Flow Diversion in Transcranial Doppler Ultrasound Is Associated with Better Improvement in Patients with Acute Middle Cerebral Artery Occlusion

Clinical applications of ultrasound in neurosurgery and neurocritical care: A narrative review

Ultrasonography (USG) has become an invaluable tool in the assessment of neurocritical patients in the operating theaters and critical care units. Due to its easy availability, reliability, safety, and repeatability, neuro-intensivists and neuro-anesthesiologists utilize USG to make a diagnosis, assess prognosis, and decide upon treatment. In neurocritical care units, USG has myriad indications for use, both systemic and neurologic. The neurological indications include the assessment of stroke, vasospasm, traumatic brain injury, brain death, acute brain damage, optic nerve sheath diameter, and pupillary reflexes to name a few. The systemic indications range from assessment of cardio-pulmonary function and intravascular volume status to detection of deep venous thromboses, vocal cord assessment in intubated patients, placement of central venous catheters, and percutaneous tracheostomy. In this narrative review, we iterate the clinical applications of USG in neuroanesthesia and neurocritical care, which we penned after searching relevant databases in PubMed, Medline, Ovid, and Google Scholar by using terms such as ‘applications of transcranial Doppler’, ‘optic nerve sheath diameter’, ‘USG applications in the critical care unit’, and so on. Our search database includes several research papers, neurocritical care books, review articles, and scientific databases. This article reviews various applications of USG in neuroanesthesia, neurosurgery, and neurocritical care.

Systematic Analysis of RNA Expression Profiles in Different Ischemic Cortices in MCAO Mice

The prognosis of ischemic stroke patients is highly associated with the collateral circulation. And the competing endogenous RNAs (ceRNAs) generated from different compensatory supply regions may also involve in the regulation of ischemic tissues prognosis. In this study, we found the apoptosis progress of ischemic neurons in posterior circulation-supplied regions (close to PCA, cortex2) was much slower than that in anterior circulation-supplied territory (close to ACA, cortex1) in MCAO-3-h mice. Using the RNA sequencing and functional enrichment analysis, we analyzed the difference between RNA expression profile in cortex1 and cortex2 and the related biological processes. The results indicated that the differential expressed ceRNAs in cortex1 were involved in cell process under acute injury, while the differential expressed ceRNAs in cortex2 was more likely to participate in long-term injury and repair process. Besides, by establishing the miRNA-ceRNA interaction network we further sorted out two specifically distributed miRNAs, namely mmu-miR446i-3p (in cortex1) and mmu-miR3473d (in cortex2). And the specifically increased mmu-miR3473d in cortex2 mainly involved the angiogenesis and cell proliferation after ischemic stroke, which may be the critical reason for the longer therapeutic time window in cortex2. In conclusion, the present study reported the specific changes of ceRNAs in distinct compensatory regions potentially involved in the evolution of cerebral ischemic tissues and the unbalance prognosis after stroke. It provided more evidence for the collateral compensatory effects on patients' prognosis and carried out the new targets for the ischemic stroke therapy.

Assessment of Atherosclerosis in Ischemic Stroke by means of Ultrasound of Extracranial/Intracranial Circulation and Serum, Urine, and Tissue Biomarkers

It is a common practice to take into consideration age, diabetes, smoking, treated and untreated systolic blood pressure, total cholesterol, and high-density lipoprotein cholesterol for the prediction of atherosclerosis and stroke. There are, however, ultrasound markers in use for the assessment of atherosclerosis and the evaluation of stroke risk. Two areas of investigation are of interest: the carotid artery and the intracranial arterial circulation. Again, within the domain of the carotid artery, two ultrasonic markers have attracted our attention: intima media thickness of the carotid artery and the presence of carotid plaque with its various focal characteristics. In the domain of intracranial circulation, the presence of arterial stenosis and the recruitment of collaterals are considered significant ultrasonic markers for the above-mentioned purpose. On the other hand, a series of serum, urine, and tissue biomarkers are found to be related to atherosclerotic disease. Future studies might address the issue of whether the addition of proven ultrasonic carotid indices to the aforementioned serum, urine, and tissue biomarkers could provide the vascular specialist with a better assessment of the atherosclerotic load and solidify their position as surrogate markers for the evaluation of atherosclerosis and stroke risk.

Leptomeningeal collateral flow in patients with middle cerebral artery occlusion assessed by transcranial Doppler

BACKGROUND AND PURPOSE

To explore the application value and clinical significance of transcranial Doppler(TCD)in assessing leptomeningeal collateral flow (LMF) status in patients with unilateral middle cerebral artery (MCA) occlusion.

METHODS

Medical records of patients with unilateral MCA occlusion confirmed by digital subtraction angiography (DSA) were analyzed retrospectively. The patients were divided into three groups according to LMF status, and the laboratory and imaging results were collected. Cerebral blood flow velocity (CBFV) of MCA, anterior cerebral artery (ACA), and posterior cerebral artery (PCA) on the affected side (ipsilateral, i) and the healthy side (contralateral, c) were measured and recorded by TCD. The results of CBFV changes detected by TCD were compared with those of DSA, and the correlation between CBFV changes and LMF status was analyzed.

RESULTS

Eighty-four patients with unilateral MCA occlusion were included. CBFViACA and CBFViPCA were significantly faster than CBFVcACA and CBFVcPCA in patients with good LMF status (p<.05). There was a significant positive correlation between CBFViACA and LMF status (r = 0.697, p<.001). There was statistical significance in receiver operating characteristic curve analysis of CBFViACA and CBFViPCA (p<.05). The area under the curve of CBFViACA and CBFViPCA, respectively, was 0.879 and 0.678, and the best cutoff value was 82 and 60.5 cm/s.

CONCLUSIONS

TCD can assess LMF status by detecting the changes of flow velocity of intracranial vessels. CBFV of ACA and PCA in patients with MCA occlusion is significantly correlated with LMF status by DSA. Assessing LMF status, CBFViACA, CBFViACA/CBFVcACA, and CBFViACA/CBFViMCA has the great diagnostic value, which is of great significance in guiding MCA occlusion patients to choose individualized treatment.

Classification of Intracranial Stenoses: Discrepancies between Transcranial Duplex Sonography and Computed Tomography Angiography

Transcranial color-coded duplex sonography (TCCS) and computed tomography angiography (CTA) are widely used to identify intracranial stenoses (ISs). We assessed concordance of IS grading between TCCS and CTA and proposed new TCCS criteria for severe IS ≥70%. One hundred two stroke patients (70 ± 13 y) with TCCS-identified IS were included. TCCS and CTA were performed within 24 h after admission. TCCS peak systolic velocity cutoffs for <50%/50%-69% stenoses were ≥155/≥220 cm/s (middle cerebral artery [MCA]-M1), ≥100/≥140 cm/s (MCA-M2), ≥120/≥155 cm/s (anterior cerebral artery [ACA]-A1), ≥100/≥145 cm/s (posterior cerebral artery [PCA]-P1 and PCA-P2), ≥90/≥120 cm/s (vertebral artery [VA]-V4) and ≥100/≥140 cm/s (basilar artery [BA]). Criteria for ≥70% stenoses were, despite variable flow velocities, post-stenotic flow alterations and/or leptomeningeal collateral flow. One hundred seventy-seven ISs were detected by TCCS. The number and grade (<50%/50%-69%/≥70%) of ISs were MCA 70 (39/19/12), BA 24 (9/11/4), ACA 21 (14/7/0), PCA 49 (29/15/5) and VA 13 (2/6/5). IS localization was confirmed by CTA in 84 of 177 cases (48%): MCA, 41/70 (59%); BA, 16/24 (67%); ACA 2/21, (10%); PCA, 17/49 (35%); VA, 8/13 (62%). Concordance between TCCS and CTA grading was (<50%/50%-69%/≥70%) 17%/19%/77%. TCCS and CTA exhibited substantial differences in the detection and grading of IS. Higher concordance rates for severe stenosis support our proposed TCCS criteria.

Guidelines for evaluation and management of cerebral collateral circulation in ischaemic stroke 2017

Collateral circulation plays a vital role in sustaining blood flow to the ischaemic areas in acute, subacute or chronic phases after an ischaemic stroke or transient ischaemic attack. Good collateral circulation has shown protective effects towards a favourable functional outcome and a lower risk of recurrence in stroke attributed to different aetiologies or undergoing medical or endovascular treatment. Over the past decade, the importance of collateral circulation has attracted more attention and is becoming a hot spot for research. However, the diversity in imaging methods and criteria to evaluate collateral circulation has hindered comparisons of findings from different cohorts and further studies in exploring the clinical relevance of collateral circulation and possible methods to enhance collateral flow. The statement is aimed to update currently available evidence and provide evidence-based recommendations regarding grading methods for collateral circulation, its significance in patients with stroke and methods under investigation to improve collateral flow.

Flow diversion within seven days after stroke onset is associated with favorable outcome in anterior circulation stroke

Anterior cerebral artery (ACA) flow diversion (FD), defined as ipsilateral mean velocity (MV) of at least 30% greater than the contralateral artery, could be seen an indirect sign of leptomeningeal collateralization in the setting of middle cerebral artery occlusion. The purpose of the study was to evaluate the association between dynamic FD and functional outcome in acute anterior stroke patients with large artery occlusion. Acute middle cerebral artery (MCA) or internal carotid artery (ICA) occlusive stroke patients within 12h were recruited. Transcranial Doppler ultrasound was done at baseline, 24h and 7d after onset and velocities of MCA and ACA were recorded. FD ratio was calculated by dividing the ipsilateral ACA MV by the contralateral ACA MV. FD was determined positive when FD ratio ≥1.3. Outcome was assessed by 90-day modified Rankin's Scale (mRS). The association between FD at different time points and functional outcome were analyzed. 16 patients (median age of 67 and 75% were male) were recruited. FD ratio showed a trend of decline but did not reach statistical significance (p=0.056). The proportion of FD at baseline (p=0.026), 24h (p=0.001) and 7d (p=0.044) was significantly higher in patients with favorable outcome. Higher FD ratio at baseline (p=0.02) and 24h (p=0.003) were significantly associated with favorable outcome. These results suggested that FD ratio showed a trend of decline after stroke onset. Presence of FD within 7days was associated with favorable functional outcome in acute MCA/ICA occlusive stroke patients.

Should We Treat a Patient's Symptoms or Angiography Image in TIA?: Two Case Reports

OBJECTIVES

Data on vascular status in the first hours after onset of transient ischemic attack (TIA) and its clinical significance are missing. Also, it is not known whether arterial occlusion, if present in TIA, should be the target for revascularization. We present 2 patients to demonstrate that TIA can be due to acute major intracranial arterial occlusion and to show how such arterial occlusion may affect the outcome.

CASE REPORTS

Two patients (54 and 63 years old) were diagnosed with TIA and at the same time had occlusion of the middle cerebral artery. No recanalization therapy was performed, as there was no or minimal neurological deficit. After several hours, the condition of both patients clinically deteriorated. One patient experienced spontaneous recanalization in the first 24 hours and clinical improvement over the subsequent days, resulting in complete resolution of the neurological deficit. The other patient did not recanalize and developed a significant brain infarction as well as hemorrhagic transformation requiring decompression surgery. Over the long term, the patient remained hemiplegic, unable to walk, and dependent on assistance for most activities of daily living.

CONCLUSIONS

The cases presented here raise important questions: (1) How frequently is arterial occlusion present in clinically asymptomatic patients? (2) If occlusion is present but not symptoms, is stroke a more correct diagnosis than TIA? and (3) What would be the benefit of recanalization therapy? Studies addressing these questions should be conducted.

Good collateral circulation predicts favorable outcomes in intravenous thrombolysis: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

Baseline collateral status has been correlated with outcomes of acute ischaemic stroke patients receiving intravenous thrombolysis (IVT) in previous studies. We carried out the current systematic review and meta-analysis to synthesize currently available evidence regarding such correlations.

METHODS

Full-text articles published since 2000 were retrieved and screened. The overall effect sizes of good versus poor collateral status over a series of outcomes and certain baseline features were estimated by random-effects models and presented in risk ratios (RRs) or mean differences.

RESULTS

Overall, 28 (3057 patients) and 14 (1584 patients) studies were included in qualitative and quantitative synthesis, respectively. Compared with poor pre-treatment collateral status, good collaterals showed a beneficial effect over the primary outcome of a favorable functional outcome at 3 or 6 months [RR, 2.45; 95% confidence interval, 1.94-3.09; P < 0.001] in acute ischaemic stroke patients receiving IVT treatment. However, such an effect tended to be different between studies with prescribed time windows of 3, 4.5 and > 4.5 h (up to 7 h), with the RRs being 2.21, 2.48 and 5.00, respectively (I²  = 53%). Good pre-treatment collaterals were also associated with a smaller infarct size at baseline, and a lower rate of symptomatic intracranial hemorrhage and a higher rate of neurological improvement early after IVT treatment.

CONCLUSIONS

The present study has demonstrated the prognostic value of baseline collateral circulation for outcomes of acute ischaemic stroke patients receiving intravenous reperfusion therapies, studied with different time windows of up to 7 h after ictus for IVT therapy.

Usefulness of transcranial Doppler ultrasound in evaluating cervical-cranial collateral circulations

Transcranial Doppler (TCD) ultrasound is a noninvasive, safe and cost-effective bedside test for evaluating cerebrovascular circulation in real time. It has been rapidly evolving from a simple noninvasive diagnostic tool to an imaging model with a broad spectrum of clinical applications. TCD can show the spectral flow waveforms, blood flow direction, velocities and intensity in the intracerebral vessels, adding physiologic information to other imaging models. TCD can also detect collateral channels through the anterior communicating artery, posterior communicating arteries, reversed ophthalmic artery, leptomeningeal collaterals, reversed basilar artery and reversed vertebral artery caused by hemodynamically significant carotid or intracranial stenosis. This article gives a brief overview of its use in evaluation of collateral circulation in carotid and intracranial steno-occlusive disease.

Early and continuous neurologic improvements after intravenous thrombolysis are strong predictors of favorable long-term outcomes in acute ischemic stroke

BACKGROUND

Intravenously administered tissue plasminogen activator (IV tPA) remains the only approved therapeutic agent for arterial recanalization in acute ischemic stroke (AIS). Considerable proportion of AIS patients demonstrate changes in their neurologic status within the first 24 hours of intravenous thrombolysis with IV tPA. However, there are little available data on the course of clinical recovery in subacute 2- to 24-hour window and its impact. We evaluated whether neurologic improvement at 2 and 24 hours after IV tPA bolus can predict functional outcomes in AIS patients at 3 months.

METHODS

Data for consecutive AIS patients treated with IV tPA within 4.5 hours of symptom onset during 2007-2011 were prospectively entered in our thrombolyzed registry. National Institutes of Health Stroke Scale (NIHSS) scores were recorded before IV tPA bolus, at 2 and 24 hours. Early neurologic improvement (ENI) at 2 hours was defined as a reduction in NIHSS score by 10 or more points from baseline or an absolute score of 4 or less points at 2 hours. Continuous neurologic improvement (CNI) was defined as a reduction of NIHSS score by 8 or more points between 2 and 24 hours or an absolute score of 4 or less points at 24 hours. Favorable functional outcomes at 3 months were determined by modified Rankin Scale (mRS) score of 0-1.

