Ultrasonografía transcraneal en el paciente crítico / Transcranial sonography in the critical patient

La ultrasonografía transcraneal es una técnica no invasiva y disponible a pie de cama que se ha convertido en una herramienta accesible y consolidada en la evaluación y el manejo clínico de los pacientes neurocríticos. Se trata de una técnica en continuo crecimiento cuyos fundamentos (y sus limitaciones) deben ser conocidos por el intensivista. Esta revisión aporta un enfoque práctico para el intensivista, incluyendo las diferentes ventanas y planos de insonación y su papel en la patología específica propia de los pacientes neurocríticos y en los pacientes críticos de otras etiologías. (AU)

Transcranial ultrasonography is a non-invasive, bedside technique that has become a widely implemented tool in the evaluation and management of neurocritically ill patients. It constitutes a technique in continuous growth whose fundamentals (and limitations) must be known by the intensivist. This review provides a practical approach for the intensivist, including the different sonographic windows and planes of insonation and its role in different conditions of the neurocritical patients and in critical care patients of other etiologies. (AU)

Imaging Pattern and the Mechanisms of Postoperative Infarction After Indirect Revascularization in Patients with Moyamoya Disease.

OBJECTIVE: To develop preventive strategies against postoperative infarction after indirect revascularization surgery in patients with moyamoya disease (MMD), we evaluated clinical information, with a specific focus on the imaging pattern of postoperative infarction. METHODS: We retrospectively evaluated 421 surgical procedures performed in 354 (262 pediatric and 159 adult) patients with MMD from April 1991 to March 2021 at our institute. In addition to clinical information, raw images of postoperative infarction were collected and categorized into subtypes by the location of the infarction. RESULTS: Symptomatic and asymptomatic postoperative infarction occurred in 47 and 12 patients (11.1% and 2.6%), respectively, and more than half (51.7%) of these cases of postoperative infarction occurred immediately or the day after the surgery. Cortical infarction around the craniotomy site was the most frequent pattern observed (50/59, 84.8%), and some of these cases seemed to occur under local compression from epidural or subdural hematomas (15/50, 30.0%). Ipsilateral white matter infarctions located in the watershed area (9/59, 15.3%) and contralateral infarctions (3/59, 5.1%) were also observed. Four patients (1.0%) showed sudden occlusions of ipsilateral or contralateral large intracranial arteries immediately after surgery. Postoperative infarction caused permanent neurologic deficits in 7 patients (1.7%), and all included the cortex outside the craniotomy site. CONCLUSIONS: Local cortical irritation, hemodynamic fluctuation, and thromboembolic events were suggested as possible mechanisms of postoperative infarction after indirect revascularization in patients with MMD. Minimizing cortical irritation, maintaining adequate cerebral blood flow, and perioperative antiplatelet agents might decrease the incidence of postoperative infarction.

Role of transcranial Doppler ultrasonography in assessing stenosis after flow diversion.

INTRODUCTION: Patients after implantation of flow diverters (FD) due to intracranial aneurysms require radiological and clinical follow-up in view of in-stent stenosis. The aim of the study was to evaluate transcranial Doppler ultrasonography (TCD) as an alternative to more invasive digital subtraction angiography in monitoring patients with FD. PATIENTS AND METHODS: Twenty-five patients after FD deployment due to internal carotid artery (ICA) aneurysms were reviewed. The degree stenosis found on TCD was compared with the results of catheter angiography. The TCD examinations were recorded from two sides at the extracranial ICA and the most proximal and distal segment of intracranial ICA. Analyzed TCD factors included: peak systolic blood flow velocity, end diastolic velocity, mean velocity, pulsatility index, and resistivity index. The side-to-side differences and ratios between particular TCD indices were calculated. RESULTS: The cumulative frequency of angiographic in-stent stenosis was 5 of 25 (20 %). The analysis showed that pulsatility index measured on the most proximal intracranial segment of ICA is a predictor for angiographic instent stenosis (AUC = 0.854; p = 0.04; 95 % CI 0.59-1.00). The threshold of pulsatility index separating stenosis and non-stenosis groups was 1.05 with a sensitivity of 50 % and a specificity of 100 %. As the cut-off threshold of PI was set 0.75 the sensitivity and specificity was 100 % and 16.7 %, respectively. CONCLUSIONS: The increased TCD-derived pulsatility index measured on the most proximal intracranial segment of ICA is associated with in-stent stenosis demonstrated on angiograms.

