The reproducibility of transcranial Doppler middle cerebral artery velocity measurements: Implications for clinical practice

Myths and methodologies: Assessment of dynamic cerebral autoregulation by the mean flow index

The mean flow index-usually referred to as Mx-has been used for assessing dynamic cerebral autoregulation (dCA) for almost 30 years. However, concerns have arisen regarding methodological consistency, construct and criterion validity, and test-retest reliability. Methodological nuances, such as choice of input (cerebral perfusion pressure, invasive or non-invasive arterial pressure), pre-processing approach and artefact handling, significantly influence mean flow index values, and previous studies correlating mean flow index with other established dCA metrics are confounded by inherent methodological flaws like heteroscedasticity, while the mean flow index also fails to discriminate individuals with presumed intact versus impaired dCA (discriminatory validity), and its prognostic performance (predictive validity) across various conditions remains inconsistent. The test-retest reliability, both within and between days, is generally poor. At present, no single approach for data collection or pre-processing has proven superior for obtaining the mean flow index, and caution is advised in the further use of mean flow index-based measures for assessing dCA, as current evidence does not support their clinical application.

Evaluation of transcranial Doppler use in patients with acute liver failure listed for emergency liver transplantation

PURPOSE

Acute liver failure (ALF) is characterized by hepatic encephalopathy (HE) often due to intracranial hypertension (ICH). The risk/benefit-balance of intraparenchymal pressure catheter monitoring is controversial during ALF.

AIMS

Perform an evaluation of transcranial Doppler (TCD) use in patients with ALF listed for emergency liver transplantation.

MATERIAL AND METHODS

Single center retrospective cohort study including all patients registered on high emergency LT list between 2012 and 2018. All TCD measurements performed during ICU stay after listing and after LT (when performed) were recorded. TCD was considered abnormal when pulsatility index (PI) was >1.2.

RESULTS

Among 106 patients with ALF, forty-seven (44%) had a TCD while on list. They had more severe liver and extrahepatic organ failure. When performed, TCD was abnormal in 51% of patients. These patients more frequently developed ICH events (45% vs. 13%, p = .02) and more frequently required increase in sedative drugs and vasopressors. While 22% of patients with normal TCD spontaneously survived, all of those with abnormal TCD died or were transplanted (p = .02). All transplanted patients who had abnormal exams normalized their TCD within 2 (1-2) days after LT.

CONCLUSION

TCD may be a useful non-invasive tool for ICH detection and management, then guide sedation withdrawal.

Generalized models for quantifying laterality using functional transcranial Doppler ultrasound

We consider how analysis of brain lateralization using functional transcranial Doppler ultrasound (fTCD) data can be brought in line with modern statistical methods typically used in functional magnetic resonance imaging (fMRI). Conventionally, a laterality index is computed in fTCD from the difference between the averages of each hemisphere's signal within a period of interest (POI) over a series of trials. We demonstrate use of generalized linear models (GLMs) and generalized additive models (GAM) to analyze data from individual participants in three published studies (N = 154, 73 and 31), and compare this with results from the conventional POI averaging approach, and with laterality assessed using fMRI (N = 31). The GLM approach was based on classic fMRI analysis that includes a hemodynamic response function as a predictor; the GAM approach estimated the response function from the data, including a term for time relative to epoch start (simple GAM), plus a categorical index corresponding to individual epochs (complex GAM). Individual estimates of the fTCD laterality index are similar across all methods, but error of measurement is lowest using complex GAM. Reliable identification of cases of bilateral language appears to be more accurate with complex GAM. We also show that the GAM-based approach can be used to efficiently analyze more complex designs that incorporate interactions between tasks.

Safety and efficacy of a novel robotic transcranial doppler system in subarachnoid hemorrhage

Delayed cerebral ischemia (DCI) secondary to vasospasm is a determinate of outcomes following non-traumatic subarachnoid hemorrhage (SAH). SAH patients are monitored using transcranial doppler (TCD) to measure cerebral blood flow velocities (CBFv). However, the accuracy and precision of manually acquired TCD can be operator dependent. The NovaGuide robotic TCD system attempts to standardize acquisition. This investigation evaluated the safety and efficacy of the NovaGuide system in SAH patients in a Neuro ICU. We retrospectively identified 48 NovaGuide scans conducted on SAH patients. Mean and maximum middle cerebral artery (MCA) CBFv were obtained from the NovaGuide and the level of agreement between CBFv and computed tomography angiography (CTA) for vasospasm was determined. Safety of NovaGuide acquisition of CBFv was evaluated based on number of complications with central venous lines (CVL) and external ventricular drains (EVD). There was significant agreement between the NovaGuide and CTA (Cohen’s Kappa = 0.74) when maximum MCA CBFv ≥ 120 cm/s was the threshold for vasospasm. 27/48 scans were carried out with CVLs and EVDs present without negative outcomes. The lack of adverse events associated with EVDs/CVLs and the strong congruence between maximal MCA CBFv and CTA illustrates the diagnostic utility of the NovaGuide.

The effect of mandala colouring on anxiety in hospitalized COVID-19 patients: A randomized controlled clinical trial

COVID-19 significantly affects patients' mental health, triggering a wide range of psychological disorders, including anxiety. The aim of this study was to investigate the effect of mandala colouring on the anxiety of hospitalized COVID-19 patients. In this randomized controlled clinical trial, 70 hospitalized patients with COVID-19 were randomly divided between the intervention and control groups. Standard care was provided for both groups. The intervention group spent 30 min/day for six consecutive days performing mandala colouring. Patient anxiety was measured prior and subsequent to the intervention in both groups using the Spielberger State-Trait Anxiety Inventory. Data were analysed using SPSS software version 25. The mean anxiety score was not significantly different between the two groups before the intervention (P = 0.08). Subsequent to the intervention, the mean anxiety score in the intervention and control groups was 44.05 ± 4.67 and 67.85 ± 6.25, respectively, indicating a statistically significant (P = 0.0001) decrease in the anxiety measured among the intervention group as compared with that of the control group. The results of this study show that 30 min of mandala colouring daily is an effective strategy for reducing anxiety in hospitalized COVID-19 patients. Mandala colouring can complement routine treatment and provides a non-pharmaceutical option for decreasing patient anxiety.

Transcranial color-coded duplex sonography assessment of cerebrovascular reactivity to carbon dioxide: an interventional study

Background

The investigation of CO₂ reactivity (CO₂-CVR) is used in the setting of, e.g., traumatic brain injury (TBI). Transcranial color-coded duplex sonography (TCCD) is a promising bedside tool for monitoring cerebral hemodynamics. This study used TCCD to investigate CO₂-CVR in volunteers, in sedated and mechanically ventilated patients without TBI and in sedated and mechanically ventilated patients in the acute phase after TBI.

Methods

This interventional investigation was performed between March 2013 and February 2016 at the surgical ICU of the University Hospital of Zurich. Ten volunteers (group 1), ten sedated and mechanically ventilated patients (group 2), and ten patients in the acute phase (12–36 h) after severe TBI (group 3) were included. CO₂-CVR to moderate hyperventilation (∆ CO₂ -5.5 mmHg) was assessed by TCCD.

Results

CO₂-CVR was 2.14 (1.20–2.70) %/mmHg in group 1, 2.03 (0.15–3.98) %/mmHg in group 2, and 3.32 (1.18–4.48)%/mmHg in group 3, without significant differences among groups.

Conclusion

Our data did not yield evidence for altered CO₂-CVR in the early phase after TBI examined by TCCD.

Trial registration

Part of this trial was performed as preparation for the interventional trial in TBI patients (clinicaltrials.gov NCT03822026, 30.01.2019, retrospectively registered).

Cerebral Emboli Monitoring Using Transcranial Doppler Ultrasonography in Adults and Children: A Review of the Current Technology and Clinical Applications in the Perioperative and Intensive Care Setting

Transcranial Doppler (TCD) ultrasonography is the only noninvasive bedside technology for the detection and monitoring of cerebral embolism. TCD may identify patients at risk of acute and chronic neurologic injury from gaseous or solid emboli. Importantly, a window of opportunity for intervention-to eliminate the source of the emboli and thereby prevent subsequent development of a clinical or subclinical stroke-may be identified using TCD. In this review, we discuss the application of TCD sonography in the perioperative and intensive care setting in adults and children known to be at increased risk of cerebral embolism. The major challenge for evaluation of emboli, especially in children, is the need to establish the ground truth and define true emboli identified by TCD. This requires the development and validation of a predictive TCD emboli monitoring technique so that appropriately designed clinical studies intended to identify specific modifiable factors and develop potential strategies to reduce pathologic cerebral embolic burden can be performed.

Investigating the effects of handedness on the consistency of lateralization for speech production and semantic processing tasks using functional transcranial Doppler sonography

The left hemisphere is dominant for language in most people, but lateralization strength varies between different tasks and individuals. A large body of literature has shown that handedness is associated with lateralization: left handers have weaker language lateralization on average, and a greater incidence of atypical (right hemisphere) lateralization; but typically, these studies have relied on a single measure of language lateralization. Here we consider the relationships between lateralization for two different language tasks. We investigated the influence of handedness on lateralization using functional transcranial Doppler sonography (fTCD), using an existing dataset (N = 151 adults, 21 left handed). We compared a speech production task (word generation) and a semantic association task. We demonstrated stronger left-lateralization for word generation than semantic association; and a moderate correlation between laterality indices for the two tasks (r = 0.59). Laterality indices were stronger for right than left handers, and left handers were more likely than right handers to have atypical (right hemisphere) lateralization or inconsistent lateralization between the two tasks. These results add to our knowledge of individual differences in lateralization and support the view that language lateralization is multifactorial rather than unitary.

Transcranial Doppler-derived indices of cerebrovascular haemodynamics are independent of depth and angle of insonation

Continuous measurement of cerebral blood flow velocity (CBFV) of the middle cerebral artery (MCA) using transcranial Doppler (TCD) and arterial blood pressure (ABP) monitoring enables assessment of cerebrovascular haemodynamics. Further indices describing cerebrovascular function can be calculated from ABP and CBFV, such as the mean index (Mxa) of cerebrovascular autoregulation, the 'time constant of the cerebral arterial bed' (tau), the 'critical closing pressure' (CrCP) and a 'non-invasive estimator of ICP' (nICP). However, TCD is operator-dependent and changes in angle and depth of MCA insonation result in different readings of CBFV. The effect of differing CBFV readings on the calculated secondary indices remains unknown. The aim of this study was to investigate variation in angle and depth of MCA insonation on these secondary indices. In eight patients continuous ABP and ipsilateral CBFV monitoring was performed using two different TCD probes, resulting in four simultaneous CBFV readings at different angles and depths per patient. From all individual recordings, the K-means clustering algorithm was applied to the four simultaneous longitudinal measurements. The average ratios of the between-clusters, sum-of-squares and total sum-of-squares were significantly higher for CBFV than for the indices Mxa, tau and CrCP (p < 0.001, p = 0.007 and p = 0.016) but not for nICP (p = 0.175). The results indicate that Mxa, tau and CrCP seemed to be not affected by depth and angle of TCD insonation, whereas nICP was.