RESULTS

Of 2460 AIS patients admitted during the study period, 263 (10.7%) received IV tPA within the time window; median age was 64 years (range 19-92), with 63.9% being men, a median NIHSS score of 17 points (range 5-35), and a median onset-to-treatment time of 145 minutes (range 57-270). Overall, 130 (49.4%) thrombolyzed patients achieved an mRS score of 0-1 at 3 months. The female gender, age, and baseline NIHSS score were found to be significantly associated with CNI on univariate analysis. On multivariate analysis, NIHSS score at onset and female gender (odds ratio [OR]: 2.218, 95% confidence interval [CI]: 1.140-4.285; P=.024) were found to be independent predictors of CNI. Factors associated with favorable outcomes at 3 months on univariate analysis were younger age, female gender, hypertension, NIHSS score at onset, recanalization on transcranial Doppler (TCD) monitoring or repeat computed tomography (CT) angiography, ENI at 2 hours, and CNI. On multivariate analysis, NIHSS score at onset (OR per 1-point increase: .835, 95% CI: .751-.929, P<.001), 2-hour TCD recanalization (OR: 3.048, 95% CI: 1.537-6.046; P=.001), 24-hour CT angiographic recanalization (OR: 4.329, 95% CI: 2.382-9.974; P=.001), ENI at 2 hours (OR: 2.536, 95% CI: 1.321-5.102; P=.004), and CNI (OR: 7.253, 95% CI: 3.682-15.115; P<.001) were independent predictors of favorable outcomes at 3 months.

CONCLUSIONS

Women are twice as likely to have CNI from the 2- to 24-hour period after IV tPA. ENI and CNI within the first 24 hours are strong predictors of favorable functional outcomes in thrombolyzed AIS patients.

The Influence of Anterior Cerebral Artery Flow Diversion Measured by Transcranial Doppler on Acute Infarct Volume and Clinical Outcome in Anterior Circulation Stroke

Introduction

Anterior cerebral artery flow diversion, measured by transcranial Doppler ultrasound, is correlated with leptomeningeal collateral flow on digital subtraction angiography in the setting of middle cerebral artery occlusion. We aimed to assess the influence of flow diversion as a marker of leptomeningeal collateralization on infarct size and penumbral volume.

Methods

We assessed consecutive patients presenting within six-hours of ischaemic stroke. Anterior cerebral artery flow diversion, defined as ipsilateral mean velocity of at least 30% greater than the contralateral artery, was used as the Doppler index of leptomeningeal collateralization. Multivariable regression analysis was performed to assess the impact of anterior cerebral artery flow diversion, controlling for other important clinical variables. Leptomeningeal collateralization was also graded on computed tomography angiography. Infarct core and penumbral volumes were defined using computed tomography perfusion thresholds of cerebral blood volume and mean transit time. Infarct volume, reperfusion, and vessel status were measured at 24 h using magnetic resonance techniques.

Results

Fifty-three patients qualified for analysis. Anterior cerebral artery flow diversion was associated with good collateral flow on computed tomography angiography ( P < 0·001) and was an independent predictor of admission infarct core volume ( P < 0·001), and 24 h infarct volume ( P < 0·001). The likelihood of a favourable outcome (modified Rankin Score 0–2) was higher (odds ratio = 27·5, P < 0·001) in those with flow diversion.

Conclusions

Anterior cerebral artery flow diversion indicates effective leptomeningeal collateralization as measured by computed tomography angiography, and independently predicts acute infarct size and 90-day clinical outcome. Flow diversion appears to provide penumbral perfusion, offering some protection against infarct expansion. Acute bedside transcranial Doppler assessment of flow diversion aids prognostication and therapeutic decision making in anterior circulation stroke.

Partial aortic occlusion and cerebral venous steal: venous effects of arterial manipulation in acute stroke

Acute ischemic stroke therapy emphasizes early arterial clot lysis or removal. Partial aortic occlusion has recently emerged as an alternative hemodynamic approach to augment cerebral perfusion in acute ischemic stroke. The exact mechanism of cerebral flow augmentation with partial aortic occlusion remains unclear and may involve more than simple diversion of arterial blood flow from the lower body to cerebral collateral circulation. The cerebral venous steal hypothesis suggests that even a small increase in tissue pressure in the ischemic area will divert blood flow to surrounding regions with lesser tissue pressures. This may cause no-reflow (absence of flow after restoration of arterial patency) in the ischemic core and "luxury perfusion" in the surrounding regions. Such maldistribution may be reversed with increased venous pressure titrated to avoid changes in intracranial pressure. We propose that partial aortic occlusion enhances perfusion in the brain by offsetting cerebral venous steal. Partial aortic occlusion redistributes blood volume into the upper part of the body, manifested by an increase in central venous pressure. Increased venous pressure recruits the collapsed vascular network and, by eliminating cerebral venous steal, corrects perifocal perfusion maldistribution analogous to positive end-expiratory pressure recruitment of collapsed airways to decrease ventilation/perfusion mismatch in the lungs.

