Carotid arterial dissection

Markedly hyperdense MCA is noted on the right associated with loss or grey - white matter differentiation in the temporal pole and insula cortex. 

A large right MCA territory infarct is present with profound diffusion restriction and early swelling. 

MRA demonstrates no flow induced signal in the right ICA, with matching high T2 signal on T2 weighted images. 

Note that the sagittal T1 images have high signal inflowing blood seen in the vertebral arteries and left carotid, but no similar signal is present on the right. 

A complete right MCA infarct is present with marked hypodensity and swelling with resultant mass effect. 

Right hemicraniectomy with locules of gas and small pockets of hematoma laterally and inferiorly, seen within the overlying soft tissues.

Extensive low attenuation within the territory of the right MCA, including the head of the right caudate nucleus is in keeping with extensive infarction. The right MCA is hyperdense in keeping with thrombosis.

Approximately 2 cm distal to the bifurcation of the right common carotid, the enhancing lumen of contrast within the right internal carotid artery is significantly narrowed mildly irregular. The outer diameter of the ICA is, however, expanded, particularly at the base of skull, consistent with a dissection. 

Right-sided craniectomy is again demonstrated, along with a stable extra-axial collection containing blood and gas. Extensive hypodensity in the right frontal, parietal and temporal lobes is unchanged and consistent with evolution of the right middle cerebral artery infarct. The M1 and M2 segments of the right middle cerebral artery remain hyperdense.

Crescentic T1 and to a lesser degree T2 hyperintensityis seen within the wall of the right internal carotid artery extending from the carotid bifurcation to the distal lacerum segment. 

Conclusion: Right internal carotid artery dissection extending from the carotid bifurcations of the distal lacerum segment.