Image-Guided Transcranial Doppler Ultrasound for Monitoring Posthemorrhagic Vasospasms of Infratentorial Arteries: A Feasibility Study

BACKGROUND

A considerable number of patients with subarachnoid hemorrhage (SAH) develop vasospasms of the infratentorial arteries. Transcranial Doppler sonography (TCD) is used to screen for vasospasm. In this study, we used a technical modification that combines TCD with an image guidance device that the operator can use to navigate to the ultrasonic window and to predefined intracranial vascular targets. Our aim was to analyze the feasibility, spatial precision, and spatial reproducibility of serial image-guided TCD of infratentorial and-for comparison-supratentorial arteries in the clinical setting of monitoring for vasospasm after SAH.

METHODS

The study included 10 SAH patients, who each received 5 serial image-guided TCD examinations. Using computed tomography angiography data, trajectories to the infratentorial and supratentorial cerebral arteries were planned and loaded into an image guidance device tracking the Doppler probe. As a measure of spatial precision and spatial reproducibility, we analyzed the distances between the positions of preplanned vascular targets and optimal Doppler signals.

RESULTS

The mean distance between preplanned and optimal target points was 4.8 ± 2.1 mm (first exam), indicating high spatial precision. The spatial precision decreased with increasing depth of the vascular target. In all patients, image-guided TCD detected all predefined supratentorial and infratentorial vascular segments. There were no significant changes in spatial precision in serial exams, indicating high reproducibility.

CONCLUSIONS

Image-guided TCD is feasible for supratentorial and infratentorial arteries. It shows high spatial precision and reproducibility. This study provides a basis for future clinical studies on image-guided TCD for post-SAH vasospasm screening.

Reproducibility of Transcranial Doppler ultrasound in the middle cerebral artery

BACKGROUND

Transcranial Doppler ultrasound remains the only imaging modality that is capable of real-time measurements of blood flow velocity and microembolic signals in the cerebral circulation. We here assessed the repeatability and reproducibility of transcranial Doppler ultrasound in healthy volunteers and patients with symptomatic carotid artery stenosis.

METHODS

Between March and August 2017, we recruited 20 healthy volunteers and 20 patients with symptomatic carotid artery stenosis. In a quiet temperature-controlled room, two 1-h transcranial Doppler measurements of blood flow velocities and microembolic signals were performed sequentially on the same day (within-day repeatability) and a third 7-14 days later (between-day reproducibility). Levels of agreement were assessed by interclass correlation co-efficient.

RESULTS

In healthy volunteers (31±9 years, 11 male), within-day repeatability of Doppler measurements were 0.880 (95% CI 0.726-0.950) for peak velocity, 0.867 (95% CI 0.700-0.945) for mean velocity, and 0.887 (95% CI 0.741-0.953) for end-diastolic velocity. Between-day reproducibility was similar but lower: 0.777 (95% CI 0.526-0.905), 0.795 (95% CI 0.558-0.913), and 0.674 (95% CI 0.349-0.856) respectively. In patients (72±11 years, 11 male), within-day repeatability of Doppler measurements were higher: 0.926 (95% CI 0.826-0.970) for peak velocity, 0.922 (95% CI 0.817-0.968) for mean velocity, and 0.868 (95% CI 0.701-0.945) for end-diastolic velocity. Similarly, between-day reproducibility revealed lower values: 0.800 (95% CI 0.567-0.915), 0.786 (95% CI 0.542-0.909), and 0.778 (95% CI 0.527-0.905) respectively. In both cohorts, the intra-observer Bland Altman analysis demonstrated acceptable mean measurement differences and limits of agreement between series of middle cerebral artery velocity measurements with very few outliers. In patients, the carotid stenoses were 30-40% (n = 9), 40-50% (n = 6), 50-70% (n = 3) and > 70% (n = 2). No spontaneous embolisation was detected in either of the groups.

CONCLUSIONS

Transcranial Doppler generates reproducible data regarding the middle cerebral artery velocities. However, larger studies are needed to validate its clinical applicability.

TRIAL REGISTRATION

ClinicalTrial.gov (ID NCT 03050567), retrospectively registered on 15/05/2017.

Time Course of Cerebrovascular Reactivity in Patients Treated for Unruptured Intracranial Aneurysms: A One-Year Transcranial Doppler and Acetazolamide Follow-Up Study

Background

Cerebrovascular reactivity (CVR) is often impaired in the early phase after aneurysmal subarachnoid hemorrhage. There is, however, little knowledge about the time course of CVR in patients treated for unruptured intracranial aneurysms (UIA).

Methods

CVR, assessed by transcranial Doppler and acetazolamide test, was examined within the first postoperative week after treatment for UIA and reexamined one year later.

