Neurodevelopmental disorders are a group of disorders that affect the
development of the nervous system
The development of the nervous system, or neural development (neurodevelopment), refers to the processes that generate, shape, and reshape the nervous system of animals, from the earliest stages of embryonic development to adulthood. The fiel ...
, leading to abnormal
brain function
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ver ...
which may affect
emotion
Emotions are mental states brought on by neurophysiological changes, variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. There is currently no scientific consensus on a definition. ...
,
learning ability,
self-control
Self-control, an aspect of inhibitory control, is the ability to regulate one's emotions, thoughts, and behavior in the face of temptations and impulses. As an executive function, it is a cognitive process that is necessary for regulating one's b ...
, and
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
. The effects of neurodevelopmental disorders tend to last for a person's lifetime.
Types
Neurodevelopmental disorders
are impairments of the growth and development of the
brain
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
and/or
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
. A narrower use of the term refers to a disorder of
brain function
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ver ...
that affects
emotion
Emotions are mental states brought on by neurophysiological changes, variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. There is currently no scientific consensus on a definition. ...
,
learning ability,
self-control
Self-control, an aspect of inhibitory control, is the ability to regulate one's emotions, thoughts, and behavior in the face of temptations and impulses. As an executive function, it is a cognitive process that is necessary for regulating one's b ...
and
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
which unfolds as an individual develops and grows.
According to the DSM-5, the
neurodevelopmental
The development of the nervous system, or neural development (neurodevelopment), refers to the processes that generate, shape, and reshape the nervous system of animals, from the earliest stages of embryonic development to adulthood. The fie ...
disorders include the following:
[
# ]Attention deficit hyperactivity disorder
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...
(ADHD)
# DLD - Developmental language disorder
Developmental language disorder (DLD) is identified when a child has problems with language development that continue into school age and beyond. The language problems have a significant impact on everyday social interactions or educational progre ...
(formerly known as SLI- Specific Language Impairment)
# Communication, speech, or language disorders, expressive language disorder
Expressive language disorder is a communication disorder in which there are difficulties with verbal and written expression. It is a specific language impairment characterized by an ability to use expressive spoken language that is markedly below t ...
, fluency disorder, social (pragmatic) communication disorder
Social (pragmatic) communication disorder (SPCD) - previously called semantic-pragmatic disorder (SPD) or pragmatic language impairment (PLI) - is a disorder in understanding pragmatic aspects of language. People with SPCD have special challenges w ...
, and speech sound disorder
A speech sound disorder (SSD) is a speech disorder in which some sounds (phonemes) are not produced or used correctly. The term "protracted phonological development" is sometimes preferred when describing children's speech, to emphasize the contin ...
.
# Autism spectrum disorder
The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental disorder, neurodevelopmental condition (or conditions) ...
(ASD)
# Intellectual disabilities (IDs) or intellectual development disorder (IDD, previously called mental retardation) and global developmental delay
Global developmental delay is an umbrella term used when children are significantly delayed in their cognitive development, cognitive and developmental biology, physical development. It can be diagnosed when a child is delayed in one or more milest ...
(GDD)
# Motor disorder
Motor disorders are disorders of the nervous system that cause abnormal and involuntary movements. They can result from damage to the motor system.
Motor disorders are defined in the fifth edition of the '' Diagnostic and Statistical Manual of Men ...
s including developmental coordination disorder
Developmental coordination disorder (DCD), also known as developmental motor coordination disorder, developmental dyspraxia or simply dyspraxia from the word 'praxis' meaning to do or act, is a neurodevelopmental disorder characterized by impair ...
, stereotypic movement disorder
Stereotypic movement disorder (SMD) is a motor disorder with onset in childhood involving restrictive and/or repetitive, nonfunctional motor behavior (e.g., hand waving or head banging), that markedly interferes with normal activities or results ...
, and tic disorder
Tic disorders are defined in the ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM) based on type (motor or phonic) and duration of tics (sudden, rapid, nonrhythmic movements). Tic disorders are defined similarly by the World Health ...
s (such as Tourette's syndrome
Tourette syndrome or Tourette's syndrome (abbreviated as TS or Tourette's) is a common neurodevelopmental disorder that begins in childhood or adolescence. It is characterized by multiple movement (motor) tics and at least one vocal (phonic) ...
), and CAS - Apraxia of speech
Apraxia of speech (AOS), also called verbal apraxia, is a speech sound disorder affecting an individual's ability to translate conscious speech plans into motor plans, which results in limited and difficult speech ability. By the definition of a ...
# Neurogenetic disorders, such as Fragile X syndrome
Fragile X syndrome (FXS) is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may ...
, Down syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...
, Rett syndrome
Rett syndrome (RTT) is a genetic disorder that typically becomes apparent after 6–18 months of age and almost exclusively in females. Symptoms include impairments in language and coordination, and repetitive movements. Those affected often h ...
, hypogonadotropic hypogonadal syndromes
# Specific learning disorders, like dyslexia
Dyslexia, also known until the 1960s as word blindness, is a disorder characterized by reading below the expected level for one's age. Different people are affected to different degrees. Problems may include difficulties in spelling words, r ...
or dyscalculia
Dyscalculia () is a disability resulting in difficulty learning or comprehending arithmetic, such as difficulty in understanding numbers, learning how to manipulate numbers, performing mathematical calculations, and learning facts in mathematics. ...
.
# Traumatic brain injury
A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity (ranging from mild traumatic brain injury TBI/concussionto severe traumatic b ...
(including congenital
A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
injuries such as those that cause cerebral palsy
Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, stiff muscles, weak muscles, and tremors. There may be problems with sensa ...
) and disorders due to neurotoxicants including Minamata disease
Minamata disease is a neurological disease caused by severe mercury poisoning. Signs and symptoms include ataxia, numbness in the hands and feet, general muscle weakness, loss of peripheral vision, and damage to hearing and speech. In extrem ...
caused by mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
, behavioral disorders including conduct disorder
Conduct disorder (CD) is a mental disorder diagnosed in childhood or adolescence that presents itself through a repetitive and persistent pattern of behavior that includes theft, lies, physical violence that may lead to destruction, and reckles ...
etc. caused by other heavy metals, such as lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
, platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Platinu ...
etc., hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...
s like dioxin, PBDEs and PCBs, medications and illegal drugs, like cocaine
Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a central nervous system (CNS) stimulant mainly recreational drug use, used recreationally for its euphoria, euphoric effects. It is primarily obtained from t ...
, radioactive metals like Po210(which is found in cigarettes), and others.
# Fetal Alcohol Spectrum Disorders (FASD) can exhibit a combination of the above, most commonly ADHD, because of this, FASD is usually under-diagnosed, yet it is estimated that about 1 in 20 people may be affected.
Currently being researched
There are neurodevelopmental
The development of the nervous system, or neural development (neurodevelopment), refers to the processes that generate, shape, and reshape the nervous system of animals, from the earliest stages of embryonic development to adulthood. The fie ...
research projects examining potential new classifications of disorders including:
# Nonverbal learning disorder
Nonverbal learning disability (NVLD) is a neurodevelopmental disorder characterized by core deficits in visual-spatial processing in the presence of intact verbal ability. Additional diagnostic criteria include Average to Superior verbal intelli ...
(NLD or NVLD), a neurodevelopmental disorder thought to be linked to white matter in the right hemisphere of the brain and generally considered to include (a) low visuospatial intelligence; (b) discrepancy between verbal and visuospatial intelligence; (c) visuoconstructive and fine-motor coordination skills; (d) visuospatial memory tasks; (e) reading better than mathematical achievement; and (f) socioemotional skills. While Nonverbal learning disorder is not categorized in the ICD or DSM as an discrete classification, "the majority of researchers and clinicians agree that the profile of NLD clearly exists (but see Spreen, 2011, for an exception), but they disagree on the need for a specific clinical category and on the criteria for its identification."
Presentation
Consequences
The multitude of neurodevelopmental disorders span a wide range of associated symptoms and severity, resulting in different degrees of mental, emotional, physical, and economic consequences for individuals, and in turn families, social groups, and society.
Causes
The development of the nervous system
The development of the nervous system, or neural development (neurodevelopment), refers to the processes that generate, shape, and reshape the nervous system of animals, from the earliest stages of embryonic development to adulthood. The fiel ...
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 neurodevelopmental disorders that may affect different areas of the nervous system at different times and ages. These range from social deprivation, genetic and metabolic disease
A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter the ...
s, immune disorder
An immune disorder is a dysfunction of the immune system. These disorders can be characterized in several different ways:
* By the component(s) of the immune system affected
* By whether the immune system is overactive or underactive
* By whether t ...
s, infectious disease
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
s, nutrition
Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient n ...
al factors, physical trauma
An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, ...
