Now, That’s What I Call High-Yield: Neurology, Part 2
- Jun 12, 2019
Neurology is such a grandiose subject on Step 1, so trimming down the plethora of material into only that which is high-yield is a necessity. But remember, what you see before you is just a place to start. It will point you in a particular direction to get the highest number of correct answers with putting in the least amount of work…pure efficiency. But don’t even think about stopping here. The more work you put in, the better your study plan, and most importantly, the more Question Bank questions you answer, the better your Step 1 score will be. It’s really that simple.
Visit part one of high-yield neurology for a good jumping off point, then feast your eyes on the high-yield material that you see below.
Ischemic Stroke and Hemorrhage
Ischemic Stroke and Hemorrhage (9) – As the 3rd leading cause of death in the US, strokes are at the epicenter of neurology. Your two main categories are ischemic and hemorrhagic. As expected, ischemic is caused by lack of oxygen in an area of the brain and hemorrhagic is secondary to bleeding. How does an area of the brain become ischemic? This can be due to an embolus that travels to a cerebral vessel, blocking blood flow; a thrombus forming from an atherosclerotic plaque; or a period of hypotension in an area without any oxygen reserve. Because blood flow is blocked by a clot, thrombolytic therapy provides the best chance of recovery. However, that can be devastating in a hemorrhagic stroke, as bleeding + blood thinning = catastrophic bleeding. Therefore, your first step is a head CT without contrast to rule out any bleed. Hemorrhagic strokes can be treated surgically or medically with blood pressure control and overall patient optimization.
Aphasia (8) – The linguistic pathway is as important as it is simple (for Step 1 purposes). Two main centers of the brain, connected by an anterior-posterior cortical pathway, are responsible for allowing us to comprehend and create language. In the temporal lobe, Wernicke’s area is responsible for language comprehension. Patients with lesions here can make and say words without issue, but the words that come out are nonsensical (Wernicke’s word salad). The arcuate fasciculus connects Wernicke’s area to Broca’s area, a section of eloquent cortex in the frontal lobe. An injury in Broca’s area doesn’t affect comprehension, but makes it very difficult for patients to get any words out. A lesion along the arcuate fasciculus can make word repetition difficult. These regions are found on the left side of the brain, and in the distribution of the middle cerebral artery (MCA).
Headaches (8) – As painful as they are prevalent, headaches can be debilitating in the afflicted. Keeping them compartmentalized into their 3 main varieties is the way to go. Tension headaches are your run-of-the-mill hatband distribution headaches. While their exact cause is elusive, they are related to muscular tension and stress, and usually respond to NSAIDs. Migraines are a bit more debilitating, and usually cause a throbbing on one side of the head. Often associated with other symptoms like photophobia and nausea, they can respond to triptans for abortive therapy. If they occur often enough, prophylactic therapy might be indicated with beta-blockers, tricyclic antidepressants, or antiepileptic drugs. Cluster headaches are the rarest of the 3, usually described as an ice pick behind the eyes. Like migraines, they are treated with triptans, but can also respond to 100% oxygen. As with any condition, if there are red flags (e.g., focal neurologic deficit, protracted duration, worst headache of life), a CT scan should be performed to rule out a bleed, stroke, or mass effect.
Neurodegenerative disorders (9) – This collection of diseases can wreak havoc on patients, as many have no great cure or management strategy. The most virulent is Creutzfeldt-Jakob disease, a rapidly progressive dementia with occasional myoclonus. Its claim to fame is being prion-driven. Alzheimer’s is quite common, and is marked by amyloid deposition and tau-proteins. Parkinson’s disease is marked by the classic triad of resting tremor, bradykinesia, and rigidity. The board loves this disease because of it’s eloquent anatomic tie-in. The dopaminergic neurons of the substantia nigra die off; therefore, we can treat the disease with dopamine analogues like levodopa. Huntington’s disease, a trinucleotide repeat disease (biochem tie-in!), is caused by atrophy of the basal ganglia. Chorea and mood changes are the symptoms you’ll most likely see.
Multiple Sclerosis (9) – Some important things you must know about MS. It’s a CNS disease, meaning you will see it affecting the brain and spinal cord, not the peripheral nervous system. When localizing the lesion, it’s useful to be able to rule out an entire subset of diseases simply by knowing which half of the nervous system is affected. The classic disease definition is multiple CNS lesions separated by time (separate presentations), and space (2+ distinct anatomical deficits). An MRI (brain or spinal cord) is necessary to visualize white matter lesions. Like most autoimmune diseases, flares are treated with IV steroids, and are kept at bay with immune therapies (e.g., interferon, glatiramer). One of the most common anatomic sites to suffer is the eye, with acute onset of optic neuritis, diplopia, nystagmus, or internuclear ophthalmoplegia (INO).
Brain Tumors (7.5) – The ability to differentiate brain tumors is something you need for Step 1 success. Most commonly you will come across glioblastoma multiforme (GBM), meningioma, and pituitary adenoma. GBM is the most aggressive, causing necrosis and hemorrhage as it eats away brain tissue. Very poor prognosis. A meningioma is much more “benign” in the sense that it’s not indiscriminately eating brain. It can be quite pathologic, however, as it compresses brain structures. Usually a well-circumscribed tumor occurring along the meninges, not in the brain parenchyma, surgery is often curative. Pituitary adenomas are testable because of both their systemic and mass effects. By compressing its neighbor, the optic chiasm, this tumor causes bitemporal hemianopia. In test questions, patients often describe “trouble changing lanes on the highway,” as peripheral vision is lost. Systemically, these tumors are usually secreting prolactin, causing menstruation and libido abnormalities, galactorrhea, and gynecomastia. Treat with surgery or Dopamine (Prolactin inhibitory factor) agonists like bromocriptine.
Upper vs. Lower motor neurons
Upper vs. Lower motor neurons (8.5) – It all comes back to localizing the lesion. Other than ALS, which affects both upper and lower motor neurons, disease processes should affect only one subset of motor neurons. For lower motor neurons, think decrease … decreased tone, decreased muscle bulk, and decreased reflexes. Think increase for upper motor neuron injuries. They cause spastic tone, hyperreflexia, and upgoing Babinski sign.
There are myriad more concepts in neurology to cover, but this will get you on a solid high-yield start. First build a foundation, then build upon it. Happy studying!
Looking for more high-yield Step 1 study? We have you covered: