Evaluation of cerebrovascular disease by combined extracranial and transcranial Doppler sonography. Experience in 1,039 patients

Physics-Informed Neural Networks for Brain Hemodynamic Predictions Using Medical Imaging

Determining brain hemodynamics plays a critical role in the diagnosis and treatment of various cerebrovascular diseases. In this work, we put forth a physics-informed deep learning framework that augments sparse clinical measurements with one-dimensional (1D) reduced-order model (ROM) simulations to generate physically consistent brain hemodynamic parameters with high spatiotemporal resolution. Transcranial Doppler (TCD) ultrasound is one of the most common techniques in the current clinical workflow that enables noninvasive and instantaneous evaluation of blood flow velocity within the cerebral arteries. However, it is spatially limited to only a handful of locations across the cerebrovasculature due to the constrained accessibility through the skull's acoustic windows. Our deep learning framework uses in vivo real-time TCD velocity measurements at several locations in the brain combined with baseline vessel cross-sectional areas acquired from 3D angiography images and provides high-resolution maps of velocity, area, and pressure in the entire brain vasculature. We validate the predictions of our model against in vivo velocity measurements obtained via four-dimensional (4D) flow magnetic resonance imaging (MRI) scans. We then showcase the clinical significance of this technique in diagnosing cerebral vasospasm (CVS) by successfully predicting the changes in vasospastic local vessel diameters based on corresponding sparse velocity measurements. We show this capability by generating synthetic blood flow data after cerebral vasospasm at various levels of stenosis. Here, we demonstrate that the physics-based deep learning approach can estimate and quantify the subject-specific cerebral hemodynamic variables with high accuracy despite lacking knowledge of inlet and outlet boundary conditions, which is a significant limitation for the accuracy of the conventional purely physics-based computational models.

Simultaneous monitoring of the middle cerebral and basilar arteries to detect right-to-left shunts using transcranial Doppler by agitated saline administration

Transcranial Doppler (TCD) is an easy, non-invasive, and real-time monitoring device for detecting right-to-left shunts (RLS). Nonetheless, it has limited benefits in patients with poor temporal windows. Therefore, we aimed to investigate whether the basilar artery (BA) window was as effective as the middle cerebral artery (MCA) in detecting RLS during TCD monitoring. Overall, we enrolled 344 patients with stroke, transient ischemic attack, headache, or dizziness. MCA and BA were monitored using a modified headset. To investigate the feasibility of the suboccipital window in detecting RLS, we instituted an evaluation tool with three tiers to evaluate microembolic signals (MESs) during TCD monitoring. Tier 1: TCD monitoring of the MCA (bilaterally) in the resting state, tier 2: TCD monitoring of the MCA (bilaterally) while performing the Valsalva maneuver, and tier 3: TCD monitoring of the index MCA and BA while performing the Valsalva maneuver. In tiers 2 and 3, a high agreement rate of 0.808 and 0.809 (p < 0.001), respectively, on the weighted kappa index, and a high intra-class correlation coefficient of 0.982 and 0.986 (p < 0.001), respectively, were observed on detecting MESs. Our data suggests that the BA window is as effective as the MCA window for detecting RLS on TCD.

Design, Development, and Operation of a Low-Intensity Focused Ultrasound Pulsation (LIFUP) System for Clinical Use

Noninvasive low-intensity focused ultrasound pulsation (LIFUP) neuromodulation provides a unique approach to both investigating and treating the brain. This work describes a well-calibrated, simple-to-use ultrasound stimulation system for neuromodulation studies. It provides a single-element 650-kHz transducer design and a straightforward control mechanism, with extensive calibration and internal electronic monitoring to prevent unwanted over or under treatment. One goal of this approach is to relieve researchers of many of the details associated with developing their own exposure equipment. A unique transducer positioning system and distinctive MRI fiducial targets simplify alignment and targeting. The system design, control software, calibration, and alignment techniques are described in detail. Examples of transducer targeting and neurostimulation using the system are provided.

Examination of Structural Variations of the Circle of Willis by 3D Time-of-Flight Magnetic Resonance Angiography

Objectives: To explore structural variations of the circle of Willis using three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA), and to compare this modality with digital subtraction angiography (DSA). Methods: A total of 819 consecutive patients suspected of having cerebral vascular diseases underwent 3D-TOF-MRA, followed by DSA within 2 weeks. We report accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 3D-TOF-MRA compared with DSA. Results: The sensitivity and specificity of combined analyses were 90-100 and 98-100%, respectively. The sensitivity and NPV of 3D-TOF-MRA images for A-, C-, D-, and H-types of circle of Willis anomalies were 100%. The specificity, accuracy and sensitivity were all 100% for detecting absence of the anterior communicating artery (ACOA). Sensitivity, specificity, PPV, and NPV were all 100% for detecting F-type. The sensitivity and PPV of volume rendered (VR) images for the B-, E-, and G-types were relatively low (85.0, 86.2, and 73.8%, respectively). Maximum intensity projection (MIP) was somewhat better (88.3, 89.2, and 81.8%, respectively). Combined analyses were better still (95.8, 96.1, and 99.0%, respectively). Specificity and NPVs were high (99.3-100%). Conclusions: 3D-TOF-MRA compares well to DSA for evaluation of the structure of the circle of Willis. As 3D-TOF-MRA is a non-invasive modality, it may be preferred as a means to evaluate structural variations of the circle of Willis.

Assessment of intracranial venous blood flow after subarachnoid hemorrhage: a new approach to diagnose vasospasm with transcranial color-coded duplex sonography

OBJECTIVETranscranial color-coded duplex sonography (TCCS) is a reliable tool that is used to assess vasospasm in the M1 segment of the middle cerebral artery (MCA) after subarachnoid hemorrhage (SAH). A distinct increase in blood flow velocity (BFV) is the principal criterion for vasospasm. The MCA/internal carotid artery (ICA) index (Lindegaard Index) is also widely used to distinguish between vasospasm and cerebral hyperperfusion. However, extracranial ultrasonography assessment of the neck vessels might be difficult in an intensive care unit. Therefore, the authors evaluated whether the relationship of intracranial arterial to venous BFV might indicate vasospasm with similar or even better accuracy.METHODSPatients who presented between 2008 and 2015 with aneurysmal SAH were prospectively enrolled in the study. Digital subtraction angiography (DSA) and TCCS were performed within 24 hours of each other to assess vasospasm 8-10 days after SAH. The following different TCCS parameters were analyzed to assess vasospasm in the MCA and were compared with the gold-standard DSA parameters: 1) mean time-averaged maximum BFV (Vmean) of the MCA, 2) peak systolic velocity (PSV) of the MCA, 3) the Lindegaard Index using Vmean as well as PSV, and 4) a new arteriovenous index (AVI) between the MCA and the basal vein of Rosenthal using Vmean and PSV. The best cutoff values for these parameters to distinguish vasospasm from normal perfusion or hyperperfusion were calculated using receiver operating characteristic curve analysis. Sensitivity, specificity, positive predictive value, and negative predictive value as well as the overall accuracy for each cutoff value were analyzed.RESULTSA total of 102 patients (mean age 52 ± 12 years) were evaluated. Bilateral MCA assessment by TCCS was successful in all patients. In 6 cases (3%), the BFV of the basal vein of Rosenthal could not be analyzed. The AVI could not be calculated in 50 of 204 cases (25%) because the insonation quality was very low in one of the ICAs. An AVI > 10 for Vmean and an AVI > 12 for systolic velocity provided the highest accuracies of 87% and 86%, respectively. Regarding the Lindegaard Index, the accuracy was highest using a threshold of > 3 for the mean BFV (84%) as well as systolic BFV (80%). BFVs in the MCA of ≥ 120 cm/sec (Vmean) and ≥ 200 cm/sec (PSV) predicted vasospasm with accuracies of 84% and 83%, respectively. A combined analysis of the MCA BFV and the AVI led to a slight increase in specificity (Vmean, 94%; PSV, 93%) and positive predictive value (Vmean, 88%; PSV 86%) without further improvement in accuracy (Vmean, 88%; PSV, 84%).CONCLUSIONSThe intracranial AVI is a reliable parameter that can be used to assess vasospasm after SAH. Its reliability for differentiating vasospasm and hyperperfusion is slightly higher than that for the established Lindegaard Index, and this method has the additional advantage of a remarkably lower failure rate.

