Definitions of Developmental Disabilities and Related Terms

Behavior Disorders - These terms describe children who act out and may cause trouble for parents, teachers, peers and others. Problems associated with defining and identifying behavior disorders, including oppositional defiant disorder or conduct disorder, are far more difficult than those relating to physical disabilities. Estimates of the prevalence of behavior disorders vary considerably depending on the criteria used for identification and on whether estimates include mild as well as severe instances. It has been estimated that 15% to 19% of U.S. children and adolescents have problems requiring some form of mental health services. Factors that contribute to the development of behavior disorders vary greatly. They are often classified as genetic or congenital versus social or psychological. Given adequate knowledge of biological history and environment, it is sometimes possible to identify children who may be at greater risk for behavior disorders than others.

Brain Plasticity - Refers to how circuits in the brain change--organize and reorganize--in response to experience, or sensory stimulation. Periods of rapid change or plasticity occur in the brain under four main conditions: when the immature brain first begins to process sensory information (developmental plasticity); second, when changes in the body, like a problem with eyesight, alter the balance of sensory activity received by the brain (activity-dependent plasticity); third, when we alter our behavior based on new sensory information (plasticity of learning and memory), and fourth, following damage to the brain (injury-induced plasticity). Scientists believe that the same brain mechanisms underlie all four types of plasticity: adjustments in the strength of connections, or synapses, between brain cells. The details of the molecular control of synaptic modification is an extraordinarily active field of research. Understanding the mechanisms of brain plasticity is essential to developing interventions to overcome brain damage.

Cerebral palsy – Cerebral palsy refers to a disorder of movement and posture that is due to a non-progressive abnormality of the immature brain.  The brain damage that causes cerebral palsy may produce a number of other disabilities, including language, learning, and behavioral problems. (reference:  Batshaw M., et al.  Children with Disabilities, a Medical Primer)

Cognitive Development - Acquisition of conscious thought, reasoning, symbol manipulation, and problem solving abilities beginning in infancy and following an orderly sequence.

Communication Disorder - a condition that interferes with one’s ability to produce, receive, or understand verbal, nonverbal, or graphic symbol systems.  This impairment may impact the individual’s level of comprehension and/or expression of ideas, experiences, knowledge, and feelings.  A communication disorder may be developmental or acquired and results in impairments in one or more of the following areas:

• Articulation: the use of the articulators (e.g, tongue, teeth, and lips) to produce speech sounds.

• Fluency: the smooth, forward flow of spoken language. 

• Receptive Language: the processing, comprehension, and integration of language.

• Expressive Language: the output and use of language.

• Morphology: the system that governs the structure of words and the construction of word forms.

• Phonology: the sound system of a language and the rules that govern the sound combinations. 

• Pragmatics: the use of functional and socially appropriate communication.

• Semantics: the system that governs the meanings of words and sentences.

• Syntax: the system governing the order and combinations of words to form sentences and the relationship among elements within a sentence.

• Voice: the highly intricate arrays of sound produced by the vocal folds in combination with the lips, tongue, lower jaw, and palate. 

American Speech-Language-Hearing Association Ad Hoc Committee on Service Delivery in the Schools. (1993). Definitions of communication disorders and variations. Asha 35 (Suppl. 10), 40-41.

Cystic Fibrosis – Cystic fibrosis is a relatively common inherited disease that is a functional disorder of the exocrine glands.  The abnormal gene causes problems with the way salt and water move in and out of the cells that make mucus, and the mucus becomes thick.  Symptoms usually appear in early childhood, and usually include respiratory problems because of mucus in the airways or problems with digestion due to problems with production of pancreatic enzymes.  There is also excess loss of salt in the sweat.

Developmental Disabilities - The Centers for Disease Control and Prevention define develomental disabilties as, "a diverse group of severe chronic conditions that are due to mental and/or physical impairments. People with developmental disabilities have problems with major life activities such as language, mobility, learning, self-help, and independent living. Developmental disabilities begin anytime during development up to 22 years of age and usually last throughout a person’s lifetime."

National Center on Birth Defects and Developmental Disabilities. (2004, October 29). Developmental Disabilities. Retrieved April 23, 2007 from: http://www.cdc.gov/ncbddd/dd/

Didactic- 1a: designed or intended to teach; b: intended to convey instruction and information as well as pleasure and entertainment; 2: making moral observations.

Down syndrome – Down syndrome or trisomy 21 (having three rather than two copies of chromosome #21) was one of the first conditions to be associated with intellectual impairment.   Children with Down syndrome are at increased risk for other medical problems, and need routine medical follow-up.

Dysgraphia – A problem with the writing process affecting how the task proceeds (Richards, 1998). Multiple factors may contribute to writing challenges and poor end results. Examination of writing products only, is not sufficient to determine the reason for reluctance, inefficient or poor handwriting.

[From: Richards, R. G. (1998). The writing dilemma: Understanding dysgraphia. Riverside, CA: RET Center Press. ]

Dyslexia - A term used to describe a condition in which an individual with normal viaual acuity is unable to properly interpret written language. Dyslexia is more common in males and is often first recognized as a reading difficulty in the first grade. Individuals can see and recognize letters but are unable to spell and write words. They have no impairment of object or picture identification. Dyslexia is not related to intelligence and in fact several famous scholars were thought to be dyslexic (for example Albert Einstein, Thomas Edison). The exact cause of dyslexia is unknown.

Dysphagia: People with dyspagia have difficulty swallowing and may also experience pain while swallowing. Conditions that weaken or damage the muscles and nerves used for swallowing may cause dysphagia. Swallowing difficulties can put a person at risk for not getting adequate nutrition.

Fetal Alcohol syndrome - Fetal alcohol syndrome is a collection of symptoms in newborns associated with maternal alcohol consumption during pregnancy and sometimes evident in varying degrees of neurological, mental, and physical problems.

Fragile X syndrome - An inherited disorder that is associated with an abnormal X chromosome, that is characterized especially by moderate to severe mental retardation, by large ears, chin, and forehead, and by enlarged testes in males, and that often has limited or no effect in heterozygous females.

Hyperammonemia - The presence of an excess of ammonia in the blood.

Mental Retardation - Subaverage intellectual originating in the developmental period and characterized by impaired adaptive skills in areas such as receptive and expressive language development, social learning, self care and vocational skills.

Motor Disabilities - Motor skills refers to the ability to use and coordinate large and small body muscles in order to move and manipulate objects. Some children experience delays in acquiring motor skills. Cerebral palsy refers to a disorder of movement and posture that is due to a nonprogressive abnormality of the immature brain. The brain damage that causes cerebral palsy also may produce a number of other disabilities, including mental retardation, seizures, visual and auditory deficits, and behavior problems. There are motor skills disorders that are not associated with brain damage or cerebral palsy that are often evident in children with other developmental disorders, e.g., mental retardation and autism. These disorders may be apparent in difficulties in learning motor tasks such as walking, running, skipping, tying shoes, and so on; they may also be apparent in difficulties in carrying out motor activities. A developmental coordination disorder exists when (1) a person's performance of activities requiring motor coordination (e.g., crawling, walking, sitting, handwriting, sports) is markedly below what would be expected for the person's age, (2) the disturbance interferes with academic achievements or activities of daily living, and (3) the disturbance is not due to a known physical disorder (e.g., cerebral palsy).

Muscular Dystrophy - Any of a group of hereditary diseases characterized by progressive wasting of muscles; also called Progressive Muscular Dystrophy.

Muscular Dystrophy (Becker's) - A less severe form of Duchenne muscular dystrophy with later onset and slower progression of the disease that is inherited as an X-linked recessive trait and is characterized by dystrophin of deficient or abnormal molecular weight.

Muscular Dystrophy (Duchenne's) - a severe progressive form of muscular dystrophy of males that appears in early childhood, affects the muscles of the legs before those of the arms and the proximal muscles of the limbs before the distal ones, is inherited as an X-linked recessive trait, is characterized by complete absence of the protein dystrophin, and usually has a fatal outcome by age 20.

Pervasive Developmental Disorders –“Pervasive Developmental Disorders are characterized by severe and pervasive impairment in several areas of development: reciprocal social interaction skills, communication skills, or the presence of stereotyped behavior, interests, and activities. The qualitative impairments that define these conditions are distinctly deviant relative to the individual’s developmental level or mental age.” (American Psychiatric Association [APA], 2000, p. 69)

The Pervasive Developmental Disorders are: 

• Autistic Disorder – “The essential features of Autistic Disorder are the presence of markedly abnormal or impaired development in  social interaction and communication and a markedly restricted repertoire of activity and interests. Manifestations of the disorder vary greatly depending on the developmental level and chronological age of the individual. Autistic Disorder is sometimes referred to  as early infantile autism, childhood autism, or Kanner’s autism…By definition, if there is a period of normal development, it cannot extend past age 3 years. The disturbance must not be better accounted for by Rett’s Disorder or Childhood Disintegrative Disorder.” (APA, 2000, p. 70-71)

