A Survey of Neuromonitoring Practices in North American Pediatric Intensive Care Units

BACKGROUND

Neuromonitoring is the use of continuous measures of brain physiology to detect clinically important events in real-time. Neuromonitoring devices can be invasive or non-invasive and are typically used on patients with acute brain injury or at high risk for brain injury. The goal of this study was to characterize neuromonitoring infrastructure and practices in North American pediatric intensive care units (PICUs).

METHODS

An electronic, web-based survey was distributed to 70 North American institutions participating in the Pediatric Neurocritical Care Research Group. Questions related to the clinical use of neuromonitoring devices, integrative multimodality neuromonitoring capabilities, and neuromonitoring infrastructure were included. Survey results were presented using descriptive statistics.

RESULTS

The survey was completed by faculty at 74% (52 of 70) of institutions. All 52 institutions measure intracranial pressure and have electroencephalography capability, whereas 87% (45 of 52) use near-infrared spectroscopy and 40% (21/52) use transcranial Doppler. Individual patient monitoring decisions were driven by institutional protocols and collaboration between critical care, neurology, and neurosurgery attendings. Reported device utilization varied by brain injury etiology. Only 15% (eight of 52) of institutions utilized a multimodality neuromonitoring platform to integrate and synchronize data from multiple devices. A database of neuromonitoring patients was maintained at 35% (18 of 52) of institutions. Funding for neuromonitoring programs was variable with contributions from hospitals (19%, 10 of 52), private donations (12%, six of 52), and research funds (12%, six of 52), although 73% (40 of 52) have no dedicated funds.

CONCLUSIONS

Neuromonitoring indications, devices, and infrastructure vary by institution in North American pediatric critical care units. Noninvasive modalities were utilized more liberally, although not uniformly, than invasive monitoring. Further studies are needed to standardize the acquisition, interpretation, and reporting of clinical neuromonitoring data, and to determine whether neuromonitoring systems impact neurological outcomes.

Monitoring of Neuroendocrine Changes in Acute Stage of Severe Craniocerebral Injury by Transcranial Doppler Ultrasound Image Features Based on Artificial Intelligence Algorithm

This study was aimed at exploring the application value of transcranial Doppler (TCD) based on artificial intelligence algorithm in monitoring the neuroendocrine changes in patients with severe head injury in the acute phase; 80 patients with severe brain injury were included in this study as the study subjects, and they were randomly divided into the control group (conventional TCD) and the experimental group (algorithm-optimized TCD), 40 patients in each group. An artificial intelligence neighborhood segmentation algorithm for TCD images was designed to comprehensively evaluate the application value of this algorithm by measuring the TCD image area segmentation error and running time of this algorithm. In addition, the Glasgow coma scale (GCS) and each neuroendocrine hormone level were used to assess the neuroendocrine status of the patients. The results showed that the running time of the artificial intelligence neighborhood segmentation algorithm for TCD was 3.14 ± 1.02 s, which was significantly shorter than 32.23 ± 9.56 s of traditional convolutional neural network (CNN) algorithms (P < 0.05). The false rejection rate (FRR) of TCD image area segmentation of this algorithm was significantly reduced, and the false acceptance rate (FAR) and true acceptance rate (TAR) were significantly increased (P < 0.05). The consistent rate of the GCS score and Doppler ultrasound imaging diagnosis results in the experimental group was 93.8%, which was significantly higher than the 80.3% in the control group (P < 0.05). The consistency rate of Doppler ultrasound imaging diagnosis results of patients in the experimental group with abnormal levels of follicle stimulating hormone (FSH), prolactin (PRL), growth hormone (GH), adrenocorticotropic hormone (ACTH), and thyroid stimulating hormone (TSH) was significantly higher than that of the control group (P < 0.05). In summary, the artificial intelligence neighborhood segmentation algorithm can significantly shorten the processing time of the TCD image and reduce the segmentation error of the image area, which significantly improves the monitoring level of TCD for patients with severe craniocerebral injury and has good clinical application value.

Changes in Care Delivery for Children With Sickle Cell Anemia During the COVID-19 Pandemic

BACKGROUND

Specialty care for children with sickle cell disease (SCD) may be disrupted during the coronavirus (COVID-19) pandemic. Our DISPLACE consortium includes 28 pediatric SCD centers.

METHODS

In May 2020, we surveyed the consortium on the impact of COVID-19 on their practice focusing on transcranial Doppler ultrasound, chronic red cell transfusions, telehealth, and COVID-19 testing.

OBSERVATION

Twenty-four DISPLACE providers completed the survey. Transcranial Doppler ultrasound screening decreased to 67% but chronic red cell transfusions remained at 96%. Most investigators (92%) used telehealth and 40% of providers had patients test positive for COVID-19.

CONCLUSION

The COVID-19 pandemic has affected routine care and necessitated changes in practice in SCD.

How is vasospasm screening using transcranial Doppler associated with delayed cerebral ischemia and outcomes in aneurysmal subarachnoid hemorrhage?

BACKGROUND

Delayed cerebral ischemia (DCI) is an independent predictor of an unfavorable outcome after aneurysmal subarachnoid hemorrhage (aSAH). Many centers, but not all, use transcranial Doppler (TCD) to screen for vasospasm to help predict DCI. We used the United Kingdom and Ireland Subarachnoid Haemorrhage (UKISAH) Registry to see if outcomes were better in centers that used TCD to identify vasospasm compared to those that did not.

METHODS

TCD screening practices were ascertained by national survey in 13 participating centers of the UKISAH. The routine use of TCD was reported by 5 "screening" centers, leaving 7 "non-screening" centers. Using a cross-sectional cohort study design, prospectively collected data from the UKISAH Registry was used to compare DCI diagnosis and favorable outcome (Glasgow Outcome Score 4 or 5) at discharge based on reported screening practice.

RESULTS

A cohort of 2028 aSAH patients treated ≤ 3 days of hemorrhage was analyzed. DCI was diagnosed in 239/1065 (22.4%) and 220/963 (22.8%) of patients in non-screening and screening centers respectively while 847/1065 (79.5%) and 648/963 (67.2%) achieved a favorable outcome. Odds ratios adjusted for age, injury severity, comorbidities, need for cerebrospinal fluid diversion, and re-bleed returned neutral odds of diagnosing DCI of 0.90 (95% CI 0.72-1.12; p value = 0.347) in screening units compared to those of non-screening units but significantly decreased odds of achieving a favorable outcome 0.56 (95% CI 0.42-0.82; p value < 0.001).

CONCLUSIONS

Centers that screened for vasospasm using TCD had poorer in-hospital outcomes and similar rates of DCI diagnosis compared to centers that did not.

The significance of inadequate transcranial Doppler studies in children with sickle cell disease

Sickle cell disease (SCD) is a common cause of cerebrovascular disease in childhood. Primary stroke prevention is effective using transcranial Doppler (TCD) scans to measure intracranial blood velocities, and regular blood transfusions or hydroxycarbamide when these are abnormal. Inadequate TCD scans occur when it is not possible to measure velocities in all the main arteries. We have investigated the prevalence and significance of this in a retrospective audit of 3915 TCD scans in 1191 children, performed between 2008 and 2015. 79% scans were normal, 6.4% conditional, 2.8% abnormal and 12% inadequate. 21.6% of 1191 patients had an inadequate scan at least once. The median age of first inadequate scan was 3.3 years (0.7-19.4), with a U-shaped frequency distribution with age: 28% aged 2-3 years, 3.5% age 10 years, 25% age 16 years. In young children reduced compliance was the main reason for inadequate TCDs, whereas in older children it was due to a poor temporal ultrasound window. The prevalence of inadequate TCD was 8% in the main Vascular Laboratory at King's College Hospital and significantly higher at 16% in the outreach clinics (P<0.0001), probably due to the use of a portable ultrasound machine. Inadequate TCD scans were not associated with underlying cerebrovascular disease.

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.