Impact of clinical training on supra-aortic duplex and transcranial doppler examination concordance

Sonographic tests are observer-dependent. With 1,527 consecutive patients, 22 trainees were assessed at baseline and after a hands-on 1:1 program, with a pre-examination median of 76 studies/trainee. We evaluated the required number of supervised examinations to reach a 0.80 kappa index (ki). Statistics included linear and exponential generalized estimating equation models. In the exponential model, 76 studies for carotid-duplex and >102 for vertebral-duplex and transcranial Doppler were needed for a 0.80 ki. "Relevant-categories" after-training ki was 0.80 in carotid-duplex and transcranial Doppler but 0.60 in vertebral-duplex. A fixed training does not guarantee a high ki. Measuring the acquired skills of every trainee would improve quality. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:571-579, 2016.

Effect of Age on Transcranial Doppler Velocities in Patients with Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

It is not well understood whether age impacts transcranial Doppler (TCD) mean flow velocities (MFVs) in patients with aneurysmal subarachnoid hemorrhage (SAH) with or without delayed cerebral ischemia (DCI). The aim of our study was to analyze the behavior of TCD MFV during the first 7 days after SAH in patients of different ages and correlate them with the occurrence of DCI.

METHODS

This study is a databank analysis of patients with SAH admitted between 2010 and 2012 in a single center. We analyzed mean MFV of bilateral middle cerebral arteries (MCAs) in all patients enrolled in the study on days 1, 3 and 7. The correlation between age and TCD MFV was analyzed using a univariate linear regression model.

RESULTS

Fifty-five patients were studied. Starting on the third day after the bleeding, increasing age was associated with slower MFVs. This trend was not affected by the interrogation of the right or left MCA. After correction to include only patients who developed DCI, the same findings persisted on days 3 and 7.

CONCLUSION

Older age was correlated with a significant decrease on TCD velocities in patients with SAH, even after correction for patients who developed DCI.

Neurovascular decoupling is associated with severity of cerebral amyloid angiopathy

OBJECTIVES

We used functional MRI (fMRI), transcranial Doppler ultrasound, and visual evoked potentials (VEPs) to determine the nature of blood flow responses to functional brain activity and carbon dioxide (CO2) inhalation in patients with cerebral amyloid angiopathy (CAA), and their association with markers of CAA severity.

METHODS

In a cross-sectional prospective cohort study, fMRI, transcranial Doppler ultrasound CO2 reactivity, and VEP data were compared between 18 patients with probable CAA (by Boston criteria) and 18 healthy controls, matched by sex and age. Functional MRI consisted of a visual task (viewing an alternating checkerboard pattern) and a motor task (tapping the fingers of the dominant hand).

RESULTS

Patients with CAA had lower amplitude of the fMRI response in visual cortex compared with controls (p = 0.01), but not in motor cortex (p = 0.22). In patients with CAA, lower visual cortex fMRI amplitude correlated with higher white matter lesion volume (r = -0.66, p = 0.003) and more microbleeds (r = -0.78, p < 0.001). VEP P100 amplitudes, however, did not differ between CAA and controls (p = 0.45). There were trends toward reduced CO2 reactivity in the middle cerebral artery (p = 0.10) and posterior cerebral artery (p = 0.08).

CONCLUSIONS

Impaired blood flow responses in CAA are more evident using a task to activate the occipital lobe than the frontal lobe, consistent with the gradient of increasing vascular amyloid severity from frontal to occipital lobe seen in pathologic studies. Reduced fMRI responses in CAA are caused, at least partly, by impaired vascular reactivity, and are strongly correlated with other neuroimaging markers of CAA severity.

Transcranial Doppler investigation of hemodynamic alterations associated with blunt cervical vascular injuries in trauma patients

OBJECTIVES

Blunt cervical vascular injuries, often missed with current screening methods, have substantial morbidity and mortality, and there is a need for improved screening. Elucidation of cerebral hemodynamic alterations may facilitate serial bedside monitoring and improved management. Thus, the objective of this study was to define cerebral flow alterations associated with single blunt cervical vascular injuries using transcranial Doppler sonography and subsequent Doppler waveform analyses in a trauma population.

METHODS

In this prospective pilot study, patients with suspected blunt cervical vascular injuries had diagnoses by computed tomographic angiography and were examined using transcranial Doppler sonography to define cerebral hemodynamics. Multiple vessel injuries were excluded for this analysis, as the focus was to identify hemodynamic alterations from isolated injuries. The inverse damping factor characterized altered extracranial flow patterns; middle cerebral artery flow velocities, the pulsatility index, and their asymmetries characterized altered intracranial flow patterns.

RESULTS

Twenty-three trauma patients were evaluated: 4 with single internal carotid artery injuries, 5 with single vertebral artery injuries, and 14 without blunt cervical vascular injuries. All internal carotid artery injuries showed a reduced inverse damping factor in the internal carotid artery and dampened ipsilateral mean flow and peak systolic velocities in the middle cerebral artery. Vertebral artery injuries produced asymmetry of a similar magnitude in the middle cerebral artery mean flow velocity with end-diastolic velocity alterations.

CONCLUSIONS

These data indicate that extracranial and intracranial hemodynamic alterations occur with internal carotid artery and vertebral artery blunt cervical vascular injuries and can be quantified in the acute injury phase by transcranial Doppler indices. Further study is required to elucidate cerebral flow changes resulting from a single blunt cervical vascular injury, which may guide future management to preserve cerebral perfusion after trauma.

Use of Transcranial Doppler (TCD) ultrasound in the Neurocritical Care Unit

Transcranial Doppler (TCD) is a portable device that uses a handheld 2-MHz transducer. It is most commonly used in subarachnoid hemorrhage where cerebral blood flow velocities in major intracranial blood vessels are measured to detect vasospasm in the first 2 to 3 weeks. TCD is used to detect vasospasm in traumatic brain injury and post-tumor resection, measurement of cerebral autoregulation and cerebrovascular reactivity, diagnosis of acute arterial occlusions in stroke, screening for patent foramen ovale and monitoring of emboli. It can be used to detect abnormally high intracranial pressure and for confirmation of total cerebral circulatory arrest in brain death.

Sickle cell anemia: reference values of cerebral blood flow determined by continuous arterial spin labeling MRI

Sickle cell anemia (SCA) is a chronic illness associated with progressive deterioration in patients' quality of life. The major complications of SCA are cerebrovascular accidents (CVA) such as asymptomatic cerebral infarct or overt stroke. The risk of CVA may be related to chronic disturbances in cerebral blood flow (CBF), but the thresholds of "normal" steady-state CBF are not well established. The reference tolerance limits of CBF can be useful to estimate the risk of CVA in asymptomatic children with SCA, who are negative for hyperemia or evidence of arterial narrowing. Continuous arterial spin labeling (CASL) MR perfusion allows for non-invasive quantification of global and regional CBF. To establish such reference tolerance limits we performed CASL MR examinations on a 3-Tesla MR scanner in a carefully selected cohort of 42 children with SCA (mean age, 8.1±3.3 years; range limits, 2.3-14.4 years; 24 females), who were not on chronic transfusion therapy, had no history of overt stroke or transient ischemic attack, were free of signs and symptoms of focal vascular territory ischemic brain injury, did not have intracranial arterial narrowing on MR angiography and were at low risk for stroke as determined by transcranial Doppler ultrasonography.

