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Transcranial Doppler Sonography (transcranial + doppler_sonography)

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Medical Sciences	100%

Selected Abstracts

A Method for the Automated Assessment of Temporal Characteristics of Functional Hemispheric Lateralization by Transcranial Doppler Sonography

JOURNAL OF NEUROIMAGING, Issue 3 2004
M. Deppe
ABSTRACT Background and Purpose. Transcranial Doppler sonography (TCD) can guide and complement investigations based on functional magnetic resonance and positron emission tomography imaging by providing continuous information on cerebral perfusion changes correlated to cerebral activation. So far, however, the role of functional TCD has been limited by a lack of sensitivity.Methods. Here, the authors present an outline of a method that increases the potential of TCD to detect perfusion changes within a vascular territory. Sensitivity on the order of 1% can be achieved by transformation of Doppler envelope curves, which accounts for systemic quasi-periodic and irregular spontaneous blood flow modulations and artificial disturbances related to the recording. A statistical technique is introduced that allows the automatic detection of time periods of significant hemispheric lateralization in evoked flow studies. Furthermore, an index of laterality is defined quantifying the extent of hemispheric dominance during stimulus processing.Results and Discussion. The analysis technique described in this article has been successfully employed in recent examinations on vision, motor activation, language, language recovery, and other cognitive tasks. Conclusion. The novel functional TCD technique permits valid and reproducible assessments of the temporal characteristics of functional hemispheric lateralization. [source]

Novel parameter for the diagnosis of distal middle cerebral artery stenosis with transcranial Doppler sonography

JOURNAL OF CLINICAL ULTRASOUND, Issue 8 2010
Suk-Won Ahn MD
Abstract Purpose Transcranial Doppler sonography (TCD) is commonly used for the diagnosis of middle cerebral artery (MCA) stenosis. However, TCD indices to predict distal MCA (M2) stenosis have not yet been established. We compared TCD and magnetic resonance angiography (MRA) to validate a new index for the diagnosis of M2 stenosis. Methods Consecutive patients who underwent TCD and MRA were included. Based on MRA, M2 stenosis was defined as >50% narrowing beyond the bifurcation area. TCD index of the M2/M1 ratio was defined as the ratio between the mean flow velocity (MFV) obtained at a depth of 30,44 mm (M2) and a depth of 45,65 mm (M1). Sensitivity and specificity of the M2/M1 ratio were calculated from the receiver operating characteristic curve. The diagnostic yield of elevated MFV (>80 cm/s) and asymmetry index of >30% for M2 stenosis were also investigated. Results Among the consecutive patients, 105 with M2 stenosis were compared with 123 without MCA stenosis. The M2/M1 ratio was significantly higher in the M2 stenosis group (1.10 versus 0.86, p < 0.001). Sensitivity and specificity for M2 stenosis were most satisfying when the M2/M1 ratio of 0.97 was adopted as the cutoff value. Diagnostic yield of the M2/M1 ratio was better than MFV or asymmetry index. Conclusions The M2/M1 ratio may be a highly specific parameter for assessing M2 stenosis with TCD. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound 38:420,425, 2010 [source]

Changes in blood flow velocity in the middle and anterior cerebral arteries evoked by walking

JOURNAL OF CLINICAL ULTRASOUND, Issue 3 2002
Krassen Nedeltchev MD
Abstract Purpose Transcranial Doppler sonography (TCD) is an established method for assessing changes in blood flow velocity (BFV) coupled to brain activity. Our objective was to investigate whether walking induces measurable changes in BFV in healthy subjects. Methods Changes in BFV in both middle cerebral arteries (MCAs) of 40 healthy adult subjects during walking on a treadmill were measured using bilateral TCD. In 8 of the 40 subjects, 1 anterior cerebral artery (ACA) was monitored simultaneously with the contralateral MCA. The percentage increase in BFV (BFVI%) compared with the baseline velocity (V0), the percentage decrease in BFV (BFVD%) compared with the V0, and the normalized ACA-MCA ratio were analyzed. Results The overall mean (± standard deviation [SD]) V0 was 59.9 ± 11.6 cm/second in the left MCA and 60.1 ± 12.9 cm/second in the right MCA. Women had higher V0 values than men had. Walking evoked an initial mean overall BFVI% in both left (8.4 ± 5.1%) and right MCAs (9.1 ± 5.1%), followed by a decrease to below baseline values in 38 of 40 subjects. A statistically significant increase of the normalized ACA-MCA ratio was measured, indicating that changes in BFV in the ACA territory were coupled to brain activation during walking. Conclusions The use of functional TCD showed different changes in BFV in the ACAs and MCAs during walking. This method may be an interesting tool for monitoring progress in patients with motor deficits of the legs, such as paresis. © 2002 Wiley Periodicals, Inc. J Clin Ultrasound 30:132,138, 2002; DOI 10.1002/jcu.10047 [source]

