Pervasive Developmental Disorder (page 2)

Every year the National Dissemination Center for Children with Disabilities (NICHCY) receives thousands of requests for information about the diagnosis, educational programming, and special needs of children and youth with Pervasive Developmental Disorders (PDD). Over the past few years, PDD has become a subject of increased attention among parents, professionals, and policymakers across the country.

NICHCY developed this Briefing Paper in response to the growing concern about, and interest in, this disability. This publication is designed to answer some of the most commonly asked questions regarding PDD and to provide concerned individuals with other resources for information and support.

The term Pervasive Developmental Disorders was first used in the 1980s to describe a class of disorders. This class of disorders has in common the following characteristics: impairments in social interaction, imaginative activity, verbal and nonverbal communication skills, and a limited number of interests and activities that tend to be repetitive.

The manual used by physicians and mental health professionals as a guide to diagnosing disorders is the Diagnostic and Statistical Manual of Mental Disorders (DSM). The DSM was last revised in 1994. In this latest revision, known as the DSM-IV, five disorders are identified under the category of Pervasive Developmental Disorders: (1) Autistic Disorder, (2) Rett's Disorder, (3) Childhood Disintegrative Disorder, (4) Asperger's Disorder, and (5) Pervasive Developmental Disorder Not Otherwise Specified, or PDDNOS. (Editor's note in 2003: The current version of the DSM is the DSM-IV-TR, published in 2000. The categorization of PDD that is described in this Briefing Paper has not changed.)

Many of the questions parents and education professionals ask NICHCY have to do with children who have been diagnosed with "PDD." Doctors are divided on the use of the term PDD. Many professionals use the term PDD as a short way of saying PDDNOS. Some doctors, however, are hesitant to diagnose very young children with a specific type of PDD, such as Autistic Disorder, and therefore only use the general category label of PDD. This approach contributes to the confusion about the term, because the term PDD actually refers to a category of disorders and is not a diagnostic label. The appropriate diagnostic label to be used is PDDNOS--Pervasive Developmental Disorder Not Otherwise Specified--not PDD (the umbrella category under which PDDNOS is found).

All of the disorders that fall under the category of PDD share, to some extent, similar characteristics. To understand how the disorders differ and how they are alike, it's useful to look at the definition of each disorder. Therefore, before we begin our discussion of PDDNOS, let us look first at the definition of the general category PDD and its specific disorders.

Definition of the PDD Category and its Five Specific Disorders

All types of PDD are neurological disorders that are usually evident by age 3. In general, children who have a type of PDD have difficulty in talking, playing with other children, and relating to others, including their family.

According to the definition set forth in the DSM-IV (American Psychiatric Association, 1994), Pervasive Developmental Disorders are characterized by severe and pervasive impairment in several areas of development:

* social interaction skills;

* communication skills; or

* the presence of stereotyped behavior, interests, and activities.

The Confusion of Diagnostic Labels

The intent behind the DSM-IV is that the diagnostic criteria not be used as a checklist but, rather, as guidelines for diagnosing pervasive developmental disorders. There are no clearly established guidelines for measuring the severity of a person's symptoms. Therefore, the line between autism and PDDNOS is blurry (Boyle, 1995).

As discussed earlier, there is still some disagreement among professionals concerning the PDDNOS label. Some professionals consider "Autistic Disorder" appropriate only for those who show extreme symptoms in every one of several developmental areas related to autism. Other professionals are more comfortable with the term Autistic Disorder and use it to cover a broad range of symptoms connected with language and social dysfunction. Therefore, an individual may be diagnosed by one practitioner as having Autistic Disorder and by another practitioner as having PDDNOS (or PDD, if the practitioner is abbreviating for PDDNOS).

Generally, an individual is diagnosed as having PDDNOS if he or she has some behaviors that are seen in autism but does not meet the full DSM-IV criteria for having Autistic Disorder. Despite the DSM-IV concept of Autistic Disorder and PDDNOS being two distinct types of PDD, there is clinical evidence suggesting that Autistic Disorder and PDDNOS are on a continuum (i.e., an individual with Autistic Disorder can improve and be rediagnosed as having PDDNOS, or a young child can begin with PDDNOS, develop more autistic features, and be rediagnosed as having Autistic Disorder).

To add to the list of labels that parents, teachers, and others may encounter, a new classification system was recently developed by ZERO TO THREE: National Center for Infants, Toddlers, and Families (1994). Under this system, called the Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood, the term Multisystem Developmental Disorder, or MSDD, is used to describe pervasive developmental disorders.

However, amidst all this confusion, it is very important to remember that, regardless of whether a child's diagnostic label is autism, PDDNOS, or MSDD, his or her treatment is similar.