Substantia Nigra Hyperechogenicity: Validation of Transcranial Sonography for Parkinson Disease Diagnosis in a Large Estonian Cohort

OBJECTIVES

Substantia nigra hyperechogenicity is a promising biomarker for Parkinson disease (PD). Substantia nigra hyperechogenicity has previously been established as a useful diagnostic criterion in several European and Asian patient cohorts. However, diagnostic cutoff values for substantia nigra hyperechogenicity remain unknown for most patient populations. This study validated the diagnostic accuracy of substantia nigra hyperechogenicity in a large cohort of patients with PD in Estonia.

METHODS

The study included 300 patients with PD from Estonia, representing 10% of the national PD patient population, and 200 healthy control participants. To define the optimal cutoff value in the PD cohort, data from a single assessment versus repetitive assessments by transcranial sonography were compared. With the use of 3 repetitive assessments, the diagnostic accuracy of the data was measured. In addition, calculations for percentile values were used to define substantia nigra hyperechogenicity among controls.

RESULTS

Our data showed that the multiassessment approach yielded higher diagnostic accuracy than a single assessment (P = .021). The highest diagnostic accuracy was achieved by using the measurement mean to define substantia nigra hyperechogenicity, which was 0.23 cm(2) (sensitivity, 88.7%; specificity, 92.2%), whereas single measurements detected PD with higher sensitivity (sensitivity, 93.2%; specificity, 85.1%). No significant difference was found between mean and median measurements (P= .18).

CONCLUSIONS

This study indicates the diagnostic merit of transcranial sonography in PD diagnosis in an additional population and demonstrates that transcranial sonography of the substantia nigra is a relevant and useful diagnostic tool for patients with PD.

Evaluation of the Temporal Acoustic Window for Transcranial Doppler in a Multi-Ethnic Population in Brazil

The aim of this study was to relate the presence of a temporal acoustic window (TAW) to the variables sex, age and race. This observational study was conducted in patients under etiologic investigation after stroke, sickle-cell anemia and hospitalization in an intensive therapy neurologic unit. TAW presence was confirmed by bilateral assessment by two neurologists via transcranial Doppler (TCD). Multiple logistic regression was performed to explain the presence of the window as a function of sex, age and race. In 20% of the 262 patients evaluated, a TAW was not present. The incidence of TAW presence was greater in men (odds ratio [OR] = 5.4, 95% confidence interval [CI] = 2.5-11.7, p < 0.01); lower with increased age (OR = 0.9, 95% CI = 0.92-0.97, p < 0.01); and lower among those of African and Asian descent (OR = 0.32, 95% CI = 0.14-0.70, p = 0.005). On the basis of the results, more men than women had TAWs, and the decrease in TAWs was associated with increased age and African or Asian descent.

Sonography for diagnosis of Parkinson disease-from theory to practice: a study on 300 participants

OBJECTIVES

Hyperechogenicity of the substantia nigra on transcranial sonography is used for diagnosing Parkinson disease (PD). Cutoff values for the substantia nigra echogenic area, defining substantia nigra hyperechogenicity, vary among ultrasound systems from different manufacturers. In this study we wanted to determine the cutoff criterion for a Toshiba (Tokyo, Japan) system and to assess its diagnostic value.

METHODS

Three hundred participants (controls, n = 138; patients with PD, n = 105; and patients with essential tremor, n = 57) underwent transcranial sonography following a standardized protocol.

RESULTS

The substantia nigra was assessable in 92.7% of all participants. The substantia nigra echogenic area (larger of bilateral measurements) was larger in patients with PD (mean ± SD, 0.24 ± 0.05 cm(2)) than controls (0.14 ± 0.05 cm(2); P < .001) and patients with essential tremor (0.14 ± 0.04 cm(2); P < .001). Substantia nigra echogenicity was larger in male participants (0.20 ± 0.07 cm(2)) than female participants (0.15 ± 0.06 cm(2); P< .001). Age did not correlate with substantia nigra echogenicity in any group. Frontal horn width was larger and lenticular nucleus hyperechogenicity and a discontinuous raphe were more frequent in the PD group than the other groups. On multivariate analysis, only substantia nigra hyperechogenicity was associated with the diagnosis of PD. The 90th-percentile substantia nigra echogenic area in the control group, which defined marked substantia nigra hyperechogenicity, also represented the optimum cutoff value for discrimination of PD from non-PD participants on receiver operating characteristic curve analysis (area under the curve, 0.913; Youden index, 0.73). This cutoff value (≥0.21 cm(2), larger of bilateral measurements) yielded sensitivity of 83% and specificity of 90% for the diagnosis of PD.

CONCLUSIONS

Transcranial sonography shows good diagnostic validity for diagnosis of PD when implemented according to a strictly standardized protocol.

[Questionnaire on the anaesthesiology treatment of patients subjected to posterior fossa neurosurgery]

OBJECTIVES

To find out, by means of a questionnaire, the procedures used by Spanish anaesthetists in peri-operative management of patients subjected to neurosurgery of the posterior cranial fossa.

MATERIAL AND METHODS

A closed-question type questionnaire was sent to Anaesthesiology Departments with a Neurosurgery Department on the participation of anaesthetists in the peri-operative treatment of patients subjected posterior fossa surgery.

RESULTS

The questionnaire was completed by 42 (57.5%) of the 73 national public hospitals with a Neurosurgery Department. The posterior fossa surgery was performed in the sitting position in 36 hospitals, although it was less frequently used than the lateral decubitus or prone decubitus position. There was little specific neurological monitoring, as well as little use of precordial and/or transcranial Doppler for detecting vascular air embolism. Nitrous oxide was used in less than 10% of the centres, and 15% avoided neuromuscular block when neurophysiological monitoring was used during the surgery. Cardiovascular problems were mentioned as being the most frequent in 29% of the centres, while in the post-operative period the most common complications were, cranial nerve déficit, airway oedema (23%), and post-operative vomiting (47%).

CONCLUSIONS

The results obtained from the questionnaire showed that the sitting position was less used than the prone position in posterior fossa surgery, and that neurophysiological monitoring is during surgery is hardly used.

Transcranial color-coded duplex sonography allows to assess cerebral perfusion pressure noninvasively following severe traumatic brain injury

OBJECTIVE

Assess optimal equation to noninvasively estimate intracranial pressure (eICP) and cerebral perfusion pressure (eCPP) following severe traumatic brain injury (TBI) using transcranial color-coded duplex sonography (TCCDS).

DESIGN AND SETTING

This is an observational clinical study in a university hospital.

PATIENTS

A total of 45 continuously sedated (BIS < 50), normoventilated (paCO(2) > 35 mmHg), and non-febrile TBI patients.

METHODS

eICP and eCPP based on TCCDS-derived flow velocities and arterial blood pressure values using three different equations were compared to actually measured ICP and CPP in severe TBI patients subjected to standard treatment. Optimal equation was assessed by Bland-Altman analysis.

RESULTS

The equations: ICP = 10:927 x PI(pulsatility index) - 1:284 and CPP = 89:646 - 8:258 PI resulted in eICP and eCPP similar to actually measured ICP and CPP with eICP 10.6 +/- 4.8 vs. ICP 10.3 +/- 2.8 and eCPP 81.1 +/- 7.9 vs. CPP 80.9 +/- 2.1 mmHg, respectively. The other two equations, eCPP = (MABP x EDV)/mFV + 14 and eCPP = mFV / (mFV - EDV)] x (MABP - RRdiast), resulted in significantly decreased eCPP values: 72.9 +/- 10.1 and 67 +/- 19.5 mmHg, respectively. Superiority of the first equation was confirmed by Bland-Altman revealing a smallest standard deviations for eCPP and eICP.

CONCLUSIONS

TCCDS-based equation (ICP = 10.927 x PI - 1.284) allows to screen patients at risk of increased ICP and decreased CPP. However, adequate therapeutic interventions need to be based on continuously determined ICP and CPP values.

[Ultrasound in acute ischemic stroke]

INTRODUCTION

Ultrasound tests are used in the cerebrovascular evaluation of stroke patients. However, the use of Transcranial Doppler (TCD) and carotid duplex ultrasound (CD) within the first hours after stroke onset in the Emergency Service is not a common practice.

