Tuesday, January 26, 2010

From allergies to amygdala to asthma to ....

I've been wondering lately about the extent to which T's allergies may be relevant to his PDD symptoms and developmental delays in general. Naturally I tried to look this up using Google.

The first thing I found was this blog. Apparently there was some study in which the autistic children were not more likely than anyone else to actually have allergies, but oddly they were more likely to have family members with allergies. That's kind of weird, don't you think?

This sentence caught my attention: "No patient in the autism and 28% in control group had symptoms of respiratory allergy (wheezing or asthma) (p <0.005)." What if a person had respiratory allergy with no symptoms. Can that happen?

I have a pretty good reason to be wondering that. T has had a very strange history of weird breathing and respiratory issues, and yet he was never diagnosed with wheezing or asthma. Except once he was diagnosed with reactive airway disease, only to have that diagnosis sort of retracted shortly thereafter. Apparently reactive airway disease is what they call asthma in small children when they don't actually KNOW what it is. Or they think it's not "real" asthma. Or something. Anyhow, not long ago I had him randomly tested and discovered that he has a fairly serious allergy to dust mites, nearly to the "severe" level. But the point is, he's been hospitalized twice since he was born with weird respiratory issues, and twice someone heard wheezing. But nearly every time anyone thought they heard wheezing, several other people heard no wheezing. Only once did anyone decide he really WAS wheezing, and shortly thereafter, the wheezing was apparently gone. by the way, it was definitely only audible through a stethoscope and then only after careful listening. Actually, I'm not sure if it was really "wheezing." Maybe it was just "crackle." Whatever that was.

Now I'm pretty sure my son has a respiratory allergy. He doesn't breathe well, especially at night, and he's clearly allergic to dust mites, so ... But I wonder. If he had been in that study, would he have been diagnosed as having wheezing or asthma?

And something else I wonder about ... T almost never coughs, no matter how sick he is. The doctor seems surprised. When she gave us the inhaler, she told me to give it to him when he coughs. I told her he didn't, but she didn't really respond. I'm pretty sure she didn't believe me.

I worried about it. I called back. Could the autism mean that for some reason he doesn't cough when he needs to? what if he can't clear out his lungs? The doctor said don't worry. Coughing is the autonomic nervous system, totally involuntary, his autism isn't relevant. Hmm. Well, okay, I thought. But I wondered. Why does she think T's disorder doesn't affect his autonomic nervous system.

Since the day he was born T hasn't nursed right, swallowed right, slept right or pooped right. Those difficulties weren't exactly voluntary.

And so ... today I wonder for the 100th time if it's really true that there is no connection between the cough reflex and the autonomic nervous system on the one hand, and autism (or whatever) on the other.

What I found is href="http://cbc.ucsd.edu/pdf/Autism_Roy_Soc_01.pdf">this article by Hirstein et al. According to these folks (whoever they are), the autonomic nervous system would seem rather definitely involved in autism.

Actually, their first point is that there is reason to believe that the amygdala is involved in autism. I don't really know how that's related but I look it up anyway. Yep. Recent studies like the one described here seem to be producing a lot of reasons to suspect amygdala involvement in autism. I remember now that I already knew that.

What I didn't know is that the amygdala is related to the autonomic nervous system. At least, according to Hirstein et al., the amygdala "has what is thought to be an excitatory role in producing autonomic responses, such as pupil dilation, sweating of the palms and decreased gastric motility, via its connections with the lateral hypothalamus(Lang et al. 1964)." Well I don't know about that sweating of the palms business, but pupil dilation? decreased gastric motility?

These things sound familiar:

1. pupil dilation -- I think this has been a known connection for some time. I found this 2006 article: http://www2.ljworld.com/news/2006/sep/30/ku_research_links_autism_pupil_dilation/. But what I really remember is an article that came out just last year in which pupil response time had over 90% accuracy in discerning autism. This article discusses in more detail the claim that The Biomarker has finally been found.

gastric motility -- as in my son's chronic constipation? And as in "the gi connection," real or sort of real?

So where does this take me? I'm not sure. So I go back to that weird failure to cough.

Well, it appears that the cough reflex is stimulated by the vagus nerve. Hmmm. Is that related at all to the amygdala? Well, I did find this:

"University of Virginia psychologists have moved the science of memory forward, reporting that stimulating the vagus nerve, which carries sensory messages to and from the brain, releases the neurotransmitter norepinephrine into the amygdala, strengthening memory storage in limbic regions of the brain that regulate arousal, memory and feeling responses to emotionally laden stimuli."