The Cause of PDDNOS

Both behavioral and biological studies have generated sufficient evidence to suggest that PDDNOS is caused by a neurological abnormality--problems with the nervous system. However, no specific cause or causes have been identified.

While studies have found various nervous-system problems, no single problem has been consistently found, and exact causes are far from clear. This may be due to the current approach of defining PDDNOS based on behaviors (as opposed to, say, genetic testing). Hence, it is possible that PDDNOS is the result of several different conditions. If this is the case, it is anticipated that future studies will identify a range of causes.

The Symptoms and Signs of PDDNOS

Generally, children are 3 to 4 years old before they exhibit enough symptoms for parents to seek a diagnosis. There is no set pattern of symptoms and signs in children with PDDNOS. It is important to realize that a very wide range of diversity is seen in children with PDDNOS. All the items of behavior described in this section are common in these children, but a single child seldom shows all the features at one time. In other words, all children with PDDNOS do not have the same degree or intensity of the disorder. PDDNOS can be mild, with the child exhibiting a few symptoms while in the school or neighborhood environment. Other children may have a more severe form of PDDNOS and have difficulties in all areas of their lives. Because of the possibility that PDDNOS and Autistic Disorder are on a continuum, many clinical features described in the following section are very similar to those being described in the literature for Autistic Disorder.

Deficits in Social Behavior

Some infants with PDDNOS tend to avoid eye contact and demonstrate little interest in the human voice. They do not usually put up their arms to be picked up in the way that typical children do. They may seem indifferent to affection and seldom show facial responsiveness. As a result, parents often think the child is deaf. In children with fewer delays, lack of social responsiveness may not be obvious until well into the second or third year of life.

In early childhood, children with PDDNOS may continue to show a lack of eye contact, but they may enjoy a tickle or may passively accept physical contact. They do not develop typical attachment behavior, and there may seem to be a failure to bond. Generally, they do not follow their parents about the house. The majority do not show normal separation or stranger anxiety. These children may approach a stranger almost as readily as they do their parents. Many such children show a lack of interest in being with or playing with other children. They may even actively avoid other children.

In middle childhood, such children may develop a greater awareness or attachment to parents and other familiar adults. However, social difficulties continue. They still have problems with group games and forming peer relationships. Some of the children with less severe PDDNOS may become involved in other children's games.

As these children grow older, they may become affectionate and friendly with their parents and siblings. However, they still have difficulty understanding the complexity of social relationships. Some individuals with less severe impairments may have a desire for friendships. But a lack of response to other people's interests and emotions, as well as a lack of understanding of humor, often results in these youngsters saying or doing things that can slow the development of friendships.

Impairment in Nonverbal Communication

In early childhood, children with PDDNOS may develop the concrete gesture of pulling adults by the hand to the object that is wanted. They often do this without the typical accompanying facial expression. They seldom nod or shake their heads to substitute for or to accompany speech. Children with PDDNOS generally do not participate in games that involve imitation. They are less likely than typical children to copy their parents' activity.

In middle and late childhood, such children may not frequently use gestures, even when they understand other people's gestures fairly well. Some children do develop imitative play, but this tends to be repetitive.

Generally, children with PDDNOS are able to show joy, fear, or anger, but they may only show the extreme of emotions. They often do not use facial expressions that ordinarily show subtle emotion.

Impairment in Understanding Speech

Comprehension of speech in children with PDDNOS is impaired to varying degrees, depending on where the child is within the wide spectrum of PDDNOS. Individuals with PDDNOS who also have mental retardation may never develop more than a limited understanding of speech. Children who have less severe impairments may follow simple instructions if given in an immediate context or with the aid of gestures (e.g., telling the child to "put your glass on the counter," while pointing to the counter). When impairment is mild, only the comprehension of subtle or abstract meanings may be affected. Humor, sarcasm, and common sayings (e.g., "it's raining cats and dogs") can be confusing for individuals with the most mild PDDNOS.

Impairment in Speech Development

Many infants with PDDNOS do not babble, or may begin to babble in their first year but then stop. When the child develops speech, he or she often exhibits abnormalities. Echolalia (seemingly meaningless repetition of words or phrases) may be the only kind of speech some children acquire. Though echolalic speech might be produced quite accurately, the child may have limited comprehension of the meaning. In the past, it was thought that echolalia had no real function. More recent studies have found that echolalia can serve several functions, such as self-stimulation (when a child says words or phrases repeatedly without a communicative purpose--just because it feels good); as a step between a child being nonverbal and verbal; or as a way to communicate (Prizant & Rydell, 1993). Other children develop the appropriate use of phrases copied from others. This is often accompanied by pronoun reversal in the early stages of language development. For instance, when the child is asked "How are you?" he or she may answer "You are fine."

