Potential and limitations of echocontrast-enhanced ultrasonography in acute stroke patients: a pilot study

Ultrasonography (US) is a well-established method used to assess the brain-supplying arteries in the acute stroke setting. However, several technical and anatomic limitations are known to reduce its diagnostic accuracy and confidence level. Echocontrast agents (ECA) are known to improve the signal-to-noise ratio by enhancing the intensity of the reflecting Doppler signal. We undertook this prospective study to evaluate the diagnostic value of ECA in a consecutive, nonselected cohort of acute stroke patients with insufficient native US investigations.

During a 1-year period, 25 patients were examined within 48 hours of the onset of stroke. The need for ECA was due to an insufficient transtemporal (n=18), transforaminal (n=4), or extracranial (n=3) imaging of arteries potentially involved in the ischemic event. In 12 patients, a diagnostic suspicion could natively be raised, whereas in the other 13 patients, the strongly reduced image quality did not allow for any neurovascular conclusions. Four grams of Levovist was injected at a concentration of 200 mg/mL and 400 mg/mL for the extracranial and transcranial insonations, respectively. The effect of the echocontrast enhancement was assessed with respect to (1) signal enhancement, (2) image quality, (3) final diagnostic confidence, and (4) the need for additional neurovascular imaging methods.

In all but one patient (96%), a strong signal enhancement was noted, leading to a moderate (n=11) or strong improvement (n=10) of the transcranial image quality. Thus in a total of 18 patients (72%), the echoenhancement provided a neurovascular diagnosis of sufficient confidence. This led to the confirmation of the previously suspected findings and disclosed three further occlusions and four stenoses of the intracranial arteries. In contrast, for the three extracranial examinations the image quality was not sufficiently improved because of persistent color artifacts derived from adjacent neck vessels. Besides the seven patients with inconclusive examinations, five patients with conclusive echoenhanced US studies (48% in total) demanded additive neurovascular imaging studies, based on the clinical decision of the attending physicians. This led to confirmation of all high-confident sonographic diagnoses.

In summary, in approximately three fourths of our acute stroke patients with insufficient native US investigations, echocontrast enhancement enabled a reliable neurovascular diagnosis, allowing the cancellation of additive neurovascular imaging procedures in half of our cohort. Our preliminary results suggest that ECA can reasonably support the early cerebrovascular workup in the acute stroke setting.