Transcranial Doppler ultrasound recording with compression test in patients with tumors involving the carotid arteries

Transcranial Doppler ultrasound (TDU) recording is presented as a diagnostic method for the evaluation of the cerebral cross-flow in patients in whom, for therapeutic reasons, ligature or resection of the common or internal carotid artery is planned. Examinations were performed under normal conditions and while using manual compression of the ipsilateral carotid artery. Patients with various skull base and neck tumors were examined and in all patients an immediate decrease of the flow velocity in the middle cerebral artery (MCA) of 25 to 90% was registered. In 39% of these patients the flow velocity of the MCA reached 90% or more of its value under normal conditions within a short interval. In 29% of the patients the flow velocity of this vessel under manual compression of the carotid artery remained under 50% of its original value. In 68% of the cases TDU recording with manual compression of the carotid artery showed reliable results for the function of cerebral collateralization as a prognostic factor of ischemic risk due to hemodynamic changes after carotid ligature. In these cases no further examination of the cerebral cross-flow conditions was carried out. This method is convenient, harmless to the patient, inexpensive, does not require sophisticated equipment, and yields reproducible results when compared with cerebral angiography.     

Comparison of measurement of stump pressure and transcranial measurement of flow velocity in the middle cerebral artery in carotid surgery

Transcranial Doppler ultrasound measurement of the velocity of blood flow in the middle cerebral artery (MCA) was performed in 24 consecutive patients undergoing carotid endarterectomy. Measurements were performed preoperatively at rest, following common carotid artery compression, and continuously during surgery. In addition, internal carotid artery stump pressures were measured and a subjective assessment of back flow was made. No relationship between MCA flow velocity and stump pressure following carotid clamping was demonstrated. Peak and mean MCA flow velocity was significantly lower in patients with stump pressures <30 mm Hg (p <0.03) and those with poor back flow (p <0.02).     

Assessment of intracranial hemodynamics in carotid artery disease by transcranial Doppler ultrasound

Noninvasive transcranial Doppler recordings were correlated to the angiographic findings in 77 patients with carotid artery disease. Stenoses reducing the luminal area of the internal carotid artery by 75% or more also reduced the pulsatility transmission index (PTI) of the ipsilateral middle cerebral artery (MCA). The PTI is the pulsatility index of the artery under study expressed as a percent of the pulsatility index of another intracranial artery with presumed unimpeded inflow in the same individual. For stenoses in the 75% to 89% category. PTI reduction was significantly greater in patients with bilateral carotid stenosis, indicating an impaired potential for collateral flow in these patients. The PTI reduction probably reflects both the pressure drop across the stenosis and the cerebral autoregulatory response. Two criteria proved useful in demonstrating collateral MCA supply through the circle of Willis. On the recipient side, retrograde flow in the proximal anterior cerebral artery was demonstrated in 29 of the 31 patients when this flow pattern was disclosed angiographically. In 26 of these patients, the anterior cerebral artery on the supplying side also had clearly increased flow velocity. Increased flow velocities in the proximal posterior cerebral artery were present in 26 of the 30 vessels that were acting as a collateral channel to the ipsilateral MCA.     

Transcranial Doppler ultrasound in internal carotid artery and middle cerebral artery disease

Using noninvasive transcranial Doppler sonography, we studied cerebral collateral patterns in 30 patients with stenosis and/or occlusion of the extracranial internal carotid artery (ICA). All patients with unilateral ICA stenosis ⩽ 80% had normal transcranial Doppler findings. 80% of patients with unilateral and 50% of patients with bilateral ICA stenosis of more than 80% including those with occlusion showed a collateralization via the ipsilateral anterior and/or posterior cerebral artery. 20% of patients with unilateral and 50% of patients with bilateral ICA stenoses of more than 80% (including occlusion) had two or three collateral pathways, including the ophthalmic artery. Another ten patients with stenosis or spasm of the middle cerebral artery (MCA) showed increased flow velocities with turbulence in the narrow segment. In four patients with severe MCA disease with a systolic peak velocity of more than 200 cm/s, the Doppler waveform distal to the lesion was damped. Decreased regional cerebral blood flow (rCBF) measured by^99mTc-HMPAO-SPECT was found in two patients with severe MCA stenosis. Another patient with moderate MCA stenosis with a systolic peak velocity of 140 cm/s showed a normal cerebral perfusion pattern.     