Results

Of 37 patients initially assessed, 34 were reexamined after one year. Bilaterally, baseline and acetazolamide-induced blood flow velocities were higher in the postoperative week compared with one year later (p < 0.001). CVR on the ipsilateral side of treatment was lower in the initial examination compared with follow-up (58.9% versus 66.1%, p = 0.04). There was no difference in CVR over time on the contralateral side (63.4% versus 65.0%, p = 0.65). When mean values of right and left sides were considered there was no difference in CVR between exams. Larger aneurysm size was associated with increased change in CVR (p = 0.04), and treatment with clipping was associated with 13.8%-point increased change in CVR compared with coiling (p = 0.03).

Conclusion

Patients with UIA may have a temporary reduction in CVR on the ipsilateral side after aneurysm treatment. The change in CVR appears more pronounced for larger-sized aneurysms and in patients treated with clipping. We recommend that ipsilateral and contralateral CVR should be assessed separately, as mean values can conceal side-differences.

Reliability of Hand-Held Transcranial Doppler with M-mode Ultrasound in Middle Cerebral Artery Measurement

Purpose

To determine the intra- and interrater agreement of mean flow velocity (MFV) and pulsatility index (PI) measurement in middle cerebral arteries, assessed by transcranial Doppler (TCD) with M-mode.

Methods

Masked experienced neurosonologists performed TCD with M-mode using handheld probe in healthy adult volunteers. The Bland–Altman method for concordance and intraclass correlation coefficient were used.

Results

Seventy-seven healthy volunteers and seven raters participated (3 on regular TCD shift and 4 off-shift). The intrarater absolute mean difference between measurements was 5.5 cm/s [95% confidence interval (CI), 4.7–6.3] for MVF and 0.073 (95% CI, 0.063–0.083) for PI. The difference between MFV measurements was significantly higher in off-shift raters (p = 0.015). The interrater absolute mean difference between measurements was 6.5 cm/s (95% CI, 5.5–7.5) for MVF and 0.065 (95% CI, 0.059–0.071) for PI. No influence was found for the middle cerebral artery side, volunteer’s sex, or age, and there was no significant difference between raters. The intraclass correlation coefficient was 82.2% (95% CI 77.8–85.6) and 72.9% (95% CI 67.4–77.6) for MFV and PI, respectively.

Conclusions

There exists good intra- and interrater agreement in MFV and PI measurements using M-mode TCD. These results support the use of this noninvasive tool and are important for clinical and investigational purposes.

A longitudinal study of cerebral blood flow under hypoxia at high altitude using 3D pseudo-continuous arterial spin labeling

Changes in cerebral blood flow (CBF) may occur with acute exposure to high altitude; however, the CBF of the brain parenchyma has not been studied to date. In this study, identical magnetic resonance scans using arterial spin labeling (ASL) were performed to study the haemodynamic changes at both sea level and high altitude. We found that with acute exposure to high altitude, the CBF in acute mountain sickness (AMS) subjects was higher (P < 0.05), while the CBF of non-AMS subjects was lower (P > 0.05) compared with those at sea level. Moreover, magnetic resonance angiography in both AMS and non-AMS subjects showed a significant increase in the cross-sectional areas of the internal carotid, basilar, and middle cerebral arteries on the first day at high altitude. These findings support that AMS may be related to increased CBF rather than vasodilation; these results contradict most previous studies that reported no relationship between CBF changes and the occurrence of AMS. This discrepancy may be attributed to the use of ASL for CBF measurement at both sea level and high altitude in this study, which has substantial advantages over transcranial Doppler for the assessment of CBF.

Transcranial Color Duplex Ultrasound: A Reliable Tool for Cerebral Hemodynamic Assessment in Brain Injuries

BACKGROUND

Transcranial color duplex ultrasound (TCCD) is becoming an important tool for cerebral monitoring of brain-injured patients. To date, TCCD reproducibility has been studied in healthy volunteers or patients with subarachnoid hemorrhage and its efficiency in many brain injuries has not been proved. Our aim was to evaluate TCCD interobserver agreement in different brain injuries.

PATIENTS AND METHODS

We performed a prospective monocentric trial conducted from January 2014 to September 2014 in intensive care unit (ICU) of Saint-Etienne university teaching hospital, France.Brain-damaged patients admitted in ICU were included, excluding those with decompressive craniectomy. Two randomized operators among the ICU medical staff consecutively performed measurements of cerebral blood flow velocities with TCCD.

RESULTS

One hundred measurements were obtained from 42 patients. Hemodynamic and end-tidal CO2 pressure were similar between both measurement set. The results obtained with the Bland-Altman method showed bias at 0.52 (95% confidence interval [CI], -4.19 to 3.16), 0.53 (95% CI, -1.86 to 2.92), and 0.002 (95% CI, -0.06 to 0.06) for mean velocity, diastolic velocity, and pulsatility index, respectively. The limits of agreement were (-32.4; 31.4), (-20.4; 21.4), (-0.5; 0.5) for mean velocity, diastolic velocity, and pulsatility index, respectively. The Passing and Bablok regression have shown a quasilinear relationship between measurements.

CONCLUSIONS

We reported the reliability of TCCD interobserver agreement in brain-damaged patients.

Image-guided transcranial Doppler sonography for monitoring of vasospasm after subarachnoid hemorrhage

OBJECTIVES

Transcranial Doppler ultrasound (TCD) is a standard method for bedside vasospasm monitoring after subarachnoid hemorrhage (SAH). Image guidance has previously been shown to reduce intra- and interobserver variability of this method. The aim of the present study was to compare image-guided and conventional TCD in vasospasm monitoring after SAH.

