Suboccipital Window Research Articles

Simultaneous monitoring of the middle cerebral and basilar arteries to detect right-to-left shunts using transcranial Doppler by agitated saline administration

Transcranial Doppler (TCD) is an easy, non-invasive, and real-time monitoring device for detecting right-to-left shunts (RLS). Nonetheless, it has limited benefits in patients with poor temporal windows. Therefore, we aimed to investigate whether the basilar artery (BA) window was as effective as the middle cerebral artery (MCA) in detecting RLS during TCD monitoring. Overall, we enrolled 344 patients with stroke, transient ischemic attack, headache, or dizziness. MCA and BA were monitored using a modified headset. To investigate the feasibility of the suboccipital window in detecting RLS, we instituted an evaluation tool with three tiers to evaluate microembolic signals (MESs) during TCD monitoring. Tier 1: TCD monitoring of the MCA (bilaterally) in the resting state, tier 2: TCD monitoring of the MCA (bilaterally) while performing the Valsalva maneuver, and tier 3: TCD monitoring of the index MCA and BA while performing the Valsalva maneuver. In tiers 2 and 3, a high agreement rate of 0.808 and 0.809 (p < 0.001), respectively, on the weighted kappa index, and a high intra-class correlation coefficient of 0.982 and 0.986 (p < 0.001), respectively, were observed on detecting MESs. Our data suggests that the BA window is as effective as the MCA window for detecting RLS on TCD.

Effects of acupuncture at GB20 on CO2 reactivity in the basilar and middle cerebral arteries during hypocapnia in healthy participants.

The acupoint GB20 is known to affect vertebrobasilar blood flow regulation. However, no previous study has used transcranial Doppler imaging to examine whether acupuncture at GB20 has a selective effect on blood flow in various cerebral arteries, such as the basilar artery (BA) and the middle cerebral arteries (MCAs). Therefore, this study sought to determine the specific effects of GB20 acupuncture on cerebral blood flow (CBF). Blood flow velocity and CO(2) reactivity were measured by transcranial Doppler imaging with a 2-MHz pulsed Doppler probe observed through both temporal windows for the MCAs and through the suboccipital window for the BA before and after GB20 acupuncture treatment in 15 healthy young male volunteers. The changes in hyperventilation-induced CO(2) reactivity and corrected blood flow velocities at 40 mmHg (CV40) were assessed for the BA and both MCAs. Blood pressure and heart rate were measured before and after the acupuncture treatment. CO(2) reactivity in the BA increased significantly after GB20 acupuncture treatment compared with baseline (p=0.041). In contrast, CO(2) reactivity in both MCAs remained unchanged. The CV40 in the BA and the MCAs showed no change after the GB20 acupuncture treatment. The mean heart rate decreased significantly after the GB20 acupuncture, whereas the mean blood pressure showed no change. This study demonstrated that acupuncture treatment on GB20 increases CO(2) reactivity specifically in the BA, with no effect in the MCAs. These results clinically support the use of GB20 to treat disorders of posterior cerebral circulation and support the idea that particular acupoints affect specific brain regions and cerebral arteries.

Effects of medetomidine and medetomidine-butorphanol on transcranial color-coded duplex ultrasonography in healthy dogs

The study was designed to determine the effects of two protocols of sedation, medetomidine and medetomidine-butorphanol, on cerebral blood flow (CBF) by transcranial color-coded Duplex ultrasonography in healthy dogs. Transcranial Doppler ultrasonographic examination was performed in 20 dogs before and 20min after sedation with either medetomidine (group 1) or medetomidine-butorphanol (group 2). The left and right middle cerebral arteries (LMCA and RMCA) were evaluated using the temporal windows, and the basilar artery (BA) was studied through the suboccipital window. Peak systolic velocity (PSV), mean velocity (MV), end diastolic velocity (EDV), resistance index (RI), and pulsatility index (PI) were measured for each vessel. Blood pressure (BP) and heart rate (HR) were also recorded before and after sedation in both groups.Statistically significant differences were found for PSV, MV and EDV when RMCA and LMCA were interrogated before and after sedation. PSV, RI and PI were found to be statistically significantly different when the study was performed on the BA. These results should be taken in account when a transcranial Doppler is performed in dogs sedated with the mentioned protocols and it might suggest some degree of neuroprotection.

