A 29-year-old woman presents with intermittent visual distur…

A 29-year-old woman presents with intermittent visual disturbances, right arm weakness, and numbness in the left leg. MRI of the brain and spinal cord reveals multiple demyelinating lesions in both supratentorial and spinal regions. Which of the following best explains the asymmetric and varied presentation of her symptoms?

A 60-year-old woman presents to the emergency department wit…

A 60-year-old woman presents to the emergency department with sudden onset of right-sided weakness and slurred speech. A non-contrast CT of the head rules out hemorrhage, and further imaging confirms a left middle cerebral artery infarct. Her past medical history includes hypertension, hyperlipidemia, and type 2 diabetes mellitus. She is a nonsmoker. What is the most likely underlying cause of this patient’s cerebrovascular accident (CVA)?