The carotid artery as an alternative site to the middle cerebral artery for reproducible estimates of autoregulation index

Temporal insonation is not always possible for the middle cerebral artery (MCA) for blood flow velocity (BFV) measurements, to estimate cerebral autoregulation. We compared BFV and cerebral autoregulation estimates from the common-carotid (CCA) and internal-carotid arteries (ICA) with the MCA. BFV was measured at the CCA, ICA and MCA, synchronously with blood pressure, heart rate and end-tidal CO2 and was recorded onto a data acquisition system. The autoregulation index (ARI) estimated using the Tiecks model. Eleven healthy volunteers (7 women, 33 ± 9 years old) were recruited. BFVs in the MCA, CCA and ICA were 60.3 ± 8.9, 64.4 ± 6.5 and 69.2 ± 4.8 cm/s, respectively. ARI estimates were not significantly different (5.6 ± 0.8, 6.0 ± 1.1 and 5.9 ± 0.5, respectively). Good reproducibility over repeated measurements was evidenced by low coefficient of variation of standard error of measurement for BFV and ARI. The CCA and ICA are alternatives to the MCA, where insonation is impossible, because of an absent trans-temporal window or where it cannot be tolerated, such as in patients with head injury.

Simultaneous bilateral real-time 3-d transcranial ultrasound imaging at 1 MHz through poor acoustic windows

Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%-29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging-the ultrasound brain helmet-and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field.

Accuracy of transcranial colour-coded sonography in the diagnosis of anterior cerebral artery vasospasm

BACKGROUND AND PURPOSE

Transcranial colour-coded sonography (TCCS) has been proven to be a method of high performance in the diagnosis of spasm of the middle cerebral artery (MCA). Relevant data concerning the anterior cerebral artery (ACA) varies amongst studies. The aim of this study was to assess the performance of TCCS in the diagnosis of spasm affecting the ACA.

MATERIAL AND METHODS

Ninety-two patients (39 women and 53 men, age 51 ± 12.1 years) were examined using TCCS before cerebral angiography. Of 184 examined ACAs, only 133 arteries could be visualized due to insufficiency of the temporal acoustic window. Therefore, only 15 out of 25 arteries in which vasospasm was diagnosed with angiography (by two neuroradiologists not informed about the sonographic findings) could be included in the analysis. Receiver operating characteristic (ROC) curves were constructed for specific blood flow velocities: peak systolic (PSV), mean (M) and end-diastolic (EDV). The area under the ROC curve was used to measure the overall diagnostic performance of TCCS.

RESULTS

The area under the ROC curve for PSV was 0.83, which indicates good performance. The PSV threshold of 98 cm/s corresponded to maximum accuracy and was associated with 71% sensitivity vs. 88% specificity. Average systolic blood flow velocity in the vessels with vasospasm was 129 cm/s, whereas in unaffected vessels it was 76 cm/s.

CONCLUSIONS

The accuracy of TCCS in the diagnosis of ACA spasm is relatively high - the value of the area under the ROC amounts to 0.83. PSV performs best and the threshold of 98 cm/s is associated with an optimal trade-off between sensitivity and specificity.

The prognostic value of pulsatility index, flow velocity, and their ratio, measured with TCD ultrasound, in patients with a recent TIA or ischemic stroke

BACKGROUND - Increased flow velocities, and combinations of low mean flow velocity (MFV) and a high pulsatility index (PI) are associated with intracranial arterial disease. We investigated the association of MFV and the ratio of PI and MFV (PI-MFV ratio) in the middle cerebral artery (MCA) with recurrence of vascular events in patients with a transient ischemic attack (TIA) or minor ischemic stroke. METHODS - Five hundred and ninety-eight consecutive patients underwent TCD investigation. Outcome events were fatal or non-fatal stroke and the composite of stroke, myocardial infarction, or vascular death (major vascular events). Hazard ratios (HR) were estimated with Cox proportional hazards multiple regression method, adjusted for age, gender, and vascular risk factors. RESULTS - TCD registration was successful in 489 patients. Mean follow-up was 2.1 years. Cumulative incidence was 9% for all stroke and 12% for major vascular events. MFV over 60.5 cm/s increased the risk for both stroke (HR 2.8; 95% CI: 1.3-6.0) and major vascular events (HR 2.6; 95% CI: 1.3-5.0). Each unit increase in PI-MFV ratio was associated with a HR 2.8 (95% CI: 1.7-4.8) for stroke and HR 2.2 (95% CI: 1.3-3.6) for major vascular events. CONCLUSION - In patients with a TIA or non-disabling ischemic stroke, MFV and the PI-MFV ratio in the MCA are independent prognostic factors for recurrent vascular events.

Sickle cell disease: reference values and interhemispheric differences of nonimaging transcranial Doppler blood flow parameters

BACKGROUND AND PURPOSE

TCD screening is widely used to identify children with SCD at high risk of stroke. Those with high mean flow velocities in major brain arteries have increased risk of stroke. Thus, our aim was to establish reference values of interhemispheric differences and ratios of blood flow Doppler parameters in the tICA, MCA, and ACA as determined by conventional TCD in children with sickle cell anemia.

MATERIALS AND METHODS

Reference limits of blood flow parameters were established on the basis of a consecutive cohort of 56 children (mean age, 100 ± 40 months; range, 29-180 months; 30 females) free of neurologic deficits and intracranial stenosis detectable by MRA, with blood flow velocities <170 cm/s by conventional TCD. Reference limits were estimated by using tolerance intervals, within which are included with a probability of .90 of all possible data values from 95% of a population.

RESULTS

Average peak systolic velocities were significantly higher in the right hemisphere in the MCA and ACA (185 ± 28 cm/s versus 179 ± 27 and 152 ± 30 cm/s versus 143 ± 34 cm/s respectively). Reference limits for left-to-right differences in the mean flow velocities were the following: -43 to 33 cm/s for the MCA; -49 to 38 cm/s for the ACA, and -38 to 34 cm/s for the tICA, respectively. Respective reference limits for left-to-right velocity ratios were the following: 0.72 to 1.25 cm/s for the MCA; 0.62 to 1.39 cm/s for the ACA, and 0.69 to 1.27 cm/s for the tICA. Flow velocities in major arteries were inversely related to age and Hct or Hgb.

CONCLUSIONS

The study provides reference intervals of TCD flow velocities and their interhemispheric differences and ratios that may be helpful in identification of intracranial arterial stenosis in children with SCD undergoing sonographic screening for stroke prevention.

Sickle cell disease and transcranial Doppler imaging: inter-hemispheric differences in blood flow Doppler parameters

BACKGROUND AND PURPOSE

to establish reference values of interhemispheric differences and ratios of blood flow Doppler parameters in the terminal internal carotid artery, middle cerebral artery, and anterior cerebral artery in children with sickle cell anemia.

METHODS

fifty-seven out of 74 recruited children (mean age, 7.8 ± 3.4 years; range limits, 3-14 years), who were free of neurological deficits and intracranial narrowing detectable by MRA and had flow velocities <170 cm/s by conventional transcranial Doppler ultrasound, underwent transcranial color-coded duplex ultrasonography. Reference limits of flow parameters corrected and uncorrected for the angle of insonation were estimated using tolerance intervals, with P=0.90 for all possible data values from 95% of a population.