The actual production of speech may be impaired. The child's speech may be like that of a robot, characterized by a monotonous, flat delivery with little change in pitch, change of emphasis, or emotional expression.

Problems of pronunciation are common in young children with PDDNOS, but these often diminish as the child gets older. There may be a striking contrast between clearly enunciated echolalic speech and poorly pronounced spontaneous speech. Some children have a chanting or singsong speech, with odd prolongation of sounds, syllables, and words. A question-like intonation may be used for statements. Odd breathing rhythms may produce staccato speech in some children.

Abnormal grammar is frequently present in the spontaneous speech of verbal children with PDDNOS. As a result: * phrases may be telegraphic (brief and monotone) and distorted; * words of similar sound or related meaning may be muddled;

* some objects may be labeled by their use;

* new words may be coined; and

* prepositions, conjunctions, and pronouns may be dropped from phrases or used incorrectly.

When children with PDDNOS do develop functional speech, they may not use it in ordinary ways. Such children tend to rely on repetitive phrases. Their speech does not usually convey imagination, abstraction, or subtle emotion. They generally have difficulty talking about anything outside of the immediate context. They may talk excessively about their special interests, and they may talk about the same pieces of information whenever the same subject is raised. The most able persons can exchange concrete pieces of information that interest them, but once the conversation departs from this level, they can become lost and may withdraw from social contact. Ordinary to-and-fro conversational chatter is lacking. Thus, they give the impression of talking "at" someone, rather than "with" someone.

Unusual Patterns of Behavior

The unusual responses of children with PDDNOS to the environment take several forms.

Resistance to change

Many children are upset by changes in the familiar environment. Even a minor change of everyday routine may lead to tantrums. Some children line up toys or objects and become very distressed if these are disturbed. Efforts to teach new activities may be resisted.

Ritualistic or compulsive behaviors

Ritualistic or compulsive behaviors usually involve rigid routines (e.g., insistence on eating particular foods) or repetitive acts, such as hand flapping or finger mannerisms (e.g., twisting, flicking movements of hands and fingers carried out near the face). Some children develop preoccupations; they may spend a great deal of time memorizing weather information, state capitals, or birth dates of family members.

Abnormal attachments and behaviors

Some children develop intense attachments to odd objects, such as pipe cleaners, batteries, or film canisters. Some children may have a preoccupation with certain features of favored objects, such as their texture, taste, smell, or shape.

Unusual responses to sensory experiences

Many children may seem underresponsive or overresponsive to sensory stimuli. Thus, they may be suspected of being deaf or visually impaired. It is common for such young children to be referred for hearing and vision tests. Some children avoid gentle physical contact, yet react with pleasure to rough-and-tumble games. Some children carry food preferences to extremes, with favored foods eaten to excess. Some children limit their diet to a small selection, while others are hearty eaters who do not seem to know when they are full.

Disturbance of Movement

The typical motor milestones (e.g., throwing, catching, kicking) may be delayed but are often within the normal range. Young children with PDDNOS usually have difficulty with imitation skills, such as clapping hands. Many such children are very overactive, yet tend to become less overactive in adolescence. Children with PDDNOS may exhibit characteristics such as grimacing, hand flapping or twisting, toe walking, lunging, jumping, darting or pacing, body rocking and swaying, or head rolling or banging. In some cases the behaviors appear only from time to time; in other cases they are present continuously.

Intelligence and Cognitive Deficits

Generally, children with PDDNOS do very well on tests requiring manipulative or visual skills or immediate memory, while they do poorly on tasks demanding symbolic or abstract thought and sequential logic. The process of learning and thinking in these children is impaired, most particularly in the capacity for imitation, comprehension of spoken words and gestures, flexibility, inventiveness, learning and applying rules, and using acquired information. Yet, a small number of children with PDDNOS show excellent rote memories and special skills in music, mechanics, mathematics, and reading.

Because many children with PDDNOS are either without functional speech or otherwise untestable, some people question the validity of testing their intelligence. Moreover, it has been observed that a number of these children show major improvements in other developmental areas during the follow-up period without a change in their tested IQ. Follow-up studies have also shown that retardation present at the time of initial diagnosis tends to persist. Those children with a low IQ show more severely impaired social development. They are more likely to display unusual social responses, such as touching or smelling people, ritualistic behavior, or self-injury.

Associated Features

The emotional expression of some children with PDDNOS may be flattened, excessive, or inappropriate to the situation. For no obvious reason, they may scream or sob inconsolably one time, yet giggle and laugh hysterically another time. Real dangers, such as moving vehicles or heights, may be ignored, yet the same child might seem frightened of a harmless object, such as a particular stuffed animal.