The article describes a woman with 53 year-old that has presented diplopia when looking down and adopted a tilted head position in order to read for the last six months. The neuro-ophthalmic examination shows isolated right superior oblique muscle paresis. The magnetic resonance and the angioresonance show the dolicoectatic basilar artery compressing the right ventral lateral brainstem.
trochlear nerve; dolichoectasy; basilar artery; ophtalmoplegy; compression