Saturday, October 30, 2010

Amnesia, herniation, and how the heck a speech bulb works

For Crowscalling, Celeste, and Bonnie (was it Bonnie? Ah, yes. Bonnie.) (And why do I read "Crowscalling" as "Crowsculling"? It gives me a charming mental picture of a whole eight of crows pulling vigorously at oars as a sparrow coxswain gives it to 'em.) (But enough about my Lortab frenzies.)

Bonnie asks, What the heck is a herniated brain, anyhow?

And I resist the temptation to reply, A brain that's not working very well any more.

Although that's basically it. Herniation is a condition where your brain gets squooshed out of position by increased intracranial pressure. A lot of things can cause that increase in ICP: stroke, tumor, hemorrhage, blunt injury, you name it. Some of those things can be stopped easily before the brain squooshes too far; others are trickier to fix.

There are actually six different ways your brain can squoosh inconveniently. Those ways are divided into two groups: the supratentorial and the infratentorial. The name "-tentorial" comes from an anatomical landmark; what you need to know is that there are four ways of squooshing the brain up high and two of squooshing it down low. And, you know, that it's...deadly, unless you stop it and fix it.

Herniation is thankfully pretty rare. Your brain can take a lot before it moves so far to one side or the other, or downward or upward, that structures actually get crushed and torn and you die. Plus, a lot of things happen *prior* to things getting to that point that clue the average observer in that Things Aren't Right. That's not to say that herniation doesn't happen suddenly--it can, and I've seen it--but thankfully, that's not all that common.

Now, on to Celeste's question, which is something along the lines of What up with all the amnesiacs in the daytime soaps, yo? Wouldn't all these people be running around with severe neurological injuries if they had amnesia this often in real life?

Celeste has, as we say in the business, hit it on the head. Amnesia is indeed very rare and is accompanied either by a pretty complex neurological injury (some strokes can do it, to varying degrees) or by a physiological and psychological disorder called "conversion disorder".

Now, this doesn't mean that people with amnesia are either completely gorked or crazy. I would point you to Oliver Sacks, who writes interesting stories about patients of his who had perfectly intact distant memories, but who couldn't form new ones. That's a type of amnesia. There are other types that wipe out middle-range memory or even old memories. It all depends on what hits your brain where. Thankfully--again--this is really rare, partly because the brain is amazingly tough, and partly because we have all these neat redundant systems built into it.

Conversion disorder is a little trickier. It's something that's normally dealt with by both psychiatrists and neurologists, because there are components of the syndrome that have to be handled in different ways. Horribly oversimplified, conversion disorder is the body's response to extreme stress. You get sick in one way or another, or have a traumatic event happen, and as you're coming out of it, you suddenly start getting sicker in weirder ways than anybody ever thought possible.

This is not malingering, and the people with CD aren't crazy. It's not something like Munchausen, where the person is actively trying to make himself sick. Instead, the protective functions of the brain and body kick in overactively in an attempt to protect the person. (Amnesia is considered one of the rarest manifestations of CD; I've seen it exactly once.) When it starts to happen, it's frightening and often more debilitating than the original insult to the person was.

And finally, to Crowscalling's question: How the heck is that speech-bulb thingy supposed to function?

To answer that question, I'm going to have to share with you some of the crash course in oral and oropharyngeal anatomy I've gotten in the last few weeks.

Look at your mouth. Now look at mine. Now back to your...shit, sorry. I turned over two pages at once.

Okay. Look at your mouth. You see how you've got a nice bony palate in the front and a nice flexible one in the back? Those help you make specific consonant sounds, like "K" and "L" and "M" and even "S" and "B". You'd be surprised how much happens at the back of your throat when you talk.

When you lose that nice flexible dome-shaped soft palate and/or the structures that make up the back of your throat, two things happen: First, you can't say "B" (comes out more like "M") or any number of other things. And, you sound like Fran Drescher gone crazy, because there's so much air escaping through your nose. "Hypernasality" is how they describe it formally; that's sort of like calling the ocean "moist".

A speech bulb is something about the size and shape of...oh, heck, I dunno...a chicken drummette, like you'd get in a wings bucket? Or maybe the first joint of your thumb? Anyway, it's not huge, but it's not petite. It's job is to sit up in the back of your throat and cover any holes there, and also cover any holes in your soft palate. That way you can sound almost completely normal right away. It moves the airflow from your sinuses to out of your piehole, and it gives your tongue and throat something to press and move against to form words.

You wouldn't think a little chunk of plastic would do all that, but it is AMAZING.

