A 24-year-old previously healthy male woke up with retroauricular pain. One day later, he developed left-sided facial droop and decreased taste sensation on the right side of the tongue. He experienced hyperacusis and right eye discomfort. No diplopia, tinnitus, hearing loss, or limb weakness were present. Examination revealed inability to wrinkle forehead and close eyes on the right side, left-sided mouth deviation when smiling, and herpes zoster in the external auditory canal and auricle. The most accurate diagnosis is: