You're probably wondering what macrocephaly is and whether this condition is particularly common among children with autism spectrum disorder (ASD).
When you're done with this article, you will know what macrocephaly is, its main symptoms, how it impacts autistic kids, the other problems that it may cause, and more.
Do children with autism have large heads?
In recent decades, researchers and scientists conducted a lot of studies about head circumference and brain size in autism spectrum disorder.
When it comes to macrocephaly (having an abnormally large head size), here are what these studies have found:
- Up to 15.7% of autistic children have macrocephaly.
- This condition typically appears in the patient's early childhood years.
- Macrocephaly impacts kids that were diagnosed with low-functioning autism more frequently than those with less severe ASD symptoms.
Other research reports point to a correlation between gender and having a large head. That is to say that autistic boys are more likely to develop macrocephaly than girls.
At times, the condition shows up when the child is still in their mother's womb, and it usually goes away by their fifth birthday.
It is hard to know exactly when and how macrocephaly affects patients. This is because the many experts who examined this topic over the last 80 years relied on different research methods and techniques.
How was this discovered?
Autism's relationship to head size is explained by almost eight decades' worth of data and analysis, starting with a paper that Leo Kanner authored in 1943.
Kanner observed 11 kids with ASD and noticed that "five had relatively large heads". However, this sample size was too small and Kanner didn't study or comment on this issue any further.
In 1999, nearly 60 years later, a report came out and indicated that macrocephaly was prevalent among 20% of autistic patients.
Yet, the Autism Phenome Project disputed these figures in 2011. They argued that the 20% estimate only accounts for children with a bigger-than-average head size.
In turn, the Autism Phenome Project looked at the number of kids with ASD whose head was disproportionately large in relation to their body size. They concluded that 15% (and not 20%) of autistic patients have macrocephaly.
Lastly, but certainly not least, is a 2015 study with over 8,000 participants that found that those with an ASD diagnosis tend to have a bigger head than typically developing children.
Nonetheless, the 2015 review didn't examine the relationship between the head and brain or body sizes.
Does macrocephaly also mean the child has a large brain?
Those with a large head are more likely to have a brain overgrowth, as well. In fact, brain enlargement impacts 9.1% of children with ASD.
Remember, though, that having a large head doesn't necessarily mean that an autistic child will also have a large brain.
Which parts of the brain are enlarged?
The cortex is the main part of the brain that gets enlarged. To clarify, the cortex is the thick outer layer that surrounds the brain from the top and takes up most of its volume.
Several studies about brain structure changes in autism explained that multiple areas experience an enlargement, including:
- Amygdala: Some autistic children might develop an enlarged amygdala (the part that processes emotions) while they're very young.
- Cerebellum: Even though most areas of the brain get bigger, kids with ASD are more likely to have less cerebellum tissues than their neurotypical peers. The cerebellum oversees functions related to bodily balance, cognition, and socializing.
- Hippocampus: Similar to the amygdala, the hippocampus (the part that creates and preserves memories) commonly increases in size, too.
Scientists and medical experts aren't sure what the enlarged parts of an autistic child's brain and cortex are made from or contain.
One finding suggests that ASD can lead to an excess in cerebrospinal fluids. This is the clear liquid that's present across the nervous system and regulates many of its physical, sensory, and other processes.
According to a separate study, autism is linked with an excess of neurons in the prefrontal cortex among boys with brain overgrowth. These neurons were identified in the parts that are responsible for a person's communication capabilities and cognitive growth.
Is macrocephaly problematic?
In addition to how it affects the brain's structure, macrocephaly is concerning because it goes hand-in-hand with other problems and issues.
Here are some examples:
- Macrocephaly is linked to shortcomings in communication and social skills, and it sets back an autistic patient's ability to speak.
- Children with enlarged brains tend to run into more difficulties with day-to-day tasks (for instance, eating with a fork and knife) than those with a normal-sized brain.
- A two-year-old or younger autistic child's head size can indicate how severe their ASD symptoms will be by the time they turn four years old.
- Kids with a relatively big brain size could see their skills and capabilities decline up until their sixth birthdays.
In light of this, if your autistic son or daughter was diagnosed with macrocephaly, you want to make sure that you prepare for the developmental hurdles that they may run into in the future.
This will allow you to address and minimize the severe symptoms as early and smoothly as possible.
If your child didn't receive an official diagnosis, you should keep an eye on the potential symptoms.
What else may macrocephaly cause?
In the immediate term, macrocephaly could lead an autistic kid to experience the following symptoms:
- Vomiting that isn't explainable or provoked
- Unusual or strange eye movements
- Head bulging
- Head tightness
- Crying in an irregularly high-pitched tone
These signs may mean that there is an overflow in brain fluids. They might also manifest themselves when the skull's bones excessively grow, as well as for other reasons.
Now that you know what the symptoms of macrocephaly are, you should take your son or daughter for a diagnosis once they start to display them.
Remember, up to 15% and 10% of autistic kids get macrocephaly and an enlarged brain, respectively.
These conditions frequently appear during the first two years of a child's life, and they suggest how severe their ASD will be in the following ones.
Therefore, if your autistic child received a macrocephaly diagnosis, you want to make sure that you prepare for more intense autism symptoms before they even show up.
This allows your child to develop and grow in the healthiest way possible.