Three hour-long lectures on child development. A student commented, “Who knew that children are blind as a bat when they are born. 20/300 vision!” Afterwards, several instructors brought in children aged one month to five years for a workshop. Each pediatrician noted specific tasks, behaviors and skills. Dorothy Disinterested was reprimanded for “not being interested in the subject material and being on her cellphone”. Dorothy explained afterwards, “I am just not interested in children.”
Also three hour-long lectures on cerebrospinal fluid (CSF) circulation. The brain is surrounded by an outer connective tissue called the meninges (meningitis is the inflammation of this connective tissue) composed of three layers (outer to inner): dura, arachnoid, and pia. The dura, a fibrous white sheet, is strongly adhered to the inside of the skull and, via dura folds, divides the cranial cavity into quadrants. The falx cerebri divides the brain into left and right hemispheres. The tentorium cerebelli is a horizontal sheet that separates the cerebrum (above) from the cerebellum (below). These dural folds are tightly adhered to the arachnoid, named for its resemblance to a spider web, a clear membrane that wraps around the exterior surface of the brain. The innermost layer is the pia, another thin membrane, follows the contours of the brain into its crevices (sulci and fissures). The subarachnoid space, the space between the arachnoid covering and the tightly adhered pia, is filled with CSF.
CSF is produced in four connected brain cavities called ventricles. The left and right lateral ventricles connect to the third ventricle through a thin constriction called the interventricular foramen of Monro. The third ventricle drains through a narrow constriction called the Aqueduct of Sylvius into the fourth ventricle of the brainstem. CSF exits the fourth ventricle into the subarachnoid space through three foramina (the two lateral Foramina of Luschka and the medial foramen of Magendie). Students appreciated that the early 19th-century anatomists who discovered these respective structures have last names whose first letters correspond to the structures’ anatomical positions: Francois Magendie for medial; Hubert von Luschka for lateral.
The CSF suspends the brain in fluid, thereby protecting the delicate tissue structure from small shocks and providing a buoyancy effect, which turns a 1500-gram brain into 25 grams. Without the buoyancy effect, the weight of the brain would crush itself. Each ventricle contains a choroid plexus where 500mL CSF, enough for four complete daily changes, is produced by ependymal cells. CSF circulates through the ventricles, draining metabolic waste products of neurological activity, such as glutamate (excitatory neurotransmitter) and potassium, into the subarachnoid space.
My favorite trauma surgeon explained the different types of hemorrhages. Blunt trauma can fracture the skull causing an epidural hemorrhage, rupture of the meningeal arteries that travel along the inside surface skull. After a car crash, the patient will go unconscious. They will then wake up for a “lucid interval” of roughly 30 minutes, then suddenly go unconscious again as the ruptured meningeal artery leaks into the brain. A subdural hemorrhage typically occurs in old age. The brain shrinks, which stretches the small veins that drain blood from the brain to the large venous sinuses in the dura. Slight trauma can then cause the veins to rupture, starting a slow bleed that brings the patient into the ED days or weeks later with headache and confusion. Both types of hemorrhages can result in sufficient elevation of pressure to cause herniation of the brain, in which parts of the cortex protrude through holes in the skull.
Our patient case: Greg, a 23-year-old male with Mike, his cardiologist father and Jennifer, his nurse mother. Jennifer’s pregnancy was completely normal until a 30-week ultrasound. The obstetrician noted an enlarged skull with a protrusion on the right side. The mother explained, “My OB told me, ‘Something came up on the ultrasound that we need to take another look at.’ I knew something was wrong. Whenever a physician sees something bad that they have to refer you out to a specialist, they refuse to tell you a definitive answer..” Jennifer waited several hours in the waiting room until the specialist could see her. “I did not want to call Mike because he was dealing with a tough heart case.”
Further ultrasound examination confirmed that Greg’s Aqueduct of Sylvius had narrowed, causing hydrocephalus (abnormal accumulation of CSF). The choroid plexus continues to produce CSF despite the increasing ventricular pressure in his lateral and third ventricles. The increased ventricular pressure and size was damaging developing brain tissue and preventing the skull from closing. The physicians told Mike and Jennifer that Greg would unlikely be able to survive and that, if he did, he would have severe cognitive deficits.
“We knew this was bad,” continued Jennifer. “We both have medical backgrounds so we were imagining the worse. Mike immediately became an expert on this condition. Keep in mind in those days Google was not around. Mike went to medical libraries to scour the limited literature on this condition and its outcomes. Our doctors recommended we terminate the pregnancy. But when I saw the ultrasound, I could not terminate. He was my boy.” Jennifer was immediately scheduled for a cesarean section. Greg was whisked away to the NICU for intensive treatment. He had a ventriculoperitoneal shunt (tube inserted through brain tissue into a ventricle to drain CSF into the peritoneal cavity) and several cranial skull surgeries to release the increased intracranial pressure.
Greg is 5’5 with a cheerful smile. He speaks slowly but carefully. “More articulate than some of our classmates,” commented one student afterwards. He chuckles after his jokes. He has terrible vision as a consequence of visual cortex damage.
Most of Greg’s medical care occurred in his infancy. He had two additional surgeries to restructure his skull at age 8 and 14. He lives with his parents and works part-time as a clerk at a local grocery store. His mother said that Greg’s social life is more active than their own: “There are all these support groups for disabled people. I feel like every week I am ferrying him to an event downtown.” He is intellectually disabled but has an encyclopedic knowledge of the Harry Potter books. Several female classmates tested his knowledge after the session.
One week before exams and Pinterest Penelope, our class social chair, released the results of “class superlatives”, one per student. One student complained about the distraction from studying: “She is just trying to sabotage us.” I received, “Most likely to ask Low Yield Questions in Lecture”. Type-A Anita got, “Most Likely to Complain About Said Low Yield Question Asker”. Our lone Canadian (we have no other foreign students) got “Most likely to curse in front of a patient.” Our class president received, “Most likely to use ‘I’m a Doctor’ line at the bar”. The shy Asian received, “Most likely to ruin his/her white coat and need to order another”. Dorothy Disinterested apparently does have at least some interests. She received “Most likely to hook-up with a patient” (as the social chair is also female, this did not generate any complaints to the deans).
Statistics for the week… Study: 20 hours. Sleep: 7 hours/night; Fun: 1 day. Example fun: a “finisher prize” for the last day of class, beer and burgers with four classmates.
This reminds me of the post where the test pilot had a career-ending concussion. So sad.