PATIENTS AND METHODS

418 TCD exams of 24 consecutive SAH patients registered in a database were evaluated. Of these, 130 image-guided exams were identified which had been performed on the same day as conventional Doppler exams. These matched pairs were taken for statistical analysis. Data were tested statistically using the sign test applied at patient level to aggregated data.

RESULTS

The rate of complete exams (both M1, A1, P1 segments) was significantly higher in image-guided exams (92% vs. 74%, p<0.001), and the superiority of image-guided exams was significantly related to smaller sizes of the temporal bone window. There were more exams with Doppler sonographic vasospasm (mean flow velocity>120cm/s) in image-guided exams (38% vs. 33%) which, however, did not reach statistical significance.

CONCLUSION

Image-guidance leads to a standardization of serial TCD exams, which resulted in significantly more complete exams, most prominent in patients with poor temporal bone windows, and a higher detection rate of Doppler sonographic vasospasms. Image-guided TCD therefore has the capability to improve bedside vasospasm monitoring after SAH.

Assessment of non-invasive ICP during CSF infusion test: an approach with transcranial Doppler

Background

This study aimed to compare four non-invasive intracranial pressure (nICP) methods in a prospective cohort of hydrocephalus patients whose cerebrospinal fluid dynamics was investigated using infusion tests involving controllable test-rise of ICP.

Method

Cerebral blood flow velocity (FV), ICP and non-invasive arterial blood pressure (ABP) were recorded in 53 patients diagnosed for hydrocephalus. Non-invasive ICP methods were based on: (1) interaction between FV and ABP using black-box model (nICP_BB); (2) diastolic FV (nICP_FVd); (3) critical closing pressure (nICP_CrCP); (4) transcranial Doppler-derived pulsatility index (nICP_PI). Correlation between rise in ICP (∆ICP) and ∆nICP and averaged correlations for changes in time between ICP and nICP during infusion test were investigated.

Results

From baseline to plateau, all nICP estimators increased significantly. Correlations between ∆ICP and ∆nICP were better represented by nICP_PI and nICP_BB: 0.45 and 0.30 (p < 0.05). nICP_FVd and nICP_CrCP presented non-significant correlations: −0.17 (p = 0.21), 0.21 (p = 0.13). For changes in ICP during individual infusion test nICP_PI, nICP_BB and nICP_FVd presented similar correlations with ICP: 0.39 ± 0.40, 0.39 ± 0.43 and 0.35 ± 0.41 respectively. However, nICP_CrCP presented a weaker correlation (R = 0.29 ± 0.24).

Conclusions

Out of the four methods, nICP_PI was the one with best performance for predicting changes in ∆ICP during infusion test, followed by nICP_BB. Unreliable correlations were shown by nICP_FVd and nICP_CrCP. Changes of ICP observed during the test were expressed by nICP values with only moderate correlations.

The diagnostic performance of ultrasonographic optic nerve sheath diameter and color Doppler indices of the ophthalmic arteries in detecting elevated intracranial pressure

OBJECTIVES

To assess the diagnostic accuracy of ultrasonographic optic nerve sheath diameter (ONSD) measurement and color Doppler indices of the ophthalmic arteries in detecting elevated intracranial pressure (ICP).

PATIENTS AND METHODS

A total 60 patients with (cases, n=30) and without (controls, n=30) acute clinical and computed tomographic findings of elevated ICP due to intracranial mass/hemorrhage were recruited from a teaching hospital. The mean binocular and maximum ultrasonographic ONSDs, as well as the mean binocular Doppler ultrasound waveform indices of the ophthalmic arteries including pulsatility index (PI), resistive index (RI), end-systolic velocity (ESV), peak systolic velocity (PSV) and end-diastolic velocity (EDV) were compared between the two groups.

RESULTS

Compared to controls, the case group had significantly higher mean binocular ONSD (5.48 ± 0.52 mm vs. 4.09 ± 0.22 mm, p<0.001), maximum ONSD (5.63 ± 0.55 mm vs. 4.16 ± 0.23 mm, p<0.001), mean PI (1.53 ± 0.16 vs. 1.45 ± 0.20, p=0.01), and mean RI (0.76 ± 0.07 vs. 0.73 ± 0.04, p=0.01). The mean EDV, in contrast, was significantly higher in controls (8.55 ± 3.09 m/s vs. 7.17 ± 2.61 m/s, p=0.01). The two groups were comparable for the mean PSV (30.73 ± 7.93 m/s in cases vs. 32.27 ± 10.39 m/s in controls, p=0.36). Among the mentioned variables, the mean binocular ONSD was the most accurate parameter in detecting elevated ICP (sensitivity and specificity of 100%, cut-off point=4.53 mm). The Doppler indices were only moderately accurate (sensitivity: 56.7-60%, specificity: 63.3-76.7%).

CONCLUSION

While the ultrasonographic mean binocular ONSD (>4.53 mm) was completely accurate in detecting elevated ICP, color Doppler indices of the ophthalmic arteries were of limited value.

