Spontaneous dissection of the extracranial internal carotid artery is a well recognized cause of headache and juvenile stroke; lower cranial nerve palsy as a complication of dissection is rare. We report the case of a female patient with bilateral dissecting aneurysm of the internal carotid artery, associated with unilateral cranial nerve XII palsy and oculosympathetic palsy. Neuroradiological findings, in particular those obtained by Magnetic Resonance imaging, allow the identification of the dissecting pathology and the correlation of the aneurysmal formation with nerve palsy.