At the emergency department, 30-year-old Lydia presents with severe headache and confusion. Clinical examination reveals low grade fever and nuchal rigidity. Past medical history reveals she has polycystic kidney disease. Non-contrast CT reveals blood between the arachnoid and the pia mater. Lydia is treated supportively and sent home. Three days later she suddenly develops a severe headache, vomiting, and confusion. Later that day, 70-year-old Amanda presents with left-sided weakness and numbness, with her foot and leg more affected than her arm. She can speak fluently and understands everything being said to her. Past medical history includes hypertension, hyperlipidemia, and a myocardial infarction last year.
Based on their presentation, the diagnosis is that both Lydia and Amanda had a cerebral vascular accident, most often referred to as a stroke. A stroke is when there’s a sudden focal neurological deficit due to a part of the brain losing its blood supply.
Now, to safeguard the brain from hypoxia, the brain has a dual circulation called the circle of Willis, divided into an anterior and posterior circulation. The anterior circulation starts in the neck, where the common carotid artery splits into the external and internal branches. The internal carotid passes through the carotid canal of the temporal bone of the skull and into the cranial cavity. Once inside, the internal carotid artery gives off branches. First are the middle cerebral arteries that supply the lateral portions of the frontal, parietal, and temporal lobes. It’s also important to remember that the middle cerebral arteries supply the two language areas, Broca’s and Wernicke’s. From the initial segment of the middle cerebral arteries, small perforating arteries called lenticulostriate arteries arise to supply a part of the basal ganglia called the striatum, which includes the caudate and putamen, as well as the internal capsule. And that’s something you absolutely must remember for the exams! The internal carotid artery also gives rise to the anterior cerebral artery, which supplies the medial portion of the frontal and parietal lobes. The two anterior arteries connect with one another via a short blood vessel called the anterior communicating artery, forming the anterior portion of the circle of Willis.