RESULTS

TCD and CD can be used as portable tests, thus allowing for bedside use in the Emergency Service. Both tests broaden the abilities of stroke neurologists to rapidly evaluate stroke patients, determine likely mechanism of stroke, and decide on reperfusion and secondary prevention strategies. Furthermore, the ultrasound tests are particularly useful for grading the severity of the arterial patency and enhancing recanalization after tPA administration.

CONCLUSIONS

TCD and CD are excellent diagnostic tools that might be used in all acute stroke patients for immediate evaluation of arterial patency. They make it possible to select treatment and enhance reperfusion after tPA. Carotid and transcranial ultrasound are an essential part of vascular neurology training and practice.

[Clinical usefulness of transcranial Doppler ultrasound imaging in the diagnosis of cerebral vasospasm in subarachnoid haemorrhage. A validation study]

INTRODUCTION

During the clinical course of aneurysmal subarachnoid haemorrhage, cerebral vasospasm is one of the most dreaded medical complications. AIM. To determine the usefulness of transcranial Doppler (TCD) ultrasound imaging in diagnosing vasospasm in patients with subarachnoid haemorrhage (SAH) who were attended in a Stroke Unit.

PATIENTS AND METHODS

The study included 89 patients with SAH of a non-traumatic origin; these patients had been admitted to a Stroke Unit and were submitted to a contrast-enhanced neurovascular study and daily monitoring with TCD. Values were determined for the sensitivity, specificity, predictive power and overall precision of the TCD ultrasound imaging, together with the differences in mean flow rate and the coefficient of correlation between the gold standard test and the results of monitoring with TCD.

RESULTS

Female patients under 50 years of age with favourable initial clinical degrees were predominant. Aneurysmal SAH was prevalent and the frequency of angiographic vasospasm was 40%, in the majority of cases located in the middle cerebral arteries. Most of the patients had mean cerebral blood flow rates of or below 120 cm/s. The peaks of mean blood flow rate were obtained between the fourth and the tenth day. Overall precision, sensitivity and the predictive negative value of TCD were good. Specificity was excellent for flow rates below 130 cm/s, and the predictive positive value was low.

CONCLUSIONS

Monitoring with TCD proved to be useful for diagnosing cerebral vasospasm in patients with a good initial clinical status.

[Recommendations of the use of transcranial Doppler to determine the existence of cerebral circulatory arrest as diagnostic support of brain death]

INTRODUCTION

The clinical criteria for brain death consist of the demonstration of the absence of any clinical sign of encephalic activity. Confirmatory testing is usually not required for the diagnosis of brain death, except in some special situations that the Spanish law details. In these situations demonstrating cerebral circulatory arrest (CCA) by cerebral flow studies is necessary to support the diagnosis of brain death.

OBJECTIVE

To review the use of transcranial Doppler ultrasonography (TCD) for confirming brain death and to establish uniform criteria for the routine use of TCD as a confirmatory test.

METHODS

Based on literature analysis, the authors developed the guidelines for performance and interpretation of TCD in clinically brain-dead patients, in order to confirm the diagnosis. The active members of the Spanish Neurosonology Society (SONES) reviewed an initial draft, until a consensus was reached.

RESULTS

In a clinically brain-dead patient, specific intracranial flow patterns indicating CCA can be visualized by TCD. The specific flow patterns are the presence of reverberating flow and/or systolic spikes, and should be detected in both middle cerebral arteries and also in the basilar artery. We recommend to repeat the examination within 30 minutes to confirm the findings.

CONCLUSIONS

TCD is a useful method detecting CCA and therefore can be used to confirm brain death in a clinically brain-dead patient. The presence of reverberating flow, systolic spikes or absence of flow in the basilar and both middle cerebral arteries observed in two examinations is highly specific for the prediction of CCA and brain death in all patients.

An automated feature extraction and emboli detection system based on the PCA and fuzzy sets

The Doppler ultrasound technique is commonly used to detect emboli in the cerebral circulation. Here an automated feature extraction and emboli detection system is proposed based on the principal components analysis (PCA) and fuzzy sets. In the system, two features, R(ry) and k, are extracted by the PCA method. Meanwhile, MMR and sigma(f min) are obtained with the traditional temporal processing and spectrogram analysis, respectively. Normal blood flow signals are firstly distinguished from abnormal signals by MMR. Then signals containing emboli and disturbance noises are further differentiated by other features based on fuzzy sets. From experiments with computer-simulated and clinical Doppler ultrasound signals, it is shown that features extracted from the PCA method achieve better classification performance than those of traditional methods. The fuzzy-based detection system not only obtains high classification accuracy but is more applicable in clinical diagnosis.

The Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis (SONIA) Trial

BACKGROUND

Transcranial Doppler ultrasound (TCD) and magnetic resonance angiography (MRA) can identify intracranial atherosclerosis but have not been rigorously validated against the gold standard, catheter angiography. The WASID trial (Warfarin Aspirin Symptomatic Intracranial Disease) required performance of angiography to verify the presence of intracranial stenosis, allowing for prospective evaluation of TCD and MRA. The aims of Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis (SONIA) trial were to define abnormalities on TCD/MRA to see how well they identify 50 to 99% intracranial stenosis of large proximal arteries on catheter angiography.

STUDY DESIGN

SONIA standardized the performance and interpretation of TCD, MRA, and angiography. Study-wide cutpoints defining positive TCD/MRA were used. Hard copy TCD/MRA were centrally read, blind to the results of angiography.

RESULTS

SONIA enrolled 407 patients at 46 sites in the United States. For prospectively tested noninvasive test cutpoints, positive predictive values (PPVs) and negative predictive values (NPVs) were TCD, PPV 36% (95% CI: 27 to 46); NPV, 86% (95% CI: 81 to 89); MRA, PPV 59% (95% CI: 54 to 65); NPV, 91% (95% CI: 89 to 93). For cutpoints modified to maximize PPV, they were TCD, PPV 50% (95% CI: 36 to 64), NPV 85% (95% CI: 81 to 88); MRA PPV 66% (95% CI: 58 to 73), NPV 87% (95% CI: 85 to 89). For each test, a characteristic performance curve showing how the predictive values vary with a changing test cutpoint was obtained.

CONCLUSIONS

Both transcranial Doppler ultrasound and magnetic resonance angiography noninvasively identify 50 to 99% intracranial large vessel stenoses with substantial negative predictive value. The Stroke Outcomes and Neuroimaging of Intracranial Atherosclerosis trial methods allow transcranial Doppler ultrasound and magnetic resonance angiography to reliably exclude the presence of intracranial stenosis. Abnormal findings on transcranial Doppler ultrasound or magnetic resonance angiography require a confirmatory test such as angiography to reliably identify stenosis.

Validation of transcranial Doppler with computed tomography angiography in acute cerebral ischemia

BACKGROUND AND PURPOSE

Both transcranial Doppler (TCD) and spiral computed tomography angiography (CTA) are used for noninvasive vascular assessment tools in acute stroke. We aimed to evaluate the diagnostic accuracy of TCD against CTA in patients with acute cerebral ischemia.

METHODS

Consecutive patients presenting to the Emergency Department with symptoms of acute (<24 hours) cerebral ischemia underwent emergent high-resolution brain CTA with a multidetector helical scanner. TCD was performed at bedside with a standardized, fast-track insonation protocol before or shortly (<2 hours) after completion of the CTA. Previously published diagnostic criteria were prospectively applied for TCD interpretation independent of angiographic findings.

RESULTS

A total of 132 patients (74 men, mean+/-SD age 63+/-15 years) underwent emergent neurovascular assessment with brain CTA and TCD. Compared with CTA, TCD showed 34 true-positive, 9 false-negative, 5 false-positive, and 84 true-negative studies (sensitivity 79.1%, specificity 94.3%, positive predictive value 87.2%, negative predictive value 90.3%, and accuracy 89.4%). In 9 cases (7%), TCD showed findings complementary to the CTA (real-time embolization, collateralization of flow with extracranial internal carotid artery disease, alternating flow signals indicative of steal phenomenon).

