TCD Monitoring Research Articles

Ultraschalldiagnostik der intra-kraniellen Hirnarterien und Monitoring-Techniken

There have been significant further developments in ultrasound diagnostics of the intracranial brain arteries in recent years. Besides the traditional transcranial Doppler sonography (TCD) the two-dimensional colour duplex technique (TCCS) has become a well-established method. This enables a safe differentiation of the basal brain arteries even without compression tests, as well as a clear definition against surrounding parenchymal structures. It is now possible to obtain safe and rapid information on the vascular status for immediate diagnosis in brain infarction patients. Since information on vascular malformations and aneurysms can be obtained only if the vascular pathology is sufficiently large, TCCS cannot replace other methods of identification as far as this aspect is concerned. The ultrasound contrast media for whom the lungs are patent greatly improve the signal-to-noise ratio of the Doppler signal. After enhancement by the ultrasound contrast media, Doppler signals may be analysed even under unfavourable conditions (for example: insufficient penetration of sound through the temporal bone). By means of haemodynamic TCD monitoring it is now possible to determine significant characteristics of brain blood supply with relatively little effort, such as changes in the median speed of flow, cerebrovascular resistance and autoregulation. The clinical application of this kind of monitoring is demonstrated by three examples. During the interventional neuroradiological experimental occlusion of the internal carotid artery the TCD data can be used to assess haemodynamic and possible clinical effects of such an occlusion. In the tilting-table test ICD can supply valuable insights into the cerebral effects of systemic dysregulations. In a subgroup of patients with orthostatic intolerance it was only TCD that showed clear pathological changes. For practical reasons it has not yet been possible to establish TCD monitoring in continuous control checking in stroke units. However, first experiences seem to point out that possibly TCD monitoring may reveal the development for critical cerebral circulatory disturbances in patients with space-occupying media infarctions and may thus supply a significant contribution to the indication for cranial decompression. By means of repeat examinations of the course, using the TCD and TTCS technique, it is possible to identify in patients with acute cerebral infarction the time of rechannelling and to estimate the space-occupying effect of an infarction by measuring the displacement of the third ventricle. Monitoring patients after thrombendarterectomy of the internal syndrome, whereas monitoring of an embolism helps to estimate the risk of a post-operative ischaemic event.

Mikroembolusdetektion mittels transkranieller Dopplersonographie

Clinically silent cerebral circulating microemboli are noninvasively detectable by transcranial Doppler sonography (TCD) leading to a characteristic transient increase in the frequency spectrum. These TCD signals are now known as „Microembolic Signals” (MES) or „High Intensity Transient Signals” (HITS). Experimental studies have shown that the acoustic properties of MES are determined by size and structural composition of the circulating microemboli. Overwhelming evidence exists that these MES possess clinical relevance enabling the assessment of the actual thromboembolic activity on an individual basis. This allowed for obtaining new etiologic and prognostic information in various patient groups suffering from, or at risk of, ischemic strokes. The recent introduction of sophisticated MES detection software and the validation of multichannel TCD monitoring has considerably improved the monitoring procedure and its diagnostic confidence as well. TCD detection of MES represents a promising novel technique to refine the prevention and therapy of cerebrovascular diseases on a more individual basis.

Dopplersonographisches Monitoring einer A. carotis interna - Dissektion unter ungünstigen Kollateralisationsbedingungen

We report on a patient with unilateral dissection of the ICA who initially presented with a severe distal ICA stenosis. Subsequent occlusion of the ICA was followed by a large subcortical infarction. CT and MRI demonstrated a pattern of characteristic low-flow infarction. Extracranial (ECD) and transcranial (TCD) Doppler sonography initially revealed findings characteristic of distal carotid artery stenosis and later complete ICA occlusion. Doppler sonography showed diminished intracranial flow velocities and no collateral flow could be detected via the anterior and posterior communicating arteries. In this case we used TCD follow-up examinations to initiate and determine the duration of limited therapeutically induced hypertensive treatment, and were able to document the improvement of cerebral perfusion. We conclude that TCD monitoring after ICA dissection will not only enable diagnosis but also follow-up of the intracranial collateralisation to initiate and control hypertensive hypervolemic treatment in specific cases of absent collateral pathways via the circle of Willis.

Correlation between central somatosensory conduction time, blood flow velocity, and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

In this retrospective study of 67 aneurysmal patients, the predictive role of central conduction time (CCT) on vasospasm occurrence evaluated by means of transcranial Doppler sonography (TCD) and the correlation of CCT to blood flow velocity measured simultaneously in postoperative course were studied. Data about the clinical state of patients at the time of admission (Hunt Hess scale), severity of subarachnoidal hemorrhage on initial CT scan (Fisher grade), timing of surgery (acute or delayed), outcome (Glasgow Outcome Scale), severity of vasospasm graded by highest mean blood flow velocity (BFV) during the entire clinical course and CCT values measured at admission (preoperatively), then postoperatively (one day after surgery) and simultaneously with later TCD investigations were collected from the files. Interhemispheric difference of CCT was also calculated. The results showed that CCT at admission was not predictive for vasospasm. CCT measured either at admission or on the first postoperative day did not differ significantly in the different grades of vasospasm. Similar results were obtained in the acute and in the late operated group of patients. The results also suggest that increased CCT and interhemispheric difference at the time of admission indicate a worse prognosis, but this can be related to higher surgical risk rather than to a higher incidence of late ischemic deterioration. Simultaneous CCT and TCD examinations demonstrated that coincident and statistically significant (p < 0.01) increase of actual CCT (6.7 msec) was found only in the severe grade of vasospasm (BFV 200 cm/s). The authors discuss the role of CCT and TCD monitoring in the management of aneurysmal subarachnoid hemorrhage.

5-07-26 Cerebral embolism as a risk factor for CVD: A TCD monitoring

5-07-26 Cerebral embolism as a risk factor for CVD: A TCD monitoring

Recognition of temporary occlusion of the middle cerebral artery by macroembolus during carotid endarterectomy by TCD monitoring relation to EEG and postoperative clinic. Two case reports S.P. Claus, H.W. Mauser, M. vd Mee, F.L. Moll, W.H. Mess, R.G.A. Ackerstaff

Recognition of temporary occlusion of the middle cerebral artery by macroembolus during carotid endarterectomy by TCD monitoring relation to EEG and postoperative clinic. Two case reports S.P. Claus, H.W. Mauser, M. vd Mee, F.L. Moll, W.H. Mess, R.G.A. Ackerstaff

Recognition of temporary occlusion of the middle cerebral artery by macroembolus during carotid endarterectomy by TCD monitoring relation to EEG and postoperative clinic. Two case reports: S.P. Claus, H.W. Mauser, M. vd Mee, F.L. Moll, W.H. Mess, R.G.A. Ackerstaff

Recognition of temporary occlusion of the middle cerebral artery by macroembolus during carotid endarterectomy by TCD monitoring relation to EEG and postoperative clinic. Two case reports: S.P. Claus, H.W. Mauser, M. vd Mee, F.L. Moll, W.H. Mess, R.G.A. Ackerstaff

Perioperative TCD monitoring in carotid endarterectomy: M. Mu¨ller 1, G. Schu¨der 1, G.-P. Langenscheidt 2, P. Walter 2, K. Schimrigk 1. 1Department of Neurology; 2Department of Surgery, University Hospital of the Saarland, Homburg/Saar

Perioperative TCD monitoring in carotid endarterectomy: M. Mu¨ller 1, G. Schu¨der 1, G.-P. Langenscheidt 2, P. Walter 2, K. Schimrigk 1. 1Department of Neurology; 2Department of Surgery, University Hospital of the Saarland, Homburg/Saar

Periodic leg movements are part of the B-wave rhythm and the cyclic alternating pattern.

