The importance of traumatic subarachnoid haemorrhage

Post-traumatic cerebral vasospasm is being increasingly recognised as a possibly significant complication after head injury. To assess the relationship between post-traumatic subarachnoid haemorrhage (tSAH) and post-traumatic vasospasm, 63 patients with severe head injury (GCS 3-8) were studied. Forty-seven patients had cerebral contusion on the initial CT scan. In 25 of these (Group I) there were only contusions, while 22 (Group II) also had tSAH. All patients had daily measurements of blood flow velocity in the basal cerebral arteries using transcranial Doppler ultrasound (TCD). The incidence of vasospasm detected by TCD was significantly higher in Group II. Furthermore there were significantly fewer good outcomes (GOS 1 and 2) in this group. These results suggest that the presence of subarachnoid blood in patients with severe head injury is associated with a risk of vasospasm, and with poorer outcome.     

Vasospasm after SAH due to aneurysm rupture of the anterior circle of Willis: value of TCD monitoring

OBJECTIVE: The aim of this study was to verify the presence of angiographic vasospasm in patients with transcranial Doppler (TCD) of high velocities after subarachnoid hemorrhage (SAH). METHODS: Seven hundred and eighty-six cases admitted within 48 hours after SAH due to the rupture of anterior circulation aneurysm, were prospectively studied with TCD. In cases of TCD velocities higher than 120 cm/s (TCD vasospasm), the patient underwent a control angiography. Hunt-Hess and Fisher's grade on admission CT and location of the aneurysm were related to occurrence of TCD vasospasm. The increase in TCD velocities within 24 hours was calculated and related to the presence of cerebral ischemia on discharge CT, considering three groups of patients: Group A with an increase in velocities higher than 60%, Group B with an increase in velocities between 30 and 60%, and Group C with an increase in velocities lower than 30%. RESULTS: TCD vasospasm was observed in 216 patients (27%). In 97% of patients with TCD vasospasm on middle cerebral artery (MCA) and in 71% with TCD vasospasm on anterior cerebral artery (ACA), control angiography confirmed the vasospasm, with a significant lower diagnostic TCD predictivity of ACA spasm (chi2=28.204, p=0.000). The overall positive predictive value of TCD was 89%. There was no significant correlation of TCD vasospasm with clinical status on admission and location of the aneurysm, but a significant correlation between occurrence of TCD vasospasm and Fisher's grade (chi2=15.470, p=0.002) and between the increase rate in TCD velocities and cerebral ischemia (chi2=56.564, p=0.000). CONCLUSION: Our study shows a good correlation between TCD and angiography to detect vasospasm on MCA, but the correlation is low for ACA. TCD alone cannot discriminate different hemodynamic pathways after SAH.     

Changes in cerebral hemodynamics assessed by transcranial Doppler ultrasonography in children after head injury

INTRODUCTION: Head injury is an important factor in children's morbidity and mortality. Arterial vasospasm and probably resulting from this, delayed ischemic deficit are important sequels of head trauma with detrimental effects on outcome. These problems have already been well studied in adults, but not in children. The noninvasiveness and ease in use of transcranial Doppler ultrasound technique (TCD) make it an ideal tool for the assessment of changes in cerebral circulation not only for the purposes of diagnosis but also for follow-up. PATIENTS AND METHODS: The authors review the present literature and analyze the usefulness of TCD as used in a group of 27 head-injured children aged 3-16 years. GCS/CCS score, CT pictures and neurological status were estimated. TCD examination was performed on the 2nd day after injury and each of the following 5 days or until normalization of flow velocities. Blood flow velocity was measured in the middle cerebral artery, the anterior cerebral artery and the extracranial portion of the internal carotid artery. The pulsatility index was also read.RESULTS: A significant correlation was found between changes in blood flow parameters and neurological status. High blood flow velocities seemed to be caused by hyperemia rather than by vasospasm. CONCLUSION: The results confirm that TCD is a useful method in the management of children after head injury.     

The relation between cerebral blood flow velocities as measured by TCD and the incidence of delayed ischemic deficits. A prospective study after subarachnoid hemorrhage

Patients (n = 127) with aneurysmal subarachnoid hemorrhage (SAH) were examined by transcranial Doppler ultrasonography (TCD) in a prospective study to follow the time course of the posthemorrhagic blood flow velocity in both the middle cerebral artery (MCA) and in the anterior cerebral artery (ACA). Results were analysed to reveal their relationship and predictive use with respect to the occurrence of delayed ischemic deficits. Mean flow velocities (MFV) higher than 120 cm sec(-1) in MCA and 90 cm sec(-1) in ACA were interpreted as indicative for significant vasospasm. In 20 of our 127 patients (16%) a delayed ischemic deficit (DID) was subsequently diagnosed clinically (DID+ group). Patients in the DID+ group can be characterized as those individuals who presented early during the observation period post-SAH with highest values of MFV, a faster increase and longer persistence of pathologically elevated MFV-values (exceeding 120 cm sec(-1) in MCA and 90 cm sec(-1) in ACA). They also show a greater difference in MFV-values if one compares the operated to the nonoperated side. Differences in MFV-values obtained in MCA or ACA were statistically significant (p < 0.05) for DID+ and DID- patients. The daily maximal increase of MFV was found between days 9 and 11 after SAH. In the DID+ group, the maximal MFV was 181 +/- 26 cm sec(-1) in MCA and 119 +/- 14 cm sec(-1) in ACA. In contrast to this, patients in the DID- group were found to present with MFV of 138 +/- 11 cm sec(-1) in MCA and 100 +/- 7 cm sec(-1) in ACA respectively. Delayed ischemic deficits appeared three times more often in DID+ patients than in patients with MFV < 120 cm sec(-1), if they showed a MFV > 120 cm sec(-1) in MCA. If pathological values were obtained in ACA, this ratio increases to about four times, if DID + patients presented with MFV > 90 cm sec(-1) versus patients with MFV < 90 cm sec(-1). Daily monitoring of vasospasm using TCD examination is thus helpful to identify patients at high risk for delayed ischemic deficits. This should allow us to implement further preventive treatment regimens.     

外伤性脑梗死的CT诊断

目的总结外伤性脑梗死的CT特征,探讨其发生机制,揭示其对疾病预后的判定价值。方法回顾性分析40例外伤性脑梗死患者头颅CT表现及相关临床资料。结果轻微外伤引起的脑梗死多发于儿童,好发部位为基底节内囊区,预后较好;重症外伤引起的脑梗死好发于成人,发病部位多见于颅内血肿同侧,且大脑后动脉支配区域最为多见,预后较差。结论CT扫描对外伤性脑梗死的诊断及预后判定有重要价值。     

Arteriovenous differences of oxygen and transcranial Doppler sonography in the management of aneurysmatic subarachnoid hemorrhage.

After subarachnoid hemorrhage (SAH) the detection of hemodynamically significant vasospasm is frequently difficult, especially in comatose patients. Most clinicians use transcranial Doppler sonography (TCD) to detect increasing mean blood flow velocities in the basal arteries as markers of cerebral vasospasm, without accounting for the effects of sedation and variations in blood pressure or pCO(2). This study was conducted to test the hypothesis that the arteriovenous difference of oxygen (avDO(2); in terms of % volume) could also be useful for the evaluation of vasospasm. A total of 22 SAH patients (M : F = 1 : 1.75, age 58+/-10 years, median Hunt and Hess grade 4) were prospectively enrolled. All patients were sedated with continuous doses of midazolam/fentanyl and/or propofol. TCD studies and avDO(2) measurements were conducted at the same time or in close succession. The blood flow velocity of the middle cerebral artery was recorded. A cranial CT scan was conducted if the avDO(2) increased by at least 0.8%. Overall, 82 measurements were recorded in 22 patients between days 1 and 13 after SAH. TCD mean flow velocities increased as expected. In contrast, avDO(2) decreased until post-hemorrhage day 4 before it increased again. Overall, after SAH, avDO(2) was significantly lower than in normal individuals. Cerebral infarction occurred primarily in patients with a maximal change of avDO(2) of more than 1%. TCD velocities alone are poor indicators of the severity of vasospasm. In contrast, daily avDO(2) seems to be a more robust parameter. However, collection of additional metabolic information is warranted.     