CONCLUSIONS

Bedside TCD examination yields satisfactory agreement with urgent brain CTA in the evaluation of patients with acute cerebral ischemia. TCD can provide real-time flow findings that are complementary to information provided by CTA.

Prevalence of patent foramen ovale in migraine patients with and without aura compared with stroke patients. A transcranial Doppler study

The aim of this study was to investigate the prevalence of patent foramen ovale (PFO) in a consecutive unselected cohort of migraine patients (with and without aura) and compare it with a group of ischaemic young and elderly stroke patients. One hundred and forty-one migraine patients were compared with 330 stroke patients (130 young patients; 200 elderly patients) selected from our hospital stroke data bank. PFO was assessed with transcranial Doppler sonography with i.v. injection of agitated saline. The prevalence of PFO was 51.7% in migraine with aura (MA) patients, 33.7% in migraine without aura (MoA) patients, 33.8% in young stroke patients and 20.5% in elderly stroke patients (P < 0.001). The prevalence of PFO in cryptogenic stroke in young and elderly stroke patients was, respectively, 41.1% and 25% (P = 0.04). The difference between MA and MoA patients was significant (odds ratio = 2.1). The prevalence of PFO in MA patients is higher than in MoA patients and in young cryptogenic stroke patients.

Transcranial Doppler ultrasonography in adults with sickle cell disease

BACKGROUND

Transcranial Doppler (TCD) is used to select children with sickle cell disease (SCD) for primary stroke prevention using regular blood transfusion. Whether it can also identify high stroke risk in adults with SCD is not known.

METHODS

The authors examined 112 adult patients from two convenience population samples with SCD and 53 healthy control subjects to compare velocities in adults to those reported in children with SCD and to evaluate the influence of age and hematocrit on TCD.

RESULTS

Adults with SCD had a higher mean time-averaged maximum mean velocity (110.9 +/- 25.7 cm/s) compared with healthy controls (71.1 +/- 12.0 cm/s), and the difference is approximately proportional to their anemia. No cases with velocities >/=200 cm/s (the threshold used in children for prophylactic treatment) were found in this sample.

CONCLUSIONS

Transcranial Doppler velocities in adults with sickle cell disease (SCD) are lower than those in children with SCD. Velocity criteria used in children cannot be used to stratify risk of stroke in adults.

Association between two distinct executive tasks in schizophrenia: a functional transcranial Doppler sonography study

BACKGROUND

Schizophrenia is a severe mental disorder involving impairments in executive functioning, which are important cognitive processes that can be assessed by planning tasks such as the Stockings of Cambridge (SOC), and tasks of rule learning/abstraction such as the Wisconsin Card Sorting Test (WCST). We undertook this study to investigate the association between performance during separate phases of SOC and WCST, including mean cerebral blood flow velocity (MFV) measurements in chronic schizophrenia.

METHODS

Functional transcranial Doppler sonography (fTCD) was used to assess bilateral MFV changes in the middle (MCA) and anterior (ACA) cerebral arteries. Twenty-two patients with chronic schizophrenia and 20 healthy subjects with similar sociodemographic characteristics performed SOC and WCST during fTCD measurements of the MCA and the ACA. The SOC was varied in terms of easy and difficult problems, and also in terms of separate phases, namely mental planning and movement execution. The WCST performance was assessed separately for maintaining set and set shifting. This allowed us to examine the impact of problem difficulty and the impact of separate phases of a planning task on distinct intervals of WCST. Simultaneous registration of MFV was carried out to investigate the linkage of brain perfusion during the tasks.

RESULTS

In patients, slowing of movement execution during easy problems (SOC) was associated with slowing during maintaining set (WCST) (P < 0.01). In healthy subjects, faster planning and movement execution during predominantly difficult problems were associated with increased performance of WCST during set shifting (P < 0.01). In the MCA, patients showed a significant and positive correlation of MFV between movement execution and WCST (P < 0.01).

CONCLUSION

The results of this study demonstrate performance and brain perfusion abnormalities in the association pattern of two different tasks of executive functioning in schizophrenia, and they support the notion that executive functions have a pathological functional correlate predominantly in the lateral hemispheres of the brain. This study also underpins the scientific potential of fTCD in assessing brain perfusion in patients with schizophrenia.

Doppler transcraniano na prática neurológica

O Doppler transcraniano (DTC) é um método relativamente novo, descrito em 1982 por Rune Aaslid e introduzido no Brasil em 1992 por Roberto Hirsch, na Universidade de São Paulo. O serviço de Neurologia do Hospital de Clínicas da Universidade Federal do Paraná (HC-UFPR) disponibilizou esse exame em 2001, com divulgação das principais vantagens do método no diagnóstico, seguimento e manejo terapêutico de pacientes com suspeita ou portadores de doença cerebrovascular. O objetivo deste trabalho é demonstrar como o DTC vem sendo utilizado em nosso meio e quais são as especialidades médicas que vêm absorvendo o auxílio do método. Embora diretrizes como a publicada pela Academia Americana de Neurologia em 2004 validem as indicações do DTC, estabelecendo especificidade e sensibilidade do método, verificamos que a solicitação do exame em nosso meio depende da divulgação do serviço, da implementação de linhas de pesquisa e, finalmente, do reconhecimento de sua utilidade na prática diária.

[Analysis on data gathered from transcranial Doppler among 1500 normal adults community]

OBJECTIVE

To study the rates of receiving doppler signal, flow velocity of cerebral artery and the relationship between flow velocity,age and gender in normal adults in China.

METHODS

A total of 1500 normal residents at the community level in Guangdong province were examined, using transcranial doppler. Data was gathered and analyzed.

RESULTS

With the increase of age, the rate of receiving signal in cerebral artery gradually decreased. Difference between males and females was noticed. Mean velocity of cerebral artery decreased in both genders but the velocity was faster in females than in males and the pulsate index increased without difference.

CONCLUSION

The rates of receiving signal and the flow velocity of cerebral artery were related to age and gender and the findings from this study offered criterion for clinical transcranial doppler.

Assessment: transcranial Doppler ultrasonography: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology

OBJECTIVE

To review the use of transcranial Doppler ultrasonography (TCD) and transcranial color-coded sonography (TCCS) for diagnosis.

METHODS

The authors searched the literature for evidence of 1) if TCD provides useful information in specific clinical settings; 2) if using this information improves clinical decision making, as reflected by improved patient outcomes; and 3) if TCD is preferable to other diagnostic tests in these clinical situations.

RESULTS

TCD is of established value in the screening of children aged 2 to 16 years with sickle cell disease for stroke risk (Type A, Class I) and the detection and monitoring of angiographic vasospasm after spontaneous subarachnoid hemorrhage (Type A, Class I to II). TCD and TCCS provide important information and may have value for detection of intracranial steno-occlusive disease (Type B, Class II to III), vasomotor reactivity testing (Type B, Class II to III), detection of cerebral circulatory arrest/brain death (Type A, Class II), monitoring carotid endarterectomy (Type B, Class II to III), monitoring cerebral thrombolysis (Type B, Class II to III), and monitoring coronary artery bypass graft operations (Type B to C, Class II to III). Contrast-enhanced TCD/TCCS can also provide useful information in right-to-left cardiac/extracardiac shunts (Type A, Class II), intracranial occlusive disease (Type B, Class II to IV), and hemorrhagic cerebrovascular disease (Type B, Class II to IV), although other techniques may be preferable in these settings.

Time Period Required for Transcranial Doppler Monitoring of Embolic Signals to Predict Recurrent Risk of Embolic Transient Ischemic Attack and Stroke From Arterial Stenosis

BACKGROUND AND PURPOSE

We aimed to investigate whether the time period of transcranial Doppler monitoring for embolic signals can be reduced without loss of clinical yield compared with routinely performed 1-hour monitoring.

METHODS

Investigations on the basis of a post hoc analysis of a previously published cohort of 86 patients (55 men, 31 women; mean age 60.6 years) with a nondisabling arterioembolic ischemic event in the anterior circulation within the last 30 days (mean 7.3) and an ipsilateral medium-grade or high-grade stenosis of the carotid or middle cerebral artery. Patients underwent 1-hour monitoring for embolic signals and were followed up prospectively for 6 weeks to evaluate the relationship between embolic signals and risk of an early ischemic recurrence. Risk was also calculated after fictitious reduction of the monitoring period from 60 minutes to 50, 40, 30, 20, and 10 minutes, respectively, and compared with the results obtained from the 1-hour period.

RESULTS

The number of patients positive for embolic signals decreased with the decreasing monitoring period. By this, the odds ratio of embolic signals for an early ischemic recurrence "decreased" from 40 (derived from the 1-hour monitoring) to 10 when the monitoring lasted < or =30 minutes. The relationship between the rate of embolic signals per hour and risk of a recurrent stroke is described by an S-shaped curve. As a consequence, risk estimated from reduced monitoring periods can differ considerably from that derived from the 1-hour monitoring if the signal frequency lies within a medium range (eg, between 3 and 15 signals in 30 minutes).

CONCLUSIONS

The time period of monitoring for embolic signals may be reduced without loss of clinical relevant information when signal frequency is low or already high during the reduced monitoring period, but it should be prolonged to maximally an hour at signal numbers within a medium range. However, our results need to be externally validated on an independent cohort of patients or confirmed by a prospective study before this modification can be recommended in general.

Ultrasound perfusion imaging in acute middle cerebral artery infarction predicts outcome

BACKGROUND AND PURPOSE

Initial reports indicate that transcranial harmonic imaging after ultrasound contrast agent bolus injection (BHI) can detect cerebral perfusion deficits in acute ischemic stroke. We evaluated parametric images of the bolus washout kinetics.

METHODS

Twenty-three patients with acute internal carotid artery infarction were investigated with perfusion harmonic imaging after SonoVue bolus injection < or =40 hour after the onset of symptoms. The findings were compared with those of cranial computed tomography (CCT) and clinical course 4 months after stroke.

RESULTS

Images of pixel-wise peak intensity (PPI) and time to peak intensity could be calculated for all patients. Spearman rank correlations of r=0.772 (P<0.001) and r=0.572 (P=0.008) between area of PPI signal decrease and area of infarction in the follow-up CCT as well as outcome after 4 months were obtained, respectively.

CONCLUSIONS

In the early phase of acute ischemic stroke, BHI after SonoVue bolus injection is a useful ultrasound tool for analyzing cerebral perfusion deficits at the patient's bedside. BHI data correlate with the definite area of infarction and outcome after 4 months.

Tilt-table test during transcranial Doppler monitoring in Parkinson's disease

Cardiovascular autonomic dysfunction can occur in Parkinson's disease (PD) and intracranial vascular modifications following orthostatism may be relevant to diagnostic and therapeutic decision-making. We performed transcranial Doppler monitoring of right middle cerebral artery (MCA) at rest and during passive 70 degrees tilt in 19 patients with idiopathic PD and in 19 age-matched normal controls. Brachial arterial blood pressure (systolic, diastolic and mean), cardiac frequency (CF), respiratory frequency and mean velocity (MV) of the MCA were recorded after 10 min of rest in supine position, and each minute during 9 min of tilting and 5 min of restored clinostatic position. The pulsatility and cerebrovascular resistances (CVR) indexes were calculated. At rest there was no significant difference in blood pressure, CF, respiratory frequency and MCA mean velocity between patients and controls. During tilt test, PD patients showed a trend to higher pulsatility index values (p=0.09) and significant lower diastolic blood pressure (p=0.001), while there was no significant difference in CVR index. In conclusion, PD patients showed mild hypotensive response to orthostatic stress, with intracranial compensatory vasodilation. Our findings suggest a preserved intracerebral autoregulation in PD without symptoms of orthostatic intolerance.

Prognostic value of Pulsatility Index in acute intracerebral hemorrhage

OBJECTIVE

To investigate whether data obtained by transcranial Doppler (TCD) have prognostic value in patients with intracerebral hemorrhage (ICH).

METHODS

A prospective study of patients with an acute (<12 hours from onset of symptoms) spontaneous supratentorial ICH was conducted. Mortality was assessed at 30-day follow-up. TCD parameters were obtained from both middle cerebral arteries: systolic, diastolic, and mean velocities and Pulsatility Index (PI) from the affected and unaffected hemispheres. The following variables were included in a univariate analysis: age, sex, hematoma volume, hypodense volume around the hematoma, total volume, midline shift, ventricular size, Glasgow Coma Scale score, intraventricular hemorrhage, body temperature, white cell count, blood glucose, mean blood pressure, and TCD data. A multivariate analysis was performed with variables that showed significance in the univariate analysis. Receiver-operator characteristic (ROC) curves were obtained.

RESULTS

Forty-eight patients (age 66.5 +/- 12.5 years; 28 men) were studied. Mortality at 30 days was 31%. The only predictor of mortality was the Glasgow Coma Scale score (odds ratio [OR] 0.67, CI 0.53 to 0.84, p = 0.001), whereas the PI from the unaffected hemisphere was correlated with mortality (OR 2.3, CI 0.92 to 5.72, p = 0.07). The area under the ROC curve was 0.92. A cutoff for PI from the unaffected hemisphere of 1.75 showed a specificity of 94% and a sensitivity of 80% as a predictor of death at 30 days.

CONCLUSIONS

The PI of the unaffected hemisphere may be a predictor of death in acute ICH. These findings suggest that intracranial hypertension is the most likely cause of death in most patients with ICH.

Arterial reocclusion in stroke patients treated with intravenous tissue plasminogen activator

BACKGROUND

Arterial reocclusion has not been systematically studied despite the fact that 13% of patients in the National Institute of Neurological Diseases and Stroke rt-PA Trial deteriorated following initial improvement, suggesting that reocclusion might be responsible for poor clinical outcome in some of these patients.

METHODS

Consecutive stroke patients treated with IV tissue plasminogen activator (TPA) within 3 hours and an M1 or M2 middle cerebral artery (MCA) occlusion on pre-TPA transcranial Doppler (TCD) were monitored up to 2 hours after TPA bolus. Reocclusion was defined as the Thrombolysis in Brain Ischemia flow decrease by >/=1 grades and no hemorrhage on repeat CT. The NIH Stroke Scale (NIHSS) and modified Rankin Scores (mRS) were obtained by a neurologist independently of TCD.

RESULTS

Sixty patients with median prebolus NIHSS score of 16 (range 6 to 28, 90% with >/=10 points) had TPA bolus at 130 +/- 32 minutes (median 120 minutes, 58% within the first 2 hours). Recanalization was complete in 18 (30%), partial in 29 (48%), and none in 13 (22%) patients. Reocclusion occurred in 34% of patients with any initial recanalization (16/47): in 4 of 16 patients with complete recanalization (22%), and in 12 of 29 patients with partial recanalization (41%). Reocclusion was detected in four patients (25%) before TPA bolus, in three (19%) by 30 minutes after bolus, in three (19%) by the end of infusion, and in six (37%) by 60 to 120 minutes. Before reocclusion, those patients had earlier median timing of recanalization: 130 versus 180 minutes after stroke onset compared with those who recanalized without reocclusion (p = 0.01). Median prebolus NIHSS score in the reocclusion group was 13.5 versus 17 (rest, NS), whereas at 2 and 24 hours, their NIHSS scores were higher: 14 versus 9 and 16 versus 6 points (p </= 0.04). Deterioration followed by improvement by >/=4 NIHSS points occurred in 8 of 16 (50%) patients with reocclusion versus 10% (rest) (p < 0.05). In-hospital mortality was 25 versus 3% (p < 0.0001). At 3 months, good outcome (mRS score of 0 to 1) was achieved by 8% of patients with no recanalization, by 33% of patients with reocclusion, and by 50% of patients with stable recanalization (p </= 0.05), and mortality was 42% with no early recanalization, 33% after reocclusion, and 8% in patients with stable recanalization (p </= 0.05).

