[A case with traumatic internal carotid artery dissection in which the extent of the pseudolumen was defined by MR angiography].

We report a 29-year-old male with traumatic internal carotid artery (ICA) dissection who presented with cerebral ischemia developed after removal of a left acute subdural hematoma and external decompression. CT scans 4 days after the operation showed infarctions of the distribution of the bilateral cerebral hemispheres. Cerebral angiography on the 11th hospital day demonstrated narrowing of the extracranial internal carotid artery at C1-C2 vertebral levels. Slight arterial dilatation and retention of the contrast medium were found just above the narrowing segment, which was suspected to be a pseudolumen. Three D time-of flight MRA showed an intramural hematoma corresponding to the narrowing on the angiography. Original axial MRA images showed that narrowing of the lumen was surrounded by a crescent hematoma and that two flow velocity areas were in the area distal to the narrowing. High flow seemed to be ordinary artery flow rate. The low flow area, including turbulent flow, led to the retention of contrast medium mimicking a pseudolumen. Precise MRA imaging will bring us an accurate diagnosis of extracranial carotid dissections.