Longitudinal monitoring of intracranial arterial stenoses with transcranial Doppler ultrasonography

Intensive Lipid-Lowering Therapy Ameliorates Asymptomatic Intracranial Atherosclerosis

Statins have proven to exert protective effects in patients with symptomatic intracranial atherosclerotic stenosis (SICAS). It is unclear whether intensive lipid-lowering therapy (ILLT) can ameliorate atherosclerosis in asymptomatic ICAS (AICAS). A single-center, prospective cohort study was performed in 71 AICAS patients with lipid-lowering therapy. Vascular stenoses were evaluated with transcranial color-coded sonography (TCCS) before and after statin treatment. With target therapeutic level of low-density lipoprotein cholesterol (LDL-C) ≤ 1.8 mmol/L or ≥ 50% reduction from baseline after the two years of follow-up, patients were divided into intensive statin treatment (IST) group and standard statin treatment (SST) group. A total of 104 stenotic intracranial arteries were detected in 51 patients belonging to the IST group and 47 arteries in 20 patients of the SST group. In the first year, LDL-C levels were significantly decreased in the IST compared with SST groups (1.48 ± 0.26 vs. 2.20 ± 0.58, P=0.000). However, the ratio of regressed ICAS in IST was not significantly higher than that in SST (26.3% vs. 5.9%, P=0.052). Forty-nine branches in 25 patients of the IST group and 16 branches in 7 patients of the SST group were followed up for two years. The LDL-C level was decreased in the IST compared with SST groups (1.55 ± 0.29 vs. 2.36 ± 0.77, P=0.048). The ratio of regressed ICAS in the IST group was significantly higher than that in SST group (34.7% vs. 6.3%, P=0.017). We concluded that the degree of stenosis in AICAS can be ameliorated with intensive lipid-lowering therapy within two years; target LDL-C level can be reached by moderate-intensity statin treatment for Chinese AICAS patients.

Natural history of intracranial atherosclerotic disease

Intracranial atherosclerotic disease was very common among stroke patients of Asians, Blacks, and Hispanics ancestry. Furthermore, stroke patients with intracranial atherosclerosis (ICAS) have higher recurrence rate of cerebral ischemia and death than those without ICAS. However, the natural history of intracranial atherosclerotic disease is still in controversy. Most of the studies were retrospective and randomized controlled trial of drugs. This review summarized the prognosis of symptomatic and asymptomatic intracranial atherosclerotic disease in order to guide clinical decision-making and further clinical research.

Endovascular Advances for Intracranial Occlusive Disease

Stroke is the fourth leading cause of death in the United States. Intracranial atherosclerotic disease accounts for 8%-10% of ischemic stroke in the United States. So far, surgical bypass has not proved to be superior to medical therapy. As both medical and endovascular therapies for intracranial atherosclerosis evolve, so too do the guidelines for treatment. Initial reports on the results of stent placement for symptomatic high-grade intracranial atherosclerotic disease were encouraging; however, recent trials suggest that initial medical management may be preferable. Currently, intracranial angioplasty and stenting for symptomatic intracranial atherosclerosis is now more controversial. Further trials are necessary to help determine which patients are ideal for endovascular therapies.

Endovascular treatment of intracranial atherosclerotic disease

Stroke is the third leading cause of death in the United States. Intracranial atherosclerotic disease plays a role in cerebrovascular accidents, with well-characterized modifiable and nonmodifiable risk factors. Surgical bypass has so far not proved to be superior to medical therapy. Both medical and endovascular therapies for intracranial atherosclerosis have evolved since the initial off-label use of cardiac devices for its treatment. Initial reports on the results of stent placement for symptomatic high-grade intracranial atherosclerotic disease were initially encouraging. However, debate remains as to the optimal treatment of symptomatic intracranial atherosclerotic disease.

Image guidance for transcranial Doppler ultrasonography

BACKGROUND

Transcranial Doppler (TCD) ultrasonography is an important tool for noninvasive detection and monitoring of vasospasm and other pathological conditions of the intracranial vessels.

OBJECTIVE

To demonstrate that image-guided TCD allows rapid identification and blood-flow analysis of specific sections of the vascular anatomy and provides excellent orientation, also allowing diagnostic procedures on pathological vascular structures.

METHODS

Three patients who underwent computed tomographic angiography scanning for reasons not related to this study were examined by neuronavigated image-guided TCD. The Doppler probe was fitted with reflective markers and tracked by a commercially available Kolibri image guidance system.

