A 30-year old man suddenly developed left hemiplegia. CT scan and cere
bral angiography showed complete thrombosis of a right internal caroti
d giant aneurysm. Anterograde propagation of the thrombus in the paren
t artery led to ipsilateral hemispheric infarction, an exceptional pre
senting symptom of such vascular malformation. The diagnostic and etio
pathogenic aspects are briefly discussed.