Neurodevelopmental disorder

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Neurodevelopmental disorder
SpecialtyPsychiatry, neurology

Neurodevelopmental disorders are a group of conditions that begin to emerge during childhood (or the development of the nervous system). According to the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, (DSM-5) published in 2013, these conditions generally appear in early childhood, usually before children start school, and can persist into adulthood.[1] The key characteristic of all these disorders is that they negatively impact a person's functioning in one or more domains of life (personal, social, academic, occupational) depending on the disorder and deficits it has caused. All of these disorders and their levels of impairment exist on a spectrum, and affected individuals can experience varying degrees of symptoms and deficits, despite having the same diagnosis.[1][2]

The DSM-5 classifies neurodevelopmental disorders into six overarching groups.

  1. Intellectual disability (Intellectual Development Disorder)
  2. Communication disorders
  3. Autism spectrum disorder (ASD)
  4. Attention-deficit/hyperactivity disorder (ADHD)
  5. Neurodevelopmental motor disorders
  6. Specific learning disorders

These disorders are commonly comorbid conditions, meaning that a person affected by one of these disorders will usually meet criteria for a second disorder.[1][2]

Classification

Intellectual disability (intellectual development disorder)

Intellectual disabilities (IDs), or intellectual development disorder, are defined by the DSM-5 as "deficits in general mental abilities".[1] They affect a person's ability to process information, learn or retain information, think critically or abstractly, and solve problems. They ultimately inhibit a person's ability to adapt to their surroundings, to the extent that individuals may fail to meet milestones of independent functioning or social responsibility in one or more activities of daily living.[1] Global developmental delay (GDD) is categorized under intellectual disability and "is diagnosed when an individual fails to meet expected developmental milestones in several areas of intellectual functioning."[1]

Communication disorders

Communication disorder

Autism spectrum disorder (ASD)

Autism spectrum disorder (ASD)

Attention-deficit/hyperactivity disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD)

Neurodevelopmental motor disorders

Tourette's syndrome), and CAS - Apraxia of speech

Specific learning disorders

Specific learning disorders

Currently being researched

There are neurodevelopmental research projects examining potential new classifications of disorders including:

  1. Nonverbal learning disorder (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.[3][4][5] 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[6]), but they disagree on the need for a specific clinical category and on the criteria for its identification."[7]

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.[8]

Causes

The

autism and other pervasive developmental disorders, are considered multifactorial syndromes which have many causes that converge to a more specific neurodevelopmental manifestation.[10]

Social deprivation

Deprivation from social and emotional care causes severe delays in brain and cognitive development.

Genetic disorders

A child with Down syndrome

A prominent example of a genetically determined neurodevelopmental disorder is

intellectual disabilities (delay of intellectual development).[14]

Less commonly known genetically determined neurodevelopmental disorders include Fragile X syndrome. Fragile X syndrome was first described in 1943 by Martin and Bell, studying persons with family history of sex-linked "mental defects".[15] Rett syndrome, another X-linked disorder, produces severe functional limitations.[16] Williams syndrome is caused by small deletions of genetic material from chromosome 7.[17] The most common recurrent Copy Number Variant disorder is

Prader-Willi syndrome and Angelman syndrome.[18]

Immune dysfunction

Immune reactions during pregnancy, both maternal and of the developing child, may produce neurodevelopmental disorders. One typical immune reaction in infants and children is PANDAS,[19] or Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection.[20] Another disorder is Sydenham's chorea, which results in more abnormal movements of the body and fewer psychological sequellae. Both are immune reactions against brain tissue that follow infection by Streptococcus bacteria. Susceptibility to these immune diseases may be genetically determined,[21] so sometimes several family members may have one or both of them following an epidemic of Strep infection.[citation needed]

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[22] Infections of the head and brain, like brain abscesses, meningitis or encephalitis have a high risk of causing neurodevelopmental problems and eventually a disorder. For example, measles can progress to subacute sclerosing panencephalitis.

A number of

infectious diseases can be transmitted congenitally (either before or at birth), and can cause serious neurodevelopmental problems, as for example the viruses HSV, CMV, rubella (congenital rubella syndrome), Zika virus, or bacteria like Treponema pallidum in congenital syphilis, which may progress to neurosyphilis if it remains untreated. Protozoa like Plasmodium[22] or Toxoplasma which can cause congenital toxoplasmosis
with multiple cysts in the brain and other organs, leading to a variety of neurological deficits.

Some cases of schizophrenia may be related to congenital infections, though the majority are of unknown causes.[23]

Metabolic disorders

inborn error of metabolism). Many such inherited diseases may directly affect the child's metabolism and neural development[24] but less commonly they can indirectly affect the child during gestation. (See also teratology
).

In a child,

Type 2 diabetes may be preceded in its onset by impaired cognitive functioning.[26]

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. Usually the neurodevelopmental symptoms will decrease in later childhood.[27]

Phenylketonuria, 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, excessive maternal phenylalanine can be absorbed by the fetus even if the fetus has not inherited the disease. This can produce intellectual disability and other disorders.[28][29]

Nutrition

folic acid deficiency in the mother, a B vitamin usually found in fruits, vegetables, whole grains, and milk products.[30][31] (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.)[32][33] Another deficiency, iodine deficiency, produces a spectrum of neurodevelopmental disorders ranging from mild emotional disturbance to severe intellectual disability. (see also congenital iodine deficiency syndrome).[34]

Excesses in both maternal and infant diets may cause disorders as well, with foods or

fetal alcohol syndrome, It has significant symptom overlap with several other entirely unrelated neurodevelopmental disorders.[35]

Physical trauma

CT scan showing epidural hematoma, a type of traumatic brain injury (upper left)

Brain trauma in the developing human is a common cause (over 400,000 injuries per year in the US alone, without clear information as to how many produce developmental sequellae)

mechanical trauma of the birth process itself.[38]

Placenta

Although it not clear yet as strong is the correlation between placenta and brain, a growing number of studies are linking placenta to fetal brain development.[39]

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.[40]

Neurodevelopmental disorders may also be confirmed by

copy-number variants, leading to greater diagnostic yield in about 20% of cases.[18] The American College of Medical Genetics and Genomics and the American Academy of Pediatrics recommend CMA as standard of care in the US.[18]

Management

See also

References

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  30. ^ "Folic Acid". March of Dimes. Archived from the original on 2021-08-26. Retrieved 2014-11-10.
  31. ^ "Folate (Folacin, Folic Acid)". Ohio State University Extension. Archived from the original on 2021-08-26. Retrieved 2008-08-06.
  32. ^ "Folic scid: topic home". Centers for Disease Control and Prevention. U.S. Department of Health and Human Services. Archived from the original on 2021-08-26. Retrieved 2008-08-02.
  33. ^ "The basics about spina bifida". Centers for Disease Control and Prevention. U.S. Department of Health and Human Services. Archived from the original on 2021-08-26. Retrieved 2008-08-02.
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  35. ^ Fetal alcohol syndrome: guidelines for referral and diagnosis (PDF). Archived 2009-04-23 at the Wayback Machine CDC (July 2004). Retrieved on 2007-04-11
  36. ^ "Facts About TBI" (PDF). U.S. Centers for Disease Control and Prevention. Archived from the original on 2021-08-26. Retrieved 2008-08-06.
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  40. ^ Neurodevelopmental Disorders (PDF), America's Children and the Environment (3 ed.), EPA, August 2017, p. 12, archived (PDF) from the original on 2021-07-20, retrieved 2019-07-10

Further reading

External links