A 64-year-old man presents to the emergency department with sudden-onset weakness in his right arm and leg, which he noticed upon waking up. He denies any speech difficulties, facial drooping, or visual disturbances. There is no headache, loss of consciousness, or chest pain. His past medical history includes hypertension and type 2 diabetes, both poorly controlled. He is a smoker with a 40-pack-year history and has not taken his antihypertensive medications regularly. Physical Examination: Vital Signs: Blood Pressure: 180/95 mmHg Heart Rate: 82 bpm Respiratory Rate: 16 bpm Temperature: 37°C Neurological Examination: Motor strength: 2/5 in the right arm and leg, normal on the left side Sensation: Intact bilaterally Cranial nerves: No deficits Speech: Normal Cerebellar signs: None noted Gait: Unable to walk due to right-sided weakness Diagnostic Workup: CT scan of the head (non-contrast): No acute intracranial hemorrhage or large infarction. MRI of the brain (with diffusion-weighted imaging): Small, acute infarction in the left posterior limb of the internal capsule. Carotid Doppler ultrasound: No significant carotid stenosis. Echocardiogram: No evidence of thrombus or cardiac embolism. Bloodwork: Glucose: 220 mg/dL HbA1c: 8.5% LDL: 140 mg/dL Complete blood count and coagulation panel: Normal Diagnosis: Lacunar stroke affecting the left internal capsule, likely secondary to small vessel disease related to chronic hypertension and diabetes. Which of the following best explains the underlying pathophysiology of a lacunar stroke?

A 52-year-old female presents to the hospital with a sudden severe headache, nausea, and neck stiffness. Imaging confirms a subarachnoid hemorrhage (SAH) due to a ruptured aneurysm. She is initially stabilized, but on day 7 of her hospital stay, she develops confusion, slurred speech, and weakness in her left arm. These symptoms suggest delayed cerebral ischemia (DCI), a known complication of SAH that can occur several days after symptom onset, leading to acute worsening of the neurologic exam and increased morbidity. What is the most likely underlying mechanism responsible for her new symptoms?