RESULTS

reference limits for left-to-right differences in cm/s in the mean angle-corrected and uncorrected flow velocities were -56 to 53 and -72 to 75 for middle cerebral artery, -49 to 57 and -81 to 91 for anterior cerebral artery, and -55 to 64 and -73 to 78 for terminal internal carotid artery, respectively. Respective reference limits for left-to-right velocity ratios were 0.31 to 1.84 and 0.38 to 1.75 for middle cerebral artery, 0.48 to 2.99 and 0.46 to 2.89 for anterior cerebral artery, and 0.61 to 2.56 and 0.56 to 2.23 for terminal internal carotid artery.

CONCLUSIONS

the study provides reference limits of interhemispheric differences and ratios of blood flow Doppler parameters that may be helpful in identification of intracranial arterial narrowing in children with sickle cell disease undergoing ultrasound screening for stroke prevention.

Patient Age and Vasospasm After Subarachnoid Hemorrhage

BACKGROUND:

Subarachnoid hemorrhage (SAH) from a ruptured intracranial aneurysm is a devastating disease with high mortality and morbidity. The incidence of SAH increases with advancing age.

OBJECTIVE:

To determine whether age is an independent predictor of angiographic vasospasm, delayed ischemic neurological deficits (DINDs), or abnormal transcranial Doppler (TCD) measurements in patients with aneurysmal subarachnoid hemorrhage.

METHODS:

Data from CONSCIOUS-1 (Clazosentan to Overcome Neurological Ischemia and Infarct Occurring After Subarachnoid Hemorrhage study), a dose-finding study of clazosentan, were used. Data on angiographic vasospasm, DINDs, and TCD abnormalities were prospectively recorded as well as baseline characteristics and treatment data. Patient age was considered in 3 ways: as a continuous variable, dichotomized at age 65 years, and categorized by decade. Age was investigated as the main variable, whereas other possible confounding variables were adjusted for in the multiple logistic regression modeling with each of 3 dichotomized vasospasm outcome measures, presence or absence of angiographic vasospasm, DINDs, and TCD abnormalities as the dependent variable.

RESULTS:

The proportions of patients with angiographic vasospasm, DINDs, and TCD abnormalities were 45%, 19%, and 81%, respectively. Age, whether considered as a continuous, dichotomous, or a categorical variable, was not significantly associated with angiographic vasospasm, DINDs, or abnormal TCD measurements.

CONCLUSION:

Age does not seem to be a significant predictor for cerebral vasospasm after subarachnoid hemorrhage.

The role of transcranial Doppler ultrasonography in the diagnosis and management of vasospasm after aneurysmal subarachnoid hemorrhage

Transcranial Doppler ultrasonography (TCD) is a tool employed by the neurosurgeon and neurointensivist in the management of vasospasm in the intensive care unit after aneurysmal subarachnoid hemorrhage. A review of the current indications, monitoring parameters, indices, and relevance of modern TCD technology is provided, as well as algorithms for the use of TCD ultrasonography in the management of patients with subarachnoid hemorrhage. Other current uses of TCD ultrasonography are also discussed in the setting of neurocritical care.

Sonothrombolysis: an emerging modality for the management of stroke

OBJECTIVE

Ischemic stroke and intracranial hemorrhage remain a persistent scourge in Western civilization. Therefore, novel therapeutic modalities are desperately needed to expand the current limitations of treatment. Sonothrombolysis possesses the potential to fill this void because it has experienced a dramatic evolution from the time of early conceptualization in the 1960s. This process began in the realm of peripheral and cardiovascular disease and has since progressed to encompass intracranial pathologies. Our purpose is to provide a comprehensive review of the historical progression and existing state of knowledge, including underlying mechanisms as well as evidence for clinical application of ultrasound thrombolysis.

METHODS

Using MEDLINE, in addition to cross-referencing existing publications, a meticulous appraisal of the literature was conducted. Additionally, personal communications were used as appropriate.

RESULTS

This appraisal revealed several different technologies close to broad clinical use. However, fundamental questions remain, especially in regard to transcranial high-intensity focused ultrasound. Currently, the evidence supporting low intensity ultrasound's potential in isolation, without tissue plasminogen, remains uncertain; however, possibilities exist in the form of microbubbles to allow for focal augmentation with minimal systemic consequences. Alternatively, the literature clearly demonstrates, the efficacy of high-intensity focused ultrasound for independent thrombolysis.

CONCLUSION

Sonothrombolysis exists as a promising modality for the noninvasive or minimally invasive management of stroke, both ischemic and hemorrhagic. Further research facilitating clinical application is warranted.

The application of ultrasound in the management of cerebral arteriovenous malformation

Ultrasound is used in the diagnosis, treatment and follow-up of cerebral arteriovenous malformation (AVM). Several parameters including flow velocity, flow volume, resistance index, pulsatility index, vasomotor reactivity and their influencing factors are reviewed. The applications of ultrasound in the preoperative evaluation, intraoperative monitor and postoperative follow-up of AVM, are summarized. Although some limits exist, ultrasound can provide more reliable information about AVM, if lesions are classified according to their characteristics, compared in different conditions between preoperation and postoperation, feeding and non-feeding side, patients and healthy adults, and if ultrasound method is combined with other examinations and different developed ultrasound techniques. With the appearance and development of new ultrasound technique, its application will be wider in management of AVM.

Unilateral versus bilateral middle cerebral artery detection of right-to-left shunt by power M-mode transcranial doppler

BACKGROUND AND PURPOSE

Comparison was performed between unilateral and bilateral power M-mode transcranial Doppler to detect right-to-left circulatory shunt (RLS).

METHODS

Recorded Doppler data from 87 patients with confirmed RLS referred for transcatheter closure of patent foramen ovale were reanalyzed for embolic tracks (ET) counted from left and right temporal bone windows during bubble study. Unilateral counts were obtained by multiplying each side by 2; bilateral counts were obtained by summing left and right ET. Both unilateral and bilateral ET were converted to a 6-point logarithmic grade. Sex and age group subanalyses were performed.

RESULTS

At rest, significantly more ET were detected with bilateral versus unilateral detection (P= .01), but not following Valsalva (P= .13). Unilateral and bilateral detection were equally able to detect large RLS (grades IV or V) following Valsalva (P= 1.00). For the group aged > or =55 years, the right-hand side yielded greater ET than the left-hand side (mean difference 9%+/- 37; 95% confidence interval -3 to 21%) at rest (P= .01), but not following Valsalva (mean difference 1%+/- 25; 95% confidence interval -7 to 9%, P= .10).

CONCLUSIONS

Unilateral detection of ET by power M-mode transcranial Doppler is equivalent to bilateral detection to assess RLS.