Cerebral perfusion during nonpulsatile cardiopulmonary bypass

The recording of middle cerebral artery (MCA) flow velocity by the transcranial Doppler method offers a new, noninvasive, continuous technique for studies of cerebral circulation. Comparative studies of electromagnetic internal carotid artery (ICA) flowmetry and MCA flow velocity by the transcranial Doppler technique have demonstrated that observed changes in MCA flow velocities reflect concomitant changes in cerebral circulation. Eleven high-risk patients undergoing cardiopulmonary bypass (CPB) procedures were included in a pilot study. Arterial blood pressure (BP), central venous pressure, and epidural intracranial pressure (EDP) were recorded during CPB. Cerebral electrical activity was recorded by a cerebral function monitor. Flow velocity in the MCA was increased during nonpulsatile CPB in 10 of the 11 patients. This increase was related to the degree of hemodilution, and the flow velocity during steady-state CPB was 80 to 300% of the prebypass value. The MCA flow velocity changed, however, in a pressure-passive manner with the cerebral perfusion pressure (CPP = BP - EDP) in the individual patient, which indicates that cerebral autoregulation was not operative. During the first 15 minutes after termination of bypass, the MCA flow velocity was reduced, but remained higher than the prebypass level, 110 to 210% of the level during the last 5 minutes preceding CPB.     

Changes in blood flow of anterior and middle cerebral arteries following carotid endarterectomy: a transcranial Doppler study

AIM: The aim of the present study was to evaluate the changes in blood flow of anterior and middle cerebral arteries following carotid endarterectomy, using transcranial Doppler (TCD) flow studies. PATIENTS AND METHODS: This study included 100 patients (72 men, mean age 65 years) who underwent carotid endarterectomy because of high-grade carotid stenosis or symptoms of ischemic stroke. Endarterectomy was performed by a distal shunt between the common carotid and internal carotid arteries. Blood flow in the anterior and middle cerebral arteries was assessed by TCD preoperatively and also in the postoperative period (1st and 4th day; 1st, 6th, and 12th month). Collateral circulation in the Willis circle was evaluated by common carotid compression. RESULTS: Patients with bilateral carotid stenosis > or =70% exhibited a significantly increased flow velocity in the ipsilateral anterior cerebral artery (ACA), middle cerebral artery (MCA), and in the contralateral ACA. Patients with entirely occluded contralateral internal carotid artery showed the most pronounced changes in cerebral hemodynamics. Blood flow velocities returned to the preoperative values at 1 to 12 months following endarterectomy. Hyperperfusion syndrome was manifested in 14 patients, who exhibited significantly higher flow velocities in the ipsilateral MCA compared with asymptomatic patients. CONCLUSIONS: A transient bilateral increase of blood flow velocity in the anterior part of the Willis circle may often occur in the immediate postoperative period following carotid endarterectomy. Although its clinical significance is not entirely understood, this increase may be associated with cerebral hyperperfusion syndrome.     

Middle cerebral artery circulation during carotid surgery. A transcranial Doppler study

OBJECTIVE: Perioperative carotid cross-clamping might induce low stump pressures as well as hypoperfusion of the middle cerebral artery. In this study blood flow velocities in the middle cerebral artery were compared with intraoperative measurements of the poststenotic carotid blood pressure. DESIGN: Forty-one patients with internal carotid artery stenosis were operated on without shunting, under general anesthesia. Poststenotic carotid pressures and middle cerebral artery flow velocities were measured before and during cross-clamping. The hemodynamic responses to preoperative carotid compressions and intraoperative cross-clamping were evaluated. RESULTS: In seven patients the poststenotic carotid blood pressure decreased on clamping despite unchanged or even increased middle cerebral artery blood flow velocities. In all other patients, pressure changes were significantly correlated to the decrease in middle cerebral artery blood flow velocities. Autoregulatory blood flow velocity responses after preoperative common carotid artery compression were not reproducible by cross-clamping. CONCLUSIONS: Stump blood pressure measurements may not reflect middle cerebral artery perfusion in about 20% of thrombendarterectomies performed under general anesthesia. A possible explanation might be dimished cerebral autoregulation and changes in collateral flow distributions.     