颅脑损伤后TCD变化及其与伤情,CT及预后的相关性研究

目的 探讨：①脑外伤后ＴＣＤ的表现和变化规律;②ＴＣＤ与伤情、ＣＴ的关系;③ＴＣＤ与预后的关系。方法 选择３０例于伤后２４￣４８ｈ内入院的成年脑外伤病人（无明显复合伤,伤前无明显心脑血管疾病及严重感染）,动态行ＴＣＤ测定,同时行ＣＴ检查,并记录ＧＣＳ。结果 ①伤后１￣３ｄ已开始出现血管痉挛,６￣８ｄ达峰值,１３￣１５ｄ已明显减轻;②ＧＣＳ的变化有关,重伤组血管痉挛的发生率和程度均明显高于轻伤组;③     

Transcranial Doppler in acute hemispheric brain infarction

We studied cerebrovascular anatomy using intra-arterial digital angiography, and blood flow velocity in the middle cerebral artery (MCA) using transcranial Doppler (TCD) ultrasonography in 42 patients with acute hemispheric ischemic brain infarction. We compared angiography with TCD and the clinical findings within 6 hours of the onset of symptoms. The location and extent of the chronic ischemic brain damage was assessed by CT performed 1 to 3 months after the ictus. Abnormal TCD, as manifested by either an unobtainable MCA flow signal or a significantly depressed MCA flow velocity, was highly associated with proximal MCA occlusions demonstrated by angiography. Abnormal TCD predicted both larger chronic CT lesions and more extensive ischemic change within the MCA territory. These data demonstrate that early TCD conveys useful information concerning cerebral tissue prognosis following hemispheric ischemia.     

Slow oscillations in middle cerebral artery cerebral blood flow velocity and aging

OBJECTIVE: A recent study using near infrared spectroscopy (NIRS) showed that low frequency oscillations of regional cerebral blood flow (CBF) decline with age. Using transcranial Doppler ultrasound (TCD), it is possible to monitor similar fluctuations in cerebral blood velocity (CBV) in basal cerebral vessels. Such oscillations have been used widely in the assessment of cerebral autoregulation. We postulated that it should be possible to observe similar age related reductions in the amplitude of slow waves recorded using TCD. METHODS: We studied 187 patients with head injury, who were admitted to Addenbrooke's Neuro Critical Care unit between 1992 and 1998. Intermittent recordings of CBV were undertaken using TCD, which were subsequently analysed using software developed in-house. Power spectra were computed in the very low frequency (VLF: 0.01-0.05 Hz) and low frequency (LF: 0.07-0.11 Hz) ranges for all signals and a regression analysis was performed to assess the correlation between power in each frequency band and age. RESULTS: No significant correlation was found between VLF or LF power and age (VLF: r=0.037; p=0.63; LF: r=-0.05, p=0.517). DISCUSSION: While remaining cogniscent of the complex nature of our patient group, we find that age dependent reductions in CBF oscillations seen using NIRS do not translate to recordings of CBV in the middle cerebral artery in patients with head injury.     

Cerebrovascular reactivity in patients with mild head injury

Transcranial Doppler sonography (TCD) is a non-invasive method that can be repeated to measure blood flow velocity in intracranial arteries and to assess cerebrovascular reactivity in patients with a variety of neurological diseases. The aim of this study was Doppler sonography evaluation of blood flow and reactivity in the middle cerebral artery in patients at different stages after mild head injuries. The dynamic assessment of blood flow velocity and pulsatility index both at rest and after hyperventilation in 73 patients with mild head injuries was carried out on the day of injury, the third day, sixth day and after 6 months to 5 years. The control group consisted of 61 healthy volunteers. Obtained results indicate an increase in blood flow velocity in the middle cerebral artery on the day of injury and a decrease within the following days in younger patients (aged xleq 30 yrs). Also their cerebrovascular reactivity was significantly lower. In older persons (age > 30 yrs) and in patients with remotely suffered injuries, neither blood flow velocity in the middle cerebral arteries nor cerebrovascular reactivity differed significantly from the results of the respective age control groups. The findings justify a conclusion that mild head injury is followed by changes both in the blood flow and cerebrovascular reactivity. In younger patients with mild head injuries these haemodynamic disturbances seem to be connected with altered activity of the autonomic system.     

经颅多谱勒检测阿尔茨海默病的对照研究

目的 了解阿尔茨海默病(AD)的颅内各大血管血流速度的改变情况,及其与认知功能改变之间的关系.方法 记录60例首次入院的AD患者经颅多谱勒(TCD)颅内血管检测结果,包括两侧大脑中动脉、两侧大脑前动脉、两侧大脑后动脉、基底动脉、两侧椎动脉.同时记录简易智力状态检查(MMSE)结果.对照组为60例血管性痴呆(VD)和60例精神分裂症(S).结果 研究组和对照组自身每一颅内动脉的两侧血流速度无显著差异(P＞0.05).AD组的TCD检测异常率为90.00%,其中以血流速度降低为突出表现,与VD组无显著性差异(P＞0.05),但明显低于S组(P＜0.01或0.05,两侧椎动脉除外).AD的颅内各动脉(右侧大脑后动脉除外)血流速度与简易智力状态检查(MMSE)分数呈正相关.结论 AD的TCD检测对该病的病因探讨、认知功能评估及治疗有一定意义.     