A Method for the Automated Assessment of Temporal Characteristics of Functional Hemispheric Lateralization by Transcranial Doppler Sonography

Impairment of cerebral autoregulation in diabetic patients with cardiovascular autonomic neuropathy and orthostatic hypotension

DIABETIC MEDICINE, Issue 2 2003
B. N. Mankovsky
Abstract Aims Impaired cerebrovascular reactivity and autoregulation has been previously reported in patients with diabetes mellitus. However, the contribution of cardiovascular diabetic autonomic neuropathy and orthostatic hypotension to the pathogenesis of such disturbances is not known. The purpose of this study was to evaluate cerebral blood flow velocity in response to standing in patients with diabetes and cardiovascular autonomic neuropathy with or without orthostatic hypotension. Methods We studied 27 patients with diabetes,eight had cardiovascular autonomic neuropathy and orthostatic hypotension (age 46.4 ± 13.5 years, diabetes duration 25.0 ± 11.0 years), seven had autonomic neuropathy without hypotension (age 47.3 ± 12.7 years, diabetes duration 26.4 ± 12.1 years), and 12 had no evidence of autonomic neuropathy (age 44.1 ± 13.8 years, diabetes duration 17.1 ± 10.2 years),and 12 control subjects (age 42.6 ± 9.7 years). Flow velocity was recorded in the right middle cerebral artery using transcranial Doppler sonography in the supine position and after active standing. Results Cerebral flow velocity in the supine position was not different between the groups studied. Active standing resulted in a significant drop of mean and diastolic flow velocities in autonomic neuropathy patients with orthostatic hypotension, while there were no such changes in the other groups. The relative changes in mean flow velocity 1 min after standing up were ,22.7 ± 16.25% in patients with neuropathy and orthostatic hypotension, +0.02 ± 9.8% in those with neuropathy without hypotension, ,2.8 ± 14.05% in patients without neuropathy, and ,9.2 ± 15.1% in controls. Conclusions Patients with diabetes and cardiovascular autonomic neuropathy with orthostatic hypotension show instability in cerebral blood flow upon active standing, which suggests impaired cerebral autoregulation. [source]

Effects of physiological aging and cerebrovascular risk factors on the hemodynamic response to brain activation: a functional transcranial Doppler study

EUROPEAN JOURNAL OF NEUROLOGY, Issue 2 2007
K. Gröschel
The influence of the vascular system on the coupling of cerebral blood flow (CBF) to focal brain activation during aging is incompletely understood. Using functional transcranial Doppler sonography and a hypercapnic challenge as a marker of intact cerebral vasoreactivity, we determined CBF velocity (CBFV) changes in response to a language and arithmetic task in a group of 43 healthy young subjects (mean age 32 ± 8.6 years), 18 healthy old subjects (mean age 64 ± 9.8 years) and 29 old subjects with risk factors for an atherosclerosis (mean age 69 ± 8.4 years). Despite a similar performance during the cognitive tasks the CBFV changes were significantly lower in the group of old subjects with vascular risk factors compared with the healthy young and old subjects. Similarly, the CBFV changes during hypercapnia were significantly lower in the group of old subjects with vascular risk factors compared with the healthy young and old subjects. In contrast, both cognitive tasks and hypercapnia produced comparable CBFV changes in the group of healthy young and old subjects. These results suggest that the hemodynamic response to neuronal activation is unaffected by aging alone, whereas the presence of cardiovascular risk factors significantly diminishes the capability of cerebral vessels to react to vasodilating stimuli. [source]

Novel parameter for the diagnosis of distal middle cerebral artery stenosis with transcranial Doppler sonography

Accuracy of transcranial Doppler sonography for predicting cerebral infarction in aneurysmal subarachnoid hemorrhage

JOURNAL OF CLINICAL ULTRASOUND, Issue 8 2006
Ji-Yong Lee MD
Abstract Purpose. To evaluate the accuracy of transcranial Doppler (TCD) sonography using different criteria for predicting cerebral infarction due to symptomatic vasospasm. Methods. We retrospectively evaluated the clinical and radiologic data of consecutive patients admitted with acute aneurysmal subarachnoid hemorrhage (SAH) in the anterior cerebral circulation between January 2001 and June 2002. TCD sonographic examinations were performed on alternate days up to 20 days after admission. Cerebral infarction was defined on CT as a new hypodensity in the vascular distribution with corresponding clinical symptoms. Vasospasm was diagnosed as mild or severe when TCD sonography revealed a mean blood flow velocity (MBFV) greater than 120 and 180 cm/s in the middle or anterior cerebral artery and in the intracranial part of the internal carotid artery, respectively. Results. A total of 93 patients with aneurysmal SAH in the anterior cerebral circulation were included. Vasospasm was demonstrated by TCD sonography in 60 patients (64.5%) and was shown via multivariable logistic regression analysis to be predictive of cerebral infarction (OR 3.11, 95% CI 1.46,6.59), with an 82.6% and 69.6% sensitivity, a 41.4% and 77.1% specificity, a 31.7% and 50.0% positive predictive value, and an 87.9% and 88.5% negative predictive value when the MBFV was greater than 120 and 180 cm/s, respectively. Conclusions. Vasospasm on TCD was found to be predictive of symptomatic cerebral infarction on CT, but its positive predictive value remained low despite the adoption of restrictive TCD criteria for vasospasm. © 2006 Wiley Periodicals, Inc. J Clin Ultrasound 34:380,384, 2006 [source]