Periodic leg movements (PLM) in sleep are supposed to constitute a frequent cause of insomnia. There is some controversy whether PLM are the cause of insomnia by provoking microarousals or whether they are simply and epiphenomenon not casually related to the insomnia. We examined four patients with PLM by overnight polysomnography and concomitant transcranial Doppler sonography (TCD) monitoring, 13 patients with suspected normal pressure hydrocephalus by concomitant overnight polysomnography and intracranial pressure recording, and 10 healthy volunteers by concomitant overnight polysomnography and TCD monitoring. EEG arousals occurred more frequently before than after the PLM. PLM were associated with increase in heart rate, breathing amplitude, and cerebral blood flow velocity assessed by TCD. PLM occurred with a mean wavelength of 40.5 s. This mean wavelength corresponded to similar values calculated for intracranial pressure B-waves (43.3 s) in 13 patients with suspected normal-pressure hydrocephalus, TCD B-wave equivalents (42.2 s) in 10 healthy young adults and the frequency of the cyclic alternating pattern in EEg recordings (40 s). Our date suggest that these cyclic variations with a wavelength of about 40 s are part of a common endogenous rhythm. PLM seem to be an epiphenomenon of this rhythm and not the cause of insomnia.

Endovascular balloon occlusion test of the internal carotid artery with increased hemodynamic monitoring for determination of circulatory reserve before planned carotid occlusion

To evaluate stroke risk assessment of balloon test occlusion of the internal carotid artery (ICA) with enlarged haemodynamic monitoring prior to permanent ICA occlusion. 24 patients with cervical metastasis (n = 18), cavernous meningiomas (n = 3) or inoperable cavernous aneurysms (n = 3) were examined. The test occlusion was monitored by EEG, neurological examinations and transcranial Doppler sonography of the ipsilateral middle cerebral artery with evaluation of the cerebrovascular reserve capacity. Additionally 99mTc-HMPAO-SPECT imaging was added showing the perfusion during test occlusion. In one (4%) patient the test occlusion had to be interrupted previously due to an acute neurological deficit. This patient and two (8%) patients with highly pathological test results in SPECT and TCD were excluded from permanent carotid occlusion. In 6 (25%) patients quantitative TCD monitoring could improve the stroke risk assessment by differentiating the patients in a low and high risk group. 6 (25%) patients were definitely occluded without haemodynamic complications, but two patients suffered from embolic infarctions which cannot be predicted by this procedure. The multimodal balloon test occlusion with enlarged haemodynamic monitoring allows haemodynamic stroke risk assessment prior to permanent occlusion of the ICA.

Scientific Session IV: Impact of Neurosonology on Therapeutic Decisions

To assess the impact of brain activation and subarachnoid haemorrhage (SAH) on flow velocity changes after visual stimulation, we examined 27 healthy controls ( 13 subjects examined with closed and opened eyes), 12 patients with SAH while eyes were kept open, 9 patients under general anesthesia without brain disease and 5 patients with vegetative state after brain injury. All subjects were examined with bilateral TCD monitoring of one PCA and contralateral MCA during rest (30s) and stimulation with 10 Hz flashlight (30s). Ten cycles of stimulation were averaged for estimation of the specific flow response (SFR), which was computed as percent increase of PCNMCA ratio. In controls, SFR was significantly higher with opened eyes (mean, 15.8%) than closed eyes (mean, 11.8%, p &lt; 0.01, Wilcoxon test). SFR was significantly decreased in early stage of SAH (mean, 4,83%, p &lt; 0.01) and normalized during course of disease. Four of 5 patients with abolished SFR suffered delayed ischemia due to vasospasm. Of 7 patients with preserved SFR, 5 had vasospasm by ultrasonic or angiographic criteria, but none had delayed ischemia. No SFR was observed in general anesthesia and apallic state. We conclude that vasoneuronal coupling depends on stimulus directed attention. Furthermore, abolished SFR in SAH might indicate a high risk of delayed ischemia due to vasospasm.

Embolus detection in different degrees of carotid disease

Carotid atherosclerotic disease is a major source for artery to artery embolism. Stroke incidence highly depends on the degree of carotid stenosis. TCD monitoring for embolic signals may help to identify patients at high risk for an impeding stroke. This study was performed to correlate the degree of carotid stenosis with the occurrence of embolic signals and the clinical outcome. We performed a bilateral simultaneous TCD study on 4 patient groups with unilateral atherosclerotic disease: We studied patients with non-stenotic ICA plaques (n = 21), 50-75% ICA stenosis (n = 20), 75-95% stenosis (n = 22), and occlusion (n = 13). Minimum insonation time was 45 minutes. Embolic signals were not detected in the control group and patients with a non-stenotic ICA lesion, but in 10% of the patients with 50-75% stenosis, 22% of the patients with a high grade stenosis and 39% of the patients with an ICA occlusion. There is a high specificity (92%) and rather low sensitivity (29%) of these microemboli for past clinical events. The occurrence of embolic signals correlated (p < 0.005) with a history of stroke, TIA or RIND. Microemboli detection may be a valuable tool to identify high risk patients.

Cerebrovascular Carbon Dioxide Reactivity in Carotid Artery Disease

In patients with carotid artery disease, poor intracerebral collateralization is reflected by impaired cerebrovascular reactivity to carbon dioxide inhalation, which will improve after endarterectomy. The relationship between preoperative reactivity to carbon dioxide using transcranial Doppler sonography (TCD) and intraoperative changes of somatosensory evoked potentials (SEP) and TCD parameters were investigated. In 94 patients, preoperative carbon dioxide reactivity was examined and defined impaired if mean blood flow velocity in the middle cerebral artery (Vm-MCA) increased less than 1.5% mmHg during carbon dioxide challenge. Patients then underwent 100 carotid operations under general anesthesia with both SEP and TCD monitoring. Shunts were placed if SEP amplitude decreased to less then 50% of control or central conduction time increased by 20% after clamping (critical SEP changes). TCD changes were defined as critical in case of a postclamping/preclamping Vm-MCA ratio < or = 0.4. The incidence of critical SEP and TCD changes was compared to preoperative carbon dioxide testing using Fisher's exact test with P < 0.05 considered significant. Postoperatively, neurologic state and carbon dioxide responsiveness were re-examined. Twelve patients showed impaired preoperative carbon dioxide reactivity on the side of operation, which improved markedly after surgery. The incidence of critical SEP changes in these cases (8.3%) was not significantly different from that in the remaining patients (14.8%). Critical SEP changes were significantly correlated with critical TCD changes (P < 0.0001). Patients with poor carbon dioxide reactivity (preoperative TCD testing) did not have an increased risk of cerebral ischemia during carotid surgery, as assessed by intraoperative SEP recording.

Transient Cerebral Circulatory Arrest Coincides With Fainting in Cough Syncope

During prolonged coughing, intrathoracic and intra-abdominal pressures are transmitted via the great veins to the intracranial compartment, causing transient elevated intracranial pressure. The resulting reduction of cerebral perfusion pressure may cause a critical impairment of cerebral blood flow (CBF). Obstructive airway disease seems to be a prerequisite to build up the intrathoracic and intracranial pressures to a degree sufficient to compromise CBF and cause cough syncope. Using transcranial Doppler sonography (TCD) monitoring of middle cerebral artery flow velocities, we studied three patients with cough syncope. During coughing, they showed a transient cerebral circulatory arrest, which coincided with loss of consciousness in the two patients who fainted during TCD monitoring. EEG showed slowing, heart rate increased, and systemic arterial BP in one patient was preserved during the syncope. Our findings support the hypothesis that a critical reduction of CBF causes cough syncope.

Transcranial Doppler sonography in experimental Cushing response.

Searching for the early warning symptoms of brain ischaemia, transcranial Doppler sonography (TCD) was used in cats during the Cushing response. The study was performed on seven cats. The intracranial pressure was increased by means of different rate lumbar infusions. The TCD changes of middle cerebral artery (MCA) and basilar artery (BA) flows were analyzed at the stage of the slightest but significant systemic blood pressure increase. The first symptoms of Cushing phenomenon were accompanied by BA flow pattern alternations while the MCA flow remained unchanged. The study suggests the necessity of BA TCD monitoring in cases at risk from brain stem ischaemia. It was shown also that in such cases the MCA TCD study can be misleading.

Comparison of Stenting and PTA for Central Venous Stenosis In Hemodialysis Patients

Central vein occlusion is a common cause of morbidity in patients with upper extremity hemodialysis (HD) access sites and a history of ipsilateral indwelling central lines. We analyzed the results of two percutaneous treatments, balloon angioplasty (PTA) and stenting (S) that were used to relieve symptomatic venous occlusion (arm edema, pain) and improve dialysis efficiency (venous pressure and recirculation fraction). Group I consisted of 26 patients (13 men, 13 women, mean age = 62 ± 14.3), with de novo lesions (innominate = 5, subclavian = 21) who underwent PTA. Group II consisted of 13 patients from Group I who underwent stent implantation (6 Palmaz stents, 7 Wallstents) for failed PTA due to suboptimal angioplasty results (n = 5) or restenosis (n = 8). We retrospectively compared the acute and long-term clinical success and restenosis rates in these two treatment groups. Acute success was defined as resolution of symptoms and resumption of dialysis. Restenosis was defined as &gt;50% stenosis by angiography. Long-term success @ mean follow-up 14 months was defined as continued dialysis without symptomatic venous occlusion or dialysis graft failure.balloon to prevent cerebral emboli. Six symptomatic patients had 7 PTAs (6 carotids, 1 vertebral). Pt. # Angioplasty Technique Transcrania Doppler Stenosis Pre→Post Complications Stenosis 3m F/U 1 Protected 73 emboli 90%→20% none 10% 2 Protected 40 emboli 90%→0% none 0% 3 Active Perf. no window 95%→0% none 0% 4 Active Perf. 10 emboli 99%→0% none 0% 5 Active Perf. no window 99→0% hemorrh→death 6 Standard no window 100%→30%→ none pending (vertebral) stent→0% Active Perf. 70%→dissec, none pending (carotid) 20%→stent→0% Maintenance of cerebral perfusion during PTA by “active” perfusion and cardiac pacing allows prolonged balloon inflations which minimize residual stenosis; when feasible, TCD monitoring is a valuable adjunct. Ongoing studies with more patients will elucidate the value of this approach for carotid angioplasty.

Transcranial Doppler sonography is at present of limited clinical value.

TranscranialDoppler sonography (TCD) is already an established diagnostic technique and of proven value in a variety of neurosurgical problems. 1 Probably the most important clinical contributions are the monitoring of vasospasm in subarachnoid hemorrhage, identifying patients at risk of delayed ischemic deficits, and for selecting patients for prophylactic antivasospasm therapy 2 or carotid occlusion. 3 The TCD is also a reliable noninvasive method for monitoring the hemodynamic effects of treatment for arteriovenous malformations. 4,5 Intraoperative TCD monitoring of blood flow velocity during carotid endarterectomy is relatively sensitive to hemodynamic events, yet its clinical usefulness has yet to be established. 6,7 It has a developing role in the evaluation of intracranial pressure changes in patients with head trauma, since it is atraumatic and repeatable and may help to avoid operative insertion of a transducer in some cases. 8,9 The TCD rapidly found a place in neurovascular research soon after the

Dynamic transcranial Doppler assessment of positional vertebrobasilar ischemia.