Update in intracranial pressure evaluation methods and translaminar pressure gradient role in glaucoma

Glaucoma is one of the leading causes of blindness worldwide. Historically, it has been considered an ocular disease primary caused by pathological intraocular pressure (IOP). Recently, researchers have emphasized intracranial pressure (ICP), as translaminar counter pressure against IOP may play a role in glaucoma development and progression. It remains controversial what is the best way to measure ICP in glaucoma. Currently, the 'gold standard' for ICP measurement is invasive measurement of the pressure in the cerebrospinal fluid via lumbar puncture or via implantation of the pressure sensor into the brains ventricle. However, the direct measurements of ICP are not without risk due to its invasiveness and potential risk of intracranial haemorrhage and infection. Therefore, invasive ICP measurements are prohibitive due to safety needs, especially in glaucoma patients. Several approaches have been proposed to estimate ICP non-invasively, including transcranial Doppler ultrasonography, tympanic membrane displacement, ophthalmodynamometry, measurement of optic nerve sheath diameter and two-depth transcranial Doppler technology. Special emphasis is put on the two-depth transcranial Doppler technology, which uses an ophthalmic artery as a natural ICP sensor. It is the only method which accurately and precisely measures absolute ICP values and may provide valuable information in glaucoma.

Neurosonological Examination: A Non-Invasive Approach for the Detection of Cerebrovascular Impairment in AD

There has been a growing interest in vascular impairment associated with Alzheimer’s disease (AD). This interest was stimulated by the findings of higher incidence of vascular risk factors in AD. Signs of vascular impairment were investigated notably in the field of imaging methods. Our aim was to explore ultrasonographic studies of extra- and intracranial vessels in patients with AD and mild cognitive impairment (MCI) and define implications for diagnosis, treatment, and prevention of the disease. The most frequently studied parameters with extracranial ultrasound are intima-media thickness in common carotid artery, carotid atherosclerosis, and total cerebral blood flow. The transcranial ultrasound concentrates mostly on flow velocities, pulsatility indices, cerebrovascular reserve capacity, and cerebral microembolization. Studies suggest that there is morphological and functional impairment of cerebral circulation in AD compared to healthy subjects. Ultrasound as a non-invasive method could be potentially useful in identifying individuals in a higher risk of progression of cognitive decline.

Cerebral hemodynamic and ventilatory responses to hypoxia, hypercapnia, and hypocapnia during 5 days at 4,350 m

This study investigated the changes in cerebral near-infrared spectroscopy (NIRS) signals, cerebrovascular and ventilatory responses to hypoxia and CO2 during altitude exposure. At sea level (SL), after 24 hours and 5 days at 4,350 m, 11 healthy subjects were exposed to normoxia, isocapnic hypoxia, hypercapnia, and hypocapnia. The following parameters were measured: prefrontal tissue oxygenation index (TOI), oxy- (HbO2), deoxy- and total hemoglobin (HbTot) concentrations with NIRS, blood velocity in the middle cerebral artery (MCAv) with transcranial Doppler and ventilation. Smaller prefrontal deoxygenation and larger ΔHbTot in response to hypoxia were observed at altitude compared with SL (day 5: ΔHbO2-0.6±1.1 versus -1.8±1.3 μmol/cmper mm Hg and ΔHbTot 1.4±1.3 versus 0.7±1.1 μmol/cm per mm Hg). The hypoxic MCAv and ventilatory responses were enhanced at altitude. Prefrontal oxygenation increased less in response to hypercapnia at altitude compared with SL (day 5: ΔTOI 0.3±0.2 versus 0.5±0.3% mm Hg). The hypercapnic MCAv and ventilatory responses were decreased and increased, respectively, at altitude. Hemodynamic responses to hypocapnia did not change at altitude. Short-term altitude exposure improves cerebral oxygenation in response to hypoxia but decreases it during hypercapnia. Although these changes may be relevant for conditions such as exercise or sleep at altitude, they were not associated with symptoms of acute mountain sickness.

Transcranial Doppler velocimetry in aneurysmal subarachnoid haemorrhage: intra- and interobserver agreement and relation to angiographic vasospasm and mortality

BACKGROUND

Transcranial Doppler measurements of the middle cerebral artery flow velocity are widely used as an indicator of vasospasm after aneurysmal subarachnoid haemorrhage (SAH). We investigated inter- and intraoperator agreement in SAH patients and healthy volunteers using colour-coded transcranial Doppler (TCCD), with the secondary aim of describing prediction of angiographic vasospasm and mortality.

METHODS

Sixty patients and 70 healthy controls were each examined in duplicate by alternating operators. A total of 939 measurements divided on 201 examination sets were conducted by four observers. The Bland-Altman limits of agreement (LoA) were calculated using a variance components analysis. Angiography was performed on clinical indication and survival recorded at 30 days.

RESULTS

Differences between measurements increased with increasing average, and therefore, we analysed log-transformed values. Thus, LoA are given as ratios between measurements. There were no systematic intra- or interobserver differences (bias). The intraobserver LoA was 0.62-1.61 in patients and 0.67-1.50 in controls. However, they were 0.55-1.82 in patients with angiographic vasospasm, whereas in patients without, they were 0.66-1.52. The interobserver LoA was 0.55-1.81 in patients and 0.65-1.55 in controls, while in patients with and without angiographic vasospasm, they were 0.45-2.22 and 0.60-1.67, respectively. Flow velocity measurements day 6-10 were positively associated with 30 day mortality risk (P=0.02, logistic regression).

CONCLUSIONS

TCCD measurement variability is wider in patient measurements than in controls. This discrepancy can largely be explained by a higher degree of error in patients with angiographic vasospasm. Despite the considerable measurement variability in TCCD, values are predictive of outcome in SAH.

The effect of formal training on the clinical utility of transcranial Doppler ultrasound monitoring in patients with aneurysmal subarachnoid haemorrhage

We have previously shown that the clinical utility of transcranial Doppler (TCD) ultrasound monitoring for vasospasm in patients with aneurysmal subarachnoid haemorrhage, as performed by untrained operators in a busy neurosurgical unit, is questionable, despite the recommendations for its use in the literature. We determined if formal training improved the utility of TCD. Twelve untrained operators and one trained operator performed a total of 206 TCD examinations. There was poor agreement of results between trained and untrained operators. For the left middle cerebral artery (MCA), right MCA, left anterior cerebral artery (ACA) and right ACA, the blood flow velocities (BFV) recorded by the trained operator were greater than those recorded by the untrained operators by a mean (95% confidence interval) of 27.7 (25.0-30.4), 24.3 (21.4-27.1), 28.2 (25.6-30.9) and 28.1 (24.9-31.1) cm/s, respectively (p<0.001 for all vessels). Greater sensitivity was observed in TCD measurements from the trained operator (100%) compared to untrained operators (40%). To improve the utility of TCD, operators should be provided with training or a professional sonographer employed.

Intracranial Pressure Monitoring: Invasive versus Non-Invasive Methods-A Review

Monitoring of intracranial pressure (ICP) has been used for decades in the fields of neurosurgery and neurology. There are multiple techniques: invasive as well as noninvasive. This paper aims to provide an overview of the advantages and disadvantages of the most common and well-known methods as well as assess whether noninvasive techniques (transcranial Doppler, tympanic membrane displacement, optic nerve sheath diameter, CT scan/MRI and fundoscopy) can be used as reliable alternatives to the invasive techniques (ventriculostomy and microtransducers). Ventriculostomy is considered the gold standard in terms of accurate measurement of pressure, although microtransducers generally are just as accurate. Both invasive techniques are associated with a minor risk of complications such as hemorrhage and infection. Furthermore, zero drift is a problem with selected microtransducers. The non-invasive techniques are without the invasive methods' risk of complication, but fail to measure ICP accurately enough to be used as routine alternatives to invasive measurement. We conclude that invasive measurement is currently the only option for accurate measurement of ICP.

Prolonged transcranial Doppler monitoring after aneurysmal subarachnoid hemorrhage fails to adequately predict ischemic risk

BACKGROUND

Stroke is common after aneurysmal subarachnoid hemorrhage (aSAH). Transcranial Doppler ultrasound (TCD) monitoring is often employed to identify vasospasm and allow intervention to avoid infarction. The required duration of monitoring has not been established. We aim to determine if 10 days of TCD monitoring identifies all patients at risk for infarction.

METHODS

A 3 year retrospective analysis of aSAH patients admitted to a neurovascular center was undertaken. Eligible patients were aged 18-85 years, presenting within 2 days of hemorrhage who had underwent TCD monitoring through post bleed day 10. Patients were assessed to determine if vasospasm onset occurred after 10 days with resulting stroke. Assessment of variables potentially impacting vasospasm onset and infarction were completed.

RESULTS

107 patients met criteria with 51 (48%) demonstrating vasospasm and 31 (29%) developing stroke. Of those suffering stroke, 22 (71%) demonstrated vasospasm while 9 (22%) did not. Two (2%) patients developed vasospasm only after day 10, neither experiencing stroke. Time to vasospasm onset (5.5 ± 2.5 days) was not impacted by common radiologic or clinical scales. Glasgow Coma Scale (GCS), Hunt and Hess Score (H&H), WFNS, ventriculostomy placement, intubation, and intraventricular hemorrhage were associated with likelihood of stroke (P < 0.05). The negative predictive value of TCD for identifying stroke risk was 84% while the sensitivity was 71%.

CONCLUSIONS

TCD identification of vasospasm after day 10 is rare. Stroke is more likely to result from poor detection than from brevity of TCD monitoring. Improved or alternative monitoring is needed to effectively identify ischemia and prevent stroke.

The role of transcranial Doppler ultrasound monitoring in patients with aneurysmal subarachnoid haemorrhage

The effect of transcranial Doppler (TCD) ultrasound monitoring of vasospasm on patient management following aneurysmal subarachnoid haemorrhage (aSAH) remains unclear. We reviewed our departmental use of TCD by retrospectively analysing 152 medical records. Results of investigations and management changes, including frequency of neurological monitoring and changes in triple H therapy, were examined. TCD monitoring occurred in 87 patients (57%) by untrained neurosurgical registrars. There was high variability in the number of operators for each patient (over 50% of patients had more than two different operators), insonation protocol and monitoring duration (at least 50% of patients were monitored for fewer than seven days). TCD results influenced management in only 18 (12%) patients, while clinical deterioration or improvement dictated more than 80% of changes in triple H therapy and neurological monitoring. Prospective validation in similar neurosurgical settings is needed to justify continued usage of TCD monitoring. Formal training for operators and a standard monitoring protocol should also be considered to increase TCD utility. Prospective evaluation of TCD at our centre has recently been completed.

