A 63-year-old man presented suddenly and spontaneously an isolated painless oculomotor palsy of the nerve abducens. As no etiology could be suspected a head MRI was performed. It showed a T1 hypersignal of the intracavernous segment of the internal carotid artery with a double-lumen pattern typical of dissection. The patient was treated with aspirin and recovered from clinical symptoms in 10 weeks. A control MRI was performed 3 months after the onset of symptoms and showed the regression of the images of dissection. There was no ischemic lesion of the brain. This case underlines the diversity of the symptoms of spontaneous dissections of cervicocephalic arteries, especially absence of pain, palsies of cranial nerve that are not always limited to lower cranial nerve, and existence of dissections limited to the intracranial segment of the carotid artery. It suggests the interest of MRI in the diagnosis of isolated oculomotor nerve palsies.