Head Circumference

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Mine is average and my son's is average. But I have heard from many sources that head circumference and autism is related. In the case of Rett's Syndrome, if I am not mistaken the head stops growing?

it's thought to be due to an early overgrowth of brain tissue in autistics.

it's far "more common" in kids... due to the "early overgrowth" but headsizes usually catch up once you grow to be an adult... though both sides do still have some watermelons representin'!

my head circ is 24"

i summarized a journal article on this subject for alex for WP. you can find it in the article section here on the site, if you're interested.

Thanks!

The first one says

"Data from 10 sites of the NICHD/NIDCD Collaborative Programs of Excellence in Autism were combined to study the distribution of head circumference and relationship to demographic and clinical variables. Three hundred thirty-eight probands with autism-spectrum disorder (ASD) including 208 probands with autism were studied along with 147 parents, 149 siblings, and typically developing controls. ASDs were diagnosed, and head circumference and clinical variables measured in a standardized manner across all sites. All subjects with autism met ADI-R, ADOS-G, DSM-IV, and ICD-10 criteria. The results show the distribution of standardized head circumference in autism is normal in shape, and the mean, variance, and rate of macrocephaly but not microcephaly are increased. Head circumference tends to be large relative to height in autism. No site, gender, age, SES, verbal, or non-verbal IQ effects were present in the autism sample. In addition to autism itself, standardized height and average parental head circumference were the most important factors predicting head circumference in individuals with autism. Mean standardized head circumference and rates of macrocephaly were similar in probands with autism and their parents. Increased head circumference was associated with a higher (more severe) ADI-R social algorithm score. Macrocephaly is associated with delayed onset of language. Although mean head circumference and rates of macrocephaly are increased in autism, a high degree of variability is present, underscoring the complex clinical heterogeneity of the disorder. The wide distribution of head circumference in autism has major implications for genetic, neuroimaging, and other neurobiological research."

from what I understand of this summary, that they found that the persons who they studied who had autism tend to have normal sized heads, but the rates of large heads (macrocephaly) are higher in persons with autism than the population in general. It also says that the parent's head size was the most important thing in determining the size of the heads of children with autism. As it would be with someone without autism. This study looked at 147 parents, 208 autistic kids, and 149 of their siblings.

The second study says that about 14% of the young children they studied who were autistic have large heads. It doesn't say what percentage of children who are not autistic have large heads. "Macrocephaly does not define a homogeneous subgroup of autistic individuals according to clinical features."

The third study was of a group of 126 children in France who were autistic. They found raised levels of large AND smaller than normal skulls in that group.

The fourth study was of 63 autistic kids. It seems to say that the higher nonverbally functioning had larger skulls than autistic kids who appeared normal in functioning and skull size. "Children with discrepantly high nonverbal abilities had a mean standardized head circumference that was more than 1 SD greater than in the reference sample, and that was significantly greater than in autistic children with a relative verbal advantage or no discrepancy in cognitive abilities, for whom mean head circumference was within normal limits." This was an extremely small study, but it certainly looks like something that I hope someone followed up on.

The fifth one studied 241 autistic kids and found that "Macrocephaly (i.e., head circumference >97th percentile) is generally part of a broader macrosomic endophenotype, characterized by highly significant correlations between head circumference, weight, and height (p < .001). A head circumference >75th percentile is associated with more impaired adaptive behaviors and with less impairment in IQ measures and motor and verbal language development." This particular study also found "larger head sizes are significantly associated with a positive history of allergic/immune disorders both in the patient and in his/her first-degree relatives."

All of these are fascinating. I would be interested to know if the findings have been replicated in other studies. As I'm sure you know, one study may have a finding that cannot be replicated - their results are, in effect, a fluke or caused by something within that particular population that is not generalizable out to the larger population. It's when you see several studies looking at the same things that come up with the same results, and those results cannot be attributed to anything else (like heredity - grandpa had a big head, etc.), that you really know you have something.

Thanks so much for taking the time to look all these up. I'm way behind on my reading!

Yeah, I have a huge-ass head.

I believe that study defined Macrocephaly as being above the 97th percentile.

So, the biggest 3% of heads, by definition, have Macrocephaly.

And 14% of the autistics in the study fit in the category.

So, this gives us statistically, 5 of 6 people with huge heads have some form of autism! (I know thats false and incorrect logic, but I left it cause it's funny!)

But, people on the spectrum are 5 times more likely then NT's to be classified as having Macrocephaly.

I never did and neither does my son, I guess we were just lucky.

My verbal function was limited, even into my twenties and thrities, though it is a little better now, even though my comprehension throughout worked fine. As for allegies and immune disorders, those might also be closely related to the nervous system where damage can more easily be recognized or identified, though I don't relate to the allergies at all. I guess it's just saying there are degrees and variances within their clinical study.

Thanks flutter, on the spell-down, that makes a little more sense to me.

I have a big head and a huge forehead, as you can see in my avatar. My 3 year old autie has a big head and big forehead as well...so does my 6 year old yet to be DX. My husband has an average size head and so did my X. My other three kids from my first marriage my two NTs have average size heads (they get to wear hats) and my 16 year old undiagnosed aspie has a big head but an average forehead.