, and toxic and environmental factors. Some neurodevelopmental disorders, such as autism
The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
and other pervasive developmental disorder
The diagnostic category pervasive developmental disorders (PDD), as opposed to specific developmental disorders (SDD), is a group of disorders characterized by delays in the development of multiple basic functions including socialization and co ...
s, are considered multifactorial syndrome
A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek σύνδρομον, meaning "concurrence". When a syndrome is paired ...
s which have many causes that converge to a more specific neurodevelopmental 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 Nicolae may refer to:
* Nicolae (name), a Romanian name
* ''Nicolae'' (novel), a 1997 novel
See also
*Nicolai (disambiguation)
*Nicolao Nicolao is an Italian given name and a surname. It may refer to the following:
Given name
*Nicolao Civitali ...
's regime reveal profound effects of social deprivation
Social deprivation is the reduction or prevention of culturally normal interaction between an individual and the rest of society. This social deprivation is included in a broad network of correlated factors that contribute to social exclusion; thes ...
and language deprivation Language deprivation is associated with the lack of linguistic stimuli that are necessary for the language acquisition processes in an individual. Research has shown that early exposure to a first language will predict future language outcomes. Exp ...
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)
In clinical and abnormal psychology, institutionalization or institutional syndrome refers to deficits or disabilities in social and life skills, which develop after a person has spent a long period living in mental hospitals, prisons or other r ...
.
Genetic disorders
A prominent example of a genetically determined neurodevelopmental disorder is Trisomy
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
21, also known as Down syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...
. This disorder usually results from an extra chromosome 21
Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, with 48 million base pairs (the building material of DNA) representing about 1.5 percent of the total DNA in cells. M ...
, although in uncommon instances it is related to other chromosomal abnormalities
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where ther ...
such as translocation of the genetic material. It is characterized by short stature, epicanthal (eyelid
An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eyel ...
) folds, abnormal fingerprint
A fingerprint is an impression left by the friction ridges of a human finger. The recovery of partial fingerprints from a crime scene is an important method of forensic science. Moisture and grease on a finger result in fingerprints on surfac ...
s, and palm prints, heart defects
A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...
, poor muscle tone
In physiology, medicine, and anatomy, muscle tone (residual muscle tension or tonus) is the continuous and passive partial muscle contraction, contraction of the muscles, or the muscle's resistance to passive stretch during resting state.O’Sull ...
(delay of neurological development), and intellectual disabilities
Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation,Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signific ...
(delay of intellectual development).[
Less commonly known genetically determined neurodevelopmental disorders include ]Fragile X syndrome
Fragile X syndrome (FXS) is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may ...
. Fragile X syndrome was first described in 1943 by Martin and Bell, studying persons with family history of sex-linked
Sex linked describes the sex-specific patterns of inheritance and presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome ( autosome). In humans, these are termed X-linked recessive, ...
"mental defects". Rett syndrome
Rett syndrome (RTT) is a genetic disorder that typically becomes apparent after 6–18 months of age and almost exclusively in females. Symptoms include impairments in language and coordination, and repetitive movements. Those affected often h ...
, another X-linked disorder, produces severe functional limitations. Williams syndrome
Williams syndrome (WS) is a genetic disorder that affects many parts of the body. Facial features frequently include a broad forehead, underdeveloped chin, short nose, and full cheeks. Mild to moderate intellectual disability is observed in people ...
is caused by small deletions of genetic material from chromosome 7
Chromosome 7 is one of the 23 pairs of chromosomes in humans, who normally have two copies of this chromosome. Chromosome 7 spans about 159 million base pairs (the building material of DNA) and represents between 5 and 5.5 percent of the total D ...
.
The most common recurrent Copy Number Variant disorder is 22q11.2 deletion syndrome
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent i ...
(formerly DiGeorge or velocardiofacial syndrome), followed by Prader-Willi syndrome and Angelman syndrome
Angelman syndrome or Angelman's syndrome (AS) is a genetic disorder that mainly affects the nervous system. Symptoms include a small head and a specific facial appearance, severe intellectual disability, developmental disability, limited to no f ...
.[
]
Immune dysfunction
Immune reactions during pregnancy
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ca ...
