patients having vascular malformations of the brain, a relatively normal vascular tree can be assumed for

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1 Intracranial Duplex Doppler: Practical Uses in Pediatric Neurology and Neurosurgery William M. Chadduck, MD; Joanna J. Seibert, MD Abstract The value of pulsed Doppler studies of the cerebral vessels of neonates, infants, and children having neurologic and neurosurgical problems is presented. In this study, Resistive Index [(peak systolic velocity - end-diastolic velocity)/peak systolic velocity] x 100 was used in correlative studies of pediatric patients having hydrocephalus, extra-axial collections, shunt malfunctions, vascular malformations, and craniocerebral injuries. Age-related normal values for Resistive Index are defined, with special attention to the expected values in patients having normally functioning ventriculoperitoneal shunts. Correlations of Resistive Index with intracranial pressure in animal models, as well as a variety of pathologic pediatric neurosurgical conditions, emphasize the usefulness of pulsed Doppler studies in some conditions as well as limitations in others. (J Child Neurol 1989;4:577-S86). High-resolution ultrasonography has exquisitely visualized the brain and spinal cord of neonates. Pulsed Doppler studies, used primarily to evaluate blood flow, using the anterior fontanelle as a sonic window, have also been extremely helpful in studying neonates and infants and more recently, transcranial pulsed Doppler hardware, for studying older children. High-frequency sound, directed into a moving column of red cells, is shifted by an amount proportional to the velocity of the moving red cells, as well as to the angle of incidence of the sound waves relative to the column of blood. A number of indices have been developed differences in the to overcome the difficulty of angle probe and vessels. For example, Pourcelotl described the Resistive Index (RI) to be an indicator of cerebral vascular resistance. RI is obtained by subtracting the end-diastolic velocity from the peak systolic velocity and dividing the difference by the peak systolic velocity. Accepted for publication June 13, From the Departments of Neurosurgery and Radiology, Arkansas Children s Hospital, University of Arkansas for Medical Sciences, Little Rock, AR. Address correspondence to Dr Chadduck, Department of Neurosurgery, Arkansas Children s Hospital, 800 Marshall, Little Rock, AR This ratio minimizes the effect of angulation of the probe and has been preferred in our laboratory for making correlations with a variety of clinical abnormalities. In the pediatric age group, except for patients having vascular malformations of the brain, a relatively normal vascular tree can be assumed for most patients. This is in distinct contrast to most of the adult population examined by pulsed Doppler studies, in as much as that population is usually seen for evaluation of occlusive cerebral vascular disease. Thus in the pediatric age group, abnormalities of Resistive Index or cerebral vascular resistance, more rather than likely represent a physiologic abnormality an anatomic one. Bada et al2 first studied cerebral blood flow velocity in newborns, measuring Doppler flow in the branches of the anterior cerebral arteries, thus demonstrating the feasibility of assessing the cerebral circulation noninvasively. Since then, many studies have correlated intracranial pathologic processes with cerebral vascular resistance assessed by transfontanelle and transcranial Doppler studies. in cerebral blood Volpe et al3 demonstrated changes flow velocity in patients with infantile hydrocephalus, intraventricular hemorrhage, pneumothorax, S77

2 patent ductus arteriosus, neonatal seizures, suctioning, respiratory distress syndrome, brain death, meningitis, apnea, asphyxia, the use of muscle relaxants, polycythemia, and cerebral vascular malformations. Griesen et al4 compared cerebral blood flow using Doppler ultrasound examinations with blood flow studies using xenon 133 clearance techniques. A good correlation was found between pulsatility index, mean flow velocity, and end-diastolic flow velocity. Moreover, the correlation coefficients were consistently better for pulsed Doppler compared with continuous wave Doppler techniques. We investigated the usefulness of pulsed Doppler for evaluating and treating neonates, infants, and older children with intracranial abnormalities. Initial studies were performed to establish normal values for RI and to determine correlative changes in RI with intracranial pathologic findings. Thereafter, the RI values were correlated with measurements of intracranial pressure in patients with intraventricular hemorrhage, hydrocephalus, subdural hematomas, acute craniocerebral injuries, and shunt malfunctions.5 Monitoring of patients having a variety of cerebral pathologic processes has also yielded very helpful guidelines for treatment. Laboratory experiments in dogs5 allowed variations of intracranial and cerebral perfusion pressures over a wide range for correlation with RI. Our studies were performed using the 5-MHz Acuson 128 Sector 519 scanner (Acuson Computed Sonography, Mountain View, CA) or the Transpect transcranial Doppler system (Medasonics, Mountain View, CA) with a 2-MHz probe. Real-time localization of each vessel through the anterior fontanelle allowed placement of cursors for measurement of flow velocities in designated regions of each artery. Anterior cerebral arteries were visualized in a parasagittal view, whereas the middle cerebral and internal carotids were best seen in the coronal plane. With the transcranial system, the vessels were usually assessed through the squamous portion of the temporal bone and identification of the vessels was accomplished by relative flow directions and by depth of gating. Normal Values Seventy-five infants judged to be normal both clinically and sonographically were evaluated for RI. Term infants (2:34 weeks gestation) had a value of 71 ± 7%, and for premature infants (<33 weeks gestation), the RI was 77 ± 9%. Studies of 27 children, 18 months to 16 years old, revealed an average RI, as determined by transcranial Doppler, of TABLE 1 Normal Values for Resistive Index (RI) 50 ± 15%. By the time of closure of the fontanelles, most children attain an RI essentially equal to adult values. Adult values by our transcranial system have averaged 47 ± 12%. The calculation of RI from the flow velocities of middle cerebral arteries of 80 normal in the studies of Arnolds and von patients reported Reutern6 and Harders and Gilsbach also indicated an RI value of 50% for normal patients. Therefore, in the first few months of life, the normal values for RI should decrease, and any tendency for an increase in the RI in the first few months of life is suggestive of intracranial pathologic lesions. Table 1 summarizes the data from the literature and our laboratories for age-related normal values for RI. Hydrocephalus We recently reported correlation of the findings on cranial Doppler ultrasonography with the criteria for ventriculoperitoneal shunting in hydrocephalic patients.8 Forty-six neonates with ventriculomegaly were evaluated on two or more occasions, before and Three additional after ventriculoperitoneal shunting. patients with mild ventriculomegaly not requiring shunts were also studied. Hydrocephalus was associated with myelomeningocele in 17 patients and posthemorrhagic, postmeningitic, or congenital hydrocephalus accounted for the rest. Criteria for shunting included massive ventriculomegaly, increasing ventriculomegaly with an abnormal rate of increase in head circumference, or clinical evidence of symptomatic hydrocephalus (lethargy, bradycardia, and tense fontanelle), often times with clinical improvement following ventricular tapping. RIs were TABLE 2 Resistive Indices (RI) in Patients with Ventriculomegaly S78

3 obtained for 628 vessels and the values of the anterior and middle cerebral arteries and the internal carotid arteries bilaterally were averaged. As shown in Table 2, those patients requiring shunts had an RI of 84 + The RI fell to 72 ± 11% after 13% Prior to shunting. shunting, with the difference being statistically significant (P <.001). Three patients who never required shunts had RIs of 74, 71, and 66%, all within the normal range. In this series of patients, the RI correlated with the ultimate need for ventriculoperitoneal shunting. Figure 1 shows correlation of ventricular size and RI in sequential studies of a representative hydrocephalic patient. The most common reason for a lack of correlation was in the patients with myelomeningocele, having ventricular decompression by leaking spinal lesions. In those patients having simultaneous repair of myelomeningocele and placement of a ventriculoperitoneal shunt, sometimes slightly higher RIs were found after shunting than before, but the values after shunting were invariably normal. Figure 1 A Figure 1 B FIGURE 1 Figure 1 C Figure 1 D A. Real-time ultrasonogram of a patient with hydrocephalus shows marked ventriculomegaly. B. Pulsed Doppler study of the right internal carotid artery shows a high Resistive Index of 86%. C. A postoperative real-time ultrasonogram shows collapse of the right lateral ventricle and the presence of the shunt tube in the frontal horn. D. A postoperative pulsed Doppler study of the right internal carotid artery after shunting shows a Resistive Index of 67%. S79

4 Bell et al9 showed that ventriculomegaly in the newborn with myelodysplasia should be evaluated by means other than palpation of the anterior fontanelle and measurement of head circumference. They suggested measuring a lateral ventricular ratio, obtained from real-time ultrasonograms, to predict those children likely to require shunts. Studies of RI add still another noninvasive means of predicting the need for shunts in myelodysplastic patients with ventriculomegaly. In patients having ventriculomegaly associated with intraventricular hemorrhages, treatment by ventricular or lumbar drainage is usually done acutely and prior to consideration of shunting. The real-time ultrasonographic measurement of the ventricular size, as well as the pulsed Doppler measurements of RI, may be utilized in planning the frequency of the drainage procedures and assessing their effectiveness during the course of the evolving encephalomalacia and possible hydrocephalus. Previously, sequential evaluations of patients with ventriculomegaly from a variety of causes were necessary to show increasing ventricular enlargement but, concomitantly, progressive insult to the brain occurred. The high correlation of an elevated RI with the need for ventriculoperitoneal shunting8 may allow the decision for shunting to be made earlier, presumably with benefit to the patient. Shunt Malfunctions At Arkansas Children s Hospital, all neurosurgical patients having ventriculoperitoneal shunts within of life routinely have a real-time the first year ultrasound evaluation of ventricular size and transfontanelle assessment of RI after placement of the baseline studies have shunt. These postoperative been used to assess the adequacy of the shunting procedures in these infants. The average RI after shunting in our initial series of 46 shunted patients was 71 ± 12%. With the expectation that RI should decrease with age, any increase in RI must be con- in terms of shunt malfunction. In sidered significant two instances, patients having only ipsilateral ventricular collapse following placement of one ventriculoperitoneal shunt had isolated ventricles requiring placement of bilateral shunts. One of these patients had no decrease in the RI after the first operation, and the other (Figure 2) had an increase in RI associated with continued increase in head circumference. As an had no increase in RI exception, another patient despite the fact that there were obvious signs of shunt malfunction and continued ventriculomegaly on real-time imaging. The shunt assembly would not refill on pumping, and fluid had dissected along the entire tract of the shunt. It was thought that the RIs were normal because the ventricular system was being decompressed by extravasation of cerebro- FIGURE 2 Figure 2A Figure 2B A. Real-time ultrasonogram in a coronal view of a shunted patient with hydrocephalus shows collapse of the right lateral ventricle and dilatation of the left lateral ventricle consistent with a trapped ventricle. B. Pulsed Doppler study of the left internal carotid artery of the patient with the trapped left lateral ventricle shows a Resistive Index of 79%. After the second shunt was placed, the Resistive Index decreased to normal. S80

5 spinal fluid along the shunt tract. In all of the other instances of neonatal shunt malfunctions, a clear with the increase in RI occurred when compared values computed immediately after shunting. In older children, the transcranial pulsed Doppler studies were done through the squamous portion of the temporal bone, using the Transpect unit. As noted previously, in a series of 27 normal patients, aged 18 months to 16 years, the RI was 50 ± 15%. In another study, 53 patients with ventriculoperitoneal shunts who were seen for routine clinic follow-up were judged clinically, and in some instances by to have nor- RI in the group was 50 ± 22%. The wide variation took into account one patient who inexplicably had an RI of 72%. Ninety