RESULTS

Image-guided TCD allowed identification of all major intracranial vessels. Unilateral acquisition of reliable Doppler signals for the internal carotid artery, carotid T, middle cerebral artery, middle cerebral artery bifurcation, and anterior cerebral artery required 14 ± 6 minutes. Preregistration of these targets and detection by neuronavigation alone shortened examination times significantly to 8 ± 2 minutes. Registering the optimal examination trajectories on the neuronavigational device and applying navigational pilot software shortened times for repetitive examination further to 4 ± 1 minutes and ensured that the examination was done at the exact same spot under the same angle as in previous examinations.

CONCLUSION

Image guidance can be applied easily and efficiently to TCD. It provides anatomic orientation and may help to standardize investigation protocols, define pathological vascular territories for repeat investigations, and thus reduce interinvestigator variations. Image guidance may also extend the use of TCD to situations of a pathological or variant vascular anatomy.

Reevaluating the transcranial Doppler criteria for estimation of anterior circulation artery stenosis: transcranial Doppler sonography versus digital subtraction angiography

OBJECTIVES

The criteria for evaluating cerebral artery stenosis by transcranial Doppler sonography are inconsistent. We aimed to identify the accuracy of transcranial Doppler criteria compared with digital subtraction angiography for diagnosis of anterior circulation artery stenosis.

METHODS

A total of 170 patients who underwent transcranial Doppler sonography and digital subtraction angiography were recruited. The anterior circulation arteries were evaluated by transcranial Doppler sonography and digital subtraction angiography. We defined the best cutoff value for substantial anterior circulation artery stenosis by receiver operating characteristic curve analyses and calculated the sensitivity, specificity, and positive and negative predictive values.

RESULTS

An anterior circulation artery peak systolic velocity (PSV) of 120 cm/s had the largest area under the receiver operating characteristic curve compared with PSVs of 110, 130, and 140 cm/s and mean flow velocities of 60, 70, and 80 cm/s. The sensitivity, specificity, false-positive rate, false-negative rate, accuracy, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, and Youden index for transcranial Doppler sonography were 90.6%, 85.0%, 15.0%, 9.4%, 87.9%, 87.2%, 88.9%, 6.04, 0.11, and 0.756, respectively. The reliability index included the agreement rate and κ value, which were 87.9% and 0.757.

CONCLUSIONS

A PSV of 120 cm/s combined with additional parameters was an accurate criterion for diagnosing anterior circulation artery stenosis. Transcranial Doppler sonography could be considered a valuable method for screening diagnosis of cerebral artery stenosis.

Transcranial Doppler ultrasonography in intensive care

Transcranial Doppler is an innovative, flexible, accessible tool for the bedside monitoring of static and dynamic cerebral flow and treatment response. Introduced by Rune Aaslid in 1982, it has become indispensable in clinical practice. The main obstacle to ultrasound penetration of the skull is bone. Low frequencies, 1-2 MHz, reduce the attenuation of the ultrasound wave caused by bone. Transcranial Doppler also provides the advantage of acoustic windows representing specific points of the skull where the bone is thin enough to allow ultrasounds to penetrate. There are four acoustic windows: transtemporal, transorbital, suboccipital and retromandibular. The identification of each intracranial vessel is based on the following elements: (a) velocity and direction; (b) depth of signal capture; (c) possibility of following the vessel its whole length; (d) spatial relationship with other vessels; and (e) response to homolateral and contralateral carotid compression. The main fields of clinical application of transcranial Doppler are assessment of vasospasm, detection of stenosis of the intracranial arteries, evaluation of cerebrovascular autoregulation, non-invasive estimation of intracranial pressure, measure of effective downstream pressure and assessment of brain death. Mean flow velocity is directly proportional to flow and inversely proportional to the section of the vessel. Any circumstance that leads to a variation of one of these factors can thus affect mean velocity. The main pathological condition affecting flow velocity is the vasospasm. Vasospasm is a frequent complication of subarachnoid haemorrhage, it often remains clinically silent and the factors that make it symptomatic are largely unknown. Threshold velocities above which vasospasm comes into place are well defined as regards the median cerebral artery, while there is no consensus for the other vessels. Nevertheless, an increase in velocity alone is not sufficient to arrive at a diagnosis of vasospasm; a condition of hyperaemia also presents with an increase in flow velocity. The Lindegaard Index has therefore been introduced, which is defined by the ratio between the mean flow velocity in the median cerebral artery and the mean flow velocity in the internal carotid artery. Criteria for diagnosis of a stenosis >50% of an intracranial vessel with transcranial Doppler include: (a) segmentary acceleration of flow velocity; (b) drop in velocity below the stenotic segment; (c) asymmetry; and (d) circumscribed flow disturbances (turbulence and musical murmur). The transcranial Doppler enables us to assess both components of self-regulation. The static component is measured by observing changes in flow velocity caused by pharmacologically induced episodes of hypertension and hypotension. The dynamic component of autoregulation can be measured using a method devised by Aaslid known as the 'cuff test'. A very effective and safe device for measuring cerebral autoregulation is the transient hyperaemic response test. This test is based on the compensatory vasodilatation of the arterioles, which occurs after brief compression of the common carotid. Csonyka proposed the following formula based on clinical observation for the calculation of cerebral perfusion pressure: CPP = MAP x FVd/FVm + 14. Brain death is defined as the irreversible cessation of all functions of the whole brain. The clinical criteria are usually considered sufficient to establish a diagnosis of brain death; however, they might not be sufficient in patients who have been on sedatives or when there are ethical or legal controversies. Many authors have demonstrated the existence of a transcranial Doppler pattern, which is typical of brain death.