Spontaneous oscillations of arterial blood pressure, cerebral and peripheral blood flow in healthy and comatose subjects.

Slow and rhythmic spontaneous oscillations of cerebral and peripheral blood flow occur within frequencies of 0.5-3 min-1 (0.008-0.05 Hz, B-waves) and 3-9 min-1 (0.05-0.15 Hz, M-waves). The generators and pathways of such oscillations are not fully understood. We compared the coefficient of variance (CoV), which serves as an indicator for the amplitude of oscillations and is calculated as the percent standard deviation of oscillations within a particular frequency band from the mean, to study the impairment of generators or pathways of such oscillations in normal subjects and comatose patients in a controlled fashion. With local ethic committee approval, data were collected from 19 healthy volunteers and nine comatose patients suffering from severe traumatic brain injury (n = 3), severe subarachnoid hemorrhage (n = 3), and intracerebral hemorrhage (n = 3). Cerebral blood flow velocities were measured by transcranial Doppler ultrasound (TCD), peripheral vasomotion by finger tip laser Doppler flowmetry (LDF), and ABP by either non-invasive continuous blood pressure recordings (Finapres method) in control subjects, or by direct radial artery recordings in comatose patients. Each recording session lasted approximately 20-30 min. Data were stored in the TCD device for offline analysis of CoV. For CoV in the cerebral B-wave frequency range there was no difference between coma patients and controls, however there was a highly significant reduction in the amplitude of peripheral B-wave LDF and ABP vasomotion (3.8 +/- 2.1 vs. 28.2 +/- 16.1 for LDF, p < 0.001; and 1.2 +/- 0.7 vs. 4.6 +/- 2.8 for ABP, p < 0.001). This observation was confirmed for spontaneous cerebral and peripheral oscillations in the M-wave frequency range. The CoV reduction in peripheral LDF and ABP oscillations suggest a severe impairment of the proposed sympathetic pathway in comatose patients. The preservation of central TCD oscillations argues in favor of different pathways and/or generators of cerebral and peripheral B- and M-waves.     

Transcranial Doppler Ultrasound: A New Method of Monitoring Hemispheric Anesthetization During the Intracarotid Amobarbital Procedure

BACKGROUND: Electroencephalography (EEG) is traditionally used to assess the duration of hemispheric anesthetization and to monitor return of function in the anesthetized hemisphere during the intracarotid amobarbital procedure (IAP), but EEG changes are not consistently seen. The authors evaluated the role of continuous transcranial Doppler (TCD) monitoring as an alternative to EEG. METHODS: The authors performed both continuous TCD monitoring and EEG during the IAP in 10 patients with medically intractable partial epilepsy. Mean velocities were monitored continuously in both middle cerebral arteries (MCAs), and changes in MCA velocities on continuous TCD monitoring were time locked with the EEG changes. RESULTS: The average mean MCA velocities were within normal limits bilaterally (50-85 cm/s) in all patients at baseline. Mean MCA velocites increased in all patients to 95-115 cm/s at the start of the test when the patients were asked to raise their hands and start counting. After injection of sodium amobarbital, mean MCA velocities in all patients dropped dramatically on the ipsilateral side to values of 12-39 cm/s and returned to the baseline average value when the hemiparesis recovered. In 8 patients, the duration of delta activity on EEG coincided with the time interval during which the mean MCA velocities were low on TCD monitoring. In 2 patients, despite the presence of hemiparesis clinically and a drop in mean MCA velocities on the ipsilateral side on continuous TCD monitoring, EEG remained normal on the ipsilateral side. CONCLUSIONS: Continuous TCD monitoring may be a more sensitive method than EEG in determining the duration of hemispheric anesthetization during IAP. Because the items for assessment of memory are presented during the period of hemispheric anesthetization, TCD may be useful in more precisely defining the time window for memory testing.     

经颅多普勒对外伤性蛛网膜下腔出血脑血管监测及临床应用的研究

目的 探讨经颅多普勒对外伤性蛛网膜下腔出血脑血变化及预后判断.方法 应用TCD对90例颅脑损伤并蛛网膜下腔出血患者24h内、3～5d、15d在大脑中动脉(MCA)平均血流速度进行监测.结果 80例患者预后良好,8例颅脑损伤后在脑中动脉(MCA)平均血流速度持续＜40cm/s或＞200cm/s,时间＞24h的病人预后较差.结论 利用TCD进行动态观察脑血流变化,对临床早期明确诊断脑损伤程度,指导临床早期及时合理用药和停药以及对预后判断有明确的意义.     

