The development of the nervous system is tightly regulated and timed; it is influenced by both genetic programs and the environment. Any significant deviation from the normal developmental trajectory early in life can result in missing or abnormal neuronal architecture or connectivity. Because of the temporal and spatial complexity of the developmental trajectory, there are many potential causes of<unk> s that may affect different areas of the nervous system at different times and ages. These range from social deprivation, genetic and metabolic diseases, immune disorders, infectious diseases, nutritional factors, physical trauma, and toxic and environmental factors. Some<unk> s, such as autism and other pervasive developmental disorders, are considered multifactorial syndromes which have many causes that converge to a more specific<unk>  manifestation. Social deprivation Deprivation from social and emotional care causes severe delays in brain and cognitive development. Studies with children growing up in Romanian orphanages during Nicolae Ceauşescu's regime reveal profound effects of social deprivation and language deprivation on the developing brain. These effects are time-dependent. The longer children stayed in negligent institutional care, the greater the consequences. By contrast, adoption at an early age mitigated some of the effects of earlier institutionalization (abnormal psychology). Genetic disorders A child with Down syndrome A prominent example of a genetically determined<unk>  is Trisomy 21, also known as Down syndrome. This disorder usually results from an extra chromosome 21, although in uncommon instances it is related to other chromosomal abnormalities such as translocation of the genetic material. It is characterized by short stature, epicanthal (eyelid) folds, abnormal fingerprints, and palm prints, heart defects, poor muscle tone (delay of neurological development) and intellectual disabilities (delay of intellectual development). Less commonly known genetically determined<unk> s include Fragile X syndrome. Fragile X syndrome was first described in 1943 by Martin and Bell, studying persons with family history of sex-linked "mental defects". Rett syndrome, another X-linked disorder, produces severe functional limitations. Williams syndrome is caused by small deletions of genetic material from chromosome 7. The most common recurrent Copy Number Variannt disorder is 22q11.2 deletion syndrome (formerly DiGeorge or velocardiofacial syndrome), followed by Prader-Willi syndrome and Angelman syndrome. Immune dysfunction Immune reactions during pregnancy, both maternal and of the developing child, may produce<unk> s. One typical immune reaction in infants and children is PANDAS, or Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection. Another disorder is Sydenham's chorea, which results in more abnormal movements of the body and fewer psychological sequellae. Both are immune reactions against brain tissue that follow infection by Streptococcus bacteria. Susceptibility to these immune diseases may be genetically determined, so sometimes several family members may have one or both of them following an epidemic of Strep infection. Infectious diseases Systemic infections can result in<unk>  consequences, when they occur in infancy and childhood of humans, but would not be called a primary<unk> . For example HIV Infections of the head and brain, like brain abscesses, meningitis or encephalitis have a high risk of causing<unk>  problems and eventually a disorder. For example, measles can progress to subacute sclerosing panencephalitis. A number of infectious diseases can be transmitted congenitally (either before or at birth), and can cause serious<unk>  problems, as for example the viruses HSV, CMV, rubella (congenital rubella syndrome), Zika virus, or bacteria like Treponema pallidum in congenital syphilis, which may progress to neurosyphilis if it remains untreated. Protozoa like Plasmodium or Toxoplasma which can cause congenital toxoplasmosis with multiple cysts in the brain and other organs, leading to a variety of neurological deficits. Some cases of schizophrenia may be related to congenital infections though the majority are of unknown causes. Metabolic disorders Metabolic disorders in either the mother or the child can cause<unk> s. Two examples are diabetes mellitus (a multifactorial disorder) and phenylketonuria (an inborn error of metabolism). Many such inherited diseases may directly affect the child's metabolism and neural development but less commonly they can indirectly affect the child during gestation. (See also teratology). In a child, type 1 diabetes can produce<unk>  damage by the effects of excess or insufficient glucose. The problems continue and may worsen throughout childhood if the diabetes is not well controlled. Type 2 diabetes may be preceded in its onset by impaired cognitive functioning. A non-diabetic fetus can also be subjected to glucose effects if its mother has undetected gestational diabetes. Maternal diabetes causes excessive birth size, making it harder for the infant to pass through the birth canal without injury or it can directly produce early<unk>  deficits. Usually the<unk>  symptoms will decrease in later childhood. Phenylketonuria, also known as PKU, can induce<unk>  problems and children with PKU require a strict diet to prevent intellectual disability and other disorders. In the maternal form of PKU, excessive maternal phenylalanine can be absorbed by the fetus even if the fetus has not inherited the disease. This can produce intellectual disability and other disorders. Nutrition Nutrition disorders and nutritional deficits may cause<unk> s, such as spina bifida, and the rarely occurring anencephaly, both of which are neural tube defects with malformation and dysfunction of the nervous system and its supporting structures, leading to serious physical disability and emotional sequelae. The most common nutritional cause of neural tube defects is folic acid deficiency in the mother, a B vitamin usually found in fruits, vegetables, whole grains, and milk products. (Neural tube defects are also caused by medications and other environmental causes, many of which interfere with folate metabolism, thus they are considered to have multifactorial causes.) Another deficiency, iodine deficiency, produces a spectrum of<unk> s ranging from mild emotional disturbance to severe intellectual disability. (see also congenital iodine deficiency syndrome) Excesses in both maternal and infant diets may cause disorders as well, with foods or food supplements proving toxic in large amounts. For instance in 1973 K.L. Jones and D.W. Smith of the University of Washington Medical School in Seattle found a pattern of "craniofacial, limb, and cardiovascular defects associated with prenatal onset growth deficiency and developmental delay" in children of alcoholic mothers, now called fetal alcohol syndrome, It has significant symptom overlap with several other entirely unrelated<unk> s. Physical trauma CT scan showing epidural hematoma, a type of traumatic brain injury (upper left) Brain trauma in the developing human is a common cause (over 400,000 injuries per year in the US alone, without clear information as to how many produce developmental sequellae) of<unk>  syndromes. It may be subdivided into two major categories, congenital injury (including injury resulting from otherwise uncomplicated premature birth) and injury occurring in infancy or childhood. Common causes of congenital injury are asphyxia (obstruction of the trachea), hypoxia (lack of oxygen to the brain) and the mechanical trauma of the birth process itself. Placenta Although it not clear yet as strong is the correlation between placenta and brain, a growing number of studies are linking placenta to fetal brain development.
Neurodevelopmental disorder
Developmental disorder
Specific developmental disorder
Developmental disability
Multiple complex developmental disorder
Frontal lobe disorder
Pervasive developmental disorder
Developmental coordination disorder