Teaching Case

A 55-year-old male patient presented to the Emergency Department complaining of right-sided face and leg numbness. Past medical history included severe stenosis of the left internal carotid artery, heavy smoking and alcohol consumption.

Brain MRI performed at presentation confirmed a left-sided acute stroke, while the patient was referred for carotid US to investigate the carotid arteries. B-mode and colour Doppler examination revealed a partially calcified plaque situated at the bulb of the left internal carotid artery with loss of blood flow signals distally; findings raising suspicion of occlusion. Spectral analysis confirmed the presence of antegrade flow with low velocity. B-flow and contrast-enhanced US revealed the presence of flow within a pre-occlusive plaque while note was made of linear ulcerations and the possibility of occlusion was excluded (Fig. 1). The next day, the patient recovered his past carotid CTA (performed two years earlier) where there was evidence of an ulcerated plaque causing severe stenosis of the internal carotid artery (Fig. 2). The patient then underwent MRA for confirmation of findings where the diagnosis of a pre-occlusive ulcerated carotid artery plaque was established (Fig. 3).

A significant percentage of strokes and transient ischaemic attacks is caused by atherosclerotic carotid plaques.[1] Current management guidelines of carotid disease primarily take into account the degree of luminal stenosis and whether or not the patient is symptomatic.[2] However, it is now well-established that there are several imaging features of carotid plaques significantly associated with the occurrence of neurologic symptoms. Such features can be investigated with virtually every imaging modality, reflect plaque histology and include surface characteristics and plaque’s content as expressed with echogenicity on ultrasound, density on CT or signal intensity on MRI.[3] As for surface morphology, a plaque can be classified as smooth, irregular or ulcerated. Based on conventional angiographic studies, carotid ulcerations have been classified to four different types depending on their morphology and geometric characteristics.[4, 5] Accurately characterising a plaque as smooth, irregular or ulcerated is clinically significant as various studies have found that ulcerations are correlated with stroke and TIA. Studies with transcranial Doppler have established a connection between ulceration and embolic signals.[6] Comparing ulcerated with non-ulcerated plaques has led to the conclusion that the former have a more than three times greater risk for stroke.[7] Finally, it has been concluded that ulcerations are responsible for the occurrence of a new stroke or TIA in asymptomatic patients.[8] Although conventional Doppler technique may detect carotid ulcerations, various degrees of sensitivity and specificity have been published, showing that it is not an adequately accurate technique.[4] CTA is considered an excellent technique for the delineation of plaque surface and ulceration detection based on its three-dimensional nature. The emergence of modern ultrasonographic techniques like B-Flow and contrast-enhanced US (CEUS) have shown promising results in the diagnosis of carotid ulceration thanks to their increased sensitivity.[4, 9] Apart from characterisation of carotid plaques, differentiating occlusion from pre-occlusion stenosis is another differential diagnosis of great clinical significance, based on the different treatment required. US may correctly detect a thread-like patent lumen if performed with caution but CTA or MRA are frequently requested for definitive diagnosis.[10] B-Flow and CEUS can also be performed for the same reason in patients with renal failure in order to avoid the use of iodinated contrast media, offering higher diagnostic accuracy compared to conventional US.[10] As a take home point, it can be stressed that the use of current ultrasonographic techniques like B-flow or CEUS are valuable for characterisation of carotid plaques and can be used for accurately grading stenosis.