Ophthalmic Artery Flow Direction on Color Flow Duplex Imaging Is Highly Specific for Severe Carotid Stenosis

JOURNAL OF NEUROIMAGING, Issue 1 2002
Patrick S. Reynolds MD
Background/Purpose. Collateral flow patterns are important risk factors for brain ischemia in the presence of internal carotid artery (ICA) stenosis or occlusion. Ophthalmic artery (OA) flow reversal, routinely studied by transcranial Doppler sonography, is an important marker for high-grade ICA stenosis or occlusion. The authors sought to define the value of assessing OA flow direction with color flow duplex ultrasonography (CDUS) in the setting of significant ICA disease. Methods. Of all patients having routine carotid ultrasound in the neurosonology laboratory between July 1995 and November 2000, 152 had both carotid and orbital (OA flow direction by reduced power orbital CDUS) examinations as well as angiographic confirmation of stenosis to which North American Symptomatic Carotid Endarterectomy Trial criteria could be applied. Degree of angiographic stenosis in these 152 patients (304 arteries) was correlated with OA flow direction. Results. Of 304 arteries, 101 had greater than 80% stenosis by angiogram. In 56 of these 101 arteries with high-grade stenosis or occlusion, the ipsilateral OA was reversed; however, OA flow direction was never reversed ipsilateral to arteries with less than 80% stenosis (sensitivity 55%, specificity 100%, negative predictive value 82%, and positive predictive value 100% for OA flow reversal as a marker of high-grade carotid lesions). Discussion/Conclusions. OA flow direction is easily studied with CDUS. Reversed OA flow direction is highly specific (100%) for severe ipsilateral ICA stenosis or occlusion, with excellent positive predictive value, moderate negative predictive value, and limited sensitivity. OA flow reversal is not only quite specific for severe ICA disease, which may be helpful if the carotid CDUS is difficult or inadequate, but may also provide additional hemodynamic insights (ie, the inadequacy of other collateral channels such as the anterior communicating artery). OA evaluation can provide important hemodynamic information and should be included as part of carotid CDUS if there is any evidence of ICA stenosis or occlusion. [source]

Effects of remifentanil/propofol in comparison with isoflurane on dynamic cerebrovascular autoregulation in humans

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 8 2001
K. Engelhard
Background: This study investigates the effects of remifentanil and propofol in comparison to isoflurane on dynamic cerebrovascular autoregulation in humans. Methods: In 16 awake patients dynamic cerebrovascular autoregulation was measured using transcranial Doppler sonography (TCD). Thereafter patients were intubated, ventilated with O2/air (FiO2=0.33) and randomly assigned to one of the following anesthetic protocols: group 1 (n=8): 0.5 ,g · kg,1 · min,1 remifentanil combined with a propofol-target plasma concentration of 1.5 ,g · ml,1; group 2 (n=8): 1.8 % isoflurane (1.5 MAC). Following 20 min of equilibration the autoregulatory challenge was repeated. Arterial blood gases and body temperature were maintained constant over time. Statistics: Mann-Whitney U-test and Wilcoxon signed-rank test. Results: Dynamic autoregulation was intact in all patients prior to induction of anesthesia expressed by an autoregulatory index (ARI) of 5.4±1.21 (mean±SD, group 1) and 5.9±0.98 (mean±SD, group 2). With remifentanil/propofol anesthesia dynamic autoregulation was similar to the awake state (group 1: ARI=4.9±0.88). In contrast, autoregulatory response was delayed with 1.5 MAC isoflurane (group 2, ARI=2.1±0.92) (P<0.05). Conclusion: These data show that dynamic cerebrovascular autoregulation is maintained with remifentanil-based total intravenous anesthesia. This is consistent with the view that narcotics (and hypnotics) do not alter the physiologic cerebrovascular responses to changes in MAP. In contrast, 1.5 MAC isoflurane delays cerebrovascular autoregulation compared to the awake state. [source]