Inadequate acoustical temporal bone window in patients with a transient ischemic attack or minor stroke: role of skull thickness and bone density

Transcranial Doppler (TCD) ultrasonography may provide important diagnostic and prognostic information in patients with ischemic stroke or transient ischemic attack. TCD also enhances the effect of thrombolytic treatment in patients with acute stroke. In some patients, especially elderly women, TCD cannot be performed because of temporal bone window failure (WF). We investigated whether skull thickness or bone density on computed tomography scans predicts WF. In 182 patients with a transient ischemic attack or minor ischemic stroke, skull thickness and bone density measurements were made at the level of the temporal bone window. Multiple logistic regression analysis was used to relate independent variables to WF and to adjust the estimates for possible confounding factors. TCD signals were absent on the symptomatic side in 22 female and 11 male patients (18%). Both skull thickness and radiodensity at the level of the temporal bone window were strongly related to WF as well as age and female gender. After adjustment according to age and gender, skull thickness at the temporal bone window was an independent prognostic factor of WF (odds ratio [OR]: 2.3 per mm increase in skull thickness, 95% confidence interval [CI]: 1.4 to 3.8). Radiodensity of the temporal bone decreased with age in women (-52 HU per 10 y over 50 y of age, 95% CI: -73 to -30) but in men (-10 HU per 10 y over 50 y of age, 95% CI: -33 to 13), no statistically significant association was observed. We computed probabilities of WF for each patient individually. With a probability cut point of 50%, 33% of the patients with WF and 97% of the patient without WF were correctly identified. The area under the receiver operating characteristic (ROC) curve of this simple prediction model including age, gender and skull thickness was 0.88; the area under the ROC curve of a gender-stratified model including age, skull thickness and radiodensity was 0.90. This difference was not statistically or clinically significant p = 0.13). WF is more common in women because density of the temporal bone in elderly women is low. Absence of WF can be predicted by a combination of three simple parameters: skull thickness, age and gender. This may help to select patients with ischemic stroke for diagnostic TCD screening and to facilitate targeted delivery of ultrasound-enhanced thrombolysis.

Transcranial Doppler monitoring and clinical decision-making after subarachnoid hemorrhage

Our objective was to examine the impact of transcranial Doppler ultrasound (TCD) vasospasm monitoring on clinical decision-making following subarachnoid hemorrhage (SAH). The records of 50 randomly selected patients undergoing serial TCD monitoring following SAH were reviewed. Dates and results of TCDs and cerebral angiograms, the use of hypertensive hemodilution (HH) therapy, and the development of new neurological deficits were recorded. The independent effects of TCD-defined vasospasm and new neurological deficits on patient management were determined with multiple logistical regression. Results were validated in a second randomly selected, 50 patient cohort. Mild or moderate TCD-defined vasospasm developed in 76% of patients 5.8 +/- 0.5 days after SAH; 38% developed severe TCD-defined vasospasm after 7.9 +/- 0.7 days. Focal neurological deficits occurred in 50% after 5.7 +/- 0.6 days with TCD abnormalities preceding the deficit by 2.5 +/- 0.7 days in 64%. TCD-defined vasospasm or a new neurological deficit explained 60% of the variance in the use of HH therapy (P = .005). New neurological deficits increased the odds of HH therapy 33-fold (P = .004) whereas there was no independent effect of TCD-defined vasospasm. These variables explained 64% of the variance in the performance of angiography (P = .0002). An abnormal TCD did not increase the odds of angiography whereas its use increased 28-fold (P = .01) after a neurological deficit developed. These results were confirmed in an independent cohort. We concluded that TCD-defined vasospasm did not independently influence the use of HH therapy or angiography with both decisions associated with the development of new neurological deficits. As TCD-defined vasospasm preceded the neurological deficit in 64%, earlier intervention might reduce the incidence of vasospasm-related stroke in institutions with similar practice patterns.

Early cerebral hemodynamic alternations in patients operated on the first, second and third day after aneurysmal subarachnoid hemorrhage

Surgery timing after aneurysmal subarachnoid hemorrhage (SAH) may influence the risk of vasospasm after early surgical procedure and is correlated with SAH extensiveness. A group consisting of 127 patients with aneurysmal SAH was studied. The changes of mean flow velocity (MFV) were measured in middle cerebral artery (MCA) and in anterior cerebral artery (ACA) by transcranial Doppler sonography (TCD) in three groups of patients divided according to the surgery timing (on the first, second and third day after SAH). Changes of MFV values in MCA and in ACA were similar in all groups. MFV values in the group of patients operated on the third day were the lowest and the pathologic values lasted for the shortest time. In patients with massive SAH (Fisher IV group) and mild SAH (Fisher II group), the lowest MFV values were observed, if patients were operated within 24 hours after SAH. In patients without SAH (Fisher I group), the MFV values were the lowest, if they were operated on the third day after SAH. In patients with severe SAH (Fisher III group), the lowest risk of vasospasm was observed, if they were operated on the second day after SAH; however, the highest risk was found in patients operated on the first day after SAH. Our study suggests: (1) in patients with severe SAH operated on the second day, the lowest risk of vasospasm was observed, and the highest risk of vasospasm was observed if those were operated on the first day; (2) the highest risk of vasospasm was observed in patients operated within 24 hours with mild and massive SAH and in patients without SAH operated on the third day after SAH.

Role of transcranial Doppler in neurocritical care

Transcranial Doppler has several practical applications in neurocritical care. It has its main application in the diagnosis and monitoring of vasospasm in patients with subarachnoid hemorrhage. In addition, it holds promise for the detection of critical elevations of intracranial pressure. Its ability to measure CO2 reactivity and autoregulation may ultimately allow intensivists to optimize cerebral perfusion pressure and ventilatory therapy for the individual patient. Transcranial Doppler findings of brain death are well described and can be useful as a screening tool.

Transcranial Doppler grading criteria for basilar artery vasospasm

OBJECTIVE

Transcranial Doppler (TCD) criteria for basilar artery (BA) vasospasm are poorly defined, and grading criteria for vertebrobasilar vasospasm are unavailable. The purpose of the present study was to define TCD grading criteria for BA vasospasm on the basis of the absolute flow velocities and the intracranial to extracranial flow velocity ratios for the posterior circulation, and to improve the sensitivity and specificity of TCD for diagnosis of BA vasospasm.

METHODS

One hundred twenty-three patients with aneurysmal subarachnoid hemorrhage underwent 144 cerebral arteriograms with views of the BA during the acute phase of vasospasm (Days 3-14 after hemorrhage). BA diameters were measured and compared with diameters obtained from baseline arteriograms. Both BA and extracranial vertebral artery flow velocities were measured by TCD within 4 hours before the arteriogram.

RESULTS

The velocity ratio between the BA and the extracranial vertebral arteries (VA) strongly correlated with the degree of BA narrowing (r2 = 0.648; P < 0.0001). A ratio higher than 2.0 was associated with 73% sensitivity and 80% specificity for BA vasospasm. A ratio higher than 2.5 with BA velocity greater than 85 cm/s was associated with 86% sensitivity and 97% specificity for BA narrowing of more than 25%. A BA/VA ratio higher than 3.0 with BA velocities higher than 85 cm/s was associated with 92% sensitivity and 97% specificity for BA narrowing of more than 50%.

CONCLUSION

The BA/VA ratio improves the sensitivity and specificity of TCD detection of BA vasospasm. On the basis of the BA/VA ratio and BA mean velocities, we suggest new TCD grading criteria for BA vasospasm.

Carotid and vertebral artery dissections: clinical aspects, imaging features and endovascular treatment

Extracranial arterial dissections are a recognised cause of stroke, particularly in young adults. Clinical diagnosis may be difficult, and the classical triad of symptoms is uncommon. Imaging plays a pivotal role in the diagnosis of extracranial arterial dissections, and this review provides a detailed discussion of the relative merits and limitations of currently available imaging modalities. Conventional arteriography has been the reference standard for demonstrating an intimal flap and double lumen, which are the hallmarks of a dissection, and for detecting complications such as stenosis, occlusion or pseudoaneurysm. Noninvasive vascular imaging methods, such as ultrasound (US), magnetic resonance angiography (MRA) and computed tomography angiography (CTA) are increasingly replacing conventional angiography for the diagnosis of carotid and vertebral dissections. Ultrasound provides dynamic and "real-time" information regarding blood flow. Source data of MRA and CTA and additional cross-sectional images can provide direct visualisation of the mural haematoma and information about the vessel lumen. Anticoagulation to prevent strokes is the mainstay of medical treatment, but randomised trials to define the optimal treatment regime are lacking. Surgery has a limited role in management of dissections, but endovascular procedures are gaining importance for treatment of complications and if medical management fails.