percent of these patients had RIs between 40 and 59%. These values, therefore, are computed tomographic (CT) scanning, mally functioning shunts. The average comparable to our normal control values. Twentyfour additional patients between the ages of 15 months and 16 years were evaluated by transcranial with other studies demons- Doppler in conjunction trating shunt malfunction. Clinical findings consisted of headache, vomiting, lethargy, seizures, and even coma. The accessory findings included shunt disconnections on the shunt series, elevated pressure by shunt tap, lumbar puncture, or direct cannulation of the ventricles, as well as an increase in ventricular size by CT scanning. In 20 of the 24 patients, RIs could be obtained prior to and following shunt revision. In four instances, we were unable to obtain because of excessive thickness of the RI, presumably the calvarium. The average RI of the 20 patients who had shunt malfunctions was 62%, with a range of 50 to 86%. The average RI just after shunt revision was 54%, with a range of 42 to 63%. Table 3 summarizes these data. Essentially identical values for RI were found in TABLE 3 Summary of Resistive Index (RI) and Shunt Malfunction Study normal patients, patients with functioning shunts, and patients having successful shunt revisions following proven malfunctions. Moreover, a significant increase in RI was found at the time the diagnosis of shunt malfunction was made. The wide range in values makes it difficult to establish an absolute number for an RI indicating shunt malfunction. On of the baseline RI after the other hand, knowledge shunting for each individual patient does give a reliable method for following that patient and assessing the likelihood of shunt malfunctions in the future. An example of the reliability of RI in indicating shunt malfunction is shown by the case of a 16- year-old girl with spina bifida who had a ventriculoperitoneal shunt and who developed headache and lethargy after an operative procedure on the urinary tract. The CT scan showed increased ventricular size, and the RI was 62%. At operation she had obstruc- After the shunt was tion in the distal shunt segment. changed, the RI fell to 39%. However, on the first postoperative day, she remained lethargic and still complained of headache; another CT scan showed malposition of the ventricular limb of the new shunt and continued ventricular dilatation. RI was back up to 52%. Another revision, this time of the ventricular limb, was associated with an immediate decrease of the RI to 32%. Five days later, when the patient was discharged, asymptomatic, the RI was 36%. Six months later, she returned to the emergency room to coma. The with headaches and rapid progression RI was markedly elevated at 86%. Following a third shunt revision, the RI dropped to 43%. In this particular patient, the degree of elevation of RI even correlated with the severity of clinical findings. Thus, transcranial Doppler evaluation of RI in older children with shunt-dependent hydrocephalus is most useful for comparing values from time to time in individual patients. In this group, however, some patients may be difficult to evaluate because of increased calvarial thickness, a common occurrence in shunt-dependent children. Subdural Collections Frequently a distinction must be made between those patients having symptomatic extra-axial fluid collections and those having encephalomalacia with large subarachnoid spaces. Certainly symptoms of increased intracranial pressure will delineate those patients who need drainage of extra-axial masses, but in some cases, it is necessary to closely monitor children with neurologic examinations, measurements of head circumference, and various imaging S81

6 techniques. Transfontanelle real-time ultrasound studies, CT scans, and magnetic resonance images (MRI) have all been helpful in delineating those children needing drainage of the subdural space. Assessment of the content of the extra-axial collections is also helpful and can be determined not only by analyzing the fluid by tap, but also by measuring its density and physical characteristics by imaging techniques. We also examined the usefulness of transcranial Doppler in evaluating some of these infants. In children having a dilated subarachnoid space as a result of an earlier brain insult, the RIs are usually normal. On the other hand, patients with chronic subdural hematomas have an elevated RI. Initial treatment of these infants consisted of transcoronal subdural taps; with each tap the intracranial pressure was measured with a water manometer and RIs were obtained immediately prior to each tap and repeated after the drainage procedure. RIs fell to normal after each tap and were consistently elevated before the tap in the range of 84%. RIs after the tap averaged 72%, well within the normal range. The RIs before the tap correlated with the direct measurement of the subdural pressure of 28 to 33 cm H20 in one patient and 18 to 33 cm H20 in another. Both of these patients with subdural effusions ultimately required subdural peritoneal shunting, following which the RIs remained normal. Transcranial Doppler studies indicated raised intracranial pressure, the need for taps, and their effectiveness in these patients. The use of repeated CT scanning was decreased as the treatment program could be monitored by ultrasound studies. Following definitive treatment with subdural peritoneal shunting, shunt function could be followed with transcranial Doppler studies even after closure of the fontanelles. Animal Studies In our canine experiments,~ the animals were anesthetized, intubated, and ventilated spontaneously. Recordings of arterial pressure were made from a catheter in the femoral artery. Intracranial pressure was measured with a Camino fiberoptic system (Camino Laboratories, San Diego, CA) calibrated with a water manometer. Intracranial pressure was varied, using a reservoir of saline solution connected to a catheter in the cisterna magna and raised or lowered to suitable heights. RIs were obtained through a craniectomy window, using the Acuson 128 system. There was a clear correlation between intracranial pressure and RI when intracranial pressure was varied over a range of 18 to 88 mm Hg. An even better correlation was obtained when perfusion pressure was plotted against RI. Even when perfusion pressures were varied within a relatively normal range, there was a correlation with RI, but when perfusion pressure fell to pathologic levels, there was a dramatic increase in RI. In plotting data from 72 measurements on 5 animals, we found a negative correlation coefficient of.77, but the slope of each curve varied from animal to animal. The results of these studies indicated two important facts. First, in a controlled situation, transcranial Doppler measurements of RI predictably reflected intracranial pressure when intracranial pressure was abnormally elevated or when cerebral perfusion pressure was critically compromised. Second, the studies showed that individual variations from animal to animal made it difficult to determine absolute values of intracranial pressure from the RI. in our correlations of Such findings were amplified intracranial pressure in head-injured patients. Craniocerebral Injuries Aaslid and Lindegaardl showed a relationship between the flow velocity of the middle cerebral artery and cerebral perfusion pressure in a group of 10 patients undergoing ventricular infusion tests, using a Fourier analysis of velocity waveforms of the middle cerebral artery and the arterial blood pressure. The possibility of assessing cerebral perfusion pressure or intracranial pressure by noninvasive transcranial Doppler monitoring has been an extremely attractive projected use for Doppler sonography. In our animal models, we found a correlation of RI with intracranial pressure and cerebral perfusion pressure over a wide range of intracranial pressures. We also evaluations of RI in a performed transcranial Doppler series of head-injured patients who were routinely monitored with Camino intracranial pressure monitors and continuous arterial pressure measurements. Because of the unknown effects of the chronic application of high-frequency ultrasound, we utilized intermittent evaluations of the RI of the middle cerebral artery utilizing the 2-MHz transcranial Doppler probe fixed to a special headband. In some instances where a craniectomy had been done as part of the standard neurosurgical treatment of the patient, utilization of the craniectomy window for evaluation of RI using 5-MHz Acuson system has been done, both to correlate the values obtained with the two systems and to correlate RIs with intracranial pressure. Table 4 shows data obtained with both the Transpect and Acuson units from a patient who sustained a fatal head injury. There was no difference S82