And then I find an abstract to a 1991 article called "Relations among autonomic nerve dysfunction, oesophageal motility, and gastric emptying in gastro-oesophageal reflux disease", from I glean this: "Recent studies suggest that vagal nerve dysfunction may be important in the aetiology of gastro-oesophageal reflux disease. [Nyx Note: T was (tentatively) diagnosed with this as a newborn, the first time he was hospitalized with respiratory problems!] Delayed oesophageal transit and slowed gastric emptying [Nyx Note: er, constipation?] occur frequently and may also be of pathogenic importance. .... We conclude that in gastro-oesophageal reflux disease there is a high prevalence of parasympathetic nerve dysfunction which relates to delayed oesophageal transit and abnormal peristalsis [Nyx Note: isn't this lower gut motility?] and may therefore be of pathogenic importance."

Hmmm. I look up vagus nerve in Wikipedia. Isn't this tantalizing?:

"The vagus nerve supplies motor parasympathetic fibers to all the organs except the suprarenal (adrenal) glands, from the neck down to the second segment of the transverse colon. The vagus also controls a few skeletal muscles, namely:

Cricothyroid muscle
Levator veli palatini muscle
Salpingopharyngeus muscle
Palatoglossus muscle
Palatopharyngeus muscle
Superior, middle and inferior pharyngeal constrictors
Muscles of the larynx (speech).

"This means that the vagus nerve is responsible for such varied tasks as heart rate, gastrointestinal peristalsis, sweating, and quite a few muscle movements in the mouth, including speech (via the recurrent laryngeal nerve) and keeping the larynx open for breathing (via action of the posterior cricoarytenoid muscle, the only abductor of the vocal folds). It also has some afferent fibers that innervate the inner (canal) portion of the outer ear, via the Auricular branch (also known as Alderman's nerve) and part of the meninges. This explains why a person may cough when tickled on their ear (such as when trying to remove ear wax with a cotton swab)."

I also learn that vagal nerve stimulation is a treatment for epilepsy. Given the link between autim and seizures (well, and the fact that at least one doctor has speculated that T may have had seizures when he had his weird respiratory episdoes as an infant), that seems kind of interesting. Oh, my grandmother's brother had epilepsy too.

Where does this get me? I really have no idea. But now I google "vagus nerve autism." Turns out I'm not exactly a pioneer.

I find this: "Link between the Vagus Nerve, Cholinergic Deficit, Inflammation, Cognitive Deficits and Inattention: the Soul of the Gut – Brain Connection." A powerpoint presentation by Dr. James Jeffrey Bradstreet MD, MD(H) FAAFP (Director, ICDRC, Adjunct Professor, Pediatrics, Southwest College of Naturopathic Medicine). I wonder ... is this legitimate or ... you know ... quackish stuff?

It will have to wait because this is the point where I just have to go to bed.

PS -- well, naturally, I couldn't just go to bed. I had to at least skim the powerpoint. Holy cow, this guy actually seems to be advocating sticking a nicotine patch on young children! Well, I know nothing about it, so I'll reserve judgment. But ... wow. It seems a little ... hasty. Or something. If you look at his diagrams, you can see that it actually looks as though the vagus nerve does not connect to the eye, so I'm thinking it doesn't explain the pupil dilation effect, so I'm skeptical. Anyway, this looks a little too pat and neat. If it were really that simple, surely everyone else would have jumped on board by now. It just can't be this easy. And given how different different children are with ASDs, it seems a little ... dangerous, let's say ... to be posting general advice like this on the internet involving a serious drug that is a known toxin for off-label use! I don't like it.

1 comment:

  1. Nyx, I came across this post from January as I searched for terms like parasympathetic and autism (and also saw the presentation by Dr. Bradstreet in my searching). I agree that there is a connection between decreased parasympathetic activity and many of the collateral symptoms of autism. I've also seen it in my own medical history, as I was diagnosed with Asperger Syndrome in my late 30s, several years after my son who was diagnosed at age 7.

    Just to address the pupil dilation - you are right that there's no direct connection between the vagus nerve and the eyes. However, both nerves emerge from the brain stem and are part of the parasympathetic nervous system. The vagus is also called cranial nerve X and the oculomotor nerve is cranial nerve III. Maybe you addressed this in a later post; I haven't read further.
    In addition to nicotine, I found information on coffee stimulating vagal activity: http://jn.nutrition.org/cgi/content/full/127/7/1422. The idea of having young children on coffee (or caffeine) probably isn't much more appealing than having them on nicotine, but I thought I'd mention it because I noticed a decrease in GI and other symptoms when I began using both drugs as an adult (fortunately I quit smoking many years ago.)