No association between postmenopausal time and the prevalence of newly discovered asymptomatic intracranial atherosclerotic stenosis: The APAC study.

INTRODUCTION: Asymptomatic intracranial atherosclerotic stenosis (AICAS) is a common cause of stroke. Elderly women were more likely than men to develop AICAS, although it indicated that a lifelong exposure to estrogen could lower the risks of cardiovascular disease (CVDs). OBJECTIVE: The present study aims to ascertain whether postmenopausal time is a risk factor of AICAS. Fostering a correct perception of menopause is of great significance for the overall well-being of the elderly women. METHODS: All participants received a questionnaire, physical examination, laboratory testing and transcranial Doppler. The menopausal population (n = 701) was divided into three groups by tertiles of postmenopausal time. Two-tailed testing and trend test were used to reveal the relationship between postmenopausal time and newly discovered AICAS. Other potential risk factors were also analyzed to ascertain whether there was a relation between postmenopausal time and the newly discovered ICAS. RESULTS: Both mean age and mean postmenopausal time were gradually increased from G0 to G2. The same trend occurred in hypertension, diabetes mellitus, total cholesterol, triglyceride, C-reactive protein and serum homocysteine. Adjusting for various confounding factors, postmenopausal time was not a risk factor for newly discovered AICAS. Multifactor analysis and stratifying analysis showed no correlation between newly discovered AICAS and postmenopausal time. CONCLUSIONS: Postmenopausal time is not an independent risk factor of AICAS. No relationship was detected between postmenopausal time and newly discovered AICAS, while vigorous control of body weight, blood pressure/glucose/lipids and smoke cessation are vital for preventing the occurrence of AICAS.

Estimación de la desviación de línea media cerebral mediante dúpplex / Transcraneal/brain midline shift assessment using sonography

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Sickle Cell Disease and Stroke.

Cerebral infarction is a common complication of sickle cell disease and may manifest as overt stroke or cognitive impairment associated with "silent" cerebral infarction on magnetic resonance imaging. Vasculopathy may be diagnosed on transcranial Doppler or magnetic resonance angiography. The risk factors in sickle cell disease for cognitive impairment, overt ischemic stroke, silent cerebral infarction, overt hemorrhagic stroke, and vasculopathy defined by transcranial Doppler or magnetic resonance angiography overlap, with severe acute and chronic anemia, acute chest crisis, reticulocytosis, and low oxygen saturation reported with the majority. However, there are differences reported in different cohorts, which may reflect age, geographic location, or neuroimaging techniques, for example, magnetic resonance imaging field strength. Regular blood transfusion reduces, but does not abolish, the risk of neurological complications in children with sickle cell disease and either previous overt stroke or silent cerebral infarction or abnormal transcranial Doppler. There are relatively few data on the use of hydroxyurea or other management strategies. Early assessment of the risk of neurocognitive complications is likely to become increasingly important in the management of sickle cell disease.

Transcranial Doppler in autonomic testing: standards and clinical applications.

When cerebral blood flow falls below a critical limit, syncope occurs and, if prolonged, ischemia leads to neuronal death. The cerebral circulation has its own complex finely tuned autoregulatory mechanisms to ensure blood supply to the brain can meet the high metabolic demands of the underlying neuronal tissue. This involves the interplay between myogenic and metabolic mechanisms, input from noradrenergic and cholinergic neurons, and the release of vasoactive substrates, including adenosine from astrocytes and nitric oxide from the endothelium. Transcranial Doppler (TCD) is a non-invasive technique that provides real-time measurements of cerebral blood flow velocity. TCD can be very useful in the work-up of a patient with recurrent syncope. Cerebral autoregulatory mechanisms help defend the brain against hypoperfusion when perfusion pressure falls on standing. Syncope occurs when hypotension is severe, and susceptibility increases with hyperventilation, hypocapnia, and cerebral vasoconstriction. Here we review clinical standards for the acquisition and analysis of TCD signals in the autonomic laboratory and the multiple methods available to assess cerebral autoregulation. We also describe the control of cerebral blood flow in autonomic disorders and functional syndromes.