Noninvasive detection of diffuse intracranial disease

BACKGROUND AND PURPOSE

Intracranial arterial stenosis increases flow velocities on the upslope of the Spencer's curve of cerebral hemodynamics. However, the velocity can decrease with long and severely narrowed vessels. We assessed the frequency and accuracy for detection of focal and diffuse intracranial stenoses using novel diagnostic criteria that take into account increased resistance to flow with widespread lesions.

METHODS

We evaluated consecutive patients referred to a neurovascular ultrasound laboratory with symptoms of cerebral ischemia. Transcranial Doppler mean flow velocities were classified as normal (30 to 99 cm/s), high and low. Pulsatility index >or=1.2 was considered high. Focal intracranial disease was defined as >or=50% diameter reduction by the Warfarin Aspirin in Symptomatic Intracranial Disease criteria. Diffuse disease was defined as stenoses in multiple intracranial arteries, multiple segments of one artery, or a long (>1 cm) stenosis in one major artery on contrast angiography (CT angiography or digital subtraction angiography) as the gold standard.

RESULTS

One hundred fifty-three patients (96 men, 76% white, age 62+/-15 years) had previous strokes (n=135) or transient ischemic attack (n=18). Transcranial Doppler detection of focal and diffuse intracranial disease had sensitivity 79.4% (95% CI: 65.8% to 93%), specificity 92.4% (95% CI: 87.7% to 97.2%), positive predictive value 75.0% (95% CI: 60.9% to 89.2%), negative predictive value 94.0% (95% CI: 89.7% to 98.3%), and overall accuracy 89.5% (95% CI: 84.5% to 94.4%). After adjustment for stroke risk factors, transcranial Doppler findings of low mean flow velocities and high pulsatility index in a single vessel were independently associated with angiographically demonstrated diffuse single vessel intracranial disease, whereas low mean flow velocities/high pulsatility index in multiple vessels were related to multivessel intracranial disease (OR: 19.7, 95% CI: 4.8 to 81.2, P<0.001).

CONCLUSIONS

Diffuse intracranial disease may have a higher than expected frequency in a select stroke population and can be detected with noninvasive screening.

Analysis of incidence and risk factors for progression in patients with intracranial steno-occlusive lesions by serial magnetic resonance angiography

OBJECTIVES

Conventional angiography and transcranial Doppler ultrasonography have usually been used for serial observation of cerebral atherosclerotic diseases. This study used magnetic resonance (MR) angiography to monitor serial changes in steno-occlusive lesions of the major intracranial arteries to elucidate the incidence of progression and investigate the risk factors for progression.

PATIENTS AND METHODS

The 151 consecutive patients, 78 males and 73 females aged 42-92 years (mean 71.1+/-10.2 years), were followed up by serial MR angiography for 5-34 months (mean 14.4+/-5.78 months). Progression was defined as increased stenosis or occlusion, or new stenotic lesion. Age, sex, duration of MR angiography follow up, hypertension, diabetes mellitus, hyperlipidemia, hyperuricemia, current smoking, and atrial fibrillation were chosen as risk factors for multiple logistic analysis.

