USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 72-year-old man comes to the emergency department because he has been unable to move or feel the right half of his face and body for the past hour. He states that he was yelling at another driver in rush hour traffic when the symptoms suddenly onset. His medical history includes long-term uncontrolled hypertension. His temperature is 37.0°C (98.6°F), pulse is 52/min, respirations are 16/min, and blood pressure is 174/106 mm Hg. Physical examination shows hemiparalysis and sensory loss of the right half of his body. Though he has articulation deficits, his speech is fluent and comprehension is intact. Visual fields are intact and he shows no signs of hemineglect. Head computed tomography shows an intracranial hemorrhage. Which of the following vessels is most likely injured?
Hemorrhagic strokes can be further split into two types, an intracerebral hemorrhage which is when bleeding occurs within the cerebrum, and a subarachnoid hemorrhage which is when bleeding occurs between the pia mater and arachnoid mater of the meninges - the inner and middle layers that wrap around the brain.
We’ll be focusing on intracerebral hemorrhages which are more common.
An intracerebral hemorrhage that involves just the brain tissue is called an intraparenchymal hemorrhage, whereas if the blood extends into the ventricles of the brain which store cerebrospinal fluid, it’s called an intraventricular hemorrhage.
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 has a cortex - an outer region - divided into four lobes including the frontal lobe, parietal lobe, temporal lobe, and the occipital lobe.
The right cerebrum controls muscles on the left side of your body and vice versa.
The frontal lobe controls movement, and executive function, which is our ability to 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.
The temporal lobe plays a role in hearing, smell, and memory, as well as visual recognition of faces and languages.
Finally, there’s the occipital lobe which is primarily responsible for vision.
Within the cortex are deeper structures like the internal capsule, which is like a highway that allows information to flow through neurons that are going to and from the cerebral cortex.
There’s also the basal ganglia, which helps controls smooth movement and cognitive function, along with the cerebellum.
The cerebellum also helps with muscle coordination and balance.
Each of the internal carotid arteries also give off branches called the anterior cerebral arteries which serve the medial portion of the frontal and parietal lobes and connect with one another with a short little connecting blood vessel called the anterior communicating artery.
Meanwhile, the vertebral arteries and basilar artery give off branches to supply the cerebellum and the brainstem.
Finally, the internal carotid arteries each give off a branch called the posterior communicating artery which attaches to the posterior arteries on each side.
So together, the main arteries and the communicating arteries complete what’s called the Circle of Willis - a ring where blood can circulate from one side to the other in case of a blockage.
Hypertension can lead to various vessel wall abnormalities.
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- "Intracranial Hemorrhage" Emergency Medicine Clinics of North America (2012)