Detecting and treating microvascular ischemia after subarachnoid hemorrhage

PURPOSE OF REVIEW

To provide an overview of the current management of cerebral vasospasm following subarachnoid hemorrhage, emphasizing the detection and treatment of delayed ischemia.

RECENT FINDINGS

Sensitive and specific monitoring methods are necessary to register the onset of cerebral vasospasm early to prevent long-term morbidity and mortality. Therefore, various techniques to measure cerebral perfusion and/or surrogate parameters have been developed. Prophylaxis with calcium antagonists such as nimodipine is administered for neuroprotection. Resolution of ongoing cerebral vasospasm can be achieved by either dilating constricted vessels or optimizing hemodynamics. Therapeutic treatment with hypertension, hypervolemia and hemodilution (HHH) has a direct influence on cerebral vasospasm, ischemic sequelae and outcome, while prophylactic HHH leads to excess complications. Other treatments, for example endothelin antagonists, statins or magnesium salts, used to prevent or treat cerebral vasospasm, are being tested. Endovascular treatment options can be used for therapy-refractory cerebral vasospasm, but they carry procedure-related risks and may be short-acting.

SUMMARY

Diagnosis of microvascular ischemia following subarachnoid hemorrhage involves clinical observation, non-invasive determination of cerebral hemodynamic variables, autoregulation studies and invasive online monitoring of cerebral oxygenation and metabolism. Nimodipine is administered prophylactically, while HHH is initiated therapeutically. New causal therapies are being evaluated.

Relationships of transcranial blood flow Doppler parameters with major vascular risk factors: TCD study in patients with a recent TIA or nondisabling ischemic stroke

PURPOSE

The relationship between intracranial vascular disease and cardiovascular risk factors such as smoking, hypertension, diabetes mellitus, and total serum cholesterol in patients with recent cerebral ischemia is not well established. We used transcranial Doppler (TCD) sonography tests as parameters of intracranial vascular disease and investigated the relationship between these parameters and conventional cardiovascular risk factors.

METHODS

We prospectively studied 598 patients with a minor ischemic stroke or transient ischemic attack (TIA). In all patients, flow velocities in the left and right middle cerebral artery (MCA), and cerebrovascular reactivity to CO2 were measured by means of TCD sonography. Student's t-test and linear regression analysis were used to determine the relationship between the baseline characteristics, vascular risk factors, and TCD parameters.

RESULTS

After adjustment for other vascular risk factors, a statistically significant relationship with mean flow velocity in the MCA was found for age (3.5 cm/s/10 years of age; 95% CI, 2.5-4.5 cm/s/10 years of age; p < 0.0001), sex (-2.9 cm/s for male sex; 95% CI, -5.5 to -0.3 cm/s; p = 0.03), diabetes (5.6 cm/s for diabetics; 95% CI, 2.1-9.1 cm/s; p = 0.002), and total serum cholesterol (2.4 cm/s per mmol increase in total serum cholesterol; 95% CI, 1.4-3.5 cm/s; p < 0.0001). Total serum cholesterol and hypertension were related to cerebrovascular reactivity to CO2.

CONCLUSIONS

Cerebral flow velocity is influenced by multiple interacting factors. Results of TCD investigations should be adjusted for age, sex, diabetes, and cholesterol when used for diagnostic or prognostic purposes.

Hyperoxia potentiated sonothrombolysis as a method of acute ischemic stroke therapy

The main goal in the treatment of acute ischemic stroke is prompt arterial recanalization. Thrombolysis with recombinant tissue plasminogen activator (rtPA) is efficient in humans, but shows significant problems including slow and incomplete recanalization and frequent bleeding complications. Limited therapeutic window (the first three hours after onset) is the major limitation resulting in reach too few patients. Therefore, adjunctive therapies extending the reperfusion time window, increasing efficacy and reducing side effects of rtPA are needed. Ultrasound augmentation of rtPA-mediated thrombolysis is suggested to overcome some of these problems, but low-frequency ultrasound (less than 1 MHz) is not safe and high frequency ultrasound (2 MHz) is not much effective. We suggest that normobaric hyperoxia (NBO) may increase the efficacy of ultrasound and rtPA combination in addition to its own efficacy in acute ischemic stroke. Briefly, NBO increases arterial partial oxygen pressure (pO(2)) significantly up to 6-fold. Increase of pO(2) results in an increase of dissolved oxygen in the blood according to Henry's law. Enhanced dissolved oxygen increases gas nuclei formation around and inside of the clot, and decreases the Blake threshold. Under ultrasound field, these small gas nuclei form nano bubbles which fuel inertial cavitation as substrates, and therefore increase the clot fragmentation and lysis. This hypothesis has not been tested so far. The combination of rtPA, therapeutic ultrasound and NBO may be more efficacious than rtPA alone or its combination with ultrasound as acute stroke treatment modality, because each has different and probably additive mechanism of action.

Absent Middle Cerebral Artery Signal in Transcranial Color-Coded Sonography: A Reliable Indicator of Occlusion?

BACKGROUND

Assess the accuracy of transcranial color-coded sonography (TCCS) for detecting middle cerebral artery (MCA) stem occlusion and compare it with cerebral angiography.

METHODS

This study enrolled a series of patients who received TCCS and cerebral angiography at the Department of Neurology in Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan, between January 1997 and July 2003. MCA stem occlusion was diagnosed based on digital subtraction angiography and/or computed tomographic angiography. The effect of the supplying artery on the insonation of MCA stem was considered. The sonographic criteria for MCA stem occlusion were defined as absent MCA stem signal + visible signal on the reference arteries, including ipsilateral posterior cerebral artery, ipsilateral anterior cerebral artery or contralateral MCA stem.

RESULTS

A total of 419 consecutive patients were enrolled. Factors that significantly influenced MCA stem insonation included > or =50% ipsilateral carotid artery stenosis, > or =50% MCA stem stenosis, female gender, and age > or =60 years. Comparing patients with <50% and those with > or =50% carotid stenosis, the MCA stem insonation rate was significantly reduced from 69.1% to 45.6% (p < 0.001). In patients with <50% ipsilateral carotid artery stenosis, the sonographic criteria had a positive predictive value of 10.5% and a negative predictive value of 98.9%, and could predict MCA stem occlusion with high specificity but low sensitivity (specificity = 89.6, sensitivity = 54.5, overall accuracy = 88.9, p < 0.001).

CONCLUSION

Absent MCA stem signal may result from MCA stem occlusion/tight stenosis and tight stenosis of ipsilateral carotid arteries, and has a limited value in detecting MCA stem occlusion. TCCS can be useful in identifying nonoccluded MCA stem, and cerebral angiography is necessary to confirm MCA stem occlusion.

Perfusion-weighted Magnetic Resonance Imaging in Patients with Vasospasm: A Useful New Tool in the Management of Patients with Subarachnoid Hemorrhage

OBJECTIVE:

Cerebral vasospasm (VSP) is one of the most important risk factors for the development of a delayed neurological deficit after subarachnoid hemorrhage (SAH). Perfusion-weighted magnetic resonance imaging (pwMRI) provides the possibility of detecting tissue at risk for infarction. The objective of our study was to evaluate the feasibility and impact of pwMRI in the management of SAH patients.

