Sunday, June 12, 2016

WILTIMS #500-501: Happy Un-anniversary! (Un-niversary?)

This is my 500th What I Learned Today In Med School post! Yay! Well... actually this is only my 372nd post, because of all of my lazy, multi-day catch-up posts (like this one).

Ok, but it's my 500th WILTIMS fact! Woohoo! Um... not quite. I've actually posted way more than 500 facts because some days are just too interesting (like Thursday).

How about it's the end of third year?! Now that's a reeeeal stretch. I have a week left of normal clerkship days then a shelf exam next Friday. And thanks to board exams and whatnot, fourth year really won't start for months.

If anything this is a perfect example of how, if you choose a career in medicine, the milestones along the way are very arbitrary. Right now on our campus, because the various academic calendars don't line up, there are two second-year classes and one third-year class, but no first- or fourth-years. Our newly-grads are now technically doctors, but they're not board certified to practice anything yet and won't be for years.

But this is the way it should be. There are lots of blurry lines as large teams of practitioners add and lose members. Everyone is always growing and moving on to new, but similar things. We are never done. In fact the end goal is just to keep learning, to keep practicing medicine.

ThursdayIL: If a significant neck injury requires it, fusing the base of the skull to the top of the spine (occiput to C1 fusion (or the far cooler sounding: atlanto-occipital assimilation)) will protect the spine but lock the patient's head at a certain angle and orientation. You've got to be very careful where you point the head during that surgery, or the patient will always be looking at the sky or their feet or sliiiiightly of the the left.

The three most common groups who get spinal cord injuries are:
1) 16-25 year old males who get into motor vehicle accidents
2) >65 year old people who fall
3) Gunshot wound victims from urban centers

FridayIL: The common fibular (aka peroneal) nerve is very bulky right around where it splits into the deep and superficial fibular nerves. Unfortunately this spit often happens right over the head of the fibula. If this area gets injured or inflamed it can pinch off that nerve causing pain, numbness and weakness. To alleviate the pressure, you cut the connective tissue along the nerves in both directions. But that knot at the bifurcation is still sitting on that bone. So what you can do is divide the nerve all the way up the leg. Since all the nerve fibers are running parallel, nothing is damaged. It's actually exactly like when your old headphones are a little too restrictive, so you pull the two wires further apart. No harm, no foul.

Thanks for reading! Here's to the next 500! Wait... that would put me most of the way through residency... hmmm...

Thursday, June 9, 2016

WILTIMS #499: A surgery revisited

Image from Kbik at English Wikipedia
Back in my surgery clerkship I spent an unusually long 3-weeks on the vascular surgery team. One of the bread-and-butter surgeries that the vascular folk do is create AV fistulas for patients starting chronic dialysis. An arteriovenous (AV) fistula is an artificial connection between an artery and vein, usually in the arm, that allows for the higher blood pressure of an artery to inflate a low-pressure vein. Dialysis machines require a high rate of blood extraction in order for the treatment time to be a brisk 3-4 hours instead of all day. That means you either need to pull from a very large, strong vein (requiring a surgical procedure to place an infection-prone catheter) or divert arterial pressures into smaller, weaker veins (if you pull too hard on small veins, they simply collapse).*

One of the potential problems of having an AV fistula placed is that, once you divert all that blood to the veins, it bypasses the lower arm and hand. If the hand doesn't get enough blood it can become painfully ischemic (starved of nutrients). This phenomenon is called "steal," as in the vein stealing the blood from the arteries that go to the hand. Steal is very easy to diagnose: pinch off the AV fistula and the hand will almost immediately feel better. Fixing it requires more work; you have to do a revision surgery ASAP.

YesterdayIL: When the hand/arm loses blood flow like that, it hurts, but why it hurts can be complicated. The tissue is essentially suffocating and it tells the hand/arm nerves to tell your brain to change something. When you return flow it usually gets better. But if the steal was too great, or left too long, or the nerves were already damaged from prior disease like diabetes, then the nerves themselves can suffocate. But nerves heal slowly, if they heal at all. This pain doesn't go away right after the blood flow is returned and may even be permanent.

Another nerve pain problem with AV fistulas can happen if a nerve is compressed by the anatomical changes from the surgery or post-op inflammation. This pain, however, should only affect whichever nerve is being pinch, not the whole limb.

