Neurodevelopmental Disorders
Encyclopedia
A neurodevelopmental disorder, or disorder of neural development
, is an impairment of the growth and development of the brain
or central nervous system
. A narrower use of the term refers to a disorder of brain function that affects emotion
, learning ability and memory
and that unfolds as the individual grows
. The term is sometimes erroneously used as an exclusive synonym for autism
and autism spectrum
disorders.
Disorders considered to be neurodevelopmental in origin or to have neurodevelopmental consequences when they occur in infancy and childhood include autism
and autism spectrum
disorders such as Asperger syndrome
, traumatic brain injury
(including congenital injuries such as those that cause cerebral palsy
), communication, speech and language disorders
, genetic disorders such as fragile-X syndrome, and Down syndrome
. Neurodevelopmental disorders are associated with widely varying degrees of mental, emotional, physical and economic burden to individuals, families and society in general.
s, nutrition
al factors, physical trauma
, and toxic and environmental factors.
Some neurodevelopmental disorders such as autism
, Nampoothiri Syndrome and other pervasive developmental disorder
s are considered to be multifactorial syndrome
s (with many causes but more specific neurodevelopmental manifestation). However other multifactorial syndromes such as Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS) are presently thought to have a more specific primary causation as well as a specific neurodevelopmental manifestation.
, was described in 1897 as a wasting away to the point of death. A sublethal form, anaclitic depression was first described by René Spitz
in the 1940s. It occurred in infants over the age of six months who suffered the loss of their mothers, who then became depressed and showed behavioral retardation
(delay in reaching developmental milestones, especially as related to social behaviors). Behavioral retardation, as in the reactive attachment disorder
s, has been observed in emotionally deprived children living with their families. However, prominent modern thought attributes other causative mechanisms to autism and autistic spectrum disorders. (see Autism
)
However, nurture is not the only cause of deprivation that leads to neurodevelopmental sequellae. A common example of sensory deprivation due to biologic factors is blindness
. Blind infants have risk of poor developmental outcomes which, left untreated, may lead to severe, autistic-like behaviors. Despite its biologic basis, caregivers can ameliorate blindness-related sensory deprivation. This can lead to positive neurodevelopmental outcome, as in the cases of author Helen Keller
, who was trained in the use of tactile sign language
, and musicians such as Arthel "Doc" Watson
and Ray Charles
who remained emotionally connected to others via their sense of hearing
.
A prominent example of a genetically determined neurodevelopmental disorder 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 fingerprint
s and palm prints
, heart defects, poor muscle tone
(delay of neurological development) and mental retardation
(delay of intellectual development).
Less commonly known genetically determined neurodevelopmental disorders include Fragile X syndrome
, Rett syndrome
and Williams syndrome
. Fragile X syndrome was first described in 1943 by J.P. Martin and J. 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.
, 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 suffer from one or both of them following an epidemic
of Strep infection.)
may progress to neurosyphilis if it remains untreated. Measles
can progress to subacute sclerosing panencephalitis
. Congenital rubella syndrome
can produce schizophrenia
in addition to multiple other symptoms.
(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 the child, type 1 diabetes
can produce neurodevelopmental damage by the effects of excessive 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.
However 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 neurodevelopmental deficits. However usually the neurodevelopmental symptoms decrease in later childhood.
Phenylketonuria
, also known as PKU is an inborn error of metabolism
that can induce neurodevelopmental disorders in children. Children with PKU require a strict diet to prevent mental retardation 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 mental retardation and other disorders.
, which is common, and anencephaly
, which is rare. Both disorders are neural tube defects
with malformation and dysfunction of the nervous system
and its supporting structures, leading to serious physical disability as well as its emotional sequellae. The most common nutritional cause of neural tube defects is maternal deficiency of folic acid
, 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 neurodevelopmental disorders from mild emotional disturbance to severe mental retardation. (see also cretinism
)
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. This disorder, now called fetal alcohol syndrome
, has significant symptom overlap with several other entirely unrelated neurodevelopmental disorders. It has been discovered that iron supplementation in baby formula is linked to lowered I.Q. and other neurodevelopmental delays.
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 neurodevelopmental 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.
Overwhelmingly, in industrial nations the most common causes of childhood brain trauma are falls and transportation-related incidents. Child maltreatment
such as shaken baby syndrome
can produce neurodevelopmental consequences including blindness, neuromotor deficits and cognitive impairment. According to information published by the American Association of Neurological Surgeons
, sports injuries account for 21% of the US incidence
, however their site includes transportation-related sports injuries. They assert that cycling
produced 64,993 head injuries requiring emergency room visits in 2007 while the second most common cause, football
, only produced 36,412.
, with a prominent 20th century example being Minamata disease
. Developmental mercury poisoning
can cause a spectrum of problems from mild impairment of emotional development to the full blown syndrome of peripheral nerve damage, visual impairment
, impaired coordination and ambulation, hallucinations, mental retardation, depression
and death. However other metals such as lead
, manganese
, arsenic
, cadmium
and iron
, as well as prenatal exposure to pesticides, tobacco
and other environmental toxins are also implicated as causative factors.
Neural development
Neural development comprises the processes that generate, shape, and reshape the nervous system, from the earliest stages of embryogenesis to the final years of life. The study of neural development aims to describe the cellular basis of brain development and to address the underlying mechanisms...
, is an impairment of the growth and development of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
or central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. A narrower use of the term refers to a disorder of brain function that affects emotion
Emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
, learning ability and memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
and that unfolds as the individual grows
Child development
Child development stages describe theoretical milestones of child development. Many stage models of development have been proposed, used as working concepts and in some cases asserted as nativist theories....
. The term is sometimes erroneously used as an exclusive synonym for autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
and autism spectrum
Autism spectrum
The term "autism spectrum" is often used to describe disorders that are currently classified as pervasive developmental disorders. Pervasive developmental disorders include autism, Asperger syndrome, Childhood disintegrative disorder, Rett syndrome and Pervasive Developmental Disorder Not Otherwise...
disorders.
Disorders considered to be neurodevelopmental in origin or to have neurodevelopmental consequences when they occur in infancy and childhood include autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
and autism spectrum
Autism spectrum
The term "autism spectrum" is often used to describe disorders that are currently classified as pervasive developmental disorders. Pervasive developmental disorders include autism, Asperger syndrome, Childhood disintegrative disorder, Rett syndrome and Pervasive Developmental Disorder Not Otherwise...
disorders such as Asperger syndrome
Asperger syndrome
Asperger's syndrome that is characterized by significant difficulties in social interaction, alongside restricted and repetitive patterns of behavior and interests. It differs from other autism spectrum disorders by its relative preservation of linguistic and cognitive development...
, traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
(including congenital injuries such as those that cause cerebral palsy
Cerebral palsy
Cerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....
), communication, speech and language disorders
Communication disorder
A communication disorder is a speech and language disorder which refers to problems in communication and in related areas such as oral motor function. The delays and disorders can range from simple sound substitution to the inability to understand or use language...
, genetic disorders such as fragile-X syndrome, and Down syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
. Neurodevelopmental disorders are associated with widely varying degrees of mental, emotional, physical and economic burden to individuals, families and society in general.
Causes
There are many causes of neurodevelopmental disorder, which can range from deprivation, genetic and metabolic diseases, immune disorders, infectious diseaseInfectious disease
Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...
s, nutrition
Nutrition
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
al factors, physical trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
, and toxic and environmental factors.
Some neurodevelopmental disorders such as autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
, Nampoothiri Syndrome and other pervasive developmental disorder
Pervasive developmental disorder
Pervasive developmental disorders is a diagnostic category refers to a group of disorders characterized by delays or impairments in communication, social behaviors, and cognitive development.Pervasive developmental disorders include Autism, Asperger's syndrome, Rett's syndrome, Childhood...
s are considered to be multifactorial syndrome
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
s (with many causes but more specific neurodevelopmental manifestation). However other multifactorial syndromes such as Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS) are presently thought to have a more specific primary causation as well as a specific neurodevelopmental manifestation.
Deprivation
Infants and children require loving emotional nurture from caregivers—there is a spectrum of problems arising from the lack of it. The most severe deprivation disorder, hospitalismHospitalism
Hospitalism was a pediatric diagnosis used in the 1930s to describe infants who wasted away while in hospital. The symptoms could include retarded physical development, and disruption of perceptual-motor skills and language...