, both maternal and of the developing child, may produce neurodevelopmental disorders. One typical immune reaction in infants and children is PANDAS
Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) is a controversial hypothetical diagnosis for a subset of children with rapid onset of obsessive-compulsive disorder (OCD) or tic disorders. Sy ...
, 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
''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occurs ...
'' 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
An epidemic (from Ancient Greek, Greek ἐπί ''epi'' "upon or above" and δῆμος ''demos'' "people") is the rapid spread of disease to a large number of patients among a given population within an area in a short period of time.
Epidemics ...
of Strep infection.
Infectious diseases
Systemic infections can result in neurodevelopmental consequences, when they occur in infancy and childhood of humans, but would not be called a primary neurodevelopmental disorder. For example HIV
The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
Infections of the head and brain, like brain abscess
Brain abscess (or cerebral abscess) is an abscess caused by inflammation and collection of infected material, coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone ...
es, meningitis
Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
or encephalitis
Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations, ...
have a high risk of causing neurodevelopmental problems and eventually a disorder. For example, measles
Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than , cough, ...
can progress to subacute sclerosing panencephalitis
Subacute sclerosing panencephalitis (SSPE)—also known as Dawson disease—is a rare form of chronic, progressive brain inflammation caused by slow infection with certain defective strains of hypermutated measles virus. The condition primarily ...
.
A number of infectious diseases
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
can be transmitted congenitally (either before or at birth), and can cause serious neurodevelopmental problems, as for example the viruses HSV, CMV, rubella (congenital rubella syndrome
Congenital rubella syndrome (CRS) can occur in a developing fetus of a pregnant woman who has contracted rubella, usually in the first trimester. If infection occurs 0–28 days before conception, the infant has a 43% risk of being affected. If ...
), Zika virus
''Zika virus'' (ZIKV; pronounced or ) is a member of the virus family ''Flaviviridae''. It is spread by daytime-active ''Aedes'' mosquitoes, such as '' A. aegypti'' and '' A. albopictus''. Its name comes from the Ziika Forest of Uganda, whe ...
, or bacteria like ''Treponema pallidum'' in congenital syphilis
Congenital syphilis is syphilis present ''in utero'' and at birth, and occurs when a child is born to a mother with syphilis. Untreated early syphilis infections results in a high risk of poor pregnancy outcomes, including saddle nose, lower ext ...
, which may progress to neurosyphilis
Neurosyphilis refers to infection of the central nervous system in a patient with syphilis. In the era of modern antibiotics the majority of neurosyphilis cases have been reported in HIV-infected patients. Meningitis is the most common neurologic ...
if it remains untreated. Protozoa like ''Plasmodium''[ or ''Toxoplasma'' which can cause congenital ]toxoplasmosis
Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or months ...
with multiple cysts in the brain and other organs, leading to a variety of neurological deficits.
Some cases of schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...
may be related to congenital infections, though the majority are of unknown causes.
Metabolic disorders
Metabolic disorders
A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as Protein, proteins, Fat, fats, and Carbohydrate, carbohydrates. Metabolic disorders can happen when abnormal chemical react ...
in either the mother or the child can cause neurodevelopmental disorders. Two examples are diabetes mellitus
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
(a multifactorial disorder) and phenylketonuria
Phenylketonuria (PKU) is an inborn error of metabolism that results in decreased metabolism of the amino acid phenylalanine. Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also resu ...
(an inborn error of metabolism
Inborn errors of metabolism form a large class of genetic diseases involving congenital disorders of enzyme activities. The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances (substrat ...
). Many such inherited diseases may directly affect the child's metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
and neural development but less commonly they can indirectly affect the child during gestation
Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
. (See also teratology
Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology. The related t ...
).
In a child, type 1 diabetes
Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin (beta cells) are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar for ...
can produce neurodevelopmental damage by the effects of excess or insufficient glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
. The problems continue and may worsen throughout childhood if the diabetes is not well controlled. Type 2 diabetes
Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...
may be preceded in its onset by impaired cognitive functioning.
A non-diabetic fetus
A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...
can also be subjected to glucose effects if its mother has undetected gestational diabetes
Gestational diabetes is a condition in which a woman without diabetes develops high blood sugar levels during pregnancy. Gestational diabetes generally results in few symptoms; however, it increases the risk of pre-eclampsia, depression, and of ...
. 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. Usually the neurodevelopmental symptoms will decrease in later childhood.