(Which makes me wonder: If I spoke French, or German, or, Frog help me, Danish with all its back-of-the-throat Rs and stuff, would my speech bulb be shaped differently? Must remember to ask Dr. DDS.)

And thus endeth the latest edition of You Ask, I'll Oversimplify! Further questions--on any topic, not just neuroscience or speech bulbs or my current favorite toenail polish--are welcome in the comments.

15 comments:

AM said...

You are so interesting. Your blog is shining monument to sharp writing and good grammar. Really, I love reading about the neuro stuff. Thanks for writing it.

Jenn Jilks said...

Nice job!

Silliyak said...

ditto

Celeste said...

Thanks for the response, Jo. I learned sumpin'.

Brian said...

So um, I've been lurking on your site for a LONG time now and really enjoy your writing. I'm sending good thoughts your way with the recovery and stuff. So anyway, you invited any questions so here is mine. I start Nursing school on Jan 5th. I've already decided that I don't think I'll stop at my BSN but my path is forking a little bit here. Background: I had a heart transplant in 2007 and because of this plan on trying to steer my Nursing to Anesthesia to avoid the whole ED scene and getting coughed on alot etc... So, I'll finish my BSN in 18 months and then have to choose between going for CRNA or AA. I'm assuming you know what an AA is but if not, it's essentially a CRNA but without the RN first. So, to get into CRNA school requires 1 year of Critical Care first before even being able to apply, and to get into AA school will require nearly that much additional chem and physics that I don't need for my BSN. My question is this, how often do you see new nurse grads getting placed into SICU, or CVICU or XXICU? Does med/surg count as critical care? The 7 AA programs in the US don't require previous critical care experience, only a heavy science course background. So, how likely do you think it is I'll be able to get into Critical Care out of the starting gate? Should I tell my new employer I've had a heart transplant? In your opinion of course. Would you?
Thanks,
Brian

Jo said...

Hiya, Brian! I can answer your questions pretty quickly:

1. No, med-surg does not count as critical care--they're two different specialties.

2. I see new grads hired into critical care *all the time*. Most places, I think, like to hire new nurses and train 'em the way they want 'em.

3. You'll increase your chances of getting hired into a CCU by working an externship during your last year of school, or working outside of school (if you can) on a CCU as a patient care tech.

4. I would definitely tell a new employer about a past heart transplant. It would affect your ability to take care of people who are ragingly immunocompromised--you'd have to take extra precautions--so it would make a difference in care, though it shouldn't in hiring.

Anonymous said...

So re. conversion disorders (fascinating stuff) - how do you know it's a conversion disorder as opposed to some other physical disorder? For example, how do you tell a real seizure from a pseudo-seizure (unless you're lucky enough to have an EEG on the patient's head)? Are there some sort of features that show it's a real seizure (unresponsiveness to pain, type of movements, ???) ?

Jo said...

Anon: With conversion disorder, the physical exam doesn't match up with the deficits the patient is experiencing. Unlike somebody who's faking, the symptoms don't change, the deficits don't move around--nothing like that. What you get is an exam that is perfectly consistent but which can't explain the problems you're seeing.

The seizures you'd see with conversion disorder *look* real--and they are real, they're just arising from a different part of the brain that an epileptic seizure. You won't see a post-ictal phase, for instance, and the seizures tend to come on much more slowly and last longer.

There are commonalities that distinguish epileptic seizures, too, in terms of eye movement, tonicity of muscles, and head movement.

JannieCPH said...

Wauw Jo. You must be great with the students at your job. I wish I had your way of making complex stuff so understandable.

And about your vocalskills: how about giving the classic Danish tonguetwister " rødgrød med fløde" a try and let us know how it works out :-)

Jo said...

Jannie, I realized as I was typing this post that I will probably never again be able to order red berry pudding with cream.

You have no idea how that fills me with despair. ;-)

Bonnie said...

Sooo...herniation = brain fall down go boom?

Jo said...

Bonnie: Or squish up go yi yi yi yi yi, or slop sideways go herk bleh, or scrunch diagonally go GLORP.

It's very important to get the sound effects in there when you're describing the situation to the doctor.

JannieCPH said...

I feel your despair Jo. Red berry pudding is a must, come summertime in Denmark.

But cudos for even understandingen our weird potato-in-mouth language :-).

simon said...

so glad to see you writing and teaching. How about head positioning after CVA, either hemorrhagic or embolic. I remember years ago you touched briefly upon this topic.

Urbie said...

Heck with the speech bulb -- what you need is a speech *balloon*, that pops up above your head whenever you want to say something. That'll fix the problem right there!

Urb