7 TABLE 4 Eighteen-Year-Old T = Transpect; A = Acuson Trauma Victim in the data obtained with the two units and elevated RIs were present when intracranial pressure was elevated. Further, when cerebral perfusion pressure was essentially zero, the RI was elevated above 100% and the typical flow reversal in diastole was present. Data obtained from another patient, 7 months old, with a closed head injury indicated a trend relating cerebral perfusion pressure and RI over a range of relatively normal intracranial pressure readings. Because the RIs possibly reflected values in transition from neonatal to childhood values, and because the monitored intracranial pressure readings did not, change over a wide range, the RIs were not as helpful as the readings of intracranial pressure in management of the patient. In this study, thus far, we have identified a number of reliable guidelines. First, in the patient with a head injury, shown by CT scanning to have no intracranial mass lesion and preservation of the perimesencephalic cisternae associated with a transcranial Doppler RI value of 35 to 45%, we did not find elevation of intracranial pressure on direct measurement. At the same time, patients having evidence of severe brain swelling by CT scanning and extremely high measurements of intracranial pressure, the RI has also been extremely high, correlating with a compromised cerebral perfusion pressure. On the other hand, there has not been a clear relation- between RI and the absolute values for cerebral ship perfusion or intracranial pressure in patients whose intracranial pressure was in the middle range. For example, it is difficult to determine with any degree is be- of certainty if a patient s intracranial pressure tween 20 and 30 mm Hg, a range important to assess during treatment programs. Although additional studies and further refinements in techniques may offer this information, a number of variables must be considered in further developing transcranial Doppler systems for monitoring head-injured patients. Many patients are maximally dehydrated compliance, and many are hyperventilated with altered brain to a maximally vasoconstricted status. An effect of arterial carbon dioxide pressure (PC02) on cerebral artery waveforms on Doppler ultrasound studies was demonstrated in pediatric patients by Archer et al. 11 Further studies taking into account these and other physiologic alterations of head-injured patients will be necessary for the development of pulsed Doppler studies as a noninvasive means of accurately measuring intracranial pressure. Hassler et al 12 also demonstrated that transcranial Doppler ultrasonography may be used to assess the degree of intracranial hypertension, providing in some instances a practicable, noninvasive monitor of therapeutic measures. Brain Death Establishing brain death is becoming more problematic in an era when transplantation of human organs is now prevalent. Beside the neurologic examination, the use of electroencephalography (EEG), brain stem evoked potentials, and other radiographic criteria such as angiography and nuclear blood flow studies, the use of transcranial Doppler may add still another noninvasive method of determining cerebral death. As early as 1974, Yoneda et al 13 demonstrated to-andfro movement and external escape of carotid arterial blood in brain death individuals using a Doppler ultrasonic study. Since then, a number of studies have augmented this information with a correlation of an extremely high RI and a reversal of diastolic flow being characteristic of essentially absent effective cerebral circulation. In infants, however, the correlation of brain death may be not as accurate as it is with adult patients. In our study of infants suspected of brain death,14 both positive and negative correlations were seen. One child, neurologically devastated by an hypoxic brain injury, had no evidence of neurologic function on detailed examinations, had no electrical activity demonstrable on EEG, but had relatively normal values for blood flow velocity on transfontanelle Doppler studies. The child promptly died when the respirator was discontinued. Two other infants with neurologic examinations consistent with brain death had transcranial Doppler studies RIs with reversal of dias- that showed extremely high tolic flow, characteristic of the brain death pattern. One of those children recovered with reasonable function and the other survived but was neurologic neurologically devastated. Thus, in the infant, caution must be exercised in utilizing transcranial Doppler as a documentation of brain death. Vascular Lesions Cardiac and more proximal vascular lesions such as patent ductus arteriosus are known to affect RI.3 In S83