Design of a PROspective multi-national CLOTBUST collaboration on reperfusion therapies for stroke (CLOTBUST-PRO)

BACKGROUND

The benefit of intravenous (i.v.) tissue plasminogen activator (tPA) in acute ischemic stroke (IS) is attributable to lysis of thrombus and restoration of perfusion to ischemic but not yet infarcted brain.

AIMS

Our multicentre collaborative group prospectively implemented a protocol for transcranial Doppler assessment of intracranial recanalization with tPA treatment based on the CLOTBUST clinical trial (CLOTBUST-PRO). We aim to determine whether early recanalization (within 1 h from tPA bolus) is independently associated with better 3-month outcome in patients with intracranial arterial occlusions and correlates to a shorter time interval elapsed from symptom onset to tPA bolus.

SUBJECTS AND METHODS

Consecutive patients with acute IS due to intracranial arterial occlusions will be treated with standard i.v.-tPA and continuously monitored with 2 MHz Transcranial Doppler for arterial recanalization. Early recanalization will be determined with the previously validated Thrombolysis in Brain Ischemia flow-grading system within 60 min after tPA bolus. Power calculations are based on the assumption of alpha=0.05 (two-sided test) and probabilities of functional independence at 3 months of 0.50 and 0.35 in patients with early complete recanalization and persisting occlusion, respectively. Detection of a 15% difference with a power of 0.824 requires an estimated sample of 480 patients of whom 25% are expected to achieve early recanalization while 75% will have persisting occlusion at 1 h after tPA bolus. We also plan to test prespecified secondary hypotheses within the projected study sample.

CONCLUSIONS

CLOTBUST-PRO is designed to determine if the timing (within 1 h from tPA bolus) of tPA-induced arterial recanalization is an independent determinant of 3-month functional recovery. We also seek to demonstrate that the sooner the tPA is given to stroke patients, the earlier the recanalization occurs and the greater is the likelihood of functional independence at 3 months.

Ultrasound-enhanced thrombolysis in acute ischemic stroke: potential, failures, and safety

Experimental and pilot clinical evidence shows that thrombolysis with intravenous tissue plasminogen activator (TPA) can be enhanced with ultrasound. Ultrasound delivers mechanical pressure waves to the clot, thus exposing more thrombus surface to circulating drug. The international multicenter phase II CLOTBUST trial showed that, in patients with acute ischemic stroke, transcranial Doppler (TCD) monitoring augments TPA-induced arterial recanalization, with a nonsignificant trend toward an increased rate of recovery from stroke, compared with placebo. In the CLOTBUST trial, the dramatic clinical recovery from stroke coupled with complete recanalization within 2 hours after TPA bolus occurred in 25% of patients treated with TPA + TCD (n = 63), compared with 8% of those who received TPA alone (n = 63, P = 0.02). Different results were achieved in smaller studies that used transcranial color-coded duplex sonography (TCCD) and a nonimaging therapeutic ultrasound system. The findings of the TRUMBI trial (26 patients) underscored the adverse bioeffects of mid-kilohertz (300 kHz) ultrasound, such as promotion of bleeding in brain areas both affected and unaffected by ischemia. Exposure to multifrequency, multielement duplex ultrasound resulted in a trend toward a higher risk of hemorrhagic transformation. To further enhance the ability of TPA to break up thrombi, current ongoing clinical trials include phase II studies of a single-beam, 2-MHz TCD with perflutren lipid microspheres. Enhancement of intra-arterial TPA delivery is being clinically tested with 1.7-2.1 MHz pulsed-wave ultrasound (EKOS catheter). Multinational dose escalation studies of microspheres and the development of an operator-independent ultrasound device are underway.