影响外伤性蛛网膜下腔出血病人预后的因素分析

目的 探讨可影响外伤性蛛网膜下腔出血（tSAH）病人治疗结果的因素及其CT变化的特点。方法 回顾性分析了一组连续收治的入院时经头颅CT检查确诊为tSAH的闭合性颅脑损伤病人资料，记录其入院时和病情加重时的头颅CT情况、入院时GCS评分、以Fisher分级法对出血量进行分级情况、伤后6个月以GOS评分法评估的治疗结果，并对数据加以统计分析。结果 多因素Logisitc回归分析显示，初次CT扫描tSAH出血量Fisher分级（OR=50．7，P〈0．001）、入院时GCS评分（OR=2．86，P〈0．001）、初次CT扫描基底池tSAH（OR=0．35，P=0．030）与tSAH患者的不良结果存在显著相关。最初CT显示脑挫裂伤与入院后CT出现恶化（OR=2．92，P=-0．003）及入院后CT示显著恶化（OR=3．21，P〈0．001）有显著相关性。结论 tSAH病人的治疗结果与入院时GCS评分、出血量及脑挫裂伤的存在或范围有关，这些也是头颅CT出现显著恶化的相关因素，说明头颅CT显示出的恶化与治疗结果是有其内在联系。     

A new pocket-sized transcranial ultrasound device (NeuroDop): comparison with standard TCD.

The NeuroDop is a new bedside assessment tool consisting of a continuous wave ultrasound probe attached to a stethoscope earpiece. This study was designed to compare middle cerebral artery (MCA) velocity assessment obtained with the NeuroDop versus standard transcranial Doppler (TCD). TCD technologists performed continuous wave NeuroDop studies followed by standard TCD studies on 60 subjects. Technologists recorded presence of MCA signal and estimated velocity based on NeuroDop auditory characteristics. Signal was obtained in 108 MCA vessels with the portable unit and in 112 vessels using standard TCD. For detection of patency, sensitivity was 96%, specificity 88%, positive predictive value 99%, and negative predictive value 58%. Auditorially estimated velocities from the NeuroDop strongly correlated with TCD velocity measures (r = 0.71). Categorical estimates of velocity as decreased (< 37 cm/sec), normal (37-81 cm/sec), or increased (> 81 cm/sec) demonstrated an accuracy rate of 85%. This novel stethoscope-continuous wave unit has excellent sensitivity in detecting presence of MCA patency. Moreover, MCA velocities can be characterized to a reasonable degree of accuracy based on NeuroDop auditory characteristics. The NeuroDop shows promise as a tool to rapidly assess and serially monitor presence and amplitude of MCA velocity and may help guide thrombolytic and other emergency management decisions in stroke patients.     

经颅多普勒对外伤性脑血管痉挛的诊断价值

目的 探讨经颅多普勒(TCD)对外伤性脑血管痉挛的诊断价值及外伤性脑梗死的早期预防价值.方法 回顾性分析348例颅脑损伤病人的临床资料,均行TCD监测及CT检查.将TCD诊断为脑血管痉挛的病人按血管痉挛程度分为轻度、中度、重度组,并进行统计学分析.结果 TCD监测发现外伤性脑血管痉挛179例(51.44％),其中轻度组92例,中度组60例,重度组27例;其多在伤后2～3 d出现,持续5～7 d,10～14d后缓解.CT证实发生外伤性脑梗死24例,其中外伤性脑血管痉挛中度组4例,重度组20例;经统计学分析,脑血管痉挛严重程度与外伤性脑梗死的发生存在正相关(P＜0.01);经治疗1个月后GOS预后评分:恢复良好3例,轻度残疾8例,重度残疾7例,死亡6例.结论 TCD诊断外伤性脑血管痉挛安全、无创、有效,对早期预防外伤性脑梗死具有重要临床意义.     