Phenylketonuria
Phenylketonuria (PKU) is an inborn error of metabolism that results in decreased metabolism of the amino acid phenylalanine. Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also resu ...
, also known as PKU, can induce neurodevelopmental problems and children with PKU require a strict diet to prevent intellectual disability and other disorders. In the maternal form of PKU
Phenylketonuria (PKU) is an inborn error of metabolism that results in decreased metabolism of the amino acid phenylalanine. Untreated PKU can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It may also resu ...
, excessive maternal phenylalanine
Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...
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 disorder
Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues ...
s and nutritional deficits may cause neurodevelopmental disorders, such as spina bifida
Spina bifida (Latin for 'split spine'; SB) 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, me ...
, and the rarely occurring anencephaly
Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fai ...
, both of which are neural tube defects
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo b ...
with malformation and dysfunction of the nervous system
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...
and its supporting structures, leading to serious physical disability and emotional sequelae. The most common nutritional cause of neural tube defects is folic acid
Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...
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
Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated cong ...
, produces a spectrum of neurodevelopmental disorders ranging from mild emotional disturbance to severe intellectual disability. (see also congenital iodine deficiency syndrome
Congenital iodine deficiency syndrome is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone ( hypothyroidism) often caused by insufficient dietary iodine during pregnancy. ...
).
Excesses in both maternal and infant diets may cause disorders as well, with foods or food supplement
A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources or that are synthetic in order ...
s proving toxic in large amounts. For instance in 1973 K.L. Jones and D.W. Smith of the University of Washington
The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington.
Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...
Medical School in Seattle
Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...
found a pattern of "craniofacial, limb, and cardiovascular defects associated with prenatal onset growth deficiency and developmental delay" in children of alcoholic
Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognized diagnostic entity. Predomin ...
mothers, now called fetal alcohol syndrome, It has significant symptom overlap with several other entirely unrelated neurodevelopmental disorders.[Fetal alcohol syndrome: guidelines for referral and diagnosis (PDF).]
CDC (July 2004). Retrieved on 2007-04-11
Physical trauma
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
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can i ...
(obstruction of the trachea
The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...
), hypoxia (lack of oxygen to the brain), and the mechanical trauma of the birth process
In probability theory, a birth process or a pure birth process is a special case of a continuous-time Markov process and a generalisation of a Poisson process. It defines a continuous process which takes values in the natural numbers and can on ...
itself.
Placenta
Although it not clear yet as strong is the correlation between placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
and brain, a growing number of studies are linking placenta to fetal brain development.
Diagnosis
Neurodevelopmental disorders are diagnosed by evaluating the presence of characteristic symptoms or behaviors in a child, typically after a parent, guardian, teacher, or other responsible adult has raised concerns to a doctor.
Neurodevelopmental disorders may also be confirmed by genetic testing
Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
. Traditionally, disease related genetic and genomic factors are detected by karyotype analysis, which detects clinically significant genetic abnormalities for 5% of children with a diagnosed disorder. , chromosomal microarray analysis (CMA) was proposed to replace karyotyping because of its ability to detect smaller chromosome abnormalities and copy-number variants, leading to greater diagnostic yield in about 20% of cases. The American College of Medical Genetics and Genomics
The American College of Medical Genetics and Genomics (ACMG) is an organization composed of biochemical, clinical, cytogenetic, medical and molecular geneticists, genetic counselors and other health care professionals committed to the practice of ...
and the American Academy of Pediatrics
The American Academy of Pediatrics (AAP) is an American professional association of pediatricians, headquartered in Itasca, Illinois. It maintains its Department of Federal Affairs office in Washington, D.C.
Background
The Academy was founded ...
recommend CMA as standard of care in the US.[
]
See also
* Developmental disability
Developmental disability is a diverse group of chronic conditions, comprising mental or physical impairments that arise before adulthood. Developmental disabilities cause individuals living with them many difficulties in certain areas of life, espe ...
* Epigenetics
In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Greek prefix '' epi-'' ( "over, outside of, around") in ''epigenetics'' implies features that are "o ...
* Microcephaly
Microcephaly (from New Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it ...
* Teratology
Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology. The related t ...
References
Further reading
*
*
External links
*
A Review of Neurodevelopmental Disorders
- Medscape review
{{DEFAULTSORT:Neurodevelopmental Disorder
Developmental neuroscience
Neurological disorders