Transcranial Doppler Ultrasonography in Sickle Cell Disease

Changes on Transcranial Doppler (TCD) ultrasonography have been proposed as significant predictors of cerebrovascular complications in sickle cell disease (SCD). However, consensus with regards to the TCD criteria to recognize abnormalities in cerebral vasculature is lacking. We studied the TCD characteristics of cerebral arteries among Omani patients with SCD and correlated them with cerebrovascular events. TCD was performed through the temporal and suboccipital windows using a 2 MHz probe (DWL). Thirty-three of 59 patients (56%) with SCD had neurological symptoms including stroke--12 (20%) and epilepsy--7. Fifteen patients (25%) had significant TCD abnormalities including: markedly increased velocities--11 (3 with stroke); turbulent flow--2; and reversal of flow--2. No patient had a time averaged maximum mean velocity of >200 cm/s in anterior circulation. On applying a modified definition of "abnormal TCD" to anterior and posterior circulation studies, increased TCD velocities in posterior circulation correlated with history of stroke (P < 0.05). TCD velocities in the 18 adult patients ( older than 15 y) were significantly lower than in children. Logistic regression analysis revealed abnormal TCD in the left posterior cerebral artery to be an independent predictor of stroke in this cohort (P = 0.035).

Evaluation of very early recanalization after tPA administration monitoring by transcranial color-coded sonography

Summary Background/aims Cerebrovascular ultrasonography was useful clinically for evaluating cerebral hemodynamics rapidly and in real-time for patients with acute ischemic stroke. We analyzed if the patients had early recanalization or not using transcranial color-coded sonography (TCCS) in order to evaluate the usefulness of real-time monitoring in systemic thrombolysis. Methods Subjects were patients who had acute ischemic stroke with intravenous tissue plasminogen activator (tPA) within 3 h from onset. We evaluated occlusion of intracranial arteries from transtemporal or suboccipital window by TC-CFI with Thrombolysis in Brain Ischemia (TIBI) flow-grading system and monitored residual flow in real-time every 15 min until 120 min after the t-PA bolus. Results We could monitor residual flow in 5 patients who had good echo windows (4 male, mean age; 60.8 ± 6.4 years). Two patients had proximal occlusion of the middle cerebral artery (MCA), one patient had distal occlusion of MCA, one patient had M2 occlusion and one patient had distal occlusion of unilateral vertebral artery. Four patients had early complete recanalization within 60 min after the t-PA bolus (two patients within 60 min and other two patients within 30 min), however, occlusion persisted during 120 min monitoring in one patient with proximal occlusion of MCA. NIH Stroke Scale of two patients with very early recanalization was 0 at the end of the treatment. There was no symptomatic and asymptomatic intracranial hemorrhage in 4 patients except for the patients without recanalization. Conclusions It is anticipated that real-time ultrasound monitoring is useful for evaluating a very early thrombolytic effect of tPA connected with early clinical recovery.

Microembolic Signals in Acute Posterior Circulation Cerebral Ischemia

The clinical significance of microembolic signals (MES) in the posterior circulation remains unclear. The aim of this study was to investigate the sources and consequences of MES in acute posterior circulation cerebral ischemia. We evaluated a total of 140 consecutive patients (93 males, mean age 62.9 years) who had acute posterior circulation cerebral ischemia. The MES monitoring was conducted at the basilar artery through the suboccipital window for a 30-minute period. MES were detected in 18 (12.9%) of the 140 patients. Clinical characteristics and laboratory data did not differ between the MES-positive and MES-negative groups. Intracranial vertebrobasilar artery (VBA) stenosis was independently associated with the presence of MES (odds ratio, 9.85; 95% confidence interval, 1.22-79.48; P=0.032), whereas the patients with vertebral artery stenosis that was limited to the extracranial portion did not show an association. Microembolic signals occurred significantly more frequently in patients with severe degree of VBA stenosis compared to those with nonsignificant stenosis (odds ratio, 9.88; 95% confidence interval, 1.23-79.07; P=0.031). In a subgroup analysis of the 79 patients who had lesions on diffusion-weighted images and relevant VBA stenosis, the MES-positive group showed more frequent embolic infarction (P=0.010) and multiple lesion patterns (P=0.007) than single perforating infarctions. In acute posterior circulation cerebral ischemia, intracranial and severe VBA stenosis is associated with MES and may be its root causes. The presence of MES in VBA stenosis suggests that multiple and embolic type infarctions are the mechanisms of stroke.

Abstract 2959: Diagnosis of Right-to-Left Shunt in Intracranial Vertebral Artery by Transcranial Color Flow Imaging

Objective: Right-to-Left shunt (RLS) detection by Transcranial Doppler is useful for diagnosis of paradoxical embolism. However, we sometimes could not monitor MCA due to insufficient temporal bone window, especially in old patients. Other insonation windows such as transorbital and suboccipital window (basilar artery) are using recently, whereas the ability to detect of intracranial arteries from these windows was not so high. We evaluated usefulness of RLS detection in intracranial vertebral artery (VA) from suboccipital approach that could be measured in almost patients. Methods: We evaluated RLS using transcranial color flow imaging (TC-CFI) in patients with ischemic stroke or transient ischemic attack who could be detected middle cerebral artery (MCA) from temporal bone window and intracranial VA from suboccipital window by TC-CFI. We monitored microembolic signal (MES) at ipsilateral MCA and VA (not hypoplastic side) for 90seconds after injection of 9ml saline agitated with 1ml of air in the right antecubital vein. The procedure was performed three times in each artery with and without Valsalva maneuver. The presence of MES was classified according to Spencer Logarithmic Scale (SLS) criteria. Results: Fifty two patients (46 male, mean age of 64.1±14.3) were included. Twelve patients were positive of MES (23.1%). VA comparison to MCA showed 10 true positive, 40 true negative, 0 false positive and 2 false negative cases (sensitivity 83.3%, specificity 100%, positive predictive value 100%, negative predictive value 95.2% and accuracy 96.2%). In 12 patients with MES, 22 of 36 examinations in MCA were positive of MES (SLS grade I was 20 examinations and grade II was 2 examinations), on the other hand, 20 of 36 examinations in VA were positive (SLS grade I was 20 examinations). The positive ratio of 36 examinations in 12 patients did not show significant difference statistically between MCA and VA. Conclusion: The evaluation of RLS in intracranial VA using TC-CFI from suboccipital window has equal diagnostic ability to MCA, and is useful for the patients with insufficient temporal bone window.

Abstract 2386: Microembolic Signals in Acute Posterior Circulation Cerebral Ischemia: Sources and Consequences

Background: The clinical significance of microembolic signals (MESs) in posterior circulation remains unclear. The aim of this study was to investigate the sources and consequences of MESs in acute posterior circulation cerebral ischemia. Methods: We evaluated a total of 140 consecutive patients (93 males, mean age 62.9 years) who had acute posterior circulation cerebral ischemia. The MES monitoring was conducted at the basilar artery through the suboccipital window during 30 minutes. Results: Microembolic signals were detected in 18 (12.9%) of the 140 patients. Clinical characteristics and laboratory data did not differ between the MES-positive and MES-negative groups. Intracranial vertebrobasilar artery (VBA) stenosis was independently associated with the presence of MES (OR: 9.37, 95% CI: 1.14-79.92, p =0.037), while the patients whose vertebral artery stenosis was limited at the extracranial portion did not show a significant difference. Microembolic signals occurred significantly more frequently in patients with a severe degree of VBA stenosis compared to those with non-significant stenosis (OR: 9.81, 95% CI: 1.21-79.87; p =0.033). In a subgroup analysis of the 79 patients who had lesions on diffusion-weighted images and relevant VBA stenosis, the MES-positive group showed more frequent embolic infarction (p=0.010) and multiple lesion patterns (p=0.007) than they did single perforating infarctions. Conclusions: In acute posterior circulation cerebral ischemia, intracranial and severe VBA stenosis is associated with MES and could be its root cause; the presence of MES in VBA stenosis may suggest multiple and embolic type infarctions as the stroke mechanism

