NEUROPSYCHOLOGY: WHAT ARE NEURODEVELOPMENTAL DISORDERS?

Medically Reviewed by Dr. Sony Sherpa (MBBS)

Neurodevelopmental disorders are neurological disorders that predominantly affect the way children grow and develop from a neurological standpoint.

Autistic spectrum disorders and attention deficit disorders are two of the most common types that affect children, as discussed in detail below. There are many other developmental disorders, a few of which are touched on briefly in this review.

Autistic Spectrum Disorders

Autistic Spectrum Disorders (ASDs) are neuropsychological disorders that tend to manifest early on in life. They affect the way children behave and respond to everyday situations[1].

Classifications for ASDs used to be split up into several unique variations of autism alongside several other disorders that were termed Pervasive Developmental Disorders[2]. With recent publications, Pervasive Developmental Disorders have now become known as Autistic Spectrum Disorders. Instead of being seen as discrete conditions, they are rather viewed as being part of an autistic continuum. Healthcare practitioners and researchers may revert back to the older way of referring to these conditions as the most recent classification is far less specific and may even hamper diagnosis.

Autism, Asperger’s Syndrome, and unspecified autistic conditions are the most common ASDs to affect children. In spite of the fact that they are now technically one condition (ASD) with variable symptoms, some of them are distinct conditions with much overlap and will be discussed as such below. Childhood Disintegrative Disorder is another condition that was formerly labeled as a developmental disorder and that has recently been reclassified as part of the ASD family.

Autism

Autism is the most common type of ASD and technically, all ASDs are a form of autism.

ASDs are typically characterized by excessively repetitive behaviors and deficits in communication, particularly an unusual disinterest or lack of social reciprocation. This lacking reciprocation is a regular disposition for these children and is not generally provoked by circumstances that could be considered a normal cause of communication avoidance behaviors, such as embarrassment, shyness, or conflict.

Children with autism tend to have co-existing mental deficits for which they may require remedial assistance. ADHD, tic disorders, obsessive-compulsive disorder, mood disorders, anxiety, and epilepsy are common in those with autism.

The prevalence of ASDs in the US is less than 2% and less than 1% globally, according to the WHO[3]. Boys are more likely to be diagnosed as having an ASD than girls. However, if girls are diagnosed, they tend to have worse mental disabilities accompanying the condition.

Data reports that roughly 9% of those with ASD in childhood experience remission from the condition as adults.

Secondary Autism

Less than 10% of autistic cases have what is known as secondary autism in which the autistic symptoms arise from another condition. Conditions that may give rise to secondary autism include:

• Tuberous sclerosis
• Fragile X Syndrome
• Congenital infections such as rubella and cytomegalovirus
• Phenylketonuria

Symptoms

Getting a diagnosis for ASD can take a long time. Symptoms will first present on average by the age of 2, in early developmental years, and become more apparent as the child ages.

Symptoms of all ASD include:

• Deficits in social interaction and communication, particularly in reciprocation
• Unusual verbal and non-verbal communication, such as lacking eye contact, abnormal body language, and failure to initiate conversation
• Repetitive behavior and activities that are unusual in intensity and/or focus
• Limited variety of interests
• Apparent disinterest in play and many activities considered normal for children
• Disinterest in others or in making friends
• Apathy, lack of emotionality, or lack of emotional receptivity
• Inability to adapt or cope with new stimuli
• Failure in adjusting behavior given unique social contexts
• Under- or over-reactivity or sensitivity to the environment
• Lack of coordination and difficulty with physical activities

It is important to note that these symptoms only constitute an ASD if they impair daily functioning for the individual in some way. Some with autism may be more prone to needing intensive care and support than others.

Asperger’s Syndrome (High-Functioning Autism)

Asperger’s Syndrome has been previously referred to as high-functioning autism. It meets many of the same criteria with the exception that those with this condition tend to have average or even superior intelligence than that of other autistic children. Furthermore, those with Asperger’s do not tend to have delays in language development or other areas of cognition.[4] Many children with this condition find themselves attracted to advanced intellectual fields of interest from a young age, however, this is not always the case.

The diagnosis of Asperger’s Syndrome is often given at later ages than classical autism, with an average age of 11 or later.

Symptoms are likely to become less intense as a person with Asperger’s ages. Many are able to maintain a set and integrate into society without difficulty, in spite of social peculiarities. Elon Musk is perhaps the most famous and successful case of someone with Asperger’s Syndrome. Greta Thunberg is another example.

Childhood Disintegrative Disorder

This is an exceedingly rare type of ASD that is sometimes referred to as “child dementia.” For every 10,000 children with ASD, 10 are likely to have this disorder.[5]

While this is not actually a form of dementia, it bears similarities in that the child cognitively regresses after successfully achieving learned developmental milestones. Skills lost include social, language, and motor abilities. For example, the child may have already mastered toilet training or have a relevant vocabulary for their age, but with the onset of this condition, the child’s progress regresses and the learned skills become lost. Forgetting words, not wiping or flushing after going to the loo, and losing social skills that were developed prior are common occurrences for those with childhood disintegrative disorder.

Childhood Disintegrative Disorder is also called Heller Syndrome or Disintegrative Psychosis. Age of onset is typically around 3-4 years of age, but may occur at later ages as well - generally up to the age of 10. The incidence of this disorder is four times higher in boys than in girls.

Deterioration of previously learned skills tends to happen rapidly (days to weeks) and the child may be conscious of their sudden ineptitude. Some children experience hallucinations and other neuro abnormalities in conjunction with skill loss. Children with this condition tend to already fall on the autistic spectrum and as a result, it may have taken them longer than average children to make developmental progress in some areas.

The majority of those with this condition are unable to integrate successfully into society, continue to regress as time passes, and tend to need lifelong specialized help.

Symptoms

To be diagnosed with this disorder, the child needs to meet the criteria for having an ASD (see above) and have lost skills previously acquired in 2 or more of the following areas:

1. Ability to play
2. Motor skills
3. Social skills and self-care
4. Bowel and bladder control
5. Language comprehension, listening and understanding
6. Expression and communication ability

Skill regression may occur between 2 and 10 years of age.

These children are prone to spontaneous episodes of extreme anxiety or terror without an apparent cause.

Social (Pragmatic) Communication Disorder

Those that do not meet the full criteria for autism or Asperger’s Syndrome, are likely to be diagnosed with Social (Pragmatic) Communication Disorder. This is considered to be part of the autistic spectrum, however, the emphasis is merely on social deficits as opposed to repetitive behaviors and restricted interests.[6] These individuals are known to have a form of mild or borderline autism, displaying autistic traits with a lesser genetic component.[7]

This was previously referred to as a “pervasive developmental disorder – not otherwise specified” or an unspecified ASD.

Risk Factors

It is not known what causes these disorders, however, there is strong evidence suggesting they are multi-factorial genetic conditions.

Risk factors include:

• Epilepsy
• Mutism
• Schizophrenia and other mental disorders
• Rett Syndrome
• Chronic brain infections
• Secondary autism
• Auto-immune conditions[8]
• Prenatal infections
• Premature birth
• Caesarean birth
• Increased parental age at conception of the child
• Maternal history of disease

The following risk factors are specific to childhood disintegrative disorder, but may contribute towards the formation of other ASDs as well:

• Leukodystrophy, a type of demyelinating disease
• Lipid storage diseases that result in excessive fats being stored in the nervous system
• Tuberous Sclerosis which is a disease characterized by the formation of multiple benign brain tumors and tumors in other body areas
• Subacute Sclerosing Panencephalitis, a rare manifestation of measles that chronically infects the brain and destroys neurons

Treatment Options

There are many treatment options available for kids with ASDs, most of which are aimed at improving skills that the child requires for success later on in life. It is often advisable for parents and physicians to collaborate in designing a treatment plan that is specifically tailored to the child’s needs.

Examples of treatments available include:

• Behavioral Therapy. These typically help autistic children to integrate into society by helping them rehearse social skills and behave in socially acceptable ways. Speech therapists, psychologists, physical therapists, and occupational therapists may all offer unique forms of behavioral therapy that can help to improve deficits in those with ASDs.
• Physical therapies and stimulation. Some kids with autism benefit from physical therapies that involve stimulating tactile senses, re-learning motor skills (like crawling), engaging in outdoor activities (e.g. horse riding), and participating in specialized exercise programs, particularly ones that promote coordination.
• Environmental stimulation. Gently expanding the child’s exposures in a safe and structured way can help to improve cognition and lower anxiety in certain cases.
• Stress management techniques. Anxiety and stress are common for those with ASDs and as such, it may help them to learn techniques to cope with stress. Breathing techniques, aromatherapy, and cathartic skills such as learning to make music, art, or crafts may be of benefit. Some children respond to weighted blankets, soft toys, or some other securing item that can soothe them.
• Medications. There is no drug available that tackles autism spectrum disorders. Healthcare practitioners may offer medications such as antipsychotics, antidepressants, and antiepileptics for repetitive behaviors, aggression, depression and epilepsy respectively.

Attention Deficit Disorders (ADD and ADHD)

Attention Deficit Disorders (ADDs) are some of the most common developmental disorders affecting children and as a result, the majority of people have heard of both ADD and ADHD. Children with these conditions display a greatly reduced ability to focus, which often affects their ability to learn during school and if left untreated, may affect their career options as adults.

Previously, ADD and ADHD were seen as distinct disorders, however, they have been lumped together in the most recent literature and re-classified into a spectrum of attention deficit disorders. There are three main subtypes in which the child is:

1. Predominantly inattentive
2. Predominantly hyperactive
3. A combination of type 1 and 2

In the older contexts, subtype 1 was considered as ADD and subtypes 2 and 3 were considered as ADHD (Attention Deficit-Hyperactivity Disorder). Of those affected by these conditions, 18.3% suffer from ADD, 8.3% suffer from a predominantly hyperactivity disorder and 70% suffer from a combo (ADHD) on average[9]. ADD is more common in girls and ADHD is more common in boys. In general, boys are more susceptible to any attention deficit disorder with a 2:1 ratio. Onset is usually before the age of 12.

Generally speaking, those with ADHD tend to have a worse prognosis than those with ADD, as the combination of inattentiveness and hyperactivity can be rather disruptive, particularly in a classroom setting. These children are often seen as genuine trouble makers, however this is usually not their underlying intention.

Research has revealed it to be a disorder of executive function, affecting brain structure and functioning in the frontal cortex and prefrontal cortex. Findings highlight that the condition impairs decision-making, judgment, and emotional control in these kids. They often find it difficult to sit still, obey instructions, follow lines of reasoning or intervene consciously in order to control their impulses. Children with ADD/ADHD are also more likely to have co-existing developmental disorders, such as autism.

Symptoms

Symptoms of ADD may include:

• Inability to focus or pay close attention
• Not appearing to listen when being spoken to
• Trouble organizing or being disorganized often
• Not completing tasks or finishing work
• Often forgetful or misplacing things
• Not being punctual
• Rushing through tasks
• Being unable to take note of small details

ADHD tends to be associated with all the above symptoms as well as:

• Hyperactivity or feeling restless/ too full of energy
• Fidgeting all the time
• Speaking out of turn or excessively
• Being loud and obtrusive
• Inability to be patient or wait for their turn
• Interrupting or disrupting others
• Impulsivity
• Emotional or irrational outbursts

To be diagnosed with the condition, 6 of the 9 main criteria need to be met, some of which are listed above. Symptoms need to be constant and present in multiple settings, affecting the child’s social, work, and academic abilities.

There may be appropriate reasons for children to act in the above ways, particularly in specific contexts, such as feeling very excited for a special occasion or directly after having had a high dose of sugar. Those with ADHD, however, may respond even more extremely to these situations than normal children. Furthermore, many mood disorders, substance abuse disorders, hearing, learning and mental disorders all have symptoms that overlap with ADD and need to first be ruled out.

As these kids age, symptoms are often better controlled, yet they tend to take on new forms such as:

• Procrastination
• Mood instability
• Low self-esteem
• High impulsivity
• Inattentiveness

It may be difficult for an adult with ADD/ADHD to be relied upon, particularly for important tasks that demand high degrees of focus.

Risk Factors

It is still unclear what causes ADD or ADHD, however, much like other developmental disorders, it is seen as a multi-factorial condition with many potential causes.

Risk factors include:

• Smoking during pregnancy
• Nutritional deficiencies in either mother or child
• Fetal Alcohol Syndrome or drinking during pregnancy
• Viral infections, particularly those affecting the brain
• Disorders in which dopamine and/or norepinephrine neurotransmitter levels are depleted or elevated in the frontal cortex (e.g. mood disorders, chronic stress disorders, substance abuse disorders, chronic pain disorders)

Treatment Options

Psychotherapy, behavioral therapy, and pharmaceutical stimulants are often employed for children and adults with ADD or ADHD. While there is no way to diagnose these conditions other than clinical guesswork, lab work may be required to understand what medications may be desirable, particularly in the case of ADHD.

Stimulants are often employed first by a physician, consisting of either an amphetamine or methylphenidate base. While symptoms improve, they may pose severe behavioral side effects (particularly later on in life)[10] and as such, may not be appropriate for all children with ADD/ADHD.

Antidepressants are another class of medication commonly prescribed to those with ADD/ADHD. These are often used in cases where the child suffers from hypertension, or severe anxiety or where stimulants are contraindicated.

Psychotherapy and behavioral therapy may help the child to intervene with their obstructive behaviors in the classroom, lessening the need for prescription medication. Plenty of physical exercise may also help to dispel excessive energy levels and serve to improve focus.

Trigeminal nerve stimulation is a new FDA-approved therapy that has been shown to lower hyperactivity in children with ADHD. A device is used that generates a low-level electric pulse in order to stimulate the trigeminal nerves.