, was described in 1897 as a wasting away to the point of death. A sublethal form, anaclitic depression was first described by René Spitz
René Spitz
René Árpád Spitz was an American psychoanalyst of Hungarian origin.- Biography :Rene Spitz was born in Vienna and died in Denver, Colorado. From a wealthy Jewish family background, he spent most of his childhood in Hungary. After finishing his medical studies in 1910 Spitz discovered the work of...
in the 1940s. It occurred in infants over the age of six months who suffered the loss of their mothers, who then became depressed and showed behavioral retardation
Retardation
Retardation is the act or result of delaying; the extent to which anything is retarded or delayed; that which retards or delays. In particular, it can mean:-In engineering:* Negative acceleration in mechanics Retardation is the act or result of delaying; the extent to which anything is retarded...
(delay in reaching developmental milestones, especially as related to social behaviors). Behavioral retardation, as in the reactive attachment disorder
Reactive attachment disorder
Reactive attachment disorder is described in clinical literature as a severe and relatively uncommon disorder that can affect children. RAD is characterized by markedly disturbed and developmentally inappropriate ways of relating socially in most contexts...
s, has been observed in emotionally deprived children living with their families. However, prominent modern thought attributes other causative mechanisms to autism and autistic spectrum disorders. (see Autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
)
However, nurture is not the only cause of deprivation that leads to neurodevelopmental sequellae. A common example of sensory deprivation due to biologic factors is blindness
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
. Blind infants have risk of poor developmental outcomes which, left untreated, may lead to severe, autistic-like behaviors. Despite its biologic basis, caregivers can ameliorate blindness-related sensory deprivation. This can lead to positive neurodevelopmental outcome, as in the cases of author Helen Keller
Helen Keller
Helen Adams Keller was an American author, political activist, and lecturer. She was the first deafblind person to earn a Bachelor of Arts degree....
, who was trained in the use of tactile sign language
Sign language
A sign language is a language which, instead of acoustically conveyed sound patterns, uses visually transmitted sign patterns to convey meaning—simultaneously combining hand shapes, orientation and movement of the hands, arms or body, and facial expressions to fluidly express a speaker's...
, and musicians such as Arthel "Doc" Watson
Doc Watson
Arthel Lane "Doc" Watson is an American guitar player, songwriter and singer of bluegrass, folk, country, blues and gospel music. He has won seven Grammy awards as well as a Grammy Lifetime Achievement Award. Watson's flatpicking skills and knowledge of traditional American music are highly regarded...
and Ray Charles
Ray Charles
Ray Charles Robinson , known by his shortened stage name Ray Charles, was an American musician. He was a pioneer in the genre of soul music during the 1950s by fusing rhythm and blues, gospel, and blues styles into his early recordings with Atlantic Records...
who remained emotionally connected to others via their sense of hearing
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
.
Genetic disorders
Trisomy
A trisomy is a type of polysomy in which there are three copies, instead of the normal two, of a particular chromosome. A trisomy is a type of aneuploidy .-Description and causes:...
21, also known as Down syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
. This disorder usually results from an extra chromosome 21
Chromosome 21 (human)
Chromosome 21 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. The trisomy of the 21st chromosome causes Down Syndrome...
, 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
Eyelid
An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...
) folds, abnormal fingerprint
Fingerprint
A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger. In a wider use of the term, fingerprints are the traces of an impression from the friction ridges of any part of a human hand. A print from the foot can also leave an impression of friction ridges...
s and palm prints
Simian crease
In humans, a single transverse palmar crease is a single crease that extends across the palm of the hand, formed by the fusion of the two palmar creases that people typically have...
, heart defects, poor muscle tone
Muscle tone
In physiology, medicine, and anatomy, muscle tone is the continuous and passive partial contraction of the muscles, or the muscle’s resistance to passive stretch during resting state. It helps maintain posture, and it declines during REM sleep.-Purpose:Unconscious nerve impulses maintain the...
(delay of neurological development) and mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
(delay of intellectual development).
Less commonly known genetically determined neurodevelopmental disorders include Fragile X syndrome
Fragile X syndrome
Fragile X syndrome , Martin–Bell syndrome, or Escalante's syndrome , is a genetic syndrome that is the most commonly known single-gene cause of autism and the most common inherited cause of intellectual disability...