Transcranial doppler ultrasonography in acute ischemic stroke predicts stroke subtype and clinical outcome: a study in Omani population

Transcranial Doppler ultrasonography (TCD) is being increasingly used for its ability to provide cerebral hemodynamic information in stroke. Few studies have explored its association with cerebral arteriographic changes and stroke subtype. This study explored the relation of TCD changes in acute stroke with stroke subtypes, MR cerebral arteriography and clinical outcome in Omani population. Adult patients presenting with acute ischemic stroke within 4days of stroke onset were subjected to TCD through the temporal and suboccipital windows using a 2MHz probe; flow velocities, pulsatility and direction of flow were recorded from arteries at the skull base. MR arteriographic (MRA) changes on corresponding arteries were graded on a scale of 1-4. ANOVA, student's t test and ROC analysis were used to evaluate TCD in relation to stroke type, outcome and stenosis on MRA. Of 60 patients recruited, 52 (M:F::36:16; mean age: 60+13years) had adequate bone window for TCD study. Large artery stroke occurred in 30 (58%) patients; lacunar stroke-11 (21%); cardioembolic and mixed groups 9 (17%), other specificed causes-2 (4%). 86.5% had evidence of intracranial disease. 10/52 patients (19%) died while 33 (63%) had good outcome (modified Rankin Score 0-3). Of the 186 arteries studied by the two methods, 52 had TCD evidence of stenosis while 42 were abnormal on MRA, giving a sensitivity of 60%, specificity: 81.25%; positive likelihood ratio: 3.18 and negative likelihood ratio: 0.5. 29/52 (56%) of patients had TCD changes in the arteries corresponding to stroke location. Abnormal TCD was associated with large artery strokes (p=0.007), poor outcome (p=0.038) and mortality (p=0.01). This study of TCD in acute stroke in Omani population demonstrates a relatively higher burden of intracranial arterial disease. TCD changes are associated with type of stroke and outcome in this population. TCD is a simple and fairly useful method of evaluation in patients with acute stroke. Adopting TCD in evaluation of stroke patients may provide useful information regarding the pathophysiology which could enhance patient management.

Effect of transient carotid artery compression during transcranial Doppler ultrasonography in dogs

Changes in blood flow in the arteries of the canine skull base following compression of the ipsilateral carotid artery were evaluated. Forty healthy conscious dogs were evaluated during examination in...

Novel Brain Model for Training of Deep Microvascular Anastomosis

Models of the brain and skull were developed using a selective laser sintering method for training in the procedures of deep microvascular anastomosis. Model A has an artificial skull with two craniotomies, providing fronto-temporal-subtemporal and suboccipital windows. The brain in Model A is soft and elastic, and consists of the brainstem and a hemispheric part with a detailed surface. Rehearsals or training for anastomosis to the insular part of the middle cerebral artery, superior cerebellar artery, posterior cerebral artery, and posterior inferior cerebellar artery can be performed through the craniotomies. Model B has an artificial skull with a bifrontal craniotomy and an artificial brain consisting of the bilateral frontal lobes with an interhemispheric fissure and corpus callosum. Rehearsals or training for anastomosis of the callosal segment of the anterior cerebral artery can be practiced through this craniotomy. These realistic models will help to develop skills for deep vascular anastomosis, which remains a challenging neurosurgical procedure, even for experienced neurosurgeons.

ASSESSING CIRCLE OF WILLIS BLOOD CIRCULATION IN DOGS WITH TRANSCRANIAL COLOR‐CODED DUPLEX SONOGRAPHY

Insonation of Circle of Willis by transcranial Doppler duplex color sonography is described in 30 healthy dogs with 15 weighing < 33 lb and 15 weighing >33 lb. Imaging was via a temporal window to explore the rostral, middle, and caudal cerebral arteries on both the left and right-hand sides; and through an suboccipital window to study the basilar artery. Normal mean values of the peak systolic velocity (PSV), end diastolic velocity, mean velocity, resistance index (RI), and pulsatility index (PI) were characterized and compared with those obtained in previous studies. There was significant differences in the PSV, RI, and PI in the rostral cerebral artery between dogs weighing < 33 vs. > 33 lb. Mean PSV was higher in weighing over 33 lb, whereas the mean resistive index and mean PI were lower in these dogs.

Real-Time 3-D Contrast-Enhanced Transcranial Ultrasound and Aberration Correction

Contrast-enhanced (CE) transcranial ultrasound (US) and reconstructed 3-D transcranial ultrasound have shown advantages over traditional methods in a variety of cerebrovascular diseases. We present the results from a novel ultrasound technique, namely real-time 3-D contrast-enhanced transcranial ultrasound. Using real-time 3-D (RT3D) ultrasound and microbubble contrast agent, we scanned 17 healthy volunteers via a single temporal window and nine via the suboccipital window and report our detection rates for the major cerebral vessels. In 71% of subjects, both of our observers identified the ipsilateral circle of Willis from the temporal window, and in 59% we imaged the entire circle of Willis. From the suboccipital window, both observers detected the entire vertebrobasilar circulation in 22% of subjects, and in 44%, the basilar artery. After performing phase aberration correction on one subject, we were able to increase the diagnostic value of the scan, detecting a vessel not present in the uncorrected scan. These preliminary results suggest that RT3D CE transcranial US and RT3D CE transcranial US with phase aberration correction have the potential to greatly impact the field of neurosonology. (E-mail: ni3@duke.edu)

Transcranial color Doppler flow imaging in detecting severe stenosis of the intracranial vertebral artery: a prospective study

Objective The aims of this prospective study were to investigate the manifestations of the hemodynamics and morphology of a normal intracranial vertebral artery (VA) and diffusely severe or localized critical vertebral artery stenosis (VAS) on transcranial color Doppler flow imaging (TCDFI) and to discuss the criteria of TCDFI in detecting severe VAS. Methods There were 30 patients suspected of having an intracranial VAS in a patient group and 30 healthy volunteers in a control group. All the patients underwent both TCDFI and digital subtraction angiography (DSA). The intracranial VA was imaged through the suboccipital window by TCDFI. The size and tortuousness of the vessels were observed. The hemodynamics of those vessels were measured by means of peak systolic velocity (PSV) and pulsatility index (PI). Results In the control group, the VA junction with basilar artery appeared as Y shaped and filled with well-distributed blue coded on color imaging, which showed flow below the baseline with fast early systolic acceleration, and normal PSV ranged from 0.42 to 0.80 m/s on pulse wave Doppler. In the patients with diffusely severe VAS (>70% lumen reduction, the length of plaque >1 cm or multiple plaques) or localized critical VAS (>90% lumen reduction) diagnosed by TCDFI and confirmed with DSA, a narrowed and tortuous VA was demonstrated with minimal flow on color Doppler imaging and decreased 50% of normal PSV and PSV <0.30 m/s accompanied by slow early systolic acceleration on Doppler spectrum. There was a significant difference ( P<.05 or P<.01) in the hemodynamic parameters (PSV and PI) between patients with severe VAS and healthy subjects. Conclusion TCDFI is a useful noninvasive tool in assessing the hemodynamics of intracranial arteries. The sensitivity was 90.9% and the specificity was 75.0% by using PSV <0.30 m/s and 50% reduction of normal PSV as low cutoff criteria in the diagnosis of diffusely severe or localized critical VAS with TCDFI.

Endoscope Assisted Removal of Jugular Foramen Schwannoma; Report of 3 Cases

Removal of the intraforaminal portion of a jugular foramen schwannoma under direct vision requires resection of the adjacent bone. Extensive resection of the bone around the jugular foramen, however, involves a potential danger for cerebrospinal fluid (CSF) leakage and for damage to the adjacent cranial nerves as well as venous outflow. To avoid such bone resection, we applied the endoscope during the removal of a jugular foramen schwannoma through the lateral suboccipital approach. Three patients with schwannomas in the jugular foramen were treated using the lateral suboccipital approach with endoscopic assistance. After the intracranial portion was first removed under the microscope, the residual tumor in the jugular foramen was subsequently removed under the side-viewing endoscope. In all cases the tumor was removed successfully without major complications. The authors conclude that if the cases are selected properly, removal of the schwannoma extending into the jugular foramen is feasible through the conventional lateral suboccipital window under endoscopic assistance.

Transcranial color-coded sonography for vertebrobasilar disorders in end-stage renal disease

Because vertebrobasilar arterial disorders seem to be common in patients with end-stage renal disease, a neuroradiological evaluation of vertebrobasilar circulation is necessary for patients with possible vertebrobasilar insufficiency. In three patients on maintenance hemodialysis, contrast-enhanced transcranial color-coded real-time sonography (TCCS) through a suboccipital window delineated occlusion of bilateral vertebral arteries with reversal of the basilar artery, reversal of the left vertebral artery mimicking left subclavian steal phenomenon, and dolichoectasia of the basilar artery and bilateral vertebral arteries with signals of turbulent flow. TCCS has several advantages over computed tomographic angiography and magnetic resonance angiography, including the direction of blood flow, handy performance even during hemodialysis, and contrast agent free from nephrotoxicity. Thus, TCCS is useful in the evaluation of intracranial circulation in patients with end-stage renal disease.

Success rate of transcranial color-coded duplex ultrasonography in visualizing the basal cerebral arteries in vascular patients over 60 years of age.

Clinically important atherosclerotic cerebrovascular disease is mainly found in patients aged >60 years. Transcranial color-coded duplex ultrasonography (TCCD) is a relatively new technique for investigating the basal cerebral arteries; however, it is often hampered by impenetrable ultrasound windows. The aim of this study was to ascertain the as yet unknown success rate of TCCD regarding visualization of the basal cerebral arteries in patients >60 years, to provide reference data, and to compare any possible male/female differences. In 112 atherosclerotic white patients >60 years of age, the anterior, middle, and posterior cerebral arteries and the vertebral and basilar arteries were insonated. In men, 99% of the temporal and 94% of the suboccipital windows could be penetrated by ultrasound compared with 77% and 95%, respectively, in women. The male versus female vessel detection rates were 91% versus 58% for the anterior cerebral artery, 97% versus 73% for the middle cerebral artery, 97% versus 68% for the posterior cerebral artery, 94% versus 93% for the vertebral artery, and 91% versus 79% for the basilar artery. In 77% of men but only 33% of women could all vascular segments be investigated. All intracranial arteries were insonated at a deeper level in men. The women showed significantly higher blood flow velocities than the men. In elderly white men the vessel detection rate is >90%. In women there is a much lower detection rate, due to impenetrable temporal windows. Visualization of all major intracranial arteries is possible in only one third of female patients >60 years of age.

