Chorionic villi sampling is the taking of genetic material within in the chorionic villi of the placenta. Chorionic sampling is done when a patient is at high risk for chromosomal abnormalities (previous pos. tests, 35yo or older, family hx.) during the 10-13 weeks of pregnancy.
Confined placental mosaicism results when the C.V.S. testing comes back back showing a trisomy, but all subsequent testing (and the fetus itself) have normal chromosomal counts. This may be due to either a trophoblastic mutation, or by "trisomic rescue," in which trisomic cells that were supposed to be in the fetus are confined to the placenta to prevent an abnormal fetus.
As the muscle works and breaks down ATP, adenosine is produced, leading to an increase in the tissues. This increased adenosine causes vasodilation, which in turn increases vascular conductance (the flow of a volume of blood through the vasculature).
Although you may think muscle contraction may lead to a decrease in flow through the vessel(s) by squeezing down on them, this mechanism is overcome by the increased cardiac output from the heart.
This patient presents with classic upper motor neuron lesion symptoms: weakness, hyperreflexia, and decreased sensation. However, the question states she "cannot tell whether her left great toe is raised or depressed" when her eyes are closed, which may make you reconsider and think there may be some proprioceptive issues they are trying to hint at. This is not the case. Especially once they mention there are no other abnormalities (i.e., no upper limb abnormalities or right sided abnormalities). If this is the case, there is no damage to the tracts at all (which are still considered UMN).
Therefore, the damage is purely motor and sensory in the left leg, which is on the medial aspect of the frontal and parietal lobes respectively. This area is supplied by the anterior cerebral artery.
Obviously no picture here, but "A" in the picture represents Broca's area, which would cause the expressive aphasia this patient is experiencing.
However, the question also states the patient has weakness of the lower two-thirds of his face. This may cause you to think there is maybe a lesion in the pre-central motor area (thinking humonculus), but realize that the motor area travels all the way down to the bottom of the frontal lobe, RIGHT BEHIND THE BROCA'S AREA. In fact, Broca's area encompasses that part of the humonculus. And since the upper part of the face is controlled by the upper part of the facial motor cortex, and the lower part is controlled by the lower part of the facial motor cortex, you can have paralysis of the lower part of the face and have expressive aphasia if the lesion is in that specific area (does not need to be a lower motor lesion to spare the upper face/forehead).
"Confounding variables" here means "confounding bias," essentially. And this is true because a prospective cohort looks at a specific exposure to a substance (environmental toxin, drug, etc.), and asks "Who will develop this disease if exposed?" PCS's look attempt to find a relative risk associated with an exposure. They do not take into account the affects other exposures. This is your confounding bias. FA gives the example of confounding bias as "Pulmonary disease is more common in workers in a coal mine; however, miners are more likely to smoke," and since smoking can also lead to pulmonary disease, you can't really say whether the smoking (first or second hand) or the coal dust causes the problem. A clinical trial, on the other hand, contains a test group and a control group, so variables such as the confounding variable mentioned above are limited.
So although Misoprostol DOES increase mucus production and is gastro-protective (and in FA does state that it decreases acid production), thereby decreasing symptoms and aiding in healing, omeprazole is the "more correct" choice. This is because omeprazole is a proton-pump inhibitor, which will act directly on the proton pumps of the stomach and decrease the offending agent more than the misoprostol will. Therefore, it is the first line drug for GERD.