Medical School 2020, Year 1, Week 30
Anatomy lab was less than 30 minutes: we removed with blunt dissection the posterior muscles around the vertebral column to prepare for next week’s laminectomy (removal of the vertebral laminae to expose the spinal cord)! We went over spine anatomy and common spine disorders such as a herniated (“slipped”) disk (the gelatinous nucleus pulposus part of the intervertebral disk herniates through the outer fibrocartilage annulus fibrosus) and spondylolisthesis (anterior or posterior displacement of a vertebra). We discussed how aging causes loss of the elastic dampening capabilities of the nucleus pulposus.
Lectures detailed two sensory systems, the anterolateral and medial lemniscal tracts. The anterolateral tract conveys tissue damage (pain), whereas the medial lemniscal tract conveys fine touch and proprioception (vibration and positional awareness). Sensing vibration requires extremely responsive transducer elements in the skin to convert rapid changes in pressure into electrical signals. All these tracts end in the postcentral gyrus in the cerebrum, which forms the sensory homunculus. The medial part receives sensory input from the lower extremity. The genitalia neurons are adjacent to the foot neurons, a potential explanation for why some humans have a foot fetish. The lateral part of the brain receives sensory input from the upper extremities.
Doctor J called the tallest student up to the front. He grabbed a measuring tape and asked the student to step on one end of it. He then measured all the way up his back to the end of his neck — 5’6. “This is the length of a single neuron in your body.” The whole class was amazed. Neurons that sense fine touch and proprioception travel from the big toe up to the spinal cord, ascend the spinal cord in large bundles, and finally synapse in the medulla (part of the brainstem). One cell.
Our patient case: Sherry, a 50-year-old overweight female accountant with uncontrolled diabetes presents to her primary care physician with a foot ulcer. During tax season she is so busy that she forgets to take care of herself. She has not refilled her medications, including metformin, for several months. A neuromuscular exam, specifically using a 256 Hz tuning fork to test for vibration sensitivity, reveals diminished sensory ability in both extremities. She explains that her foot has felt numb for weeks. A cut on the foot went unnoticed, and got infected.
Sherry suffers from diabetic peripheral neuropathy. Uncontrolled glucose levels lead to non-enzymatic glycosylation (adding sugar groups) of proteins,lipids, and nucleic acids. These advanced-glycosylated products (AGEs) interfere with normal function and activate inflammatory pathways. A familiar complication of diabetes is vascular (arteries and veins) damage, which leads to increased risk of atherosclerosis, heart attack, and stroke. This inflammation also damages neurons and their companion Schwann cells (cells that myelinate peripheral nervous system axons). The longest axons are affected first. The neurological deficits such as numbness, loss of pain sensation and balance difficulty start in the foot and travel up the leg. By mid-calf, the sensation loss also begins in the hands. Fifty percent of diabetics have peripheral neuropathy (eighty percent after 15 years). Interestingly, the physician mentioned that twenty percent of prediabetics have some sign of developing nerve damage, suggesting that vibration tests should be used as a screening tool for diabetes.
Sherry had trouble simply walking. As is common among laypeople, classmates associate diabetes with laziness: failure to exercise, overeating. This case prompted us to ask “How could someone exercise if they cannot walk?” The physician concluded, “It is critical for diabetics to check their feet daily. They might not even realize they have a cut or foot ulcer. The infection can spread to the bone requiring hospitalization and, too commonly, amputation.” He reminded us that diabetes is the leading cause of amputations [73,000 in 2010]. Sherry described her diabetic foot ulcer, now cured, as a wake-up call. She was discharged from the hospital three months ago and has been taking her medications regularly.
A diagnostic radiologist and an interventional radiologist led a lunch session about their respective specialities. Diagnostic radiologists complete 5 years of training: an internship year typically on general surgery followed by a 4-year radiology residency. Interventional radiologists conventionally would complete a separate 2-year interventional radiology (IR) fellowship, making for a total of 7 years of post-MD training. There are now direct IR residencies that take just 5-6 years.
IR is a subspecialty of radiology. Interventional Radiologists perform minimally-invasive procedures using imaging guidance such as x-ray and ultrasound. These procedures include: central line placement, endovascular (e.g., stents and thrombectomy of blood clots) procedures, radiation treatment, and bile duct obstruction procedures. Other specialities overlap with many of these. Indeed, there is sometimes tension what specialty group performs a given procedure at different health systems. For example, stents can be placed by IR or interventional cardiology; strokes can be treated by neurosurgery or IR.
