Imaging description

Isolated cortical venous thrombosis (ICVT) is a rare but underdiagnosed occurrence. The difficulty in diagnosis arises because of variability in the cortical venous system, and the small size and peripheral location of the cortical veins. The “definitive imaging proof” of ICVT is the demonstration of thrombus in the cortical vein and lack of visualization of this vessel on CT or MR venography (CTV or MRV) [1].

Thrombus in the cortical vein may be visualized on CT as the “cord sign,” with high density of the thrombus appearing similar to the hyperdense middle cerebral artery (MCA) sign in acute ischemic stroke. Signal-intensity changes on MRI depend on the age of the thrombus at the time of imaging. Acute thrombus has a predominantly isointense signal on T1-weighted and hypointense signal on T2-weighted sequences, reflecting the presence of deoxyhemoglobin. Accumulation of methemoglobin may result in hyperintense signal on T1- and T2-weighted sequences [1,2]. In general, the sequences that display sensitivity to the paramagnetic products of hemoglobin (T2*, susceptibility-weighted imaging) can play an important role in diagnosis by demonstrating a tubular area of hypointense signal in the thrombosed vessel (Figs. 14.1, 14.2) [3]. The vascular studies (MRV, CTV, or DSA) complement MRI in establishing the diagnosis by demonstrating lack of filling or partial opacification (Fig. 14.1) of the corresponding vein(s). Digital subtraction angiography (DSA) may be helpful in demonstrating the collateral pathways and their adequacy.