RESULTS

Twenty-three of the patients (15.2%) had progression, caused by total occlusion in 10, increased stenosis in 10, and new stenosis in 3, 15 patients had regression, and 113 patients had no change. Diabetes (odds ratio: 6.771, p value: 0.0004) and current smoking (odds ratio: 7.574, p value: 0.0019) were determined as significant risk factors for progression.

CONCLUSIONS

Patients with intracranial steno-occlusive lesion and either diabetes or smoking habit should be carefully followed up by serial MR angiography.

Use of stents to treat intracranial cerebrovascular disease

Intracranial atherosclerosis is a common cause of stroke. Although it has been recognized for decades, the lack of successful treatment strategies has limited clinical interest until recently. We review the natural history and pathophysiology of intracranial atherosclerosis. Vascular biomechanics are important to define differences between cerebral arteries and extracranial vessels and partly explain the technical challenges facing cerebral artery revascularization as compared with revascularization of coronary arteries. Pharmacological interventions to prevent stroke have had limited success, but technological developments offer improved methods for endovascular revascularization of symptomatic and asymptomatic cerebral artery stenosis. Identification of appropriate candidates for treatment also remains a challenge, and our knowledge about the natural history of the disease is limited. At this time, patients with significant intracranial stenosis should receive information on the benefits and risks of revascularization therapy. Determining which patients should undergo revascularization procedures will require carefully planned, randomized clinical trials.

The accuracy of transcranial Doppler in the diagnosis of middle cerebral artery stenosis

BACKGROUND AND PURPOSE

It was the aim of this study to systematically review available literature on the accuracy of transcranial Doppler (TCD) compared with angiography for the diagnosis of > or =50% middle cerebral artery stenosis in patients with transient ischemic attack or ischemic stroke.

METHODS

We performed a systematic review that included original articles published on TCD accuracy from 1982 until the end of December 2005 using angiography as the gold standard. The following measures of diagnostic accuracy were obtained from each primary study: sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Weighted mean averages were then calculated from individual results for different velocity cutoffs.

RESULTS

Six papers met our selection criteria. Using laboratory-specific variable mean flow velocity cutoffs, self-reported best accuracy results yield a mean weighted average sensitivity of 92%, specificity of 92%, PPV of 88% and NPV of 98% for 80 cm/s cutoff. For 100 cm/s cutoff, the sensitivities were 100%, specificity 97%, PPV 88% and NPV 100%.

CONCLUSIONS

Although limited to few reports, this analysis demonstrates fair TCD performance against angiography. Since increasing velocity cutoffs do not yield decreasing sensitivity and increasing specificity, further studies are required to determine optimal velocity values and possibly other criteria such as velocity ratios to develop a screening test with balanced performance parameters.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Intracranial Angioplasty and Stent Placement for Cerebral Atherosclerosis

Intracranial atherosclerotic stenoses have been estimated to account for 8%-10% of all ischemic strokes. A substantial number of patients fail the best medical treatment, which includes control of vascular risk factors and administration of antithrombotics (platelet-active drugs or warfarin), statins, and angiotensin-converting enzyme inhibitors. In these patients, angioplasty with stent placement is one reasonable treatment option for preventing massive ischemic stroke. Herein, we discuss basic pathophysiologic concepts and their effect on endovascular revascularization procedures.

Evolving atherosclerosis at carotid and intracranial arteries in Japanese patients with ischemic heart disease: a 5-year longitudinal study with MR angiography

Progression of atherosclerosis at extracranial carotid and intracranial arteries in patients with ischemic heart disease (IHD) is not well defined. We carried out a 5-year longitudinal study with magnetic resonance angiography (MRA) of patients with IHD to assess the incidence of progression of atherosclerosis at extracranial carotid and intracranial arteries and to determine predictors of the progression. We previously performed carotid and intracranial MRA on 67 patients who had received selective coronary angiography for the clinical diagnosis of IHD. Of these 67 subjects, 41 patients gave informed consent to undergo MRA reexaminations to evaluate changes of extra- and intracranial arteries over a 5-year period. The degree of stenosis was divided into five grades depending on the narrowness of the arteries, i.e. normal, mild, moderate, severe and occluded. The average of follow-up period with MRA examination was 58.8 months. The progression of atherosclerosis, as defined as an increase of one grade of the stenosis rating, including both the exacerbation of pre-existing stenosis and the appearance of new stenotic lesions, were found in five patients (12.2%) for the cervical carotid artery and in only one patient (2.4%) for the intracranial artery. A multiple logistic regression analysis revealed that baseline carotid artery stenosis (P = 0.008), age (P = 0.047), and coronary events during the follow-up period (P = 0.048) were significant and independent predictors of progression of carotid atherosclerosis. In conclusion, our findings suggest that follow-up evaluation of the carotid artery is indicated for patients with IHD in whom carotid artery stenosis was detected on an initial examination. Further study is needed with larger numbers of patients to confirm these findings.