A hemodynamic as opposed to an embolic origin of vertebrobasilar ischemia may be suspected when symptoms are brief and triggered by changes in the position of the head or neck. It may be difficult, and not without risk, to reproduce the symptoms and to prove the short-lived hemodynamic changes during angiography. If transcranial Doppler sonography (TCD) could detect these changes, it would be useful as a noninvasive screening method to select patients for further diagnostic evaluation. TCD monitoring of the P1 segments of both posterior cerebral arteries was performed during different head movements in 14 patients referred for evaluation of suspected hemodynamic vertebrobasilar ischemia and in 10 healthy control subjects with a two-channel, 2-MHz, computerized Doppler system. Patients' symptoms were correlated with the Doppler findings. Four patients with stereotypical symptoms had a severe drop in posterior cerebral artery blood flow velocities (BFVs) to 20% of baseline (mean; SD, 14.3; range, 0% to 48%) and subsequent reactive hyperemia with an increase in BFV to 149% (mean; SD, 20.6; range, 110% to 186%) dependent on head rotation to one side (group 1). Compared with the values found in group 2 patients and in control subjects, these drops were significant (P = .0001 for both). Symptoms together with BFV changes could be reproduced several times. Angiography confirmed severe vertebral artery obstruction during head rotation and the presence of anomalies in the posterior circulation. In 10 patients (group 2), symptoms were not short-lived, stereotyped, or clearly dependent on head movements and could not be reproduced during TCD testing. Their BFVs dropped to 88% (mean; SD, 9.0; range, 64% to 102%) of baseline values during maximal head rotation, to 86% (mean; SD, 10.3; range, 64% to 100%) during flexion, and to 88% (mean; SD, 6.7; range, 75% to 103%) during extension. In the 10 control subjects, BFVs dropped to 86% (mean; SD, 8.8; range, 61% to 98%) of baseline values during rotation, to 90% (mean; SD, 10.3; range, 74% to 107%) during flexion, and to 76% (mean; SD, 17.1; range, 54% to 104%) during extension. Monitoring posterior cerebral artery BFV during head movements is a simple, noninvasive method to document a hemodynamic etiology of symptoms in patients with suspected positional vertebrobasilar ischemia. The correlation of symptoms to the hemodynamic findings proved a useful screening method to identify those patients with true position-evoked hemodynamic insufficiency in the posterior circulation. These patients should be selected for angiographic evaluation to identify the source and site of arterial compression.

Carotid endarterectomy with TCD and EEG monitoring.

Carotid endarterectomy with TCD and EEG monitoring.

Continuous Transcranial Doppler Ultrasonography and Electroencephalography During Carotid Endarterectomy: A Multimodal Monitoring System to Detect Intraoperative Ischemia

Transcranial Doppler ultrasonography (TCD) and EEG monitoring during carotid endarterectomy provide continuous information on the electrical activity of the cerebral cortex, blood flow velocities in the ipsilateral middle cerebral artery, and the occurrence of microemboli. One hundred thirty carotid endarterectomies performed with TCD and EEG monitoring were studied prospectively. During cross-clamping of the carotid artery a high correlation was found between EEG asymmetry and reduction of blood flow velocity in the middle cerebral artery (p < 10(-6), Student's t test). Microemboli were detected in 80 patients during the operation. Although not statistically significant, this occurrence of microemboli was associated with signs and symptoms of intraoperative ischemia (p = 0.08, Fisher's exact test). In comparison with earlier studies, a tendency toward intraoperative stroke reduction was noted. Only one nondisabling intraoperative stroke occurred (0.8%). In addition to the EEG, TCD monitoring of hemodynamic changes and microemboli in the middle cerebral artery provides important information to the surgeon instantaneously. TCD monitoring of blood flow velocities and embolism during carotid endarterectomy may help to reduce the number and gravity of intraoperative stroke.