Predictors and Timing of Recanalization in Intracranial Carotid Artery and Siphon Dissection: An Ultrasound Follow-up Study

Abstract

Background: Intra- and extracranial internal carotid artery dissections (ICD) are two different pathological conditions. Extracranial dissection is considered to be among the most frequent causes of stroke in the young and the segment generally reopens in 2 out of 3 cases, completely or partially, within 6 months. Intracranial ICD (IICD) is considered a rare occurrence in stroke and, accordingly, there are few systematic published data. However, it is a clinically significant condition that may cause severely disabling ischemic stroke or subarachnoid hemorrhage. In the past, sole availability of invasive imaging methods for its detection may have induced an underreporting. The aim of the study was to analyze ultrasound findings, timing and predictors of recanalization in patients with IICD. Methods: IICD acute patients admitted to our Stroke Unit were submitted to carotid sonographic seriated monitoring, daily for the 1st week after symptom onset, at day 14, at month 1 and every 3 months thereafter up to a follow-up of 4 years. Contrast carotid ultrasound was performed in patients with persistent occlusion after month 1. Results: Fourteen acute patients with IICD were enrolled. Extracranial internal carotid patency was observed in 8 patients at first ultrasound scans; all of these showed complete intracranial recanalization within the 1st week and oral anticoagulants were withdrawn after 6 months. Conversely, in 6 patients retrograde extracranial internal carotid thrombosis was immediately observed, since the first ultrasound scans. In 4 of these the occlusion persisted after 4 years while 2 of them had only a partial recanalization, with evidence at contrast ultrasound of still late remodeling processes in the extracranial thrombus up to 2 years after the first observation; for this reason, in these 2 patients anticoagulation was not discontinued, while in the 4 patients with persistent, stable, occlusion, therapy was suspended 1 year after the diagnosis. Conclusions: Identification of the site of dissection - i.e. extra- versus intracranial - is fundamental in clinical studies for outcome and prognosis evaluation. Carotid ultrasound strict surveillance is important to monitor eventual recanalization in patients with ICD, even in a late phase. Retrograde internal carotid thrombosis seems to be correlated with persistent occlusion and partial recanalization. Remodeling of thrombotic material in the internal carotid artery may, however, continue for up to 2 years. In these cases, contrast ultrasound evidence of thrombus morphological changes may support the decision to continue anticoagulation.