CONCLUSIONS

Early reocclusion occurs in 34% of TPA-treated patients with any initial recanalization, accounting for two-thirds of deteriorations following improvement. Reocclusion occurs more often in patients with earlier and partial recanalization, leading to neurologic deterioration and higher in-hospital mortality. However, patients with reocclusion have better long-term outcomes than patients without any early recanalization.

Multimodal quantitation of the effects of endovascular therapy for vasospasm on cerebral blood flow, transcranial doppler ultrasonographic velocities, and cerebral artery diameters

OBJECTIVE

The goal of this study was to quantify the effects of endovascular therapy on vasospastic cerebral vessels.

METHODS

We reviewed the medical records for 387 patients with ruptured intracranial aneurysms who were treated at a single institution (University of California, Los Angeles) between May 1, 1993, and March 31, 2001. Patients who developed cerebral vasospasm and underwent cerebral arteriographic, transcranial Doppler ultrasonographic, and cerebral blood flow (CBF) studies before and after endovascular therapy for cerebral arterial spasm (vasospasm) were included in this study.

RESULTS

Forty-five patients fulfilled the aforementioned criteria and were treated with either papaverine infusion, papaverine infusion with angioplasty, or angioplasty alone. After balloon angioplasty (12 patients), CBF increased from 27.8 +/- 2.8 ml/100 g/min to 28.4 +/- 3.0 ml/100 g/min (P = 0.87); the middle cerebral artery blood flow velocity was 1 57.6 +/- 9.4 cm/s and decreased to 76.3 +/- 9.3 cm/s (P < 0.05), with a mean increase in cerebral artery diameters of 24.4%. Papaverine infusion (20 patients) transiently increased the CBF from 27.5 +/- 2.1 ml/100 g/min to 38.7 +/- 2.8 ml/100 g/min (P < 0.05) and decreased the middle cerebral artery blood flow velocity from 109.9 +/- 9.1 cm/s to 82.8 +/- 8.6 cm/s (P < 0.05). There was a mean increase in vessel diameters of 30.1% after papaverine infusion. Combined treatment (13 patients) significantly increased the CBF from 33.3 +/- 3.2 ml/100 g/min to 41.7 +/- 2.8 ml/100 g/min (P< 0.05) and decreased the transcranial Doppler velocities from 148.9 +/- 12.7 cm/s to 111.4 +/- 10.6 cm/s (P < 0.05), with a mean increase in vessel diameters of 42.2%.

CONCLUSION

Balloon angioplasty increased proximal vessel diameters, whereas papaverine treatment effectively dilated distal cerebral vessels. In our small series, we observed no correlation between early clinical improvement or clinical outcomes and any of our quantitative or physiological data (CBF, transcranial Doppler velocities, or vessel diameters).

Echogenicity of the substantia nigra: association with increased iron content and marker for susceptibility to nigrostriatal injury

BACKGROUND

Patients with Parkinson disease characteristically exhibit an increased echogenicity of the substantia nigra (SN) on transcranial sonography, a new neuroimaging technique. The same echo feature of the SN can be identified in 9% of healthy adults.

OBJECTIVE

To evaluate the relevance of the echogenic SN in healthy adults.

DESIGN

In the first part of the study, 10 healthy subjects younger than 40 years with a distinct SN hyperechogenicity underwent extensive neurological, motor, neuropsychological, and fluorine 18-dopa positron emission tomographic ([18F]-dopa PET) examinations. Results were compared with those of 10 subjects with a low echogenic SN. In the second part of the study, the postmortem brains of 20 patients without extrapyramidal disorders during their lifetime were sonographically examined with a particular focus on SN echogenicity. Subsequently, one half of the brain was prepared for heavy metal analysis, the other for a histological examination.

RESULTS

Healthy subjects with SN hyperechogenicity exhibited a significant reduction of the [18F]-dopa uptake, especially in the putamen (Wilcoxon matched pair test: left side, P =.006; right side, P =.009), whereas their neuropsychological and motor performance were normal. Postmortem studies showed that the echogenicity of the SN correlated with its iron content.

CONCLUSIONS

Increased echogenicity of the SN, characteristically seen in Parkinson disease, is related to a functional impairment of the nigrostriatal system (even in young healthy adults) that can be revealed by [18F]-dopa PET studies. Substantia nigra hyperechogenicity is related to a higher tissue iron level, which is known to enhance the cells' generation of reactive oxygen specimens. Therefore, we hypothesize that transcranial sonography may identify a susceptibility marker for the development of nigral injury that can be detected early in life, prior to the onset of Parkinson disease.

Diagnosing brain death using the transcranial Doppler with a transorbital approach

BACKGROUND

Transcranial Doppler is a sensitive instrument for the diagnosis of brain death. The guidelines for the determination of brain death include the demonstration of specific blood flow patterns in the anterior and posterior circulation systems. A limitation of this method is the frequent false finding of no flow, especially when using the transtemporal approach in older women.

OBJECTIVE

To evaluate the efficacy of the transorbital approach in the diagnosis of brain death using transcranial Doppler.

METHODS

A prospective controlled, diagnostic test study was performed. Transorbital, transtemporal, and transforaminal approaches were used. Fifty-seven patients (29 men and 28 women; mean +/- SD age, 68.2 +/- 12.1 years) with clinically determined brain death were examined.

RESULTS

In 45 patients, oscillatory flow or systolic spikes were found in all approaches. In 4 patients, no flow was detected. In 6 patients, oscillatory flow or systolic spikes were found in 2 approaches, including the transorbital one. In 2 patients, a positive finding was demonstrated only using the transorbital approach. Using the transorbital approach, the percentage of positive findings with definitive diagnoses of brain death rose from 79% to 88%.

CONCLUSION

The transorbital approach is a useful addition for the diagnosis of brain death, using the transcranial Doppler technique.

The quest for early predictors of stroke evolution: can TCD be a guiding light?

BACKGROUND AND PURPOSE

The present study aimed at evaluating the prognostic value of transcranial Doppler ultrasonography (TCD) in the acute phase of ischemic stroke, when major therapeutic decisions must be made.

METHODS

Seventy-three patients with a first-ever ischemic hemispheric stroke underwent neurological assessment according to the Unified Neurological Stroke Scale, clinical subgrouping according to the criteria of Bamford, CT scan, cervical duplex sonography, and TCD, all within 12 hours from stroke onset. TCD was repeated on days 2 and 7. Patients were followed for 90 days, during which we calculated the fatality rate and then assessed clinical outcome.

RESULTS

Emergency TCD revealed middle cerebral artery (MCA) no-flow in 24 cases and MCA asymmetry in 30 subjects. Serial TCD showed early (<24 hours) MCA recanalization in 6 patients. After 90 days, no patient with MCA occlusion at admission was autonomous, while 17 of 19 patients (89.5%) with a normal baseline TCD were independent. The fatality rate at 3 months was 21% but was 46% in patients with MCA occlusion and 61% in patients without signs of early MCA recanalization. Total anterior circulation infarct and abnormal TCD were significantly correlated (P:<0.001) with higher mortality rate and worse outcome (Barthel Index score </=60), whereas early CT ischemic signs and severe carotid disease were not. Furthermore, TCD identified within the total anterior circulation infarct subgroup 2 prognostic clusters according to MCA patency at admission (P:<0.001). Logistic regression selected normal baseline TCD as an independent predictor of good long-term outcome and MCA no-flow as an independent predictor of disability or death.

CONCLUSIONS

TCD findings play an important role in the early prognosis of anterior circulation stroke, providing possible guidance for therapeutic interventions.

Dynamic cerebral autoregulation is unaffected by aging

BACKGROUND AND PURPOSE

Normal aging is associated with marked changes in the cardiovascular and cerebrovascular systems. Although cerebral autoregulation (CA) is impaired in certain disease states, the effect of age per se on dynamic CA in humans is unknown and the focus of this study.