Evaluating middle cerebral artery collateral blood flow reserve using acetazolamide transcranial Doppler ultrasound in patients with carotid occlusive disease

BACKGROUND: The objective of this study is to examine the utility of acetazolamide TCD ultrasound in the evaluation of MCA collateral blood flow reserve in patients with carotid occlusive disease. METHODS: Acetazolamide TCD and cerebral angiography were performed for 28 carotid territories in 14 patients with carotid occlusive disease. The percentage change in mean blood flow velocity and PI in the MCA was measured before and after 1 g of acetazolamide was administered. The carotid territories were divided into groups according their angiographic findings: (1) mild/moderate (<70%) vs severe (> or =70%) extracranial carotid artery stenosis, and (2) active collateral blood flow to the MCA territory vs no collateral blood flow to the MCA. RESULTS: After acetazolamide injection, the percentage increase in mean MCA velocity for mild/moderate vs severe carotid artery stenosis was 43% +/- 10% and 19% +/- 6%, respectively, indicating less collateral blood flow reserve in patients with severe stenosis (P = .04). The percentage decrease in the PI for MCA territories with vs without angiographic evidence of collateral blood flow was 4.6% +/- 4% and 16% +/- 3%, respectively (P = .04), indicating an exhausted vascular reserve in patients with evidence of active collateral blood flow on angiography. CONCLUSIONS: A decrease in the PI after acetazolamide administration represents a safe and noninvasive indicator of limited collateral blood flow reserve to the MCA territory ipsilateral to an extracranial carotid stenosis. Further study into the role acetazolamide TCD has in the preoperative evaluation of these patients, including threshold values, is warranted.     

Middle Cerebral Artery Circulation During Carotid Surgery: A Transcranial Doppler Study

Objective - Perioperative carotid cross-clamping might induce low stump pressures as well as hypoperfusion of the middle cerebral artery. In this study blood flow velocities in the middle cerebral artery were compared with intraoperative measurements of the poststenotic carotid blood pressure. Design - Forty-one patients with internal carotid artery stenosis were operated on without shunting, under general anesthesia. Poststenotic carotid pressures and middle cerebral artery flow velocities were measured before and during cross-clamping. The hemodynamic responses to preoperative carotid compressions and intraoperative cross-clamping were evaluated. Results - In seven patients the poststenotic carotid blood pressure decreased on clamping despite unchanged or even increased middle cerebral artery blood flow velocities. In all other patients, pressure changes were significantly correlated to the decrease in middle cerebral artery blood flow velocities. Autoregulatory blood flow velocity responses after preoperative common carotid artery compression were not reproducible by cross-clamping. Conclusions - Stump blood pressure measurements may not reflect middle cerebral artery perfusion in about 20% of thrombendarterectomies performed under general anesthesia. A possible explanation might be dimished cerebral autoregulation and changes in collateral flow distributions.     

Evaluation of cerebral hemodynamics by transcranial Doppler ultrasonography in carotid endarterectomy

The authors studied the linear blood flow rate (LBFR) in the middle cerebral artery (MCA) which was measured by means of transcranial dopplerography during carotid endarterectomy in 25 patients. Analysis of the results showed that the changes of LBFR in the MCA correlate with alterations in blood pressure: LBFR in the MCA reduced most during compression of the common carotid artery in patients with considerable affection of the contralateral carotid artery. The maximal increase of the blood flow during compression of the common carotid artery occurred when the initial LBFR in the MCA was lowest. After the blood flow in the common carotid artery is restored the LBFR in the MCA is determined by the degree of stenosis of the artery which is operated on and the degree of collateral circulation. The method makes it possible to determine in time the need for additional measures of protection of the brain from ischemia.     

Monitoring cerebral perfusion during carotid endarterectomy

Transcranial pulsed Doppler ultrasound was used to monitor blood velocity in the middle cerebral artery (MCA) of two patients during ipsilateral carotid endarterectomy. In the first patient the ultrasound data demonstrated a non-functioning shunt which was corrected by repositioning the distal end of the shunt. In the second patient MCA blood velocity data demonstrated that clamping of the external carotid artery would have resulted in complete cessation of MCA flow throughout endarterectomy. These cases illustrate the benefit that this technique offers to the individual patient undergoing carotid surgery.     

