adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'
twitching; quivering
Describes a small, repeated, involuntary movement, often of a body part such as an eyelid, cheek, or muscle. Used adverbially with と or as a する-verb.
緊張でまぶたがひくひくした。
My eyelid twitched from nervousness.
彼の口
The corners of his mouth were quivering.