Severe outflow lesion of the internal carotid artery

Clinical History

A 66 year-old female patient was referred to our department to perform a Doppler ultrasound examination of the extracranial cerebral circulation.

Imaging Findings

A 66 year-old female patient was referred to our department to perform a Doppler ultrasound examination of the extracranial cerebral circulation. On pulsed Doppler examination of the internal carotid arteries it was seen assimetric peak systolic velocities, with a marked reduction on the right – 16 cm/s (figure 1). Spectral examination showed high-resistance flow in the right common carotid artery (figure 2). A retrograde flow was noted in the right ophthalmic artery (figure 3). These findings were considered to be due to a severe outflow lesion of the right internal carotid artery. The patient performed a CT scan which demonstrated bilateral calcificated atheromatosis of the carotid siphon, more severe on the right, without other lesions (figure 4).

Discussion

On occasion it may be difficult to visualize portions of the internal carotid artery and these imaging gaps can easily hide the presence of high-grade stenosis. Normal flow in the common carotid artery is usually greater than 45 cm/s. Internal carotid artery (ICA ) peak systolic velocities (PSV) are normally 80 to 100 cm/s in younger patients and 60 to 80 cm/s in older patients. Depressed velocities in the carotid arteries should raise the possibility of low cardiac output, proximal stenosis, tandem lesions or distal obstruction or dissection. A velocity difference of greater than 20 cm/s between the right and left CCAs indicates asymmetric flow. (1, 2). Depressed velocities in the ICA , especially when diastolic flow is depressed (high resistance), should suggest the possibility of a high-grade obstruction in the intracranial portion of the internal carotid. With stenosis of sufficient severity, mostly above 80%, the velocity of the CCA will perceptibly decrease. In older patients, a stenotic lesion of the carotid near the siphon is a rare but likely explanation. In the younger patient, the possibility of a dissection should be considered. Depressed velocity signals in the ICA can also be secondary to poor inflow, either due to a stenosis at the origin of the common carotid or innominate arteries or a depressed cardiac output. In the latter the changes are bilateral. In the case of a severe proximal lesion, there is a reduction in the PSV on the side of the obstruction (parvus), a slow systolic rise time (tardus) and a relative increase in the amount of blood flow during diastole (low resistance).

Differential Diagnosis List

Final Diagnosis

Severe outflow lesion of the internal carotid artery

URL:	https://www.eurorad.org/case/5366
DOI:	10.1594/EURORAD/CASE.5366
ISSN:	1563-4086