Management morbidity and mortality in grade IV and V patients with aneurysmal subarachnoid haemorrhage

Summary Intracranial haemodynamics were studied in 20 patients with diffuse and focal brain injury and experimental animals with acute intracranial hypertension by the use of TCD ultrasound. The mean flow velocity in the middle cerebral artery (MCA) commonly decreased on the side of the haematoma depending on intracranial pressure (ICP) elevation and cerebral perfusion pressure (CPP) reduction in focal injury. The decrease of the MCA flow velocity returned to normal after treatment. The flow velocities decreased bilaterally and there was no difference between the right and left side in diffuse injury. But the velocities increased in spite of ICP elevation when diffuse cerebral swelling developed. Cerebrovascular CO₂ reactivity was impaired in two groups of patients with low Glasgow Coma Scale (GCS) scores. The mean velocity of the MCA and blood flow in the internal carotid artery exhibited flow patterns which changed correlatively depending on CPP reduction in experimental animals. Noninvasive study by use of TCD ultrasound can provide valuable information on variant haemodynamic phenomena in patients with diffuse and focal brain injury.     

Factors affecting assessment of cerebral autoregulation using the transient hyperaemic response test

The transient hyperaemic response in the middle cerebral artery blood flow velocity on the release of brief compression of the ipsilateral common carotid artery has been validated as an indicator of cerebral autoregulation. We evaluated, in three stages, the effect of experimental factors such as duration of compression of the common carotid artery and magnitude of the decrease in blood flow velocity during common carotid artery compression on the transient hyperaemic response. In stage 1, 13 healthy volunteers underwent six transient hyperaemic response tests each; two tests each for either 3, 6 or 10 s duration of compression of the common carotid artery. In stage 2, 10 volunteers underwent four transient hyperaemic response tests each; two tests each for either 10 or 15 s duration of compression of the common carotid artery. In stage 3, data from the transient hyperaemic response tests using 10 s compression from the 23 volunteers who participated in stages 1 and 2 were analysed to evaluate the relationship between magnitude of decrease in blood flow velocity at the onset of compression and the transient hyperaemic response. The transient hyperaemic response ratio (blood flow velocity after the release of compression/baseline blood flow velocity) increased significantly when the duration of common carotid artery compression increased from 3 to 6 s, or from 6 to 10 s (stage 1); increase in the duration from 10 to 15 s did not have any significant effect (stage 2). The transient hyperaemic response ratio correlated significantly with the magnitude of decrease in blood flow velocity after compression, up to the values of the compression ratio (percent decrease in blood flow velocity at the onset of compression) of 40% but not more (stage 3). We conclude that experimental factors such as duration of common carotid artery compression and magnitude of the decrease in blood flow velocity during common carotid artery compression can significantly influence the transient hyperaemic response. These factors should be controlled if the transient hyperaemic response test is used for a comparison between repeated measurements. A compression time of 10 s and a compression ratio of 40% or more, allow maximum expression of the hyperaemic response in healthy volunteers.      

Influence of the Collateral Function of the Circle of Willis on Hemispherical Perfusion During Carotid Occlusion as Assessed by Transcranial Colour-coded Duplex Ultrasonography

OBJECTIVES: to investigate the collateral potential of the circle of Willis with transcranial colour-coded duplex ultrasonography and common carotid artery (CCA) compression. MATERIALS AND METHODS: in 46 atherosclerotic patients without cerebrovascular disease, the functional patency of the collaterals of the circle of Willis, the anterior and posterior communicating arteries, was assessed. The Peak Systolic Velocity (PSV) decrease in the middle cerebral artery (MCA) during CCA compression between complete and incomplete circles was compared. RESULTS: in 10 (22%) patients a complete and in 36 (78%) patients an incomplete circle of Willis was found, mainly due to non-functioning posterior communicating arteries. In hemispheres with collateral supply through both the anterior and the posterior communicating artery, the median PSV decrease in the MCA during CCA compression was 43%. When the posterior, anterior or both communicating arteries (1 hemisphere) were missing the PSV decrease was 58% (p =0.003), 70% (p =0.001) and 75%, respectively. CONCLUSIONS: collateral flow from the basilar to the carotid territory is often hampered by non-functioning posterior communicating arteries. A non-functioning anterior communicating artery is rare. A complete collateral circulation provides better perfusion of the MCA during carotid occlusion as compared with collateral supply through only the anterior or the posterior communicating artery in the case of an incomplete circle of Willis.     

The role of transcranial Doppler in carotid artery surgery.

In order to evaluate the usefulness of transcranial Doppler (TCD) in carotid artery surgery, 90 patients who underwent carotid endarterectomy were studied. Transcranial Doppler was performed preoperatively with digital compression of the carotid artery and intraoperatively at the time of cross-clamping, together with routine EEG monitoring. The percentage residual middle cerebral artery velocity (%MCAV) during carotid artery compression or cross-clamping was considered. The intraoperative %MCAV at cross-clamping was compared with the values obtained in the preoperative examination during the compression test and with the EEG data; the EEG records were blindly reviewed by a neurologist and divided into three groups: group A, normal; group B, moderate anomalies and group C, major anomalies. There were no significant differences between preoperative %MCAV (compression test) and intraoperative %MCAV (cross-clamping) by separate analysis of the data related to systolic, diastolic and mean velocity. The systolic, diastolic, mean %MCAV and the Gosling index after cross-clamping were then compared with the EEG data: no significant differences were seen between groups A and B; on the other hand, in all patients with major EEG anomalies (group C) the %MCAV at TCD was reduced to 0. In conclusion, preoperative TCD associated with carotid artery compression appears a safe and useful way of identifying patients at risk of cerebral ischaemia during carotid artery cross-clamping. Patients with no residual flow at intraoperative TCD need to be considered as presenting a very high risk of ischaemia and in this group the use of a shunt is mandatory.     

Is transcranial Doppler useful in the detection of internal carotid artery cross-clamp intolerance?

The aim of this study was to test the hypothesis that a drop in the systolic blood flow velocity in the middle cerebral artery of 70% or more, measured by transcranial Doppler, is a better criteria in the detection of cross-clamp intolerance than electroencephalogram (EEG) and somatosensory evoked potential (SSEP) monitoring. After exclusion of patients with a recent stroke, urgent procedures and combined procedures, a transcranial Doppler with compression test was scheduled in 85 patients. In 13 patients the drop was 70% or more and in these patients a transcranial Doppler was also performed during the reconstruction of the internal carotid artery (the study group) under general anaesthesia. A shunt was used because of EEG and SSEP abnormality in one patient. No changes were observed in the remaining patients and no intraoperative strokes were seen. The transcranial Doppler monitoring was unreliable in three patients. During cross-clamp, the systolic blood flow velocity in the middle cerebral artery dropped less than 70% in four and 70% or more in six patients. It is concluded that using a drop of 70% or more of the systolic blood flow velocity in the middle cerebral artery during internal carotid artery cross-clamp, as an indicator of cross-clamp intolerance, will lead to unnecessary shunting.     

The haemodynamic effect of carotid endarterectomy.

OBJECTIVES: to assess the haemodynamic effect of carotid artery surgery, and to relate postoperative changes to the state of cerebral circulation before revascularisation. MATERIALS AND METHODS: using transcranial Doppler we studied bilateral middle cerebral artery (MCA) flow velocities before and on 1st day, 2nd or 3rd day and 4th or 5th day and 3 months after carotid surgery in 61 patients. In addition, ipsilateral MCA flow velocity was monitored continuously during surgery. Data were related to the internal carotid artery (ICA) perfusion pressure (cerebral perfusion pressure index, CPPI), measured directly before ICA clamping. RESULTS: postoperatively, MCA flow velocities increased significantly overall (p<0.01), mainly due to pronounced and longer lasting flow velocities in the group of 18 patients with CPPI<0.7 (p<0.05). Flow velocities peaked - absolute as well as relative - on the first postoperative day and then gradually levelled off to reach preoperative values after 4-5 days in patients with high CPPI, whereas MCA flow velocities remained increased in the group of patients with low CPPI. At 3 months flow velocities in both groups were normalised. New neurological symptoms occurred in four patients, who all had low CPPI preoperatively (22% (4/18) vs 0%; Fisher's exact test: p=0.006). CONCLUSION: some degree of hyperperfusion was seen in most patients, but the changes were significantly more pronounced in patients with preoperative hypoperfusion, who also suffered significantly more neurological complications.     