8 FIGURE 3 Figure 3A Figure 3B of the A. Doppler study of the right anterior cerebral artery of a patient with an aneurysm vein of Galen shows a Resistive Index of 36%. B. Pulsed Doppler study of the right middle cerebral artery of the same patient shows a Resistive Index of 73%. the absence of such lesions, Doppler studies of the cerebral circulation provide useful information about vascular anomalies, especially the high-flow arteriovenous malformations. Real-time imaging may effectively demonstrate FIGURE 4 Right carotid angiogram (lateral projection) shows major contributions of blood flow through the fistula in the vein of Galen by the anterior and posterior cerebral arteries. little contribution to flow is evident from the middle Very cerebral artery complex, consistent with the pulsed Doppler studies noted in Figure 3. an aneurysm of the vein of Galen. Pulsed Doppler studies of the major feeding vessels can give additional information regarding flow through the fistula. For example, a newborn with high output cardiac failure due to an aneurysm in the vein of Galen had RIs of 24% and 36% in the anterior cerebral arteries closure of the arteriovenous fistula. prior to surgical The middle cerebral arteries, on the other hand, had values of 73% and 77% (Figure 3). Cerebral angiography disclosed that the primary flow through the fistula was from the anterior and posterior cerebral arteries with very little contribution by the middle cerebral vessels, correlating well with the Doppler evaluations (Figure 4). Following ligation of the lesion, the RIs returned to normal values. Sequential measurements of RI in feeding vessels during transtorcular occlusive techniques may also be useful. In another instance, a lesion extending from the posterior part of the third ventricle into the upper part of the fourth ventricle through the aqueduct was evaluated by transfontanelle Doppler studies. A relatively high-flow velocity through the lesion was consistent with the diagnosis of choroid plexus papilloma (Figure 5). Another 4-month-old child presented with a massive cerebellar hemorrhage; pathologic examination of tissue removed at the time of evacuation of the cerebellar hematoma showed a telangiectatic vascular malformation. Pulsed Doppler studies obtained by scanning the entire posterior fossa showed no flow velocities suggestive of a residual vascular lesion. As yet we have not had the opportunity to S84

9 Figure 5A Nichols IS were able to detect intracranial vasculopathies associated with sickle-cell disease. We also obtained segmental increases in flow velocities in the middle cerebral artery in a patient with sicklecell disease, who clinically had occlusive vascular complications. The value of pulsed Doppler studies used in conjunction with real-time cranial ultrasonography can be appreciated in the management of an infant with a cerebellar hemorrhage due to deficiency of factor VIII. Although some ventriculomegaly was noted, RI never increased above 68% (Figure 6). Careful follow-up and repeated examinations disclosed spontaneous resolution of the hematoma and ventriculomegaly as well as satisfactory recovery of the patient. The normal RIs significantly affected the decision to withhold surgical removal of the hematoma. Finally, the changes in cerebral blood flow associated with anemias in general can be detected by transcranial Doppler evaluations. FIGURE 5 Figure 5B A. Real-time ultrasonogram in a coronal view of a patient with a choroid plexus papilloma shows the lesion extending from the posterior part of the third ventricle through the aqueduct and into the fourth ventricle. There is associated hydrocephalus. B. Using the same projection, a pulsed Doppler study showed high blood flow velocities and waveforms consistent with the vascular lesion, a choroid plexus papilloma. study pediatric patients with moyamoya disease by transcranial Doppler ultrasonography. Hematologic Abnormalities Among the conditions producing pediatric vascular disease are the hemoglobinopathies. Adams and Other Applications Sekhar et al 16 demonstrated the value of transcranial Doppler examinations in the diagnosis of cerebral vasospasm after subarachnoid hemorrhage. Although spontaneous subarachnoid hemorrhage is clearly a less frequent occurrence in children, the value of