*The reason you can't just use arteries is that they are complicated with nerves and muscles that give them thick walls and make them very painful to access. Veins are just thin stretchy tubes.

Tuesday, June 7, 2016

WILTIMS #498: O.o

TIL: Parinaud's syndrome is a weird collection of neurological eye exam findings usually caused by a tumor in the pineal or midbrain regions of the brain. The most prominent symptom is the inability to look up. The eyes can still move up, but the patient can't look up voluntarily. This can be demonstrated with a "doll's head test" where you have the patient relax looking straight ahead when you suddenly rotate their head forward. Another part of the brain controls this reflex, so the eyes will roll up in their sockets just like a doll's, before reverting. If one of the eyes is more affected than the other, then the patient may have double vision from one eye being stuck lower than the other.

Image from here
The next sign of Parinaud's has a fun name: pseudo-Argyll Robertson pupils. This is when the pupils are dilated (the black of the eyes is larger than normal) and they won't constrict when you point light at them. You can still make them constrict though if you use a trick. When you look way off in the distance, your pupils dilate a little; when you look at an object really close to your face (like your nose), the pupils constrict a bit. This reflex should be preserved in patients with Parinaud's syndrome. Again, if one eye is more affected than the other then the pupils may be different sizes at rest.
Then we have a whole bunch of related problems with moving the eyes in unison. These patients have a problem when you have them rapidly look at an object close or far away from them. Normally, you want both eyes to move in unison and stop at the precise spot to properly focus on an object. When that doesn't happen (e.g. one eye moves faster than the other, or overshoots the target, or stutters to the spot rather than moving smoothly), the patient will experience temporary double vision. Often these patients will have a particularly weird problem called convergence retraction nystagmus, where the eyes will retract into the socket when you have them look at their nose. This is because the ocular nerve is getting confused and instead of using some of the eye muscles to look in a direction, it contracts all of them. This pulls the eyes inward. See the GIF for an example!

Image from here
Lastly we have Collier's sign, marked by bilateral upper eyelid retraction. This makes the patient look a little "bug-eyed," but specifically results in an uneven amount of white above the irises. For an example, take a gander at this fantastically mustachioed man on the left. He has white visible above the irises of the eyes; for comparison, see that neither of the persons pictured above have white visible there. If patients with Collier's sign could look up (which they usually can't, as per exam finding #1, above) the eyelid would match the movement of the pupil and recede even further up.

Monday, June 6, 2016

WILTIMS #496-7: Ohhh myyy-a!

FridayIL: The only place in the body where an artery empties into a larger vessel is at the junction where the vertebral arteries become the larger basilar artery. To get an idea of how weird this is it would be like two branches of a tree growing into each other to form a single bigger branch.

The only purely visual manifestation of an increased intracranial pressure due to hydrocephalus (too much cerebrospinal fluid in the head) is an increase in the area of the blind spot that everyone has in their eyes. This normal blind spot is caused by retina having a hole in it where the optic nerve enters the eye. If you have too much fluid/pressure, this hole can stretch wider. This symptom would be great for speeding up diagnosis, but it's very hard to notice or test. Do you notice your blind spots now? Would you notice if they doubled in size? Probably not.

Monday: Today I switched over to the consult team. Much like my two elective rotations in pulmonology and nephrology, on this service, the patients' primary problems are not neurological, but the primary team wants us to take a look for some reason. Compared to my previous neuro teams, the patients in this group are far more diverse in presentation (and interesting, imho). Whereas on epilepsy all the patients were being worked up for some form of seizures, and on the stroke team we saw variations on stroke, consults could be anyone in the hospital with any vaguely neurological complaint. One guy was shot in a gunfight, another had a heart attack, one fell and broke her leg, and someone else had muscle breakdown after a likely overdose. Sometimes our team's involvement is extensive, other times it's very brief. The consult for the lady who fell and broke her leg simply asked if we thought anything neurological could explain the fall. We're pretty darn sure that this was blood pressure related, not neurological, so we write a note to that effect for the primary team, and we probably won't see that patient again on this admission.

An ommaya reservoir
MondayIL: {This fact is very boring; feel free to skip below.}You can differentiate between a sciatic nerve injury and sacral plexus/spinal nerve root injury by testing the gluteus medius muscle. The leg nerves and all the gluteal nerves come through the same roots and nerve plexus, but the superior gluteal nerve which innervates the gluteus medius muscle breaks off from the rest after the sacral plexus but before the consolidation of the sciatic nerve. So if a patient has leg weakness and has difficulty abducting the leg (lifting it to the side) the injury is likely proximal to the start of the sciatic nerve.

