raised central nervous system pressure, raising

456-713: A number of faunal and human remains, dated to about 6,000 to 4,000 BP . The remains are diverse in terms of taxonomy and time period. A number of faunal remains were found at Adrar Bous, ranging from the Aterian to the Tenerian, and into the Neolithic. The Aterian specimens showed aging and mineralization most frequently, followed by the Kiffian and Tenerian specimens, respectively. Of the Aterian faunal remains, there are mostly indeterminate mammalian fossils and members of

532-452: A particularly serious concern. The most common approach to avoid developing an allergy is to avoid contact with latex-containing products such as examination gloves and catheters that do not specify they are latex-free, and many other products, such as some commonly used by dentists. The spinal cord lesion or the scarring due to surgery may result in a tethered spinal cord . In some individuals, this causes significant traction and stress on

608-735: A possible 2450 Ma red alga from the Kola Peninsula , 1650 Ma carbonaceous biosignatures in north China, the 1600 Ma Rafatazmia , and a possible 1047 Ma Bangiomorpha red alga from the Canadian Arctic. The earliest fossils widely accepted as complex multicellular organisms date from the Ediacaran Period. A very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota . Hard-shelled creatures appeared toward

684-426: A significant role. Other risk factors include certain antiseizure medications, obesity, and poorly managed diabetes . Alcohol misuse can trigger macrocytosis which discards folate . After stopping the drinking of alcohol , a time period of months is needed to rejuvenate bone marrow and recover from the macrocytosis. Certain mutations in the gene VANGL1 have been linked with spina bifida in some families with

760-453: A time when there was a concentrated focus on pastoralism in the area. Its bone structure describes it as a small, short-horned West African cow. Its presence at Adrar Bous helps to delineate the adaptation of pastoral practices to African climates. There were four human burials recovered from Adrar Bous, two of which were discovered at Agorass n'Tast. Several burials were found with ornamentation, such as shells and beaded necklaces. One burial

836-950: A very early age, as infants with spina bifida lag behind their peers in orienting to faces. Individuals with spina bifida may struggle academically, especially in the subjects of mathematics and reading . In one study, 60% of children with spina bifida were diagnosed with a learning disability. In addition to brain abnormalities directly related to various academic skills, achievement is likely affected by impaired attentional control and executive functioning. Children with spina bifida may perform well in elementary school, but begin to struggle as academic demands increase. Children with spina bifida are more likely than their peers without spina bifida to be dyscalculic . Individuals with spina bifida have demonstrated stable difficulties with arithmetic accuracy and speed, mathematical problem-solving, and general use and understanding of numbers in everyday life. Mathematics difficulties may be directly related to

SECTION 10

#1732764719200

912-502: Is an isolated malformation. Risks of amniocentesis, which may occur in approximately 1 in 900 tests, include leaking amniotic fluid, though this generally has no effect on pregnancy. However, second-trimester amniocentesis carries a slight risk of miscarriage of 0.1% to 0.3% when done by a skilled person using ultrasound, though research suggests that the risk of miscarriage is higher for amniocentesis done before 15 weeks of pregnancy. Infection transmission may occur from mother to child if

988-417: Is believed to be caused by a combination of genetic and environmental factors. The genetic component is estimated at 60–70%, but few causative genes have been identified, despite much information gathered from mouse models. After having one child with the condition, or if a parent has the condition, there is a 4% chance the next child will also be affected. A folic acid deficiency during pregnancy also plays

1064-500: Is crucial. Individuals with spina bifida tend to have better reading skills than mathematics skills. Children and adults with spina bifida have stronger abilities in reading accuracy than in reading comprehension. Comprehension may be especially impaired for text that requires an abstract synthesis of information rather than a more literal understanding. Individuals with spina bifida may have difficulty with writing due to deficits in fine motor control and working memory. Spina bifida

