A 44-year-old man has had drooping of the right side of his face for three days. He drools from the right corner of his mouth, the right nasolabial fold is flattened, food collects between his teeth and his right cheek, his 'p' and 'b' sounds are slurred, and he cannot close the right eye tightly.
Which one of these findings shows that the weakness arises in the facial nerve itself rather than in the corticobulbar fibres supplying the facial nucleus?