Autism spectrum disorder (ASD)

Autism spectrum disorder (ASD) is a neurological and developmental condition that affects the way an individual interacts with others and the world around them. More and more is it seen as cognitive variation. It is not seen as an illness or disease. Rather it is a heterogenous spectrum associated with certain disabilities and poses its own set of daily challenges, but at the same time it is associated with cognitive strengths and talents.

Before being seen as a spectrum we would segment the spectrum of presentations by labelling the diagnosis as autism, Asperger syndrome, childhood disintegrative disorder, pervasive development disorder etc. A lot of these presentations overlapped and therefore in 2013 the DSM-V grouped them all into the umbrella term of ASD.

ASD in short is characterised by persistent impairments in social interactions and communication as well as restricted, repetitive and stereotyped patterns of behaviours, interests or activities.

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Neurodivergent or neurotypical?

Let’s lay out some definitions first and foremost:

• Neurotypical - this term describes an individual who thinks, processes information and interacts in ways that are typical in relation to the given context and situation. It can be described as “normal” in informal settings.
• Neurodivergent - this refers to individuals whose neurological development and patterns of behaviour deviate from the “norm”. It encompasses a wide range of neurodevelopmental and neuropsychiatric conditions. ASD patients are deemed to be neurodivergent. Other conditions that fall under this term are ADHD, dyslexia, Tourette syndrome.

Being aware of these terms is important to provide individualised care, reduce stigma and enhance communication of such issues. It is important to know both terms. They both have their place and can be used appropriately in their given contexts.

🏘️ Epidemiology

ASD’s prevalence has increased over time. This may be due to an increased awareness, broadening of the criteria for diagnosis, improved access to specialists. Approximately 1-2% of the population has ASD.

It was previously underdiagnosed in girls (possibly as they were more able to mask it by copying their neurotypical peers). The ratio previously was 3-4:1 in boys versus girls. Now it is closer to 1-2:1.

Around 50% of children with ASD have intellectual disabilities.

Pathophysiology

The exact mechanism behind the development of ASD is not well understood. It is due to multi-factorial interplay (both genetic and non-genetic factors) that interact to create this heterogenous presentation.

There are strong genetic components in the devlopment of ASD, but the majority of people with ASD don’t have relatives with ASD. This indicates that there are non-heritable components to the disorder. There are certain conditions associated with ASD that have detectable chromosomal abnormalities (such as fragile X syndrome, neurofibromatosis type 1, tuberous sclerosis, Down’s syndrome).

Maternal health is also associated with the disease. This may be seen with emerging evidence that sodium valproate use in-utero has been linked to the disorder (although more evidence is still needed with regards to these factors).

As mentioned in the summary, it is a neurodevelopmental disorder. This means that there are modifications to brain development early on in life with children that have ASD. These modifications may lead to shuffling of neural networks that control cognition and behaviour. This is highlighted when looking at the connections that are involved in low-level sensory processing.

Brain growth is also seen to be different in children with ASD. It starts off with larger (on average) growth until the age of 4. It then slows down and reaches a similar volume by the ages of 10-15 years old.

⚠️ Risk factors

• Family history of ASD
• Prematurity
• Perinatal hypoxia
• Increased testosterone levels in the womb
• Gestational diabetes
• Polycystic ovarian syndrome

😷 Presentation

There are few/no physical features of ASD (unless if related to a syndrome which we will mention below) but as mentioned previously, children sometimes have macrocephaly (an enlarged head).

Behavioural features of ASD include:

• Reduced/negative responses towards others
• Reduced/absent interactions with others - within the first year the children are not seen having the to-and-fro playful interactions with their parents. For example, imitative games such as peek-a-boo doesn’t yield the typical response.
• Reduced eye contact, reduced pointing and other gestures
• Reduced/absent imagination and reduced variety of pretend play - pretend play refers to children playing in make believe situations. It helps develops the child's social, emotional, language and thinking skills whilst nurturing their imagination.
• Overreaction or under-reaction to sensory stimuli - they may be distressed by the smell, taste, texture of food and may have extreme fads and only eat certain foods for a while. They may even be distressed to the way food is arranged on a plate.
• Repetitive and rigid behaviours, language and interests:
• Repetitive movements - such as hand flapping, body rocking, spinning, finger flicking. This is known as stimming.
• Overly focused or unusual interests
• Rigid expectations of how other children should adhere to rules of play
• Need for routine and predictability
• Toys and possessions have to be in a certain place
• Intense interests - such as in trains, postcodes or car registration numbers. Females tend to have interests in more “typical” domains such as art or music.
• Language delay or regression - children are seen to have delays in their babble and vocalisation within the first year. They fail to acquire vocabulary or vocalisations and may subsequently lose these skills. They may have stereotyped speech meaning they use phrases they have heard others use in their daily language to a greater degree.

In a pre-school child:

• Language delay may present with diminished babbling and delayed acquisition of words for their expected age (e.g. less than 10 words by the age of 2 years)
• Regression or loss of use of speech may result in using single words when previously 2-3 word sentences were used to hold a conversation.
• Unusual characteristics of spoken language include repetition of words or phrases (echolalia) and reference to themselves by “you” or “he/she” beyond 3 years.

