Hemianopsia related to dissection of the internal carotid artery

Spontaneous dissection of the internal carotid artery is typically associat ed with cerebral vascular infarction along the anterior and middle cerebral distribution, whereas occipital infarction is usually related to posterior circulation abnormalities. Hemianopsia with occipital infarction related t o carotid artery dissection has therefore rarely been reported. A 40-year-o ld woman in whom acute-onset hemianopsia developed, related to occipital in farction secondary to internal artery dissection, is described. This atypic al association is explained by anatomic variations of the posterior part of the circle of Willis. Neuroimages showed occipital infarction related to i nternal carotid artery dissection associated with hypoplasia of the proxima l portion of the cerebral posterior artery (P1). The anatomic correlation o f this atypical association and a review of the literature are presented.