The ICV sign as a marker of increased cerebral blood transit time.

Objective/background: We describe the internal cerebral vein (ICV) sign, which is a hypo-opacification of the ICV on computed tomogram angiography (CTA) as a new marker of increased cerebral blood transit-time in ipsilateral internal carotid artery occlusions (ICAO).

Methods: A retrospective analysis of 153 patients with acute unilateral M1 middle cerebral artery (MCA) occlusions ± ICAOs was performed. The degree of contrast opacification of the ICV on the ipsilesional side was compared to that of the unaffected side.

Results: Of 153 patients in our study, 135 had M1 MCA occlusions ± intra-cranial ICAO (M1±iICAO) and 18 had isolated extracranial ICAO (eICAO). In the patients with proximal M1±iICAO, 57/65 (87.1%) showed the ICV sign. Of the 8 patients without the ICV sign in this group, 6 had prominent lenticulostriate arteries arising from the non-occluded M1 segment, 1 had a recurrent artery of Huebner, and 1 had filling of distal ICA/M1 segment through prominent Circle of Willis collaterals. For the 70 patients with isolated distal M1±iICAO, 7/70 (10%) showed the ICV sign, with all 7 showing occluded lenticulostriate arteries. Of the patients with eICAO, 8/18 showed the ICV sign, all 8 with the ICV sign had poor Circle of Willis collaterals.

Conclusions: The ICV sign correlates well with presence of proximal M1±iICAO in patients with either occluded lenticulostriate arteries or poor Circle of Willis collaterals. In patients with eICAO, the sign correlates with reduced Circle of Willis collaterals and may be a marker of increased ipsilateral cerebral blood transit time.