In a primary or secondary school child:

• Limited use of speech
• Speaking in a monotonous tone
• Repetitive speech and excessive discussion on topics they are interested in.
• Talking at others rather than sharing a conversation.
• Responses may seem rude or inappropriate.

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Echolalia

Echolalia is the term that describes the repetition of vocalisations or phrases made by another person. “Echo” means to repeat and “lalia” means speech. It is a normal part of childhood development even in neurotypical toddlers. We all imitate the sounds we hear. However, as the child grows and acquires a broader vocabulary, they begin to craft their own sentences. By the age of 3 echolalia should be absent.

For example:

• When asking the child, “Do you want a snack?”, they repeat, “Do you want a snack?” instead of saying yes. This is known as immediate echolalia.
• Whenever someone walks into a room the child begins to sing Happy Birthday. This is an example of delayed echolalia.

📝 Criteria

The diagnostic criteria for autism is laid out by DSM-V. To meet the criteria a child must have:

• Persistent deficits in each of the 3 areas of social communication and interaction (A1-A3).

AND

• At least 2 of 4 types of restricted, repetitive patterns of behaviour, interests or activities (B1-B4).

Persistent deficits in social communication and social interaction

All 3 of the areas must be met.

It must be across multiple contexts and manifested by history or currently with the following:

1. Deficits in social-emotional reciprocity
1. Abnormal social approach and failure of normal back-and-forth conversation.
2. Reduced sharing of interests, emotions or affect.
3. Failure to initiate or respond to social interactions.

2. Deficits in nonverbal communicative behaviours used for social interaction
1. Poorly integrated verbal and nonverbal communication.
2. Abnormalities in eye contact and body language or deficits in understanding/use of gestures.
3. Total lack of facial expressions and nonverbal communication.

3. Deficits in developing, maintaining and understanding relationships
1. Difficulties adjusting behaviour to suit various social contexts.
2. Difficulties in sharing imaginative play or in making friends.
3. Absence of interest in peers.

Restricted, repetitive patterns of behaviour, interests or activities:

2 of 4 of the areas must be met.

It must be across multiple contexts and manifested by history or currently with the following:

1. Stereotyped or repetitive motor movements, use of objects or speech

For example, simple motor stereotypes, lining up toys or flipping objects, echolalia, idiosyncratic phrases.

2. Insistence on sameness, inflexible adherence to routines, or ritualised patterns of verbal or nonverbal behaviour

For example, extreme distress at small changes, difficulties with transitions, rigid thinking patterns, greeting rituals, and need to take same route or eat same food every day.

3. Highly restricted, fixated interests that are abnormal in intensity or focus

For example, strong attachment to or preoccupation with unusual objects, and excessively circumscribed or perseverative interests.

4. Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment

For example, apparent indifference to pain/temperature, adverse response to specific sounds or textures, excessive smelling or touching of objects, and visual fascination with lights or movement.

Once these criterion are met, to make the diagnosis there symptoms should be:

• Symptoms must be present in the early developmental period (but may not become fully manifest until social demands exceed limited capabilities, or may be masked by learnt strategies in later life).
• Symptoms cause clinically significant impairment in social, occupational, or other important areas of current functioning.
• These disturbances are not better explained by intellectual development disorder (intellectual disability) or global development delay. Intellectual development disorder and ASD frequently co-occur; in order to make comorbid diagnoses of ASD and intellectual development disorder, social communication should be below that expected for the general developmental level.

There are 3 accompanying levels to the severity of the DSM-V criterion:

• Level 1 - requires support.
• Level 2 - requires substantial support.
• Level 3 - requires very substantial support.

It may be difficult to diagnose autism in:

• A child under 24 months of age.
• A child with a developmental age of less than 18 months.
• A child where there is a lack of information about their early life (for example if looked-after or adopted).
• A child with a severe sensory impairment (such as hearing or vision) or a motor disorder (such as cerebral palsy).
• A child with milder symptoms and/or average or above average intelligence.

🔍 Investigations

As mentioned above we need to assess if the child meets the criterion mentioned. To do so we should take a structured history and observe the child (appearance, behaviour and social skills).

We should also conduct a physical examination. This is to rule out other differential diagnoses that ASD may be a feature of.

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Associated conditions:

1. Tuberous sclerosis

It is also known as tuberous sclerosis complex or Bourneville disease. It is a rare genetic condition that causes benign tumours to develop in different parts of the body. The tumours most commonly are in the brain, skin, kidneys, heart, eyes, and lungs as these all derive from ectodermal origin.

It is also associated with epilepsy, spasms, ashleaf macules (hypopigmentation) and angiofibromas (a benign vascular tumour appearing in the nasal cavity).

2. Neurofibromatosis type 1 (NF1)

NF1 is a genetic condition causing tumours to grow along nerves. The tumours are most commonly benign and lead to lumps on/under the skin. It also presents with cafe-au-lait, intertriginous freckles (freckles in skin folds), neurofibromas and spinal deformities.

3. Angelman syndrome

A rare genetic condition of chromosome 15 (a deletion mutation) that affects the nervous system leading to physical disabilities and learning disabilities. It presents with frequent laughter and smiling, easily excitable, flapping of the hands and hyperactivity.

🧰 Management