1140-601: Is difficult for women to get the recommended 400 micrograms of folic acid a day from unfortified foods. Globally, fortified wheat flour and other cereal grains are credited with preventing 50,000–61,000 neural tube birth defects such as spina bifida yearly, which is estimated to be 22% of total possible preventable neural tube defects assuming universal and worldwide folic acid fortification. Many countries in Africa, Asia, and Europe have yet to implement fortification Folate fortification of enriched grain products has been mandatory in

1216-664: Is known to occur during the RNA replication of extant coronaviruses . Evidence of the details of plate motions and other tectonic activity in the Precambrian is difficult to interpret. It is generally believed that small proto-continents existed before 4280 Ma, and that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia , broke up around 750 Ma. A number of glacial periods have been identified going as far back as

1292-476: Is neither a single cause of spina bifida nor any known way to prevent it entirely. However, dietary supplementation with folic acid has been shown to be helpful in reducing the incidence of spina bifida. Folate supplementation prior to conception has been found to reduce the risk of neural tube defects, including spina bifida, by 70%. Sources of folic acid include whole grains , fortified breakfast cereals , dried beans , leaf vegetables and fruits . However it

1368-408: Is partly responsible for the decline in new cases, because many pregnancies are terminated out of fear that a newborn might have a poor future quality of life . With modern medical care, the quality of life of patients has greatly improved. There is no known cure for the nerve damage caused by spina bifida. Standard treatment is surgery after delivery. This surgery aims to prevent further damage of

1444-400: Is present. Incomplete posterior fusion is not a true spina bifida and is very rarely of neurological significance. A posterior meningocele ( / m ɪ ˈ n ɪ ŋ ɡ ə ˌ s iː l / ) or meningeal cyst ( / m ɪ ˈ n ɪ n dʒ i əl / ) is the least common form of spina bifida. In this form, a single developmental defect allows the meninges to herniate between the vertebrae. As

1520-406: Is represented only by a fragment of the skull. One of the individuals excavated from Adrar Bous shows spina bifida of indeterminate type, as well as osteoarthritis in the knees and back. Precambrian The Precambrian ( / p r i ˈ k æ m b r i . ə n , - ˈ k eɪ m -/ pree- KAM -bree-ən, -⁠KAYM- ; or Pre-Cambrian , sometimes abbreviated pC , or Cryptozoic )

1596-431: Is sometimes a genetic basis for the condition. Human spina bifida likely results from the interaction of multiple genes and environmental factors. Research has shown the lack of folic acid (folate) is a contributing factor in the pathogenesis of neural tube defects, including spina bifida. Supplementation of the mother's diet with folate can reduce the incidence of neural tube defects by about 70%, and can also decrease

SECTION 20

#1732764719200

1672-539: Is the lower back , but in rare cases it may be in the middle back or neck . Occulta has no or only mild signs, which may include a hairy patch, dimple, dark spot or swelling on the back at the site of the gap in the spine. Meningocele typically causes mild problems, with a sac of fluid present at the gap in the spine. Myelomeningocele, also known as open spina bifida , is the most severe form. Problems associated with this form include poor ability to walk, impaired bladder or bowel control , accumulation of fluid in

1748-668: Is the earliest part of Earth's history , set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian , the first period of the Phanerozoic Eon , which is named after Cambria , the Latinized name for Wales , where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean , Archean , Proterozoic ) of

1824-409: Is the namesake of the Kiffian technocomplex . A site lying to the west of the main massif, Agorass n'Tast, did not contain as many Kiffian remains as the other sites but boasts a spate of Tenerian artifacts and fauna, including many pieces of pottery, and the later noted Adrar Bous cow. There is a measurable point in this area where the frequency of artifacts lessens significantly, possibly delineating

1900-505: Is the risk of preterm birth. Broadly, there are two forms of prenatal treatment. The first is open fetal surgery, where the uterus is opened and the spina bifida repair performed. The second is via fetoscopy. These techniques may be an option to standard therapy. Most individuals with myelomeningocele will need periodic evaluations by a variety of specialists: Although many children's hospitals feature integrated multidisciplinary teams to coordinate healthcare of youth with spina bifida,