Is Doppler ultrasound sufficient as the sole investigation before carotid endarterectomy?

BACKGROUND AND AIMS

Doppler ultrasound (DU) of the extracranial carotid arteries has been advocated as the sole imaging modality in carotid endarterectomy (CE) candidates. However this approach fails to identify patients with potentially significant intracranial disease, at high risk of stroke and death. Therefore, many stroke clinicians recommend angiography after screening DU. We aimed to identify the proportion of cases referred for CE in whom the identification of intracranial disease could have altered management.

METHODS

Two neuroradiologists, blinded to the clinical history, reviewed the films of 111 CE candidates, predominantly of Caucasian background, who had undergone carotid angiography after screening DU. Intracranial stenoses >50% luminal diameter, incidental aneurysms and non-atherosclerotic lesions were documented. Demographic and epidemiological data were collected.

RESULTS

Of the 111 patients, 87 had >50% extracranial stenoses although two thirds were asymptomatic. Intracranial stenotic lesions were recorded in 29% of patients. Over half of these were tandem lesions, distal to an extracranial stenosis. Aneurysms were found in 4.5% of patients.

CONCLUSIONS

DU alone would have failed to detect significant intracranial disease in nearly a third of cases. These patients are at high risk of stroke. The identification of this group allows more aggressive stroke prevention therapy.

Progression of middle cerebral artery occlusive disease and its relationship with further vascular events after stroke

BACKGROUND

Serial changes of flow velocities of transcranial Doppler ultrasound (TCD) in symptomatic middle cerebral artery (MCA) occlusive disease may be related to the occurrence of further vascular events, but prospective data are lacking.

METHODS

We conducted a prospective study on patients with cerebral ischemia who were hospitalized with symptomatic MCA stenosis or occlusion. We repeated TCD examinations 6 months after the initial examinations and recorded any stroke or coronary events during this period. The changes of MCA flow velocities were categorized as normalized artery, stable artery, and progressed artery, which were determined according to the changes of MCA velocities at 6 months.

RESULTS

We studied 143 consecutive patients who had relevant MCA occlusive diseases (107 with stenosis and 36 with occlusion). At 6 months, the velocities in the MCA returned to normal in 42 patients (29%), they were stable in 80 patients (62%), and they progressed in 13 patients (9%). The number of clinical events varied significantly among the 3 groups: there were 2 patients (4.8%) with clinical events in the normal group, 11 patients (12.5%) with clinical events in the stable group, and 5 patients (38.5%) with clinical events in the progressed group (P=0.004). The 18 recurrent events included 10 recurrent strokes, 5 transient ischemic attacks, and 3 acute coronary syndromes.

CONCLUSIONS

Progression of MCA occlusive diseases is associated with an increased risk of vascular events. Further studies are required to establish the value of serial TCD examinations in predicting future clinical events.

Comparison of transcranial color-coded sonography and magnetic resonance angiography in acute ischemic stroke

BACKGROUND AND PURPOSE

This study was designed to assess the accuracy of transcranial color-coded sonography (TCCS) as compared to magnetic resonance angiography (MRA) for detecting intracranial arterial stenosis in patients with acute cerebral ischemia.

METHODS

The authors prospectively identified 120 consecutive patients admitted with acute ischemic stroke and performed both TCCS and MRA with a mean interval of 1 day. TCCS data (sampling depth, peak systolic and end diastolic angle-corrected velocity, mean angle-corrected velocity, and pulsatility index) for middle cerebral arteries (MCAs) were compared to MRA data and classified into 4 grades: normal (grade 1): normal caliber and signal; mild stenosis (grade 2): irregular lumen with reduced signal; severe stenosis (grade 3): absent signal in the stenotic segment (flow gap) and reconstituted distal signal; and possible occlusion (grade 4): absent signal. The cutoffs were chosen to maximize diagnostic accuracy.