METHODS:

From a consecutive series of 180 patients experiencing SAH and treated at our institution over a 3-year period, we identified 20 who underwent pwMRI during their acute illness. For these 20 patients, the results of pwMRI were compared with the results of diffusion-weighted MRI, transcranial Doppler sonography, and neurological examinations performed at the same time and with repeated pwMRI examinations of the same patient at different times.

RESULTS:

Nineteen of 20 patients showed perfusion changes predominantly in the time maps. Fifteen of 19 patients with changes in pwMRI had a neurological deficit at the same time. In 7 of 15 patients with neurological deterioration, transcranial Doppler sonography showed signs of VSP, whereas all 15 patients showed alterations in pwMRI. The areas of perfusion changes in pwMRI correlated well with the neurological deficits of the patients and were larger than the areas of changed diffusion in diffusion-weighted MRI performed at the same time. There were no clinical complications with regard to the pwMRI examinations.

CONCLUSION:

pwMRI is safe and helpful in the management of patients with VSP after SAH. The sensitivity of pwMRI is higher than that of transcranial Doppler sonography in the detection of decreased perfusion as a result of VSP. pwMRI can detect tissue at risk before definitive infarction occurs and therefore may lead to a change of therapy in those patients.

Standardization of flow velocities with respect to age and sex improves the accuracy of transcranial color Doppler sonography of middle cerebral artery spasm

OBJECTIVE

The overall accuracy of transcranial Doppler sonography in the diagnosis of middle cerebral artery spasm has not been established. Moreover, the factors of age and sex have not been addressed in most studies. In this article, we present receiver operating characteristic (ROC) curve analysis of the accuracy of transcranial color Doppler sonography in diagnosing middle cerebral artery spasm on the basis of flow velocities standardized for age and sex. SUBJECTS AND METHODS. We prospectively studied 214 consecutive patients (110 male, 104 female; age range, 12-77 years) who were routinely referred for cerebral angiography. Middle cerebral artery spasm was graded as mild (</= 25% of vessel caliber reduction) and moderate to severe (> 25% reduction). Angle-corrected blood velocity measurements were obtained using a 2.5-MHz probe. The velocity values were reexpressed as a percentage of the mean of normal reference values for the relevant age, for subjects younger than 40 years, and for sex.

RESULTS

The prevalence of spasm among 335 arteries studied was 8.1% for mild and 12.8% for moderate to severe middle cerebral artery narrowing. For distinguishing all or moderate to severe vasospasm from lesser grades of vasospasm, peak systolic velocity was the best parameter. Areas under ROC curves for all and moderate to severe middle cerebral artery spasms were 0.83 and 0.92, respectively. After standardization, the ROC areas increased significantly (p < 0.05) for all, to 0.86, and only slightly, to 0.93, for moderate to severe spasms. For all grades of middle cerebral artery spasm, the best efficiencies were found at standardized velocity value of 170%.

CONCLUSION

The accuracy of transcranial color Doppler sonography is high in the identification of middle cerebral artery spasm. Standardization of velocities with respect to age and sex increases the accuracy of the method in diagnosing mild middle cerebral artery spasms.

Ultrasound-enhanced thrombolysis for stroke: clinical significance

In the pivotal clinical trials of intravenous tissue plasminogen activator (TPA) therapy for ischemic stroke, a low rate of early arterial recanalization was suspected due to the small numbers of patients who had early dramatic clinical improvement. TPA activity can be enhanced with ultrasound including 2 MHz transcranial Doppler (TCD). TCD can identify residual signals around the thrombus with the thrombolysis in brain ischemia (TIBI) flow grading system and therefore expose more thrombus surface to circulating TPA. A phase I clinical study, monitoring TPA infusion with diagnostic ultrasound resulted in an unexpectedly high rate of complete recanalization (36% of proximal middle cerebral artery (MCA) occlusions) and associated early dramatic clinical recovery (24%) among treated patients. The external application of diagnostic ultrasound in our studies raised the possibility that a synergistic TPA and ultrasound action accelerated flow improvement and achieved faster and more complete thrombus dissolution as predicted from experimental models. The CLOTBUST (combined lysis of thrombus in brain ischemia using transcranial ultrasound and systemic TPA) trial is testing this hypothesis in a phase II clinical randomized multi-center setting. Dramatic clinical recovery from stroke and complete recanalization shortly after TPA bolus are feasible goals for thrombolysis assisted with TCD monitoring.

The relation between cerebral blood flow velocities as measured by TCD and the incidence of delayed ischemic deficits. A prospective study after subarachnoid hemorrhage

Patients (n = 127) with aneurysmal subarachnoid hemorrhage (SAH) were examined by transcranial Doppler ultrasonography (TCD) in a prospective study to follow the time course of the posthemorrhagic blood flow velocity in both the middle cerebral artery (MCA) and in the anterior cerebral artery (ACA). Results were analysed to reveal their relationship and predictive use with respect to the occurrence of delayed ischemic deficits. Mean flow velocities (MFV) higher than 120 cm sec(-1) in MCA and 90 cm sec(-1) in ACA were interpreted as indicative for significant vasospasm. In 20 of our 127 patients (16%) a delayed ischemic deficit (DID) was subsequently diagnosed clinically (DID+ group). Patients in the DID+ group can be characterized as those individuals who presented early during the observation period post-SAH with highest values of MFV, a faster increase and longer persistence of pathologically elevated MFV-values (exceeding 120 cm sec(-1) in MCA and 90 cm sec(-1) in ACA). They also show a greater difference in MFV-values if one compares the operated to the nonoperated side. Differences in MFV-values obtained in MCA or ACA were statistically significant (p < 0.05) for DID+ and DID- patients. The daily maximal increase of MFV was found between days 9 and 11 after SAH. In the DID+ group, the maximal MFV was 181 +/- 26 cm sec(-1) in MCA and 119 +/- 14 cm sec(-1) in ACA. In contrast to this, patients in the DID- group were found to present with MFV of 138 +/- 11 cm sec(-1) in MCA and 100 +/- 7 cm sec(-1) in ACA respectively. Delayed ischemic deficits appeared three times more often in DID+ patients than in patients with MFV < 120 cm sec(-1), if they showed a MFV > 120 cm sec(-1) in MCA. If pathological values were obtained in ACA, this ratio increases to about four times, if DID + patients presented with MFV > 90 cm sec(-1) versus patients with MFV < 90 cm sec(-1). Daily monitoring of vasospasm using TCD examination is thus helpful to identify patients at high risk for delayed ischemic deficits. This should allow us to implement further preventive treatment regimens.

Accuracy of transcranial color Doppler ultrasonography in the diagnosis of middle cerebral artery spasm determined by receiver operating characteristic analysis

OBJECT

The value of transcranial Doppler ultrasonography for the detection of middle cerebral artery (MCA) spasm has been asserted. None of the published studies, however, has adequately scrutinized the overall diagnostic accuracy of this procedure. There are only sporadic reports concerning the utility of transcranial color Doppler (TCCD) ultrasonography, although this method has been proved to be more precise. In this study the authors attempted to estimate the performance of TCCD ultrasonography in detecting MCA narrowing by using receiver operating characteristic (ROC) curve analysis, based on TCCD studies obtained in a relatively large, randomly selected population of patients.