Distribution of delayed ischemic neurological deficits after aneurysmal subarachnoid hemorrhage and implications for regional neuromonitoring

OBJECTIVES

Many neuromonitoring devices provide data applicable to a limited region of the brain. Risk of DIND is common after aSAH and may occur near or remote from the ruptured aneurysm. The aim of this study is to determine the distribution of DIND after aneurysms rupture as it relates to the potential value of regional monitoring in detection of vasospasm.

PATIENTS AND METHODS

The study enrolled aSAH patients presenting to a tertiary referral center over a three year period who received treatment for an identified ruptured aneurysm and survived >10 days with subsequent DIND. Only those patients receiving routine neuroimaging were included. To account for the anticipated effect on infarct distribution, patients were divided into groups of midline and non-midline aneurysms and assessed for vasospasm and stroke with respect to vascular distribution. Comparisons of clinical characteristics were made to determine factors predisposing to remote infarction.

RESULTS

Twenty-nine patients met criteria with 15 patients harboring non-midline aneurysms. The rarity of isolated remote DIND prohibited adequate assessment of predictive clinical characteristics. For non-midline aneurysms, DIND occurred ipsilateral to the ruptured aneurysm in 93% and within the same vascular territory in 86% of patients. Midline anterior circulation aneurysms frequently resulted in ACA infarction. A neuromonitoring device with 100% sensitivity for ischemia placed in the MCA territory ipsilateral to a non-midline ruptured aneurysm would identify 71% of DIND.

CONCLUSION

Vasospasm related infarction occurs most commonly ipsilateral to or in the same distribution of the ruptured aneurysm. Less anatomical correlation is seen with midline aneurysms. Rupture of posterior circulation aneurysms infrequently results in supratentorial infarction. Decisions regarding placement of regional monitors for the purpose of vasospasm detection should consider this distribution of ischemic risk.

Admission risk factors for cerebral vasospasm in ruptured brain arteriovenous malformations: an observational study

Introduction

Cerebral vasospasm is a well-documented complication of aneurismal subarachnoid hemorrhage but has not been extensively studied in brain arteriovenous malformations (BAVMs). Here, our purpose was to identify risk factors for cerebral vasospasm after BAVM rupture in patients requiring intensive care unit (ICU) admission.

Methods

Patients admitted to our ICU from January 2003 to May 2010 for BAVM rupture were included in this observational study. Clinical, laboratory and radiological features from admission to ICU discharge were recorded. The primary endpoint was cerebral vasospasm by transcranial Doppler (TCD-VS) or cerebral infarction (CI) associated with vasospasm. Secondary endpoints included the Glasgow Outcome Scale (GOS) at ICU discharge.

Results

Of 2,734 patients admitted to our ICU during the study period, 72 (2.6%) with ruptured BAVM were included. TCD-VS occurred in 12 (17%) and CI in 6 (8%) patients. All patients with CI had a previous diagnosis of TCD-VS. A Glasgow Coma Scale score <8 was a risk factor for both TCD-VS (relative risk (RR), 4.7; 95% confidence interval (95% CI), 1.6 to 26) and CI (RR, 7.8; 95% CI, 0.1 to 63). Independent risk factors for TCD-VS by multivariate analysis were lower Glasgow Coma Scale score (odds ratio (OR) per unit decrease, 1.38; 95% CI, 1.13 to 1.80), female gender (OR, 4.86; 95% CI, 1.09 to 25.85), and younger age (OR per decade decrease, 1.39; 95% CI, 1.05 to 1.82). The risk of a poor outcome (GOS <4) at ICU discharge was non-significantly increased in the patients with TCD-VS (RR, 4.9; 95% CI, 0.7 to 35; P = 0.09). All six patients with CI had poor outcomes.

Conclusions

This is the first cohort study describing the incidence and risk factors for cerebral vasospasm after BAVM rupture. Larger studies are needed to investigate the significance of TCD-vasospasm and CI in these patients.

Clinical utility of quantitative magnetic resonance angiography in the assessment of the underlying pathophysiology in a variety of cerebrovascular disorders

BACKGROUND

Quantitative MRA (qMRA) is a relatively new technique that uses traditional time-of-flight and phase-contrast MRI to visualize extracranial and intracranial vascular anatomy and measure volumetric blood flow. We aimed to assess the clinical utility of qMRA in assessing the hypothesized pathophysiology (HP) in a range of cerebrovascular diseases. Moreover, we postulated that evaluation of the arterial waveforms, can improve the evaluation of the hypothesized pathophysiology by qMRA.

METHODS

We reviewed studies from 10 patients who underwent qMRA examinations before and after their treatments. Two reviewers assessed the anatomy, volumetric flow rates and arterial waveforms for each vessel sampled and reached a consensus as to whether the above parameters supported the clinical diagnosis/hypothesized pathophysiology and the subsequent management.

FINDINGS

All 20 qMRA studies were technically adequate. qMRA supported the HP in all 10 patients as determined by abnormal volumetric flow values in the affected vessels before treatment and by the correction of these abnormal values in the patients whose treatment was successful. Each of our five patients with occlusive disease/vasoconstriction demonstrated evidence of dampening of the arterial waveforms distally to the narrowed artery (parvus-tardus phenomenon). The parvus-tardus effect disappeared after treatment.

CONCLUSION

qMRA is unique in combining time-of-flight MRA in a complementary manner with phase-contrast MRA to obtain volumetric flow values and potentially important physiologic information from arterial waveform analysis in patients with a range of cerebrovascular diseases during the course of a single MR examination.

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.