, Rett syndrome
Rett syndrome
Rett syndrome is a neurodevelopmental disorder of the grey matter of the brain that almost exclusively affects females. The clinical features include small hands and feet and a deceleration of the rate of head growth . Repetitive hand movements, such as wringing and/or repeatedly putting hands into...
and Williams syndrome
Williams syndrome
Williams syndrome is a rare neurodevelopmental disorder characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems, such as...
. Fragile X syndrome was first described in 1943 by J.P. Martin and J. Bell, studying persons with family history of sex-linked
Sex linkage
Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of inheritance...
"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.
Immune dysfunction
Immune reactions during pregnancy, both maternal and of the developing child can produce neurodevelopmental disorders. One typical immune reaction in infants and children is PANDAS, or Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection produce abnormal movements of the body, emotional disturbance and obsessive compulsive disorder symptoms. Another disorder is Sydenham's choreaSydenham's chorea
Sydenham's chorea or chorea minor is a disease characterized by rapid, uncoordinated jerking movements affecting primarily the face, feet and hands. Sydenham's chorea results from childhood infection with Group A beta-hemolytic Streptococci and is reported to occur in 20-30% of patients with...
, 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
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
bacteria. (Susceptibility to these immune diseases may be genetically determined, so sometimes several family members may suffer from one or both of them following an epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
of Strep infection.)
Infectious diseases
A number of infectious diseases can be transmitted either congenitally or in early childhood, and can cause serious neurodevelopmental disorders, such as schizophrenia. Congenital toxoplasmosis may result in formation of cysts in the brain and other organs, causing a variety of neurological deficits. Congenital syphilisCongenital syphilis
Congenital syphilis is syphilis present in utero and at birth, and occurs when a child is born to a mother with secondary syphilis. Untreated syphilis results in a high risk of a bad outcome of pregnancy, including mulberry molars in the fetus. Syphilis can cause miscarriages, premature births,...
may progress to neurosyphilis if it remains untreated. Measles
Measles
Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
can progress to subacute sclerosing panencephalitis
Subacute sclerosing panencephalitis
Subacute sclerosing panencephalitis is a rare chronic, progressive encephalitis that affects primarily children and young adults, caused by a persistent infection of immune resistant measles virus . No cure for SSPE exists, but the condition can be managed by medication if treatment is started at...
. Congenital rubella syndrome
Congenital rubella syndrome
Congenital rubella syndrome can occur in a developing fetus of a pregnant woman who has contracted rubella during her first trimester. If infection occurs 0–28 days before conception, there is a 43% chance the infant will be affected. If the infection occurs 0–12 weeks after conception, there is a...
can produce schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
in addition to multiple other symptoms.
Metabolic disorders
Metabolic disorders, present in either the mother or the child, can cause neurodevelopmental disorders. Two examples are diabetes mellitusDiabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
(a multifactorial disorder) and phenylketonuria
Phenylketonuria
Phenylketonuria is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase , rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine to the amino acid tyrosine...
(an inborn error of metabolism
Inborn error of metabolism
Inborn errors of metabolism comprise a large class of genetic diseases involving disorders of metabolism. The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances into others...
). Many such inherited diseases may directly affect the child's metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
and neural development but less commonly they can indirectly affect the child during gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
. (See also teratology
Teratology
Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human birth defects, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants.- Etymology :The...
).
In the child, type 1 diabetes
Diabetes mellitus type 1
Diabetes mellitus type 1 is a form of diabetes mellitus that results from autoimmune destruction of insulin-producing beta cells of the pancreas. The subsequent lack of insulin leads to increased blood and urine glucose...
can produce neurodevelopmental damage by the effects of excessive or insufficient glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
. The problems continue and may worsen throughout childhood if the diabetes is not well controlled. Type 2 diabetes
Diabetes mellitus type 2
Diabetes mellitus type 2formerly non-insulin-dependent diabetes mellitus or adult-onset diabetesis a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and...
may be preceded in its onset by impaired cognitive functioning.