1976-521: Is thought that the Earth coalesced from material in orbit around the Sun at roughly 4,543 Ma, and may have been struck by another planet called Theia shortly after it formed, splitting off material that formed the Moon (see Giant-impact hypothesis ). A stable crust was apparently in place by 4,433 Ma, since zircon crystals from Western Australia have been dated at 4,404 ± 8 Ma. The term "Precambrian"

2052-617: Is thought to have formed about 1300-900 Ma, to have included most or all of Earth's continents and to have broken up into eight continents around 750–600 million years ago. Spina bifida Spina bifida ( SB ; /ˌspaɪnə ˈbɪfɪdə/, Latin for 'split spine') is a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy . There are three main types: spina bifida occulta , meningocele and myelomeningocele . Meningocele and myelomeningocele may be grouped as spina bifida cystica . The most common location

2128-731: Is used by geologists and paleontologists for general discussions not requiring a more specific eon name. However, both the United States Geological Survey and the International Commission on Stratigraphy regard the term as informal. Because the span of time falling under the Precambrian consists of three eons (the Hadean , the Archean , and the Proterozoic ), it is sometimes described as

2204-574: The Clariidae taxa, as well as four hippopotamus specimens and one indeterminate large mammal. The Kiffian remains (derived from Adrar n'Kiffi and Diatomite 1) include a larger variety of both Mammalian and fish-like fossils, including members of the genera Bovini (cows), Syondontis (tigerfish), and Sus (wild boar), among other native African fauna. The boar specimen extracted from Diatomite 1 had significantly longer teeth than its modern counterpart. The Tenerian faunal remains showed by far

2280-534: The Huronian epoch, roughly 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a " Snowball Earth ". The atmosphere of the early Earth is not well understood. Most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and

2356-413: The abdomen or chest wall. Standard treatment is after delivery. There is tentative evidence about treatment for severe disease before delivery while the baby is inside the womb. As of 2014, however, the evidence remains insufficient to determine benefits and harms. Treatment of spina bifida during pregnancy is not without risk. To the mother, this includes scarring of the uterus. To the baby, there

Adrar Bous - Misplaced Pages Continue

2432-584: The frontal lobes of the brain, individuals with spina bifida have intact frontal lobes; therefore, other areas of the brain may be implicated. Individuals with spina bifida, especially those with shunted hydrocephalus, often have attention problems. Children with spina bifida and shunted hydrocephalus have higher rates of ADHD than children without those conditions (31% vs. 17%). Deficits have been observed for selective attention and focused attention, although poor motor speed may contribute to poor scores on tests of attention. Attention deficits may be evident at

2508-522: The geologic time scale . It spans from the formation of Earth about 4.6 billion years ago ( Ga ) to the beginning of the Cambrian Period, about 538.8 million years ago ( Ma ), when hard-shelled creatures first appeared in abundance. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history , and what is known has largely been discovered from

2584-482: The oxygen catastrophe . At first, oxygen would have quickly combined with other elements in Earth's crust, primarily iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, and the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides. A terminology has evolved covering

2660-401: The 1960s onwards. The Precambrian fossil record is poorer than that of the succeeding Phanerozoic , and fossils from the Precambrian (e.g. stromatolites ) are of limited biostratigraphic use. This is because many Precambrian rocks have been heavily metamorphosed , obscuring their origins, while others have been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata. It

2736-487: The Adrar Bous Massif, several occurrences of diatomites yielded small stone tools and other artifacts, as well as the remains of aquatic and amphibious animals. Among the stone tools, scraper-type utensils were the most frequently found. A site lying to the southeast of the main massif yielding a larger amount of truncated blades and crescent-shaped microlithic tools than other nearby sites. Whether or not it