RESULTS

Interobserver agreement for MRA grading resulted in a weighted-kappa value of 0.776. The rate of poor temporal window was 37% (89/240). Doppler signals were obtained in 135 vessels, and the angle-corrected velocities (peak systolic, end diastolic, mean) were significantly different (P = .001, P = .006, and P < .001) among the MRA grades: grade 1 (100, 47, 68 cm/s), grade 2 (171, 72, 110 cm/s), grade 3 (226, 79, 134 cm/s), grade 4 (61, 26, 39 cm/s). Additionally, an angle-corrected MCA peak systolic velocity > or = 120 cm/s correlates with intracranial stenosis on MRA (grade 2 or worse) with high specificity (90.5%; 95% confidence interval = 78.5%-96.8%) and positive predictive value (93.9%) but relatively low sensitivity (66.7%; 95% confidence interval = 61.2%-69.5%) and negative predictive value (55.1%).

CONCLUSION

Elevated MCA velocities on TCCS correlate with intracranial stenosis detected on MRA. An angle-corrected peak systolic velocity > or = 120 cm/s is highly specific for detecting intracranial stenosis as defined by significant MRA abnormality.

Detection of stenoses in the anterior circulation using frequency-based transcranial color-coded sonography

Atherosclerotic stenoses of the intracranial vessels are less frequent than those of the extracranial vessels, but they are associated with a considerable annual stroke rate. The aim of the present study was to investigate the usefulness of frequency-based transcranial color-coded sonography (TCCS), transcranial Doppler sonography (TCD) and digital subtraction angiography (DSA) in patients with middle cerebral artery (MCA) and intracranial internal carotid artery (ICA) stenosis. Forty patients presenting with 48 intracranial stenoses of the anterior circulation were involved in the study. The stenoses were detected in the neurovascular laboratory during routine TCD examinations. All patients underwent an additional frequency-based TCCS examination. Both the axial and coronal planes were obtained to allow the exact localization of MCA stenosis and differentiation from intracranial ICA stenosis. Angle-corrected flow velocity measurements were performed if straight vessel compartments were 20 mm or more in length. A total of 18 stenoses (44%) were investigated additionally with DSA. According to the investigation with TCD, 20 (42%) stenoses were low-grade, 12 (25%) were moderate, and the remaining 16 (33%) were severe. Angle-corrected flow velocity measurements obtained with the integrated pulse-wave Doppler device of the TCCS machine were highly correlated (0.912, p < 0.001) with those obtained with TCD. TCCS achieved a reliable differentiation of MCA main stem stenosis vs. intracranial ICA stenosis in 7 patients and vs. MCA branch stenosis in 4 patients, but TCD failed in these two subgroups. The agreement between DSA and TCCS to evaluate semiquantitatively 18 intracranial stenoses resulted in a weighted-kappa value of 0.764. The major clinically relevant advantages of TCCS over TCD in MCA stenosis are its ability to differentiate MCA trunk stenosis from terminal ICA or MCA branch stenosis reliably and to perform angle-corrected flow velocity measurements.

Transcranial Doppler ultrasonography: year 2000 update

In this update, the main clinical applications of transcranial Doppler ultrasonography are reassessed. A specific format for technology assessment, personal experience, and an extensive review of the literature form the basis of the evaluation. The document is approved by the American Society of Neuroimaging and the Neurosonology Research Group of the World Federation of Neurology.

Natural history of stenosis from intracranial atherosclerosis by serial angiography

BACKGROUND AND PURPOSE

Knowledge of the natural history of stenoses due to intracranial atherosclerosis may be useful for evaluating possible treatments such as angioplasty.

METHODS

We retrospectively reviewed records over a 7-year period to identify patients with intracranial atherosclerotic stenoses and serial angiograms. Quantitative measurements of stenoses were made in a blinded manner, and clinical outcomes were reviewed.

RESULTS

We identified 21 patients with 45 intracranial stenoses who underwent repeat angiography at an average interval of 26.7 months. The average stenosis for all intracranial lesions was 43.9% initially and 51.8% on follow-up (P=.032). The average stenosis in the intracranial internal carotid artery (ICA) was stable (51.2% versus 52.6%). The average stenosis in the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) progressed from 32.4% to 49.7% (P=.037). Based on a minimum 10% change, 20% of intracranial ICA lesions progressed compared with 61% of ACA, MCA, and PCA lesions. Regression occurred in 14% of the intracranial ICA group and 28% of the ACA-MCA-PCA group. Cerebrovascular events were infrequent during this period, with 4 transient ischemic attacks and 1 intracerebral hemorrhage.

CONCLUSIONS

Intracranial atherosclerotic stenoses are dynamic lesions demonstrating both progression and regression.