USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 74-year-old man is brought in by ambulance alone to the emergency department. He has a past history of mild vascular dementia. After examination, it is determined that he needs an emergent procedure. Which of the following is necessary to invoke implied consent in an emergent situation?
OK, let’s start with some basic brain anatomy. The brain has a few regions - the most obvious is the cerebrum, which is divided into two cerebral hemispheres, each of which is divided into four lobes: the frontal, parietal, temporal, and occipital lobe.
The frontal lobe controls movement, and our personalities, it also handles our ability to count and spell, and make decisions.
The parietal lobe processes sensory information, which lets us locate exactly where we are physically and guides movements in a three dimensional space.
Finally there’s the occipital lobe which is primarily responsible for processing visual information.
All the cells in the body need oxygen - and that’s particularly relevant for neurons, which can only function in aerobic conditions, meaning with constant supply of oxygen.
Neurons also don’t have long term energy stores, so they need a constant supply of glucose to keep working.
Once they reach the base of the brain, these arteries join to form a ring, called the circle of Willis, which then branches off into smaller and smaller arteries, the smallest being the perforating arteries, that eventually supply the entire brain with oxygen and glucose.
That’s when there’s a buildup of plaque that thickens and hardens the artery wall.
Sometimes, small parts of the plaques can break away and these bits can drift up towards the brain, and can then eventually block a smaller artery, completely stopping the blood supply to the part of the brain that’s supplied by that artery.
Other times, the tiny perforating arteries are affected by atherosclerosis and can get completely blocked off by plaque growing within them.
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- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "Management of Behavioral and Psychological Symptoms of Dementia" Noro Psikiyatri Arsivi (2014)
- "Distinguishing Alzheimer’s disease from other major forms of dementia" Expert Review of Neurotherapeutics (2011)
- "Comparison of Different Diagnostic Criteria for Vascular Dementia (ADDTC, DSM-IV, ICD-10, NINDS-AIREN)" Stroke (1996)