Transcranial Doppler: state of the art

Introduction. Transcranial color Doppler sonography permits the accurate assessment of intracranial arteries. The latest Doppler units, using the color and power techniques, can show even very small flow volumes (1×1 mm). Low frequency (2–2.5 MHz) and very focused transducers are used in transcranial color Doppler. The skull is a very strong barrier for ultrasounds, which requires the use of some acoustic windows like some thin portions of the skull bone or some natural skull foramina. The use of echocontrast agents in color Doppler seems to increase the applications of transcranial studies. Objective. (1) To report on transcranial color Doppler technique and findings. (2) To assess the role of contrast agents in the visualization of intracranial vessels. (3) To define the main indications of this technique. Material and methods. The temporal, the orbital and the suboccipital are the main acoustic windows used for transcranial color Doppler studies. We use phased-array transducers (2–2.5 MHz) and, preferrably, the echocontrast agent. We examined 15 patients with severe internal carotid artery stenoses after the infusion of Levovist™ (Schering AG, Berlin, Germany) suspension (8 ml at 300 mg Galactose/ml, infused at 0.5 ml/s). Results. Levovist™ infusion permitted to depict the main intracranial vessels in all cases. The middle and the anterior cerebral arteries are shown through the temporal window. The former is the main cerebral artery, it is the easiest to identify and presents the highest peak systolic velocity. The orbital window can be used to visualize the ophthalmic artery and the internal carotid artery siphon, while the vertebral and the basilar arteries are demonstrated through the suboccipital window. Discussion. We report the most important findings and discuss the main indications of transcranial color Doppler studies. In addition to flow presence and direction, the main indices of arterial flow can be measured thanks to contrast agent administration, namely the peak systolic velocity, the end diastolic velocity, the resistance index and the pulsatility index. A morphological assessment of the Willis circle can also be carried out with color and power Doppler. Functional studies can be performed to assess the residual autoregulatory function of the cerebral circle in the patients with internal carotid artery stenosis or occlusion. The development of intracranial collateral circles can also be studied in these patients. Moreover, the M1 segment of the middle cerebral artery and the internal carotid artery siphon can be demonstrated directly. Transcranial color Doppler is also a useful tool to detect vasospasm after subarachnoid hemorrhage and to monitor blood flow velocity in the middle cerebral artery during carotid endarterectomy. The assessment of blood supply to arteriovenous malformations and to intracranial neoplasms is another application. Conclusion. With reference to internal carotid stenoses, the main applications of transcranial color Doppler are the study of intracranial vessels, of intracranial arterial stenosis, of arteriovenous malformations and of Willis circle aneurysms, as well as the monitoring of blood flow velocity during carotid endarterectomy. Echocontrast agents play an important role in the visualization of intracranial vessels.

Evaluation of the Basilar Artery Flow Velocity by TCD Examination

We measured flow velocities of the basilar artery (BA) via the suboccipital window by TCD in 115 subjects to investigate BA hemodynamics. Twenty one of the subjects had posterior circulation pathology, 37 had anterior circulation pathology, and the remaining 57 cases had no lesions. The vascular lesion was confirmed by cerebral angiography in all cases. The characteristic findings of the BA flow velocity by the site of vascular lesion were as follows. 1) Normal: signal obtainable from a depth of 80 mm to depths beyond 95 mm. Timeaveraged mean velocity was between 20 and 45 cm/s and velocity variations occurred at different depths<16 cm/s. 2) BA occlusion: a) Total occlusion: no signal or signal only from the site adjacent to the vertebrobasilar junction. b) Distal occlusion: continuous low velocity (<20 cm/s) .c) Proximal occlusion: continuous retrograde flow. 3) Stenosis of the BA: sudden increase in flow velocity at the stenotic portion or continuous low velocity proximal to the site of severe stenosis. 4) Occlusion of the bilateral vertebral arteries (VA) : flow from the anterior spinal artery detectable. 5) Unilateral occlusion of the VA: no distinctive flow pattern. 6) Internal carotid artery occlusion or vascular rich tumor in the posterior lobe: increased flow velocity along the BA. 7) Other anterior circulation pathology: no characteristic signal.

Evaluation of the Basilar Artery Flow Velocity by Transcranial Doppler Ultrasonography

Using transcranial Doppler ultrasonography (TCD), we measured flow velocities along the vertebrobasilar axis via the suboccipital window in 99 patients to investigate the hemodynamics of the basilar artery (BA). Nineteen of them had posterior circulation pathology (occlusive lesions of the BA or vertebral arteries), 36 had anterior circulation pathology, 1 had multiple aneurysms and the remaining 43 cases had no lesions. Confirmation was obtained by cerebral angiography in all cases. In the subjects without lesions, the mean BA velocity was 32.8 ± 12.4 cm/s, and it was almost constant along the vessel. On the other hand, abnormal findings such as no flow signal, constant low velocity flow, retrograde flow, a signal from the anterior spinal artery or an abrupt increment of velocity; were noted in most patients with posterior circulation pathology. Constant high velocity was noted in patients with anterior circulation pathology and collateral flow from the posterior circulation. Thus, TCD appears to be useful for assessing BA circulation.