METHODS

Transcranial color Doppler ultrasonography studies were obtained in 100 consecutive patients (54 men and 46 women ages 18-74 years, median age 50 years) routinely referred by neurosurgeons for intraarterial angiography. The M1 segment of the MCA was insonated using a 2.5-MHz probe via a temporal acoustic window, and angle-corrected flow velocities were obtained. Angiographically depicted vasospasm was graded as none, mild (< or = 25% vessel caliber reduction), and moderate to severe (> 25% vessel caliber reduction). The effectiveness of TCCD ultrasonography in diagnosing MCA spasm was evaluated by calculating the areas under the ROC curves (Az). Of the 200 MCAs examined, 173 were successfully visualized with the aid of TCCD ultrasonography. Mild vasospasm was angiographically diagnosed in 15 arteries and moderate-to-severe vasospasm in 28. The best-performing TCCD parameter for the detection of MCA narrowing was revealed to be peak systolic velocity. The Az value for moderate-to-severe vasospasm only was 0.93 and that for all vasospasms was 0.8. The best efficiency, that is, the optimal tradeoff between sensitivity and specificity in diagnosing vasospasms, was associated with a peak systolic velocity of 182 cm/second.

CONCLUSIONS

The performance of TCCD ultrasonography in the diagnosis of advanced MCA narrowing is very good, and is acceptable for all vasospasms. The best-performing parameter was peak systolic velocity.

Blood flow velocity and pulsatility index differences in patients with unilateral migraine

OBJECTIVE

To evaluate blood flow velocity and pulsatility in unilateral migraine without aura during the headache-free period using transcranial Doppler (TCD) sonography.

METHODS

Patients with unilateral headache were recruited during the headache-free period. Maximum mean flow velocity (MFV) and pulsatility index (PI) were measured in the middle cerebral (MCA) and basilar arteries. Controls were headache-free individuals without cerebrovascular disease.

RESULTS

Twenty-five patients with right-sided migraine, 25 patients with left-sided migraine, and 19 controls were studied. The MCA PI was higher on the right headache side versus the left headache side (0.97 +/- 0.2 versus 0.86 +/- 0.1 cm/s, P =.02) and versus controls (0.9 +/- 0.2 cm/s, NS). The basilar artery MFV was higher in patients with right-sided headache versus left-sided headache (39.5 +/- 5.6 versus 34.7 +/- 8.2 cm/s, P =.02) and versus controls (38.2 +/- 8 cm/s, NS). No decrease in MFV with age was observed in patients with migraine.

CONCLUSIONS

Middle cerebral artery flow pulsatility and basilar artery velocity are higher in patients with right-sided migraine compared with left-sided migraineurs, during the headache-free period. Although these parameters were similar to controls, the differences found during the headache-free period in migraineurs may indicate vascular involvement predisposing to the unilateral headache recurrence.

Role of bedside microdialysis in the diagnosis of cerebral vasospasm following aneurysmal subarachnoid hemorrhage

OBJECT

Ischemia due to vasospasm is a feared complication in patients following aneurysmal subarachnoid hemorrhage (SAH). Cerebral online microdialysis monitoring may detect the metabolic changes in the extracellular fluid associated with ischemia. The aims of the present study were to correlate clinical course, microdialysis-recorded data, transcranial Doppler (TCD) ultrasonography findings, and angiographic findings in patients with SAH.

METHODS

In 60 patients a microdialysis catheter was inserted into the brain parenchyma that is most likely to be affected by vasospasm directly after aneurysm clipping. Hourly analyses of glucose, pyruvate, lactate, and glutamate levels were performed using a bedside device. Blood-flow velocities were obtained using serial TCD measurements. Cerebral angiography was routinely performed on Day 7 after aneurysm clipping or earlier in cases of clinical deterioration (30 patients). In all patients the results of microdialysis monitoring, TCD ultrasonography, and angiography were correlated. The mean duration of monitoring was 7.3+/-2.5 days. In patients with acute ischemic neurological deficits (18 patients) immediate microdialysis-recorded alterations were observed if the probe was placed close to the malperfused region. In 13 of 15 patients with symptomatic vasospasm (delayed ischemic neurological deficit [DIND]), the microdialysis-recorded values revealed secondary deterioration. In terms of confirming DIND, microdialysis had the highest specificity (0.89, 95% confidence interval [CI] 0.78-1) compared with TCD ultrasonography (0.63, 95% CI 0.46-0.8) and angiography (0.53, 95% CI 0.35-0.7). For microdialysis, the positive likelihood ratio was 7.8, whereas this was significantly lower for TCD ultrasonography (1.7) and angiography (2.1).

CONCLUSIONS

Although angiography also demonstrates vessel narrowing in asymptomatic patients, online microdialysis reveals characteristic metabolic changes that occur during vasospasm. Thus, online microdialysis may be used to confirm the diagnosis of vasospasm.

The influence of ruptured cerebral aneurysm localization on the blood flow velocity evaluated by transcranial Doppler ultrasonography

The relationship between changes of blood flow velocities in cerebral arteries measured by transcranial Doppler ultrasonography and aneurysm localization was investigated in a group of 165 patients after aneurysmal subarachnoid hemorrhage (SAH). Mean blood flow velocities (MFV) in the middle cerebral artery (MCA) and anterior cerebral artery (ACA) were registered. In patients with aneurysm of internal carotid artery and MCA (group A) statistically significant higher values of MFV from the 1st to the 5th day and on the 12th, 13th, 14th, 15th, and 19th day after SAH were found compared to patients with aneurysm of the anterior communicating artery, ACA, and pericallosal artery (group B). Pathological values of MFV exceeding 120 cm sec-1 in MCA were registered during 14 days in group A and during eight days in group B. Blood flow velocities in ACA were statistically significantly higher in group B on the 2nd, 7th, 9th and 11th day compared to group A. Pathological values of MFV exceeding 90 cm sec-1 in ACA were registered during nine days in both groups. MFV differences between group A and group B in 38 patients subjected to delayed surgery were not observed. The influence of aneurysm localization was observed between the 7th and 14th day after SAH. Critical MFV values for vasospasm in the MCA should be 120 cm sec-1 and in the ACA 90 cm sec-1.

The role of transcranial Doppler in the management of patients with subarachnoid haemorrhage--a review

Introduced 15 years ago, transcranial Doppler (TCD) recordings of blood-velocity in patients with recent subarachnoid haemorrhage (SAH) have two objectives: to detect elevated blood velocities suggesting cerebral vasospasm (VSP) and to identify patients at risk for delayed cerebral ischemic deficits (DID). The pathophysiological cascade causing DID is complex. Discrepancies between blood velocities and DID (presuming that there actually is an "ischemic threshold" for blood velocity in absolute terms, which seems most unlikely) have been demonstrated, particularly in patients with elevated intracranial pressure (ICP) levels. Furthermore, the vessel showing the highest blood velocity is not always the one perfusing the area where ischemic symptoms arise, nor does the site of the greatest subarachnoid blood clot always relate to the ischemic brain region. Moreover, it is probable that the complex haemodynamic changes following SAH and the subsequent development of VSP may be underestimated if only considering the crude intracranial artery blood velocities. Cerebral blood flow measurements combined with TCD to assess both flow and velocity have emphasised this point. Despite these findings and ignoring the basic principles of cerebral haemodynamics, cerebral vasospasm is still being assessed from the intracranial velocity measurement alone. The addition of at least a careful measurement from the extracranial internal carotid artery--using the same TCD equipment and taking only a few short minutes to perform--allows a much more accurate assessment of the degree and the effects of vasospasm. This probably explains why the clinical value of TCD is still debated. There is still uncertainty as to the best method to prevent and to treat VSP, and the overall outcome after SAH depends on so many factors besides VSP. Conclusive evidence may therefore be hard to obtain, and it appears sound to conclude that even with advanced investigation technology available, proper selection, pre- peri- and postoperative care and timing of surgery remain cornerstones in the management of these patients,--equal in importance to their treatment in the operating room or in the interventional angiography suite.