METHODS

Twenty-seven young subjects (</=40 years) and 27 older subjects (>/=55 years), matched for sex and systolic blood pressure (BP), underwent measurement of cerebral blood flow velocity by transcranial Doppler ultrasound and noninvasive beat-to-beat arterial BP measurement during induced and spontaneous dynamic BP stimuli. A standard dynamic autoregulatory index (ARI) was derived for each spontaneous and induced dynamic BP stimulus to include the step response, as well as cardiac baroreceptor sensitivity (BRS), for the 2 groups.

RESULTS

The mean age of the young group was 29+/-5 years, and that of the older group was 68+/-5 years. Cardiac BRS was reduced in the older group (8. 6+/-4.5 versus 16.9+/-8.8 ms/mm Hg; P:<0.0001). However, no age-related differences were demonstrated in step response plots or in ARI values for any pressor or depressor dynamic BP stimulus (P:=0. 62), with mean ARI values for all stimuli combined being 4.9+/-1.8 for the young group and 5.0+/-2.3 for the older group.

CONCLUSIONS

Although increasing age is associated with a decrease in cardiac BRS, dynamic CA, as assessed by step response analysis as well as cerebral blood flow responses to transient and induced BP stimuli, is unaffected by aging.

Serum ferritin and C282Y mutation of the hemochromatosis gene as predictors of asymptomatic carotid atherosclerosis in a community population

BACKGROUND AND PURPOSE

Serum ferritin and heterozygosity for the C282Y mutation of the hemochromatosis gene have both been associated with an increased risk of cardiovascular events. The purpose of the study was to test whether either is a risk predictor for asymptomatic carotid atherosclerosis.

METHODS

We assessed carotid intima-media wall thickness (IMT) and focal plaque formation by high-resolution B-mode ultrasound, conventional risk factors, serum ferritin levels, and the C282Y mutation of the hemochromatosis gene in a randomly selected community population of 1098 subjects (545 women and 553 men) aged 27 to 77 years.

RESULTS

After adjustment for conventional risk factors, serum ferritin was not associated with carotid mean IMT. Women with ferritin values over the first quartile (>34 microg/L) had an adjusted odds ratio of 2.1 (95% CI, 1. 3 to 3.4; P:=0.0016) for carotid plaque compared with the first quartile. Ferritin was not associated with carotid plaque in men. Subjects who were heterozygous for the C282Y mutation constituted 11. 4% of the population, and there was no independent association of this genotype with either carotid IMT or focal plaque formation.

CONCLUSIONS

We conclude that in our community population, C282Y genotype status was not a risk predictor for either carotid mean IMT or plaque formation. Serum ferritin values in women were independently associated with carotid plaque.

Micro-emboli detection: an ultrasound Doppler signal processing viewpoint

Several studies have been carried out in the last twenty years on the characterization and detection of cerebral artery emboli. From the detection point of view, the existing methods are largely based on the classical Fourier analysis of which the well known limitations provide poor accuracy. This paper first recalls existing methods based on Fourier, Wigner-Ville and wavelet approaches. It then presents new emboli detection methods based on parametric signal processing approaches. The basic idea of these parametric methods is to compare the Doppler embolic signal to its autoregressive model. The detection principle consists in constructing a decision information which contains the signature of the micro-embolus being sought. The detection is finally evaluated using receiver operating characteristic (ROC) curves. Comparison between the new methods and classical approaches is performed using a realistic embolic signal simulation. Furthermore, to validate our theoretical study, we tested our new algorithms using in vivo signals. This comparison shows the significant inaccuracy of existing methods to detect micro-emboli.

Microembolic signals and clinical outcome in patients with acute stroke--a prospective study

The occurrence of microembolic signals (MES) in patients with transient ischemic attack (TIA) or stroke has already been described; the influence of the time interval between onset of symptoms and transcranial Doppler monitoring (TCD) on the MES rate or MES prevalence and the possible prognostic value of the early detected MES rate on the outcome of TIA or stroke symptoms in a 3 month interval are discussed. In a prospective study we evaluated 61 patients consecutively admitted to our stroke unit after their first ischemic neurological deficit involving the vascular territory of MCA and/or ACA. All of the patients underwent a 30-minute bilateral transcranial Doppler monitoring of their MCAs for the identification of MES. Monitoring was performed within 12.3 + -9.3 (average mean + -SD) hours of stroke onset for the first time, the second time 48 hours after first TCD monitoring. Prognosis for the recovery of neurological deficits was evaluated by using the Barthel index (BI) and Scandinavian Stroke Scale (SSS) at the time of admission of the patient to the stroke unit, and with Barthel indices after one month and after 3 months. As a result, 56% of all patients showed MES in at least one of the two registrations. MES were recorded not only on the symptomatic side. The MES prevalence between both TCD monitorings was significantly different (total MES prevalence: 1st TCD: 26 patients: 2nd TCD: 13 patients; p < 0.04; ipsilateral MES prevalence: 1st TCD: 19 patients; 2nd TCD: 9 patients; p < 0.01). The regression analysis showed a significant influence of the total MES rate on both neurological scores at admission (SSS: 0.03; Barthel index: 0.04), but not for the Barthel scores after one and three months. In conclusion, we found an influence of the time interval between onset of neurological symptoms of TIA or stroke on the MES rate and the prevalence of MES. The prevalence of MES or the MES rate, found after a short time interval to the onset of symptoms, did not have a prognostic value on the outcome of neurological deficits up to a three month follow-up.

Evaluating the outcome of severe head injury with transcranial Doppler ultrasonography

The authors conducted a study to determine the value of transcranial Doppler (TCD) ultrasonography in evaluating the outcome of severely head injured patients and to correlate the TCD values with those obtained from intracranial pressure (ICP) and cerebral perfusion pressure (CPP) monitoring. The authors conducted a prospective study of 125 patients with severe head injury (Glascow Coma Scale scores of less than 9) who underwent TCD ultrasonography according to the standard technique of insonating the middle cerebral artery (MCA) and measuring the mean blood flow velocity and pulsatility index within the first 24 hours of admission. The ICP and CPP values, as well as other clinical, analytical, and neuroimaging data, were also recorded. After 6 months, outcome was evaluated using the Glasgow Outcome Scale. Moderate disability and complete recovery were considered "good" outcome; death, vegetative state, and severe disability were considered "poor." In 67 patients (54%) good outcome was demonstrated whereas in 58 (46%) it was poor. The mean blood flow velocity of the MCA in patients with good outcome was 44 cm/second; in those with poor outcomes it was 36 cm/second (p < 0.003). The mean PI in cases of good outcome was 1 whereas in poor outcome was 1.56 (p < 0.0001). The correlations of ICP and CPP to PI were statistically significant (r2 = 0.6; p < 0.0001). When performed in the first 24 hours of severe head injury, TCD ultrasonography is valid in predicting the patient's outcome at 6 months and correlates significantly with ICP and CPP values.

[Normal values for transcranial doppler studies in our medium]

OBJECTIVE

Transcranial Doppler is a technique which is being used ever more frequently in the study of intracranial arteries and is very useful in the study of cerebrovascular disease. The typical values of a healthy population in our country are unknown. The aim of this study was determine mean velocity and pulsatility index reference values in a healthy population.

PATIENTS AND METHOD

Transcranial Doppler basal examination was carried out on 118 healthy volunteers without prior haematological or cerebrovascular conditions. Those found to have extracranial arterial stenoses were excluded as were those in whom bilateral temporal bone hyperostosis did not permit insonation in either middle cerebral arteries. The nine intracranial arteries were sounded systematically at fixed depths. The mean and standard deviations of each variable were calculated for side, age group and sex.

RESULTS

49% were males and average age was of 56 years (range, 21-87 years). A sufficient signal to determine the parameters of the study was obtained in 89% of middle cerebral arteries. Statistically significant differences in mean velocity and pulsatility index were found between age groups and sexes.