Comparison Between Magnetic Resonance Phase Contrast Imaging and Transcranial Doppler Ultrasound With Regard to Blood Flow Velocity in Intracranial Arteries: Work in Progress

OBJECTIVE: The authors evaluate blood flow velocities in the medial cerebral artery (MCA) and the basilar artery using magnetic resonance (MR) phase contrast technique in comparison with transcranial Doppler ultrasound (TCD). Eleven healthy male volunteers were studied. TCD of the MCA (n = 22) and basilar artery (n = 11) was performed. MR phase velocity mapping was done in each vessel at the same location where the TCD signal had been acquired. A 2-dimensional FLASH sequence with retrospective cardiac gating and an average temporal resolution of 45 ms was used. Resistance indices (RIs) and pulsatility indices (PIs) were calculated for both modalities. The TCD insonation angle was measured retrospectively with MR, and TCD velocities were corrected based on these measurements. The comparison of flow velocities obtained with TCD and MR led to a low correlation coefficient with regard to the basilar artery and the MCA: maximum systolic velocity, r = 0.02 and r = 0.50, respectively; enddiastolic velocity, r = 0.47 and r = 0.65, respectively; mean velocity, r = 0.52 and r = 0.66, respectively. The average PIs in the basilar artery and the MCA were 0.80 and 0.81 with MR and 0.65 and 0.85 with TCD, respectively. The average RIs in the basilar artery and the MCA were 0.52 and 0.54 with MR and 0.52 and 0.55 with TCD, respectively. The TCD insonation angle differed significantly from the ideal value in the basilar artery (mean value = 32.6 degrees) and the MCA (mean value = 26.5 degrees). The authors find a low correlation between velocities measured with MRI and TCD but similar results with regard to the PIs and RIs. Several sources of error, such as a nonideal TCD insonation angle, were identified.     

Spontaneous oscillations of arterial blood pressure,cerebral and peripheral blood flow in healthy and comatose subjects

Abstract

Slow and rhythmic spontaneous oscillations of cerebral and peripheral blood flow occur within frequencies of 0.5-3 min~1 (0.008-0.05 Hz, B-waves) and 3-9 min~1 (0.05-0.15 Hz, M-waves). The generators and pathways of such oscillations are not fully understood. We compared the coefficient of variance (CoV), which serves as an indicator for the amplitude of oscillations and is calculated as the percent standard deviation of oscillations within a particular frequency band from the mean, to study the impairment of generators or pathways of such oscillations in normal subjects and comatose patients in a controlled fashion. With local ethic committee approval, data were collected from 19 healthy volunteers and nine comatose patients suffering from severe traumatic brain injury (n = 3), severe subarachnoid hemorrhage (n = 3), and intracerebral hemorrhage (n = 3). Cerebral blood flow velocities were measured by transcranial Doppler ultrasound (TCD), peripheral vasomotion by finger tip laser Doppler flowmetry (LDF), and ABP by either non-invasive continuous blood pressure recordings (Finapres method) in control subjects, or by direct radial artery recordings in comatose patients. Each recording session lasted ~ 20-30 min. Data were stored in the TCD device for offline analysis of CoV. For CoV in the cerebral B-wave frequency range there was no difference between coma patients and controls, however there was a highly significant reduction in the amplitude of peripheral B-wave LDF and ABP vasomotion (3.8 ±2.1 vs. 28.2 ± 76.7 for LDF, p < 0.00 7; and 1.2±0.7 vs. 4.6±2.8 for ABP, p < 0.001) This observation was confirmed for spontaneous cerebral and peripheral oscillations in the M-wave frequency range. The CoV reduction in peripheral LDF and ABP oscillations suggest a severe impairment of the proposed sympathetic pathway in comatose patients. The preservation of central TCD oscillations argues in favor of different pathways and/or generators of cerebral and peripheral B- and M-waves. [Neurol Res 1999; 21: 665-669]     

Transcranial Doppler ultrasonography in the neurologic intensive care unit

Transcranial doppler ultrasonography (TCD) is a noninvasive monitoring tool which allows imaging of blood flow velocities in intracranial blood vessels. It is safe, portable, easy to perform and provides accurate information regarding underlying physiology which may help to guide therapy in critically ill neurologic patients. It has significantly contributed to the management of vasospasm related to subarachnoid hemorrhage in the neurologic intensive care unit. TCD is also helpful in the early diagnosis of a variety of complications that can occur in patients with head injury such as vasospasm, elevated intracranial pressure and disordered cerebral autoregulation. Careful performance of the test and experienced interpretation can identify TCD waveforms indicative of cerebral circulatory arrest, an ancillary finding used for the diagnosis of brain death. TCD is likely to play a larger role in evaluation of the patient in the future because of its safety, portability and ability to define moment-to-moment changes in cerebral blood flow velocities and cerebral blood flow.