Accuracy of serial National Institutes of Health Stroke Scale scores to identify artery status in acute ischemic stroke

BACKGROUND

Early recovery after intravenous thrombolysis can be observed in stroke; however, the utility of measuring clinical improvement to assess artery status has not been established. We sought to determine the accuracy of serial National Institutes of Health Stroke Scale (NIHSS) scores to detect complete early recanalization of the middle cerebral artery.

METHODS AND RESULTS

Data from the CLOTBUST trial (Combined Lysis of Thrombus in Brain Ischemia Using Transcranial Ultrasound and Systemic tPA) were used to determine the most sensitive and specific NIHSS-derived parameter to identify complete recanalization. Then, reproducibility was tested against a separate patient population (Barcelona data set). NIHSS scores were determined before tissue plasminogen activator bolus and at 60 and 120 minutes in both data sets. Receiver operating characteristic curves were used to compare test performance. The accuracy of individual cutoffs was demonstrated by sensitivity, specificity, and positive and negative predictive values. A total of 122 patients in the CLOTBUST data set and 98 in the Barcelona data set received 0.9 mg/kg intravenous tissue plasminogen activator [mean age 69+/-12 versus 72+/-12 years, 57% male versus 51% male, median NIHSS 16 versus 17 points, mean time from onset to treatment 140+/-32 versus 177+/-59 minutes, and complete recanalization of the middle cerebral artery in 19% versus 17%). For identification of recanalization, an NIHSS score reduction of > or = 40% offered the best tradeoff, with sensitivity, specificity, positive predictive value, and negative predictive value of 65%, 85%, 50%, and 91% at 60 minutes and 74%, 80%, 58%, and 89% at 120 minutes, respectively. Test performance was equal in the Barcelona data set.

CONCLUSIONS

Relative changes in serial NIHSS scores can serve as a simple clinical indicator of arterial status after intravenous thrombolysis. Accuracy parameters are affected by the process of recanalization and its varying clinical significance.

Ultrasound enhanced thrombolysis: applications in acute cerebral ischemia

Intravenous tissue plasminogen activator (TPA) improves patient chances to recover from stroke by inducing mostly partial recanalization of large intracranial thrombi. TPA activity can be enhanced with ultrasound including 2 MHz transcranial Doppler (TCD). TCD identifies residual blood flow signals around thrombi, and, by delivering mechanical pressure waves, exposes more thrombus surface to circulating TPA. The international multi-center CLOTBUST trial showed that ultrasound enhances thrombolytic activity of a drug in humans thereby confirming multi-disciplinary experimental research conducted worldwide for the past 30 years.

In the CLOTBUST trial, the dramatic clinical recovery from stroke coupled with complete recanalization within 2 hours after TPA bolus occurred in 25% of patients treated with TPA+TCD compared to 8% who received TPA alone (p=0.02). Complete clearance of a thrombus and dramatic recovery of brain functions during treatment are feasible goals for ultrasound-enhanced thrombolysis that can lead to sustained recovery. An early boost in brain perfusion seen in the Target CLOTBUST group resulted in a trend of 13% more patients achieving favorable outcome at 3 months, subject for a pivotal trial. However, different results were achieved in a small TRUMBI trial and another study that used Transcranial Color-Coded Duplex Sonography (TCCD). Adverse bio-effects of mid-KHz (300) ultrasound promote bleeding, including brain areas not-affected by ischemia while exposure to multi-frequency / multi-element duplex ultrasound resulted in a trend towards higher risk of hemorrhagic transformations.

To further enhance the ability of TPA to break up thrombi, current ongoing clinical trials include phase II studies of a single beam 2 MHz TCD with perflutren-lipid microspheres. Enhancement of intra-arterial TPA delivery is being clinically tested with 1.7-2.1 MHz pulsed wave ultrasound (EKOS catheter). Multi-national dose escalation studies of microspheres and the development of an operator independent ultrasound device are underway.