2812-629: The United States since 1998. This prevents an estimated 600 to 700 incidents of spina bifida a year in the U.S. and saves $ 400–600 million in healthcare expenses. The U.S. Food and Drug Administration , Public Health Agency of Canada and the UK Department of Health and Social Care (DHSC) recommended amount of folic acid for women of childbearing age and women planning to become pregnant is at least 0.4 mg/day of folic acid from at least three months before conception , and continued for

2888-424: The United States, it occurs in about 0.4 per 1,000 births. In India, it affects about 1.9 per 1,000 births. Europeans are at higher risk compared to Africans . Occulta is Latin for 'hidden'. This is the mildest form of spina bifida. In occulta, the outer part of some of the vertebrae is not completely closed. The splits in the vertebrae are so small that the spinal cord does not protrude. The skin at

2964-534: The adolescent's medical care, including information about medications, surgery, therapies, and recommendations. A transition plan and aid in identifying adult healthcare professionals are also helpful to include in the transition process. Further complicating the transition process is the tendency for youths with spina bifida to be delayed in the development of autonomy, with boys particularly at risk for slower development of independence. An increased dependence on others (in particular family members) may interfere with

3040-758: The adolescent's self-management of health-related tasks, such as catheterization, bowel management, and taking medications. As part of the transition process, it is beneficial to begin discussions at an early age about educational and vocational goals, independent living, and community involvement. Certain locations feature multidisciplinary clinics in order to offer coordinated care between specialists, such as Cincinnati Children's Center for Spina Bifida. Rates of spina bifida vary significantly by country from 0.1 to 5 per 1000 births. In high income and upper-middle income countries with folate fortification of foodstuffs public health programs, including in North America,

3116-423: The brain , a tethered spinal cord and latex allergy . Some experts believe such an allergy can be caused by frequent exposure to latex, which is common for people with spina bifida who have shunts and have had many surgeries. Learning problems are relatively uncommon. Spina bifida is believed to be due to a combination of genetic and environmental factors. After having one child with the condition, or if one of

Adrar Bous - Misplaced Pages Continue

3192-742: The brain are also associated with increased cortical folding. Neurons within the cortex may also be displaced. Several studies have demonstrated difficulties with executive functions in youth with spina bifida, with greater deficits observed in youth with shunted hydrocephalus. Unlike typically developing children, youths with spina bifida do not tend to improve in their executive functioning as they grow older. Specific areas of difficulty in some individuals include planning, organizing, initiating, and working memory . Problem-solving, abstraction , and visual planning may also be impaired. Further, children with spina bifida may have poor cognitive flexibility . Although executive functions are often attributed to

3268-461: The communication processes between the left and right brain hemispheres. Further, white matter tracts connecting posterior brain regions with anterior regions appear less organized. White matter tracts between frontal regions have also been found to be impaired. Cortex abnormalities may also be present. For example, frontal regions of the brain tend to be thicker than expected, while posterior and parietal regions are thinner. Thinner sections of

3344-418: The condition is asymptomatic in most cases. A systematic review of radiographic research studies found no relationship between spina bifida occulta and back pain. More recent studies not included in the review support the negative findings. However other studies suggest spina bifida occulta is not always harmless. One study found that among patients with back pain severity is worse if spina bifida occulta

3420-401: The current scheme based upon numerical ages. Such a system could rely on events in the stratigraphic record and be demarcated by GSSPs . The Precambrian could be divided into five "natural" eons, characterized as follows: The movement of Earth's plates has caused the formation and break-up of continents over time, including occasional formation of a supercontinent containing most or all of

3496-453: The early years of the Earth's existence, as radiometric dating has allowed absolute dates to be assigned to specific formations and features. The Precambrian is divided into three eons: the Hadean (4567.3–4031 Ma), Archean (4031-2500 Ma) and Proterozoic (2500-538.8 Ma). See Timetable of the Precambrian . It has been proposed that the Precambrian should be divided into eons and eras that reflect stages of planetary evolution, rather than