Other Neurodevelopmental Disorders

The following disorders are less commonly observed than autism and ADD/ADHD. They consist of communication, learning, and motor deficits, as well as genetic diseases that affect neurological development.

Communication Disorders

Communication disorders pertain to conditions in which children have difficulty expressing themselves, either in writing or verbally. They also consist of disorders in which the child may not be able to comprehend or express components of language, such as being unable to acquire fluency in their native language or being unable to pronounce certain sounds (e.g. stuttering, slurring, etc).

Social disorders also count as communication disorders and include social anxiety, selective mutism, and social (pragmatic) communication disorder. These are conditions in which the child is socially inept, in spite of potentially being able to communicate.

Learning Disorders

Learning disorders impair a child’s ability to learn and are generally specific to a learning area. Examples include:

• Dyslexia is a condition in which a child has trouble reading and decoding spoken language from written words. Words are typically inverted, letters are missed out by the child when reading or writing and it may take the child a longer time to increase their written and spoken vocabulary. Another name for dyslexia is reading disorder.[11]
• Dyscalculia is a condition in which the child experiences learning difficulty with numbers, mathematics, and performing calculations. Sometimes referred to as ‘math dyslexia’ or ‘number dyslexia,’ a child with dyscalculia tends to find some or all concepts related to numbers challenging. Basic arithmetic concepts, such as how to do sums, estimate amounts, or even count numbers may be a frustrating task for someone with dyscalculia.[12]

A child with an intellectual disability may present with multiple learning disorders due to having a very low IQ score. Intellectual disabilities are typically severe mental impairments that persist into adulthood. Individuals with such disabilities are regarded as mentally handicapped.

Motor Disorders

Motor disorders are developmental conditions that affect some aspects of movement in children, often persisting into adulthood. Examples include:

• Developmental Coordination Disorder (Developmental Dyspraxia) is a disorder that makes a child less coordinated, and more clumsy and may detract from basic daily functions such as walking, running, dressing, and being able to perform tasks that require fine coordination such as griping and writing with a pencil.[13]
• Stereotypic Movement Disorders are disorders in which the child engages in persistent, repetitive, and often non-functional movements such as head-banging, waving, or excessive thumb-sucking. The disorder sets in before 3 years of age and usually lasts for the rest of the child’s life.[14]
• Tic Disorders are disorders characterized by sudden movements, twitches or sounds that a person has no control over and tends to do repeatedly many times throughout a day. Tourette’s Syndrome is the most common tic disorder, which includes a combination of motor and verbal tics. Common tics include blinking, twitching or shrugging.[15]

Neurogenetic Developmental Disorders

These are genetic conditions that severely hamper the development of a child and tend to have very poor outcomes. Intellectual disabilities are often the result of neurogenetic developmental disorders. Common examples include:

• Rett disorder is constituted by a regression in development after a period of normal development. Unlike childhood disintegrative disorder, Rett disorder tends to have very physical aspects and may affect a child’s physical growth moving forward. A classic symptom is that the head size stops increasing or grows at a much slower pace, resulting in neurologic disabilities. Speech and motor development are also often affected and the child may regress in talking and walking milestones or suddenly become unable to perform simple movements that had been previously learned.[16]
• Fragile X Syndrome is a genetic disorder characterized by the lack of a specific protein required for brain development known as FMR (Fragile X Mental Retardation) protein. The FMR1 gene is required to make this protein. Symptoms tend to include substantially impaired development, learning ability, and social skills. Boys tend to have more severe intellectual disabilities than girls with the condition.[17]
• Down’s Syndrome (also known as trisomy 21) is a well-known genetic disorder that is caused by a cell division anomaly in a developing embryo. As a result, chromosome 21 produces an extra copy of itself in all cells moving forward, creating the typical Down Syndrome phenotype. The condition tends to be symptomatic of intellectual disabilities, severe developmental delays, and other health conditions. It is difficult to say how the condition will affect the child in the long run as each case tends to be unique. However, some with Down’s are less affected than others and not every case requires specialized care.[18]

General Risk Factors for Neurodevelopmental Disorders

While many developmental disorders remain mysterious in their origins, there are a few gestational risk factors that may increase their occurrence in general. These include[19] [20]:

• Drinking and/or smoking during pregnancy
• Being exposed to chemical agents or heavy metals such as lead or mercury during gestation
• Pre-natal hypoxia or oxygen deprivation
• Nuchal cord (umbilical cord wrapped around the babies neck)
• Premature or cesarean births
• Falling pregnant at older ages
• Endocrine disruption, such as fetal exposure to PCB’s and other plastic compounds

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