The neuroprotective effect of focused ultrasound: New perspectives on an old tool.

INTRODUCTION: Transcranial focused ultrasound (tFUS) is a novel technique that can noninvasively modulate the cortical function. Moreover, there are rapidly replicating evidence suggesting the role of tFUS for targeted neuroprotective drug delivery by increasing the permeability of the central nervous system barrier that results with increased neuroprotective activity. In contrast to the indirect neuroprotective effect, there is rare evidence suggesting the direct parenchymal neuroprotective effect of transcranial focused ultrasound (tFUS). In the light of these findings, we aimed to review the direct and indirect neuroprotective effect of FUS in various animal models of Stroke, Parkinson's Disease, Alzheimer's Disease and Major Depressive Disorder. METHODS: A literary search was conducted, utilizing search terms "animal", "focused ultrasound", "neuroprotection", "Alzheimer's Disease", "Parkinson's Disease ", "Stroke", "Neurodegenerative disease" and "Major Depressive Disorder". Items were excluded if they failed to: (1) include patients, (2) editorials, and letters. RESULTS: This mini-review article presents an up-to-date review of the neuroprotective effects of tFUS in animal studies and suggests the dual neurotherapeutic role of tFUS in various neurodegenerative diseases. CONCLUSION: Future well-conducted human studies are emergently needed to assess the neuroprotective effects of FUS.

Trends in Transcranial Doppler Monitoring in Aneurysmal Subarachnoid Hemorrhage: A 10-Year Analysis of the Nationwide Inpatient Sample.

BACKGROUND: Transcranial Doppler (TCD) is endorsed by national guidelines for use in aneurysmal subarachnoid hemorrhage (aSAH) for surveillance of cerebral vasospasm (CV). However, nationwide data on utilization of TCD for CV detection and monitoring in aSAH are lacking. METHODS: Analysis of nationwide trends in TCD prevalence was performed using Nationwide Inpatient Sample (NIS) data from 2002 to 2011. Raw counts were converted into weighted counts, which were used to generate national estimates. Teaching hospitals were examined separately for TCD utilization rates. All analyses accounted for the complex sampling design and sample discharge weights of the NIS, following Healthcare Cost and Utilization Project-NIS recommendations. The objective was to estimate the proportion of patients with aSAH receiving TCD monitoring using the NIS. RESULTS: Between 2002 and 2011, a total of 256,089 patients were discharged with a diagnosis of aSAH, of which 3850 underwent TCD monitoring. aSAH accounted for an average of 67.1 discharges per 100,000 annually (95% confidence interval [CI] 61.3-72.8). Of these, 1.5% (95% CI 0.4-2.6) underwent TCD examination. In teaching hospitals, aSAH accounted for an average of 108.5 discharges per 100,000 biennially (95% CI, 96.2-120.8), of which 2% (95% CI 1.0-4.0) underwent TCD examination. TCD utilization increased from <1% during the 2002-2005 period to ≥1.5% during the 2006-2011 period (odds ratio 2.3, 95% CI 1.0-5.7), an increase also seen in teaching hospitals. CONCLUSIONS: TCD is underused nationally in the care of aSAH. Whereas the prevalence of TCD is low in teaching hospitals, it is nearly nonexistent in nonteaching hospitals.

Use of Transcranial Doppler in Patients with Severe Traumatic Brain Injuries.