3572-705: The end of that time span, marking the beginning of the Phanerozoic Eon. By the middle of the following Cambrian Period, a very diverse fauna is recorded in the Burgess Shale , including some which may represent stem groups of modern taxa. The increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Tracks from an animal with leg-like appendages have been found in what

3648-434: The fetal spine and amniocentesis of the mother's amniotic fluid (to test for alpha-fetoprotein and acetylcholinesterase ). AFP tests are now mandated by some state laws (including California ) and failure to provide them can have legal ramifications. Spina bifida may be associated with other malformations as in dysmorphic syndromes, often resulting in spontaneous miscarriage . In the majority of cases, though, spina bifida

3724-403: The first 12 weeks of pregnancy. The United States Preventive Services Task Force (USPSTF) recommends all people who may become pregnant or are attempting pregnancy take a folic acid supplement containing 0.4–0.8 mg (400–800 mcg) of folic acid daily. Women who have already had a baby with spina bifida or other type of neural tube defect, or are taking anticonvulsant medication, should take

3800-445: The incidence of spina bifida is 34–37 cases per 100,000 live births. In countries without folate fortification programs nor widespread maternal folate supplementation, the incidence is 54–87 cases per 100,000 live births. And in low income countries or regions without folic acid supplementation nor fortification, the incidence is 300 cases per 100,000 live births. In India, about 1.9 per 1000 live births are affected by spina bifida. In

3876-454: The involved area is represented by a flattened, plate-like mass of nervous tissue with no overlying membrane. The exposure of these nerves and tissues make the baby more prone to life-threatening infections such as meningitis . The protruding portion of the spinal cord and the nerves that originate at that level of the cord are damaged or not properly developed. As a result, there is usually some degree of paralysis and loss of sensation below

SECTION 50

#1732764719200

3952-541: The landmass. The earliest known supercontinent was Vaalbara . It formed from proto-continents and was a supercontinent 3.636 billion years ago. Vaalbara broke up c. 2.845–2.803 Ga ago. The supercontinent Kenorland was formed c. 2.72 Ga ago and then broke sometime after 2.45–2.1 Ga into the proto-continent cratons called Laurentia , Baltica , Yilgarn craton and Kalahari . The supercontinent Columbia , or Nuna, formed 2.1–1.8 billion years ago and broke up about 1.3–1.2 billion years ago. The supercontinent Rodinia

4028-501: The level of the spinal cord defect. Thus, the more cranial the level of the defect, the more severe the associated nerve dysfunction and resultant paralysis may be. Symptoms may include ambulatory problems, loss of sensation, deformities of the hips, knees or feet, and loss of muscle tone. Physical signs of spina bifida may include: 68% of children with spina bifida have an allergy to latex , ranging from mild to life-threatening. The common use of latex in medical facilities makes this

4104-706: The main massif, Diatomite 1/Gisement 10, is dated to about 9130-9030 BP . This site contained several terrestrial Kiffian fauna, as well as some aquatic specimens from the same time period. Lying to the north of the main massif, the Well Area site yielded similar tools to Diatomite 1/Gisement 10, without indication of a lake. It contains many similar artifacts to Diatomite 1 and Adrar n'Kiffi. A number of Late Acheulean, Tenerian (~6950 – 4450 BP), and Kiffian (~9950 – 7950 BP) artifacts were discovered at Adrar Bous. Hand axes, found in highest number, were found among cleavers, adzes , and other objects. Adrar Bous also contains

4180-478: The most taxonomic diversity, with the bulk of researched specimens being mammals. Nearly half of the cataloged remains belonged to domestic cattle specifically of the Bos genus, some of whose bones were burnt likely by human cohabitants. A notable find in Adrar Bous is that of a young, fully articulated cow skeleton, discovered in 1976 on an exploration by Carter and Clark. The cow skeleton has been dated to 4145±45 BP,