Transcranial Doppler in cerebral vasospasm

Transcranial Doppler provides a noninvasive method for recording blood flow velocity (and indirectly, diameter) in the basal cerebral arteries and therefore is especially useful in detecting vasospasm following subarachnoid hemorrhage. Vasospasm most commonly involves the basal arteries, where the changes in vessel diameter will be inversely proportional to the mean velocity measurements. Examination of patients requires that the examiner be experienced and familiar with the vascular anatomy and the various TCD indicators of vasospasm. Normal mean velocity for the MCA is 62 +/- 12 cm/sec. Significant spasm on angiogram of the MCA corresponds to a mean velocity of 120 cm/sec. Mean velocities of the MCA of 200 cm/sec or greater indicate severe spasm and correlate with 50% or greater narrowing on angiogram. Cerebral blood flow changes that can occur after subarachnoid hemorrhage and as a result of vasospasm may affect velocity values. A simultaneous index of CBF with either direct flow measurement techniques or by recording extracranial carotid artery velocity measurements may be helpful in reflecting these changes. Knowledge of the time course of the development and resolution of vasospasm using TCD can help the clinician predict which patients are at higher and lower risk of developing ischemic deficits, thereby guiding treatment. Several features of TCD assessment of vasospasm are similar to angiography. High TCD velocities, like severe angiographic vasospasm, are associated with delayed ischemic deficits and infarction, although some patients can remain asymptomatic despite these changes. Delayed ischemic deficits or infarctions in patients following subarachnoid hemorrhage usually will be preceded by markedly elevated velocity or other indicators of severe vasospasm.     

Evaluation of posttraumatic cerebral blood flow velocities by transcranial Doppler ultrasonography

Thirty-five patients were admitted to the hospital with Glasgow coma scale scores of 4 to 7 after severe, blunt head injury. Blood flow velocities of the middle cerebral artery (MCA) and the ipsilateral internal carotid artery (ICA), high in the neck, were recorded noninvasively by Doppler ultrasonography. Serial examinations were begun within 48 hours of trauma and continued until the patient either died or was discharged. Spasm of the MCA was assumed if the ratio of the velocity of blood flow in the MCA (VMCA) to the velocity of blood flow in the ICA (VICA) exceeded 3 (normal value, 1.7 +/- 0.4). In cases of severe MCA spasm, this ratio is higher because of increased flow velocity in the MCA and reduced flow in the ICA due to increased cerebrovascular resistance. Higher MCA velocities with VMCA/VICA above 3, consistent with MCA spasm, were found in 14 of the 35 patients (40%). The increase began as early as 48 hours after injury, reached a maximum between Days 5 and 7, and lasted until 2 weeks after injury. There was a significant correlation between the occurrence of vasospasm and the quantity of cisternal or intracerebral blood seen on a computed tomographic scan. No correlation was found with the age of the patients, the Glasgow coma scale score at admission, the intracranial pressure, or the functional outcome 6 months after injury. The occurrence of a secondary infarction in a patient with severe MCA spasm suggests that, at least in some cases, spasm may influence the prognosis.     

Changes in middle cerebral artery flow velocity and pulsatility index after carotid endarterectomy.

Transcranial Doppler sonography (TCD) was used in 33 patients undergoing carotid endarterectomy (CEA). Mean flow velocity (MCA MV) and the pulsatility index in the middle cerebral artery (MCA PI) were measured pre- and on six occasions postoperatively. The MCA MV was reduced by anaesthesia but was increased postoperatively (+43%, p less than 0.001) compared to the preoperative value and was still increased at late follow-up after several months. The MCA PI, which was lower preoperatively than normally reported in this age group, was not changed by anaesthesia but then rose and remained elevated, i.e. within normal limits 72 h postoperatively (+30%, p less than 0.01) as well as at late follow-up. No significant changes in MCA MV or MCA PI were noted on the contralateral side. The results from this study support earlier findings from invasive studies showing that CEA results in an increased flow in the middle cerebral artery on the operated side and an increased MCA PI suggests an increased resistance on the operated side. The findings are compatible with an increased cerebral blood flow during the first days after CEA and with the operated side supplying a greater part of the cerebral blood flow even several months after surgery.