Severe traumatic brain injuries (TBI) are associated with a high rate of mortality and disability. Transcranial Doppler (TCD) sonography permits a noninvasive measurement of cerebral blood flow. The purpose of this study is to determine the usefulness of TCD in patients with severe TBI. TCD was performed, from April 2008 to April 2013, on 255 patients with severe TBI, defined as a Glasgow Coma Scale score of ≤8 on admission. TCD was performed on hospital days 1, 2, 3, and 7. Hypoperfusion was defined by having two out of three of the following: 1) mean velocity (Vm) of the middle cerebral artery <35 cm/sec, 2) diastolic velocity (Vd) of the middle cerebral artery <20 cm/sec, or 3) pulsatility index (PI) of >1.4. Vasospasm was defined by the following: Vm of the middle cerebral artery >120 cm/sec and/or a Lindegaard index (LI) >3. One hundred fourteen (45%) had normal measurements. Of these, 92 (80.7%) had a good outcome, 6 (5.3%) had moderate disability, and 16 (14%) died, 4 from brain death. Seventy-two patients (28%) had hypoperfusion and 71 (98.6%) died, 65 from brain death, and 1 patient survived with moderate disability. Sixty-nine patients (27%) had vasospasm, 31 (44.9%) had a good outcome, 16 (23.2%) had severe disability, and 22 (31.9%) died, 13 from brain death. The vasospasm was detected on hospital day 1 in 8 patients, on day 2 in 23 patients, on day 3 in 22 patients, and on day 7 in 16 patients. Patients with normal measurements can be expected to survive. Patients with hypoperfusion have a poor prognosis. Patients with vasospasm have a high incidence of mortality and severe disability. TCD is useful in determining early prognosis.

Longitudinal changes in cerebral blood flow velocities in different clinical courses of migraine.

Objective To assess longitudinal changes in cerebral blood flow velocities (ΔCBFVs) according to the clinical course of migraine. Methods We retrospectively included migraine patients with two or more attacks per month at baseline who were followed up within 2 years with transcranial Doppler in a tertiary headache clinic. ΔCBFVs were analyzed in relation to clinical courses, defined as remission (0-1 headache days/month), persistence (2-14/month), or progression (≥15/month) in episodic migraine (EM), and conversion to EM (<15/month) and persistence (≥15/month) in chronic migraine (CM). Results A total of 166 patients (90 EM and 76 CM) were included. In EM, the remission group ( n = 30) showed a decrease in CBFV in the middle cerebral artery (MCA) and the basilar artery (BA). The progression group ( n = 10) showed increasing CBFVs in the bilateral MCAs. Patients with the persistence course ( n = 50) showed generally unchanged CBFVs. In CM, ΔCBFVs decreased in the BA and increased in the posterior cerebral artery (PCA) after conversion to EM ( n = 61), whereas they remained unchanged in the persistence group ( n = 15). In all patients, % change in headache days was positively correlated with the %ΔCBFVs of the bilateral MCAs and the BA. Conclusions CBFV changes are associated with the different clinical courses of migraine. The association is more prominent in EM than CM.

Transcranial Color-Coded Duplex in Acute Encephalitis: Current Status and Future Prospects.

BACKGROUP AND PURPOSE: There are limited data regarding the diagnostic yield of transcranial color-coded Doppler (TCCD) in acute encephalitis. We present our preliminary observations of consecutive ultrasound evaluations in 2 patients with acute encephalitis and we review the possible diagnostic role of TCCD in such cases. METHODS: We describe two cases of acute encephalitis that presented with aphasia and confusion and underwent repeat TCCD evaluation at baseline and after 48 hours in both patients. We also critically review the current literature regarding potential TCCD applications in acute central nervous system infections. RESULTS: Serial TCCD evaluations revealed the following triad of abnormal findings in both patients: (i) elevated pulsatility index (PI) in the left middle cerebral artery (M1 MCA) at baseline (>1.2), (ii) increased PI in left M1 MCA by >25% in comparison to right M1 MCA, and (iii) decrease in PI in left M1 MCA by >25% at the follow-up evaluation at 48 hours. The decrease in PI in left M1 MCA coincided with symptom improvement in both patients. DISCUSSION: The focal transient increase in left M1 MCA PI may be attributed to focally increased intracranial pressure or peripheral vasospasm of distal left MCA branches. Since there are limited reports in the literature concerning TCCD evaluation of patients with central nervous system infections, our preliminary findings require independent confirmation in a larger series of patients.

Current Opinion and Use of Transcranial Doppler Ultrasonography in Traumatic Brain Injury in the Pediatric Intensive Care Unit.