4256-590: The mother gets enough folate before and during pregnancy. Adding folic acid to flour has been found to be effective for most women. Open spina bifida can be surgically closed before or after birth. A shunt may be needed in those with hydrocephalus, and a tethered spinal cord may be surgically repaired. Devices to help with movement such as crutches or wheelchairs may be useful. Urinary catheterization may also be needed. Rates of other types of spina bifida vary significantly by country, from 0.1 to 5 per 1,000 births . On average, in developed countries , including

4332-529: The mother has infections such as hepatitis C, toxoplasmosis, or HIV/AIDS, or Rh sensitization, which ultimately damages the fetus' red blood cells. Needle injury to the fetus may occur, though serious injury is very rare, along with triggering a uterine infection, which is also very rare. Genetic counseling and further genetic testing through amniocentesis may be offered during the pregnancy, as some neural tube defects are associated with genetic disorders such as trisomy 18 . Ultrasound screening for spina bifida

4408-498: The nervous system remains undamaged, individuals with meningocele are unlikely to have long-term health problems, although cases of tethered cord have been reported. Causes of meningocele include teratoma and other tumors of the sacrococcyx and of the presacral space , and Currarino syndrome . A meningocele may also form through dehiscences in the base of the skull. These may be classified by their localisation as occipital, frontoethmoidal or nasal. Endonasal meningoceles lie at

4484-413: The nervous tissue and to prevent infection; pediatric neurosurgeons operate to close the opening on the back. The spinal cord and its nerve roots are put back inside the spine and covered with meninges . In addition, a shunt may be surgically installed to provide a continuous drain for the excess cerebrospinal fluid produced in the brain, as happens with hydrocephalus . Shunts most commonly drain into

4560-527: The outskirts of a settlement. There are also stone circles within this settlement, thought to be used for wind shelter. A site lying to the north of the main massif, Agorass n'Tchissikian, is south of the Well Area. This site contains a number of potsherds , as well as a number of tumuli . Two of the burials located there have been recovered. They were discovered to have been relocated to Cambridge, England, where all of their skulls were found to be missing and have not yet been located. A small site southeast of

4636-400: The parents has the condition, there is a 4% chance that the next child will also be affected. Not having enough folate ( vitamin B 9 ) in the diet before and during pregnancy also plays a significant role. Other risk factors include certain antiseizure medications , obesity and poorly controlled diabetes . Diagnosis may occur either before or after a child is born. Before birth, if

SECTION 60

#1732764719200

4712-453: The people with myelomeningocele, hydrocephalus also occurs because the displaced cerebellum interferes with the normal flow of cerebrospinal fluid , causing an excess of the fluid to accumulate. In fact, the cerebellum also tends to be smaller in individuals with spina bifida, especially for those with higher lesion levels. The corpus callosum is abnormally developed in 70–90% of individuals with spina bifida myelomeningocele; this affects

4788-499: The possibility of a dual pathogenesis. In normal circumstances, the closure of the neural tube occurs around the 23rd (rostral closure) and 27th (caudal closure) day after fertilization . However, if something interferes and the tube fails to close properly, a neural tube defect will occur. Maternal diabetes , anti-seizure medication use, obesity are known risk factors for the development of spina bifida. Extensive evidence from mouse strains with spina bifida indicates that there

4864-399: The roof of the nasal cavity and may be mistaken for a nasal polyp . They are treated surgically. Encephalomeningoceles are classified in the same way and also contain brain tissue. Myelomeningocele (MMC), also known as meningomyelocele, is the type of spina bifida that often results in the most severe complications and affects the meninges and nerves. In individuals with myelomeningocele,

4940-526: The same area. However, there is evidence that life could have evolved over 4.280 billion years ago. There is a fairly solid record of bacterial life throughout the remainder (Proterozoic Eon) of the Precambrian. Complex multicellular organisms may have appeared as early as 2100 Ma. However, the interpretation of ancient fossils is problematic, and "... some definitions of multicellularity encompass everything from simple bacterial colonies to badgers." Other possible early complex multicellular organisms include