CONCLUSIONS

Sex and age must be taken into account in establishing typical patterns in transcranial Doppler examination. Our results enable parameters of typical values to be established for the adult population in Spain.

Resting energy expenditure in brain death

OBJECTIVE

To evaluate resting energy expenditure (REE) in brain dead patients and to investigate the hypothesis that the reduction in REE results from a decrease in cerebral blood flow.

DESIGN

Prospective, open labeled, control study.

SETTING

General intensive care unit of a tertiary referral teaching hospital.

PATIENTS

30 critically ill patients with isolated head injury divided in two groups: group 1 patients (n = 10) with a Glasgow Coma Scale (GCS) score of 4 to 8 and group 2 patients (n = 20), in whom the final outcome was brain death (GCS = 3). Group 2 patients were divided into two subgroups: Group 2 a (n = 11) were admitted as brain dead (GCS = 3) and group 2 b (n = 9) were admitted with a GCS > 3 and progressed to brain death.

INTERVENTIONS

Clinical and instrumental, using transcranial Doppler sonography (TCD), diagnosis of brain death. Cerebral blood flow studies of the middle cerebral artery bilaterally by bidimensional TCD and measurement of REE using indirect calorimetry.

MEASUREMENTS AND RESULTS

Measurements of REE and TCD studies were performed simultaneously on admission and after hemodynamic and neurologic stabilization. In cases with progressive neurologic deterioration, serial measurements were performed REE values were expressed as percentage of basal metabolic rate (%BMR), which were estimated according to each patient's gender, age, height, and weight. Group 1 patients, had normal TCD patterns throughout their hospitalization and their REE value was 21 +/- 11 % higher than BMR. Group 2 patients demonstrated TCD patterns compatible with brain death and their REE value was 24.5 +/- 11 % lower than BMR (p < 0.01). Group 2 a patients, who were admitted as brain dead and remained brain dead, had REE values 30 +/- 11 % lower than BMR (p < 0.01). Group 2 b patients, who were not brain dead on admission but progressed to brain death, in serial measurements revealed a significant relationship between REE and TCD findings (R = -0.77, p < 0.0001). In this subgroup of patients, with multiple regression analysis a significant relationship was found only between REE and the TCD pattern, but not with body temperature.

CONCLUSIONS

In brain dead patients, REE decreases to values lower than BMR. This can be attributed to the cessation of cerebral blood flow and consequently cerebral metabolism and not to hypothermia.

Application of a new blood-mimicking fluid in a flow Doppler test object

OBJECTIVE

To construct and apply a flow Doppler test object and its flow rig.

METHODS

In this flow rig, particular attention was given to use of a long inlet length and to ensure the absence of disturbing particles. The latter was obtained by proper degassing, use of a filter and application of a fungicide. Two blood-mimicking fluids were used, with a viscosity of 4 and 8 mPa s respectively.

RESULTS

Predictable Poiseuille flow profiles were obtained. The velocity range could be extended by increasing the viscosity of the blood-mimicking fluid. Predictable axial velocities up to 2.5 m/s were obtained in an 8-mm tube and 5 m/s in a 4-mm tube.

CONCLUSION

Well-defined flow conditions that can be applied to investigate clinical ultrasound Doppler systems in a number of situations have been obtained.

Bilateral cerebral emboli monitoring during extracorporeal circulation

Microembolism generated during extracorporeal circulation is thought to be responsible for stroke and neuropsychological deficits. Before one can investigate the pathogenetic role in more detail, reproducible and reliable quantitative methods need to be developed. In several previous studies, microemboli detection was performed unilaterally. We questioned if this reflects the bihemispheric embolic load. In 42 patients undergoing coronary artery bypass grafting, bilateral embolus detection was performed during extracorporeal circulation. The side-to-side correlation of microembolus counts was strong (0.91), but there was a significant difference in number (p < 0.01) comparing left and right emboli. The side of higher embolus counts cannot be predicted in the individual because either side may show higher counts. Doubling the unilateral count may deviate from the bilateral count by as much as 51% in the individual patient. The total embolic load to the brain during extracorporeal circulation cannot be precisely predicted from unilateral transcranial insonation alone.

Frequency filtering improves ultrasonic embolic signal detection

Problems in detection of Doppler cerebral embolic signals primarily occur for embolic signals of low relative intensity. A characteristic feature of embolic signals is that the intensity increase is maximal over a narrow frequency band. Therefore, frequency filtering of the data might improve embolic signal relative intensity and detectability. We implemented an off-line finite impulse response filter in software running on a commercially available transcranial Doppler system, using the time-domain audio data as input. The range of the filter was chosen by placing a box around the embolic signal on the spectral display. One hundred consecutive embolic signals from patients with carotid stenosis were analyzed; all had been recorded by a bigate system and the signal was analyzed in both proximal and distal channels. There was a highly significant increase in embolic signal relative intensity following frequency filtering; mean (SD) proximal channel prefiltering 12.75 (4.83) dB, postfiltering 16.36 (4.93) dB; distal channel prefiltering 13.42 (4.98) dB, postfiltering 16.60 (5.11) dB, for both p < 0.001. Despite all embolic signals being audible and visible in at least one channel on the frequency spectral display, in 17 cases, the amplitude increase associated with the embolic signal could not be clearly seen in time-domain data of one or both channels prior to filtering. Following frequency filtering, this was reduced to 5. Incorporation of such a frequency-filtering approach to an online system is likely to improve the sensitivity of online detection for embolic signals of low relative intensity.

Middle cerebral artery anatomy and characteristics of embolic signals: a dual gate computer simulation study

In terms of microembolic signal (MES) detection, the anatomy of the middle cerebral artery (MCA) mainstem has only scarcely been considered. The vessel itself, however, could be at least partly responsible for the enormous variation when calculating the essential time difference (deltat) values of MES using the dual-gate technique. Therefore, we studied the time characteristics of MES in a computer simulation applying an anatomically realistic vessel and a dual-gate TCD approach. Three different MCA anatomies and two MES to blood intensities were simulated as well as two different sample volume settings. The MES length (proximal sample volume t1; distal sample volume t2) and deltat were calculated for different angles of insonation and sample volume depths. The calculations of the time characteristics of MES showed extreme variation, with only modest changes of the insonation angle (t1 4-34 ms; deltat 9-27 ms) or the sample volume depth (t1 7-27 ms; deltat 6-32 ms). The variation could be considerably reduced with modified TCD settings i.e., a shorter gate separation combined with a shorter receiver gate time in the distal sample volume (deltat with changing insonation angles 6-19 ms; deltat with changing insonation depths 13-17 ms). These results not only urge us to a cautious interpretation of the properties of single MES, but also contribute to an understanding of the marked deltat variation using the dual-gate technique.

Cerebral arteriovenous transit time (CTT): a sonographic assessment of cerebral microcirculation using ultrasound contrast agents

Transcranial color-coded sonography (TCCS) has been used to investigate major brain-supplying arteries, draining veins and brain parenchyma. Here, we describe a contrast-enhanced TCCS analysis of cerebral arteriovenous transit time (cTT) as a measure of cerebral microcirculation. We evaluate its reproducibility and its correlation with clinical impairment of brain function and neuropsychological tests. A total of 27 patients with cerebral microangiopathy and 30 healthy controls were examined. CTT is defined by the time an ultrasound contrast agent requires to pass from the P2-segment of the posterior cerebral artery to the vein of Galen. This was measured by comparison of power Doppler intensity in two off-line defined regions of interest. Serial intraindividual cTT measurements within several min showed a good reproducibility of this parameter. cTT was significantly longer in patients with cerebral microangiopathy than in controls (Mann-Whitney U test,p < 0.001) and related to cognitive impairment measured by the Mini-Mental-State examination. We conclude that it is a quick and reliable parameter related to increased vascular resistance of the microcirculation or a rarefaction of microvessels. Further studies are needed to show the sensitivity and specificity of cTT in the diagnosis of small vessel disease and the interference of important circulation factors, such as heart failure or blood viscosity.