The purpose of this study was to identify and review clinical studies using transcranial Doppler (TCD) ultrasonography in children with severe traumatic brain injury (TBI) in the pediatric intensive care unit (PICU). We identified 16 articles from January 2005 to July 2015 that met inclusion (TBI, five or more cases in case series, subjects <18 years old, TCD performed in PICU) and exclusion criteria (age not stated, data from subjects <18 years not separated from adult data, <85% study population <18 years in mixed population with adults). TCD parameters were used to assess autoregulation, intracranial pressure, and vasospasm, and to predict neurological outcome. Incidence of impaired autoregulation varied in severe TBI from 25% to 80%. Altered TCD flows and pulsatility index variably predicted intracranial hypertension across studies. Sonographic vasospasm in the middle cerebral artery occurred in 34% of 69 children with severe TBI. Outcomes seem to be related to altered TCD-derived flow velocities while in the ICU. TCD may be a useful tool to assess autoregulation, intracranial pressure, and vasospasm following TBI in the PICU. Further research is needed to establish gold standards and validate the findings in children. TCD may then impact day-to-day management in the PICU, and potentially improve outcomes in children with severe TBI.

Noninvasive measurement of intracranial pressure via the pulsatility index on transcranial Doppler sonography: Is improvement possible?

PURPOSE: We hypothesized that using hemodynamic variables could improve the prediction of intracranial pressure (ICP) from the middle cerebral artery pulsatility index (PI) measured with transcranial Doppler sonography. METHODS: In this prospective study, 39 patients with traumatic brain injury were routinely examined with transcranial Doppler sonography, and the middle cerebral artery PI was calculated. A multivariate model including hematocrit, mean arterial blood pressure, heart rate, and arterial CO2 pressure (PaCO2 ) was evaluated. RESULTS: Thirty-nine comatose patients (16 women and 23 men; age range 18-73 years; median 44 years) were included, and 234 data pairs (consisting of ICP and corresponding PI values) were analyzed. ICP ranged from -3 mmHg to +52 mmHg, and PI from 0.6 to 2.85. We found a significant but weak correlation between PI and the square root of ICP (R(2) between 0.29 and 0.34, p < 0.0001). A slightly stronger correlation was detected when hemodynamic variables were incorporated (R(2) between 0.37 and 0.43). Of these variables, mean arterial blood pressure had the most significant influence. CONCLUSIONS: In this study, PI was not a sufficiently strong predictor of ICP to be used in clinical practice. Its reliability did not improve even when hemodynamic variables were considered. Therefore, we recommend abandoning the use of PI for the noninvasive measurement of ICP in clinical practice.

Transcranial Doppler after traumatic brain injury: is there a role?

PURPOSE OF REVIEW: To present the practical aspects of transcranial Doppler (TCD) and provide evidence supporting its use for the management of traumatic brain injury (TBI) patients. RECENT FINDINGS: TCD measures systolic, mean, and diastolic cerebral blood flow (CBF) velocities and calculates the pulsatility index from basal intracranial arteries. These variables reflect the brain circulation, provided there is control of potential confounding factors. TCD can be useful in patients with severe TBI to detect low CBF, for example, during intracranial hypertension, and to assess cerebral autoregulation. In the emergency room, TCD might complement brain computed tomography (CT) scan and clinical examination to screen patients at risk for further neurological deterioration after mild-to-moderate TBI. SUMMARY: The diagnostic value of TCD should be incorporated into other findings from multimodal brain monitoring and CT scan to optimize the bedside management of patients with TBI and help guide the choice of appropriate therapies.

Advances in transcranial Doppler US: imaging ahead.

Transcranial Doppler ultrasonography (US) is a noninvasive, portable technique for evaluating the intracranial vasculature. It has found its most useful clinical application in the detection of vasospasm involving the cerebral vessels after subarachnoid hemorrhage due to aneurysm rupture. The technique has become an integral part of monitoring and managing patients with subarachnoid hemorrhage in the neurologic intensive care unit. In addition, it has proved useful for evaluating the intracranial vasculature in patients with sickle cell disease, stroke, or brain death. Transcranial US originated as a "blind" nonimaging study in which pulsed Doppler technology was used. Identification of the major intracranial vessels and evaluation of those vessels for vasospasm relied on spectral waveforms obtained in each vessel and was based on the depth of the vessel from the skull, the direction of blood flow, and the orientation of the transducer. Recent advances in US technology allow the use of gray-scale, spectral Doppler, and color Doppler flow imaging to directly visualize intracranial vessels, thereby simplifying flow velocity measurements and enhancing their accuracy for vasospasm detection. In particular, measurements of peak systolic velocity and mean flow velocity and calculation of the Lindegaard ratio facilitate the identification of vessels that may be in vasospasm and help differentiate vasospasm from physiologic conditions such as hyperemia and autoregulation. Thus, gray-scale and color Doppler flow imaging offer many advantages over the original pulsed Doppler technique for evaluating the intracranial vasculature.