5016-435: The severity of these defects when they occur. It is unknown how or why folic acid has this effect. Spina bifida does not follow direct patterns of heredity as do muscular dystrophy or haemophilia . Studies show a woman having had one child with a neural tube defect such as spina bifida has about a 3% risk of having another affected child. This risk can be reduced with folic acid supplementation before pregnancy. There

5092-491: The site of the lesion may be normal, or it may have some hair growing from it; there may be a dimple in the skin, or a birthmark . Unlike most other types of neural tube defects, spina bifida occulta is not associated with increased AFP , a common screening tool used to detect neural tube defects in utero. This is because, unlike in most of the other neural tube defects, the dural lining is maintained. Many people with this type of spina bifida do not even know they have it, as

5168-474: The spinal cord and can lead to a worsening of associated paralysis, scoliosis , back pain, and worsening bowel and/or bladder function. Many individuals with spina bifida have an associated abnormality of the cerebellum , called the Arnold Chiari II malformation . In affected individuals, the back portion of the brain is displaced from the back of the skull down into the upper neck. In about 90% of

5244-419: The spinal cord and nerve roots. Myelomeningocele is also associated with club foot deformity, and Arnold–Chiari malformation , necessitating a VP shunt placement. Toxins and conditions associated with MMC formation include: calcium-channel blockers , carbamazepine , cytochalasins , hyperthermia , and valproic acid . Spina bifida with myelocele is the most severe form of myelomeningocele. In this type,

5320-569: The thinning of the parietal lobes (regions implicated in mathematical functioning) and indirectly associated with deformities of the cerebellum and midbrain that affect other functions involved in mathematical skills. Further, higher numbers of shunt revisions are associated with poorer mathematics abilities. Working memory and inhibitory control deficiencies have been implicated for math difficulties, although visual-spatial difficulties are not likely involved. Early intervention to address mathematics difficulties and associated executive functions

5396-415: The transition to adult healthcare can be difficult because the above healthcare professionals operate independently of each other, requiring separate appointments, and communicate among each other much less frequently. Healthcare professionals working with adults may also be less knowledgeable about spina bifida because it is considered a childhood chronic health condition. Due to the potential difficulties of

5472-439: The transition, adolescents with spina bifida and their families are encouraged to begin to prepare for the transition around ages 14–16, although this may vary depending on the adolescent's cognitive and physical abilities and available family support. The transition itself should be gradual and flexible. The adolescent's multidisciplinary treatment team may aid in the process by preparing comprehensive, up-to-date documents detailing

5548-426: The unfused portion of the spinal column allows the spinal cord to protrude through an opening. Myelomeningocele occurs in the third week of embryonic development, during neural tube pore closure. MMC is a failure of this to occur completely. The meningeal membranes that cover the spinal cord also protrude through the opening, forming a sac enclosing the spinal elements, such as meninges, cerebrospinal fluid, and parts of

5624-404: Was inhabited at the same time as the other Tenerian formations is under debate, as its tools appear to be slightly older than those found at other sites nearby. A site lying south of the main massif, Adrar n'Kiffi, shows the remnants of a lake, with a number of tools made of bone and stone including a stone harpoon and some dotted wavy-line pottery , as well as amphibious and fish-like remains. It

5700-482: Was lacking in free oxygen . There is, however, evidence that an oxygen-rich atmosphere existed since the early Archean. At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism . This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis , sometimes called

5776-852: Was mud 551 million years ago. The RNA world hypothesis asserts that RNA evolved before coded proteins and DNA genomes. During the Hadean Eon (4,567–4,031 Ma) abundant geothermal microenvironments were present that may have had the potential to support the synthesis and replication of RNA and thus possibly the evolution of a primitive life form. It was shown that porous rock systems comprising heated air-water interfaces could allow ribozyme - catalyzed RNA replication of sense and antisense strands that could be followed by strand-dissociation, thus enabling combined synthesis, release and folding of active ribozymes. This primitive RNA replicative system also may have been able to undergo template strand switching during replication ( genetic recombination ) as

#199800