However a non-diabetic fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
can also be subjected to glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
effects if its mother has undetected gestational diabetes
Gestational diabetes
Gestational diabetes is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy . It is widely accepted as a disease only in the United States, there is some question whether the condition is natural during pregnancy...
. 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 neurodevelopmental deficits. However usually the neurodevelopmental symptoms decrease in later childhood.
Phenylketonuria
Phenylketonuria
Phenylketonuria is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase , rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine to the amino acid tyrosine...
, also known as PKU is an inborn error of metabolism
Inborn error of metabolism
Inborn errors of metabolism comprise a large class of genetic diseases involving disorders of metabolism. The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances into others...
that can induce neurodevelopmental disorders in children. Children with PKU require a strict diet to prevent mental retardation and other disorders. In the maternal form of PKU
Phenylketonuria
Phenylketonuria is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase , rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine to the amino acid tyrosine...
, excessive maternal phenylalanine
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
can be absorbed by the fetus even if the fetus has not inherited the disease. This can produce mental retardation and other disorders.
Nutrition
Nutritional deficits may cause neurodevelopmental disorders, such as spina bifidaSpina bifida
Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...
, which is common, and anencephaly
Anencephaly
Anencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp...
, which is rare. Both disorders are neural tube defects
Neural tube defects
Neural tube defects are one of the most common birth defects, occurring in approximately one in 1,000 live births in the United States. An NTD is an opening in the spinal cord or brain that occurs very early in human development. In the 2nd week of pregnancy called gastrulation, specialized cells...
with malformation and dysfunction of the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
and its supporting structures, leading to serious physical disability as well as its emotional sequellae. The most common nutritional cause of neural tube defects is maternal deficiency of folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
, a B vitamin usually found in fruits, vegetables, whole grains and milk
Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...
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
Iodine deficiency
Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inlandareas where no marine foods are eaten—iodine deficiency gives rise to...
, produces a spectrum of neurodevelopmental disorders from mild emotional disturbance to severe mental retardation. (see also cretinism
Cretinism
Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones usually due to maternal hypothyroidism.-Etymology and use of cretin:...
)
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
University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
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
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
mothers. This disorder, now called fetal alcohol syndrome
Fetal alcohol syndrome
Fetal alcohol syndrome is a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Current research also implicates other lifestyle choices made by the prospective mother...
, has significant symptom overlap with several other entirely unrelated neurodevelopmental disorders. It has been discovered that iron supplementation in baby formula is linked to lowered I.Q. and other neurodevelopmental delays.
Trauma
Cerebral palsy
Cerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....
(including injury resulting from otherwise uncomplicated premature birth) and injury occurring in infancy or childhood. Common causes of congenital injury are asphyxia
Asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...
(obstruction of the trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
), hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
(lack of oxygen to the brain) and the mechanical trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
of the birth process
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
itself.
Overwhelmingly, in industrial nations the most common causes of childhood brain trauma are falls and transportation-related incidents. Child maltreatment
Child abuse
Child abuse is the physical, sexual, emotional mistreatment, or neglect of a child. In the United States, the Centers for Disease Control and Prevention and the Department of Children And Families define child maltreatment as any act or series of acts of commission or omission by a parent or...
such as shaken baby syndrome
Shaken baby syndrome
Shaken baby syndrome is a triad of medical symptoms: subdural hematoma, retinal hemorrhage, and brain swelling from which doctors, consistent with current medical understanding, infer child abuse caused by intentional shaking...
can produce neurodevelopmental consequences including blindness, neuromotor deficits and cognitive impairment. According to information published by the American Association of Neurological Surgeons
American Association of Neurological Surgeons
The American Association of Neurological Surgeons is a professional body based in the United States with more than 8,000 members worldwide. The AANS is dedicated to advancing the specialty of neurological surgery in order to provide the highest quality of neurosurgical care to the public...
, sports injuries account for 21% of the US incidence
Incidence (epidemiology)
Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
, however their site includes transportation-related sports injuries. They assert that cycling
Cycling
Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...
produced 64,993 head injuries requiring emergency room visits in 2007 while the second most common cause, football
American football
American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...
, only produced 36,412.
Toxic and environmental factors
One well known environmental toxic cause of neurodevelopmental disorders is heavy metal poisoningHeavy Metal Poisoning
Heavy Metal Poisoning is a song by American rock band Styx. It was included as the fifth track on their 1983 studio album Kilroy Was Here.The song in the story of Kilroy Was Here has the character of Dr Righteous preaching the evils of rock and roll...
, with a prominent 20th century example being Minamata disease
Minamata disease
', sometimes referred to as , is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech. In extreme cases, insanity, paralysis, coma, and death...
. Developmental mercury poisoning
Mercury poisoning
Mercury poisoning is a disease caused by exposure to mercury or its compounds. Mercury is a heavy metal occurring in several forms, all of which can produce toxic effects in high enough doses...
can cause a spectrum of problems from mild impairment of emotional development to the full blown syndrome of peripheral nerve damage, visual impairment
Visual impairment
Visual impairment is vision loss to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive...
, impaired coordination and ambulation, hallucinations, mental retardation, depression
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
and death. However other metals such as lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
, arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, as well as prenatal exposure to pesticides, tobacco
Tobacco
Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...
and other environmental toxins are also implicated as causative factors.
See also
- Asperger syndromeAsperger syndromeAsperger's syndrome that is characterized by significant difficulties in social interaction, alongside restricted and repetitive patterns of behavior and interests. It differs from other autism spectrum disorders by its relative preservation of linguistic and cognitive development...
- Attachment theoryAttachment theoryAttachment theory describes the dynamics of long-term relationships between humans. Its most important tenet is that an infant needs to develop a relationship with at least one primary caregiver for social and emotional development to occur normally. Attachment theory is an interdisciplinary study...
- Child developmentChild developmentChild development stages describe theoretical milestones of child development. Many stage models of development have been proposed, used as working concepts and in some cases asserted as nativist theories....
- Controversies in autismControversies in autismControversies in autism encompass the disagreement over the exact nature of autism, its causes and manifestations. Autism is considered to be a neurodevelopmental condition which manifests itself in markedly abnormal social interaction, communication ability, and patterns of interests.The cause of...
- Environmental toxins and fetal developmentEnvironmental toxins and fetal developmentIt has long been known that the fetus can be sensitive to impacts from adverse environmental exposures. Fetal development can be affected by exposures that occur to either parent prior to conception and to the mother post conception.-Fetal development:...
- EpigeneticsEpigeneticsIn biology, and specifically genetics, epigenetics is the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence – hence the name epi- -genetics...
- MicrocephalyMicrocephalyMicrocephaly is a neurodevelopmental disorder in which the circumference of the head is more than two standard deviations smaller than average for the person's age and sex. Microcephaly may be congenital or it may develop in the first few years of life...
- NeuropsychologyNeuropsychologyNeuropsychology studies the structure and function of the brain related to specific psychological processes and behaviors. The term neuropsychology has been applied to lesion studies in humans and animals. It has also been applied to efforts to record electrical activity from individual cells in...
- Pervasive developmental disorderPervasive developmental disorderPervasive developmental disorders is a diagnostic category refers to a group of disorders characterized by delays or impairments in communication, social behaviors, and cognitive development.Pervasive developmental disorders include Autism, Asperger's syndrome, Rett's syndrome, Childhood...
- Reverse learningReverse learningReverse learning is a neurobiological theory of dreams. In 1983, in a paper published in the famous science journal Nature, Crick and Mitchison's reverse learning model likened the process of dreaming to a computer in that it was "off-line" during dreaming or the REM phase of sleep...
- TeratologyTeratologyTeratology is the study of abnormalities of physiological development. It is often thought of as the study of human birth defects, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants.- Etymology :The...
External links
- A Classification of "Neurodevelopmental Disorders" - The Hunterdon Developmental Center
- A Review of Neurodevelopmental Disorders - Medscape review
- Developmental Fx (The Developmental and Fragile X Resource site)
- Mary Ann Knight Institute (portal for Miami Hospital children's services)
- Medical Information on Neurodevelopmental Disorders (M.I.N.D.) - The Hunterdon Developmental Center
- Neurogenetic and neurodevelopmental disorders - listing of neurodevelopmental disorders of interest to the Stanford University School of Medicine CoGENT project. (see also http://cogent.stanford.edu/ CoGENT home page)
- UC Davis M.I.N.D. Institute (portal for the UC Davis site)