A 24-year-old male, previously healthy, woke up with retroauricular pain. After 1 day, he developed left-sided facial droop and decreased taste sensation on the right side of the tongue. He also experienced hyperacusis and right eye discomfort. No diplopia, tinnitus, hearing loss, or limb weakness were noted. Examination: Right-sided inability to frown, raise eyebrows, or close the eye; left-sided facial droop on grinning; decreased taste sensation on the anterior right tongue. The most likely site of lesion is: