Phase I: Transcranial Echo Contrast Studies in Healthy Volunteers

206

151

Background and Purpose-Functional transcranial Doppler ultrasonography (fTCD) can assess event-related changes in cerebral blood flow velocities and, by comparison between sides, can provide a measure of hemispheric perfusional lateralization. It is easily applicable, insensitive to movement artifacts, and can be used in patients with less than perfect cooperation. In the present study we investigated the validity of fTCD in determining the hemispheric dominance for language by direct comparison of fTCD with intracarotid amobarbital anesthesia (Wada test). Methods-fTCD and the Wada test were performed in 19 patients evaluated for epilepsy surgery. By the Wada test, 13 patients were classified as left-hemisphere dominant and 6 as right-hemisphere dominant for language. fTCD was based on the continuous bilateral measurements of blood flow velocities in the middle cerebral arteries and event-related averaging during a cued word generation task previously shown to activate lateralized language areas in normal adults. Results-In 4 patients fTCD assessment was not possible because of lack of an acoustic temporal bone window. In the remaining 15 candidates, determination of language dominance was concordant with the Wada test in every case. Moreover, the correlation of the lateralization measures from both procedures was highly significant (rϭ.92, PϽ.0001). Conclusions-This strong correlation validates fTCD as a noninvasive and practical tool for the determination of language lateralization that can be applied for clinical and investigative purposes. (Stroke. 1998;29:82-86.)

Section: Discussionmentioning

confidence: 99%

Noninvasive Determination of Language Lateralization by Functional Transcranial Doppler Sonography

Knecht

Deppe

Ebner

et al. 1998

206

151

“…A few seconds later, the effect of the ECA could then efficiently used. Criteria for an occlusion of an intracranial artery were in accordance with those described by Kaps et al 15,20 Diagnosis of an intracranial stenosis was made if a focal increase of the systolic blood flow velocity Ͼ160 cm/s or a relative increase of Ͼ50% compared with the prestenotic and poststenotic vessel segments was present, together with low-frequency noise caused by vessel wall covibrations. 21 The effect of the echocontrast enhancement was assessed in agreement of at least two experienced US investigators (D.G.N., D.W.D., V.K., G.S.A.)…”

Section: Methodsmentioning

confidence: 99%

Potential and Limitations of Echocontrast-Enhanced Ultrasonography in Acute Stroke Patients

Nabavi

Droste

Kemény

et al. 1998

Background and Purpose-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. Methods-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 (nϭ18), transforaminal (nϭ4), or extracranial (nϭ3) 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. Results-In all but one patient (96%), a strong signal enhancement was noted, leading to a moderate (nϭ11) or strong improvement (nϭ10) 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. Conclusions-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. (Stroke. 1998;29:949-954.)

“…[11][12][13] Recently published studies have shown their diagnostic potential in cerebrovascular disease.…”

Section: Discussionmentioning

confidence: 99%

Transient Response Harmonic Imaging

Postert

Muhs

Meves

et al. 1998

Background and Purpose-Gray-scale harmonic imaging is the first method to visualize blood perfusion and capillary blood flow with ultrasound after intravenous contrast agent application. The purpose of the present study was to evaluate the potential of transient response second harmonic imaging (TRsHI) to assess normal echo contrast characteristics in different brain areas by transcranial ultrasound. Methods-In 18 patients without cerebrovascular diseases, TRsHI examinations were performed bilaterally with the use of the transtemporal approach after application of 6.5 mL of a galactose-based microbubble suspension (400 mg/mL). The transmission rate was once every 4 cardiac cycles. Regional cerebral contrast was visually assessed and then quantified off-line with the use of time-intensity curves. In 4 different regions of interest (ROI)