Here, we report a case where bedside carotid ultrasound enabled early detection and hemodynamic assessment of CAEAD in a critically ill patient. A number of sonographic features are shown, such as luminal stenosis, a perfused false lumen, and a dissection membrane. Features not present include a thickened and hypoechogenic vessel wall, intracranial stenosis or occlusion, and pseudoaneurysm .
Four imaging modalities are primarily used in the diagnosis of carotid dissections. Digital subtraction angiography (DSA), i.e., contrast-enhanced invasive vascular imaging, remains the gold standard. Dynamic magnetic resonance angiography (MRA) may also be performed, especially in patients with iodinated contrast allergy or renal impairment. Fat-saturation sequences are useful to detect intramural hematoma, even if the lumen itself is not narrowed. Compared to DSA, MRA offers a variable performance at a sensitivity of 50–100% and a specificity of 29–100%  and is considered by the American Heart Association and the American Stroke Association to be the best initial screening test . However, the speed of image acquisition is slow and MRA is not always feasible in intensive care unit (ICU) patients. Conversely, CTA is widely available, offers rapid image acquisition and compares favorably with DSA at a sensitivity of 64–100% and specificity of 67–100% .
Carotid ultrasound offers a number of advantages over static vessel imaging. Doppler mode yields information on flow characteristics including the peak systolic as well as diastolic flow velocities. This method is used to diagnose and grade stenosis and is especially valuable in the indirect assessment of the petrous ICA segment, where CTA is limited due to vessel wall calcifications or skull base artifacts. Using additional brightness-mode (B-mode) imaging with color-coded Doppler significantly increases the sensitivity in detecting carotid dissections, as compared to MRA, with no false-positive diagnoses . Carotid ultrasound is also portable, which enables bedside examination and avoids unnecessary transports in ICU patients, which are associated with a number of serious adverse events . Lastly, carotid ultrasound is the least invasive method, avoiding radiation exposure or the administration of a contrast agent. Hence, bedside carotid ultrasound is a safe and effective imaging modality in carotid dissections, suitable for use in critically ill patients.
Limitations may apply. Minor vessel damage, such as an intimal tear or small mural hematoma, may not be readily apparent on ultrasound. This applies especially to locations where B-mode imaging cannot be carried out, such as the skull base. Here, alternate imaging modalities, such as fat-saturation MRI or (contrast-enhanced) MRA, may be useful as complementary diagnostic tools.