Conocimiento del estado vascular para la toma de decisiones terapéuticas en el ictus isquémico agudo: ¿cuál es el papel de la neurosonología? / Knowledge of vascular status for therapeutic decision-making in acute ischemic stroke: which is the role of neurosonology?

Existe en los últimos años un interés creciente en el conocimiento del estado vascular de los pacientes con ictus agudo. La detección y localización de una oclusión arterial resultan de gran interés para un enfoque pronóstico adecuado y la selección del tratamiento recanalizador agudo más apropiado. La neurosonología constituye una herramienta diagnóstica útil en el estudio del estado vascular del paciente con ictus agudo. En el presente trabajo se revisan diversas situaciones en las que los ultrasonidos aportan información diagnóstica valiosa, como en el caso de la oclusión de la arteria cerebral media (ACM), oclusión ‘en T’ de la arteria carótida interna (ACI), oclusión ‘en tándem’ ACI-ACM, monitorización de oclusiones de arterias intracraneales, oclusión aguda de la ACI extracraneal y presencias de trombos flotantes intracarotídeos. La neurosonología aporta ventajas evidentes frente a otras técnicas diagnósticas: es rápida, dinámica, económica, inocua, accesible, permite la monitorización del estado vascular del paciente en tiempo real, evita retrasos en la administración de tratamientos agudos y posee un efecto terapéutico (sonotrombólisis). Por todo ello, la neurosonología ocupa un papel fundamental en el diagnóstico del estado vascular y en la toma de decisiones terapéuticas en el paciente con ictus isquémico agudo (AU)

In the last years there is an increasing interest in the knowledge of vascular status in patients with acute stroke. Detection and localization of an artery occlusion is of great interest for an accurate prognosis and the selection of the most appropriate recanalizing therapy. Neurosonology is a useful diagnostic tool for vascular status study in patients with acute stroke. Different situations where ultrasounds offer a valuable diagnostic information are reviewed, such as middle cerebral artery (MCA) occlusion, ‘T’ internal carotid artery (ICA) occlusion, ‘tandem’ ICA-MCA occlusion, monitoring of intracranial artery occlusions, acute occlusion of extracranial ICA, and free-floating thrombus in the ICA. Neurosonology offers evident advantages compared with other diagnostic techniques: it is faster, dynamic, cheaper, harmless, and accessible, allows real-time monitoring of patients vascular status, avoids delays in acute treatments and has a therapeutic effect (sonothrombolysis). Neurosonology has an essential role in the diagnosis of vascular status and in therapeutic decisionmaking of acute ischemic stroke patients (AU)

Towards a hemodynamic BCI using transcranial Doppler without user-specific training data.

UNLABELLED: Transcranial Doppler (TCD) was recently introduced as a new brain-computer interface (BCI) modality for detecting task-induced hemispheric lateralization. To date, single-trial discrimination between a lateralized mental activity and a rest state has been demonstrated with long (45 s) activation time periods. However, the possibility of detecting successive activations in a user-independent framework (i.e. without training data from the user) remains an open question. OBJECTIVE: The objective of this research was to assess TCD-based detection of lateralized mental activity with a user-independent classifier. In so doing, we also investigated the accuracy of detecting successive lateralizations. Approach. TCD data from 18 participants were collected during verbal fluency, mental rotation tasks and baseline counting tasks. Linear discriminant analysis and a set of four time-domain features were used to classify successive left and right brain activations. MAIN RESULTS: In a user-independent framework, accuracies up to 74.6 ± 12.6% were achieved using training data from a single participant, and lateralization task durations of 18 s. SIGNIFICANCE: Subject-independent, algorithmic classification of TCD signals corresponding to successive brain lateralization may be a feasible paradigm for TCD-BCI design.