This is a Long Post

Some days, I have about three topics to write about in my head. Usually, I pick just one, but today I think I'll write about two.

By about the third week of a clerkship, you get this "mini-"cold that exists just to make you miserable. It's not bad enough to make you want to stay home, but it's bad enough to make being on the wards uncomfortable. (Especially on psychiatry where there are no tissues in sight, and truly no alcohol gel. Well, okay, there is in the locked break room.) The cold is a warning about just how much effort you are expending. While the hours are long, it's difficult to communicate how hard functioning on a clerkship is: your brain is working on multiple levels at the same time. For instance, you're trying to ask your patient the appropriate questions. You're trying to remember what they say. You're trying to select the appropriate physical exam. You're trying to remember your findings. You're trying to synthesize your findings. You're trying to answer your preceptor's questions. You're trying to be "well-groomed" (and not spill chicken juice on yourself...yes, I bought a new coat but still haven't thrown the old one out). You're trying to be amiable. And competent. And responsible. And helpful. And not pass-out from dehydration because no one ever eats, drinks, pees, or sleeps in medicine. And you're trying to join the "tribe." There is such a tribal nature to medicine. Alright, so poor me. I guess the point is that you're exhausted, but nowhere does that come into more focus than during the Basic Science block, where before you were up at 4 AM to iron your clothes and pre-round before 6:15, now getting up for an 8:30 lecture is a super chore.

Which brings me to my second topic: autism. I really didn't want to wake up this morning. In fact, I had food poisoning yesterday. (Bad tempura...although I had a brief moment of horror when I considered the cookies. And this was originally topic three - wow, do people with inflammatory bowel disease, i.e. your Crohn's Disease and your Ulcerative Colitis patients, ever have it hard!) But I'm glad I went this morning.

The lecturer was a very thin, older woman with an entire bottle of foundation on her face and a bad orange dye job. She looked like a cartoon character that I am unable to remember. She appeared nervous at first, and had a slight tremor and possibly some vasospasm/Raynaud's syndrome in her hands. She seemed nervous and regimented at first, but then it made sense that she was simply that older generation of female scientist that you don't seem much of these days. The really serious but freakishly successful types. In any event, she begins by stating that we know more about autism than we do the other psychiatric conditions, schizophrenia for instance. Interesting premise.

And she begins to talk about some Scandinavian data that can pinpoint the exact timing of the environmental insult that led to autism to the day. In other words, mothers who took thalidomide (that famous anti-morning sickness drug that caused massive birth defects) or valproic acid (an anti-seizure medication whose brand name is Depakote) at around 24 days gestation had babies who were later diagnosed with autism. And this is where it gets really interesting. At 24 days gestation, any medical student can tell you that the embryo has no brain. All it has is a long tube, the neural tube, which will become the spinal cord and close at both ends. The "caudal" or head end will close and then expand to become the brain at around days 25-28 of gestation. The "rostral" or tail end will also close, and is important because if mom lacks folic acid at days 25-28 wil not close and the baby will have some variant of spina bifida. At day 24, then, the embryo has no brain. Yet, she pointed out that the embryo does have a few neurons, namely those that will become cranial nerves VI and VII.

A brief digression: there are 12 cranial nerves that you struggle to learn in your first year. Eventually, once you get past the point where your professors care whether this one is a general visceral efferent and this one is a special visceral efferent, they become easy to master. They control everything from your eye movements, to tongue movements, to the muscles that chew, to your senses of taste, smell, sight, touch, hearing, and balance. Cranial nerve VI, the abducens nerve, controls sideways eye movement, such that the eyeball is pulled horizontally away from the nose. Cranial nerve VII, the facial nerve, does a lot of things: it controls the muscles of facial expression, it causes lacrimation, it pulls the eyelids down, and it conveys taste from the front 2/3 of the tongue.

I've often noticed that the kids I know with autism have rather flat facies (medical term for face), meaning that there's a "funniness" or "fuzziness" about the nose. In fact, this is known as Moebius syndrome (which may or may not be associated with autism) and it is caused by poorly-developed VI and VIIth cranial nerves. The muscles of facial expression are essentially paralyzed. So, if an insult occurs around day 24 of gestation that leads to autism, it will likely damage the developing VI and VIIth nerves, leading to a paucity of facial expression (as well as taste and the phenomenon of "crocodile tears" - crying when you smell food). This was such a satisfying explanation for why some kids with autism look the way they do.

And then there are all sorts of questions...do kids with autism have trouble with social interaction because their inability to produce facial expressions limits their abilities to interact and bond with others, and hence their socialization centers fail to develop? Or does the initial insult at day 24 also affect larger association cortex development, such that the whole brain, even though it hasn't formed yet, is affected? In other words, are the developing cranial nerves VI and VII scaffolds on which the rest of the neurons grow, so that damage to them leads to abnormal brain development all around?

I could go on about this lecture, and some other interesting points about autism (how it appears to be a phenomenon of genomic imprinting, how incredibly good this woman's data was and how freakishly lucky she was to have so many experiments work), but I'll end there.