• Asperger’s Disorder (also referred to as Asperger’s Syndrome) – “The essential features of Asperger’s Disorder are severe and sustained impairments in social interaction and the development of restricted, repetitive patterns of behavior, interests, and activities. The disturbance must cause clinically significant impairment in social, occupational, or other important areas of functioning. In contrast to Autistic Disorder, there are no clinically significant delays of deviance in language acquisition (e.g., single non-echoed words are used communicatively by age 2 years, and spontaneous communicative phrases are used by age 3 years), although more subtle aspects of social communication (e.g., typical give-and-take in conversation) may be affected. In addition, during the first 3 years of life, there are no clinically significant delays in cognitive development as manifested by expressing normal curiosity about the environment or in the acquisition of age-appropriate learning skills and adaptive behavior (other than in social interaction).” (APA, 2000, p. 80)

• Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS; also referred to as atypical autism) – “when there is a severe and pervasive impairment in the development of reciprocal social interaction associated with impairment in either verbal or nonverbal communication skills or with the presence of stereotyped behavior, interests, and activities, but the criteria are not met for a specific Pervasive Developmental Disorder, Schizophrenia, Schizotypal Personality Disorder, or Avoidant Personality Disorder. For example, this category includes “atypical autism”—presentations that do not meet the criteria for Autistic Disorder because of late age at onset, atypical symptomatology, or subthreshold symptomatology, or all of these.” (APA, 2000, p. 84)

• Rett’s Disorder – “The essential feature of Rett’s Disorder is the development of multiple specific deficits following a period of normal functioning after birth. Individuals have an apparently normal prenatal and perinatal period…Between ages 5 and 48 months, head growth decelerates. There is loss of previously acquired purposeful hand skills between ages 5 and 30 months, with the subsequent development of characteristic stereotyped hand movements resembling hand wringing or hand washing. Interest in the social environment diminishes in the first few years after the onset of the disorder, although social interaction may often develop later in the course. Problems develop in the coordination of gait and trunk movements. There is also severe expressive and receptive language development…Retts Disorder is typically associated with Severe or Profound Mental Retardation…” (APA, 2000, p. 76)

• Childhood Disintegrative Disorder – “The essential feature of Childhood Disintegrative Disorder is marked regression in multiple areas of functioning following a period of at least 2 years of apparently normal development. Apparently normal development is reflected in age-appropriate verbal and nonverbal communication, social relationships, play, and adaptive behavior. After the first 2 years of live (but before age 10 years), the child has a clinically significant loss of previously acquired skills in at least two fo the following areas: expressive of receptive language, social skills, or adaptive behavior, bowel or bladder control, play, or motor skills. Most typically, acquired skills are lost in almost all areas.” (APA, 2000, p. 77)

The National Institute of Mental Health (NIMH) also refers to Pervasive Developmental Disorders as autism spectrum disorders and in a 2004 publication, reported a prevalence of 2 to 6 per 1,000 children (Strock, 2004, p. 4).

In February of 2007, the Centers for Disease Control and Prevention’s (CDC) Autism and Developmental Disabilities Monitoring Network reported “about 1 in every 150 8-year-old children in multiple areas of the United States had an autism spectrum disorder (ASD)” (National Center on Birth Defects and Developmental Disabilities [NCBDDD], 2007).

References

American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Washington, DC, American Psychiatric Association, 2000.

National Center on Birth Defects and Developmental Disabilities. (2007, February 9). Autism Spectrum Disorders Overview. Retrieved April 25, 2007, from http://www.cdc.gov/ncbddd/autism/overview.htm

Strock, Margaret (2004). Autism Spectrum Disorders (Pervasive Developmental Disorders). NIH Publication No. NIH-04-5511, National Institute of Mental Health, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, MD, 40 pp. http://www.nimh.nih.gov/publicat/autism.cfm

Prader-Willi syndrome (PWS) – Prader-Willi syndrome is a disorder associated with an abnormality on chromosome 15.  In addition to intellectually disability, Prader-Willi syndrome is associated with a severe eating disorder typically leading to obesity and associated health problems. PWS is named after the Swiss doctors who discovered the condition in 1956.

Spina Bifida - A congenital cleft of the spinal column with hernial protrusion of the meninges and sometimes the spinal cord.