Voluntary vertical nystagmus.
A patient with hypertropia caused by fourth-nerve palsy manifested primary position oscillations characteristic of voluntary nystagmus. This benign condition must be kept in mind even when dealing with primary position vertical nystagmus to avoid extensive and potentially dangerous investigations.
D000328:Adult; D005133:Eye Movements; D005260:Female; D006801:Humans; D010243:Paralysis / Q000150:complications; D013285:Strabismus / Q000209:etiology / Q000503:physiopathology*; D014321:Trochlear Nerve