The interventional radiologist explained why he chose IR: “I loved anatomy. And I like working with my hands doing procedures.” The diagnostic radiologist explained why she choose radiology: “I had the worst internal medicine rotation fourth-year. Day after day, I would have a patient die on me. The worst was a 30-year-old cystic fibrosis patient, the exact same age I was. I was so miserable I considered quitting medical school or not completing a residency. A radiologist lived upstairs of me and noticed how miserable I was. He suggested I shadow radiology. Never looked back.”
She described radiology as the “experts’ expert.” Clinicians increasingly rely on imaging procedures as opposed to physical examination skills. “Do not go into radiology if you cannot wield responsibility. You decide if someone in the ED goes to the OR or gets sent home.” We learned that radiologists are highly compensated, but also have a higher liability profile: “Every radiologist will be sued several times.”
What will the role of machine learning play in radiology? “Computers will not replace radiologists. They will just make radiologists much better at their jobs.” The diagnostic radiologist elaborated, “Computer algorithms in some areas are just as good as radiologists in identifying if something is wrong with a patient [high sensitivity]. However, computers are terrible at ruling out issues [low specificity].” I attended a neurosurgery informal dinner where I asked a similar question about radiology. The neurosurgeon was shocked by the radiologist’s response, and exclaimed, “Radiologists are terrible at ruling things out. Every report is littered with: ‘cannot rule out x, y, or z’. Give me a break, they will be replaced.” (See “A.I. Versus M.D.,” New Yorker, April 3, 2017.)
I’ve been working on a personal project in the evenings. My favorite trauma surgeon comes in most Wednesdays at noon to evaluate my progress. She tidies up my dissection then sends me on another mission that our class did not have time to explore during formal anatomy lab. Examples: Find the annular ligament of the radius, the ulnar nerve, or the anterior humeral circumflex arteries. One thing that makes medical school different is that an after-hours project may involve a dead body. In this case, I have a whole cadaver to myself, unlike in anatomy lab where we switch bodies every few months. The cadaver was a black 60-year-old, mildly overweight female. I have developed a deep sense of appreciation for this woman who donated her body so that I could pursue this upper extremity (arms) project focused on nerve and blood vessel anatomy.
One evening around 9:30 pm there was a knock on the locked door. I took off my soaked gloves and opened the door to find the head dean escorting a fundraiser group of dressed-up bankers and business people. They wanted to see the wet lab. I forgot how quickly one adjusts to the sight of cadavers in a formaldehyde-scented room. As I was there by myself, the whole head was uncovered and several chunks of removed fat lay exposed. A few people approached the body, but most were hesitant and stayed at least several feet away. I showed them the nerves and vessels of the arm.
A visitor asked about the purpose of cadavers. I explained that cadavers give unparalleled understanding of human anatomy. Textbooks cannot replicate this experience, especially the geometric relations of anatomical structures. An important part of the learning experience is discovering how the individual died and what diseases he or she lived with. I mentioned that one cadaver had a heart attack, prompting a question from a gentleman in his late 50s regarding what the heart looks like after a heart attack. I explained the cadaver suffered a heart attack in his left anterior descending (LAD) artery, as evidenced by a small, hardened discoloration on the surface of his left ventricle (see previous post). He did not die from the myocardial infarction because hardened scar tissue replaced the infarcted region. If he did die from the MI, the infarcted region would have the same firmness as the rest of the myocardium. The gentleman thanked me, took a peek at the cadaver and left. The next day the dean told me that the wet lab had been the guests’ favorite part of the event.
Statistics for the week… Study: 8 hours. Sleep: 6 hours/night; Fun: 1 nights. Example fun: Two classmates and I attended this year’s SonoSlam in Orlando, Florida. SonoSlam is an ultrasound competition among medical schools held on a Saturday by the American Institute of Ultrasound in Medicine (AIUM). My favorite part was using the most advanced ultrasound machines. Several of machines were controlled via iPads. One bluetooth-enabled ultrasound probe was only slightly larger than a smartphone and could be controlled via an iPhone app. The competition ended around 6:00 pm. As first-year students without the pathology training of the fourth years, we had low expectations for the competition and we did not exceed them. However, we celebrated our failure with post-competition drinks at a local brewery and “Cutthroat” at a nearby billiards parlor.
More: http://fifthchance.com/MedicalSchool2020
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