An ommaya reservoir is a port that gives you access to the cerebral spinal fluid within the brain. It can be used to remove fluid just like a lumbar puncture (aka spinal tap) or to administer chemotherapy for a brain tumor in or around the ventricles of the brain. Patients with one of these have a little plastic bubble on or under their scalp that connects with a tube to the space in the middle of their brain. Trippy.

For people with a congenital valgus leg deformity ("knock-knees"), having a knee replacement surgery can cause nerve injury. The peroneal nerve normally runs very close to the head of the fibula, but in valgus people, there is often more space between these structures. A knee replacement surgery will fix the angle of the leg and put normal pressure back on the nerve. But as the nerve in one of these patients isn't used to that pressure, it reacts like it's being pinched, causing numbness and/or weakness.

Thursday, June 2, 2016

WILTIMS #495: The Beatle-CT Connection

Today we had an optional lecture near the end of the day that was meant for the senior residents and was way, way over the heads of med students like myself. One classmate and I decided to go anyways (since we had to be in that room after the lecture anyway) and we ended up getting a little heart-to-heart time with a neuroradiologist. He told me a story that I could barely believe and knew I'd have to fact check before sharing with anyone. Turns out it was totally true!

TIL: Sir Godfrey Hounsfield, the Nobel Prize-winning inventor of the CT scanner, funded his first prototype with the EMI record company's profits from the Beatles. Here's a quote from this 2005 In Memorium post in the journal Radiology:
"EMI, at that time, were concerned principally with the manufacture of records and electronic components and had no experience of radiological equipment. The Beatles, who recorded under the EMI label provided the most significant financial input to the company. The Department of Health and Social Security (DHHS)—as it was then—was approached by Hounsfield and radiologists James Ambrose and Louis Kreel and with commendable foresight agreed to support, with EMI, the development of a head scanner. Hounsfield and a small team were installed in the radiological department of the Atkinson Morley’s Hospital in Wimbledon—a location chosen to avoid wide spread publicity in the development phase. The Consultant Radiologist, James Ambrose, provided clinical advice and conducted the first clinical trials on a prototype EMI head scanner (Mark I) in 1972. The first clinical image of a patient with a suspected brain lesion revealed the presence and location of a cystic tumour."

Wednesday, June 1, 2016

WILTIMS #494: Lies, LIES!

We had an interesting case today where a patient had certain symptoms but was probably lying about or at least embellishing his/her symptoms. The amazing part was that my attending called it after listening to me present the patient for about 30 seconds. I was shocked, because I had totally believed the patient and this doctor hadn't even seen him! What I had described as the patient's story just didn't make sense from a physiologic perspective. I tried to withhold judgement until the attending actually saw the patient. Once he did, it only took a few insider-knowledge tricks and almost immediately he had secretly exposed to the resident and I that the patient was lying.

One of the tell-tale signs was simply biological. People with a brain injury usually display slow eye movements. Normal people's eyes (and this patient's) dart around as they think. It's actually nearly impossible to smoothly move your eyes voluntarily if you aren't tracking an object. Try it! Keeping your head still, follow your own finger as you slowly point from left to right and back. Now try to do that same smooth eye movement without a finger to follow. It's really easy to see when someone else tries this in front of you, but you should still be able to feel that you're eyes are jerking across the path.

This other trick was not biological, but psychological. The patient answered several questions wrong, but always nearly right. If someone does this enough times it shows that they must know the right answer and are trying to be just the right amount of wrong. When people really don't know it's random and sometimes they're right, sometimes they're close, and sometimes they're totally wrong.

TIL: Vasculitides (autoimmune inflammatory diseases of blood vessels) that affect the brain are very often associated with headaches. But the brain has no pain sensation, so what is actually hurting? Well, while the fat and nerves of the brain itself don't feel pain, but the large blood vessels of the brain do and that's what is damaged in these diseases. Specifically, the arteries feel pain up to about an inch out from the Circle of Willis and the veins feel pain when they are of a similar size to the arteries, though the anatomic locations are harder to describe.

There are two modifiable predisposing factors for multiple sclerosis: smoking and vitamin D deficiency.