this monitoring modality may be extended to the pediatric age group. Earlier studies comparing the RI vessel to vessel have shown no significant difference in the RI obtained in the internal carotid, middle cerebral, or anterior cerebral arteries. Further, there is rarely any significant difference from side to side. These findings were borne out in correlative studies of more than 700 vessels previously studied at our institution. We have, however, found several instances of focal be seen in distal occlusive changes in RI as might cerebral vascular disease in adults. For example, one patient with a subdural empyema and preferential lobar edema, had selective increase in the RI of the middle cerebral artery on the side of the subdural empyema. In another instance, a patient with cranial cerebral trauma had focal contusion and herniation of frontal lobe through a craniectomy defect. In that instance also, there was selective increase in the RI of the middle cerebral artery supplying that region of the brain. These preliminary findings indicate that segmental or lobar pathologic processes within the brain may alter blood flow locally at a time when intracranial pressure reflects a generalized assess- S85

10 Doppler ultrasonography provide the basis for future research and begin to expand the exciting possibilities of this modality for diagnosing and monitoring pediatric patients with a variety of nervous system diseases. Figure 6A Figure 6B FIGURE 6 A. A real-time ultrasonogram in the sagittal view shows hematoma in the third ventricle and posterior fossa in a patient with factor VIII deficiency. B. An assessment of the Resistive Index of the right anterior cerebral artery in the same patient shows a value of 67%, a normal value. ment of the intracranial contents. Thus, the identification of focal disease within the brain, other than as a future use of vascular disease, can be anticipated transcranial Doppler studies. These and other potential uses for transcranial References 1. Pourcelot L: Applications cliniques de examen Doppler transcutane, in Peronneau P (ed): Velocimetrie ultrasonore Doppler. Paris, Institut National de la Santé et de la Recherche Médicale, 1975, p Bada HS, Jajjar W, Chua C, Sumner DS: Noninvasive diagnosis of neonatal asphyxia and intraventricular hemorrhage by Doppler ultrasound. J Pediatr 1975;95: Volpe JJ, Perlman JM, Hill A, McMenamin JB: Cerebral blood flow velocity in the human newborn: the value and its determination. Pediatrics 1982;70: Greisen G, Johansen K, Ellison PH, et al: Cerebral blood flow in the newborn infant: comparison of Doppler ultrasound and 133 xenon clearance. J J Pediatr 1984;104: Seibert JJ, McCowan TC, Chadduck WM, et al: Duplex pulsed Doppler US versus intracranial pressure in the neonate: clinical and experimental studies. Radiology 1989;171: Arnolds BJ, von Reutern G-M. Transcranial Doppler sonography. Examination of technique and normal reference values. Ultrasound Med Biol 1986;12: Harders A, Gilsbach J. Transcranial Doppler sonography and its application in extracranial-intracranial bypass surgery. Neurol Res 1985;7: Chadduck WM, Seibert JJ, Adametz JR: Cranial Doppler ultrasonography. Correlates with criteria for ventriculoperitoneal shunting. Surg Neurol 1989;31: Bell WO, Sumner TE, Volberg FM: The significance of ventriculomegaly in the newborn with myelodysplasia. Childs Nerv Syst 1987;3: Aaslid R, Lindegaard KF: Cerebral hemodynamics, in Aaslid R (ed): Transcranial Doppler Sonography. New York, Springer, 1986, pp Archer LNJ, Evans DH, Paton JY, Levene MI: Controlled hypercapnia and neonatal cerebral artery Doppler ultrasound wave forms. Pediatr Res 1986;20: Hassler W, Steinmetz H, Gawlowski J: Transcranial Doppler ultrasonography in raised intracranial pressure and in intracranial circulatory arrest. J Neurosurg 1988;68: Yoneda YS, Nishimoto A, Nukada T: To and fro movement and external escape of carotid arterial blood in brain death cases. A Doppler ultrasonic study. Stroke 1974;5: Glasier CM, Seibert JJ, Chadduck WM, et al: Doppler ultrasound findings in infants suspected of cerebral death. Radiology 1989;172: Adams RJ, Nichols FT, Aaslid R, et al: Detection of intracranial vasculopathy in sickle cell anemia with transcranial Doppler and magnetic resonance imaging. Stroke 1988;19: Sekhar LN, Wechsler LR, Yonas H, et al: Value of Transcranial Doppler examination in the diagnosis of cerebral vasospasm after subarachnoid hemorrhage. Neurosurgery 1988;22: S86