Duplex-scanning of the deep venous drainage in the evaluation of blood flow velocity of the cerebral vascular system in infants

CSF and venous blood flow from childhood to adulthood studied by real-time phase-contrast MRI

PURPOSE

In vivo measurements of CSF and venous flow using real-time phase-contrast (RT-PC) MRI facilitate new insights into the dynamics and physiology of both fluid systems. In clinical practice, however, use of RT-PC MRI is still limited. Because many forms of hydrocephalus manifest in infancy and childhood, it is a prerequisite to investigate normal flow parameters during this period to assess pathologies of CSF circulation. This study aims to establish reference values of CSF and venous flow in healthy subjects using RT-PC MRI and to determine their age dependency.

METHODS

RT-PC MRI was performed in 44 healthy volunteers (20 females, age 5-40 years). CSF flow was quantified at the aqueduct (Aqd), cervical (C3) and lumbar (L3) spinal levels. Venous flow measurements comprised epidural veins, internal jugular veins and inferior vena cava. Parameters analyzed were peak velocity, net flow, pulsatility, and area of region of interest (ROI).

STATISTICAL TESTS

linear regression, student's t-test and analysis of variance (ANOVA).

RESULTS

In adults volunteers, no significant changes in flow parameters were observed. In contrast, pediatric subjects exhibited a significant age-dependent decrease of CSF net flow and pulsatility in Aqd, C3 and L3. Several venous flow parameters decreased significantly over age at C3 and changed more variably at L3.

CONCLUSION

Flow parameters varies depending on anatomical location and age. We established changes of brain and spinal fluid dynamics over an age range from 5-40 years. The application of RT-PC MRI in clinical care may improve our understanding of CSF flow pathology in individual patients.

Cerebral microcirculatory pulse wave propagation and pulse wave amplitude mapping in retrospectively gated MRI

To analyze cerebral arteriovenous pulse propagation and to generate phase-resolved pulse amplitude maps from a fast gradient-echo sequence offering flow-related enhancement (FREE). Brain MRI was performed using a balanced steady-state free precession sequence at 3T followed by retrospective k-space gating. The time interval of the pulse wave between anterior-, middle- and posterior cerebral artery territories and the superior sagittal sinus were calculated and compared between and older and younger groups within 24 healthy volunteers. Pulse amplitude maps were generated and compared to pseudo-Continuous Arterial Spin Labeling (pCASL) MRI maps by voxel-wise Pearson correlation, Sørensen-Dice maps and in regards to signal contrast. The arteriovenous delays between all vascular territories and the superior sagittal sinus were significantly shorter in the older age group (11 individuals, ≥ 31 years) ranging between 169 ± 112 and 246 ± 299 ms versus 286 ± 244 to 419 ± 299 ms in the younger age group (13 individuals) (P ≤ 0.04). The voxel-wise pulse wave amplitude values and perfusion-weighted pCASL values correlated significantly (Pearson-r = 0.33, P < 0.01). Mean Dice overlaps of high (gray) and low (white matter) regions were 73 ± 3% and 59 ± 5%. No differences in image contrast were seen in the whole brain and the white matter, but significantly higher mean contrast of 0.73 ± 0.23% in cortical gray matter in FREE-MRI compared to 0.52 ± 0.12% in pCASL-MRI (P = 0.01). The dynamic information of flow-related enhancement allows analysis of the cerebral pulse wave propagation potentially providing information about the (micro)circulation on a regional level. However, the pulse wave amplitude reveals weaknesses in comparison to true perfusion-weighting and could rather be used to calculate a pulsatility index.

Potential of three-dimensional ultrasound in neonatal and paediatric neurosonography

The aim of this study was to describe the potential of three-dimensional ultrasound (3D US) in paediatric and neonatal neurosonography. The potential applications are illustrated based on our experience in 150 patients using three different 3D US techniques at two different sites. Various disease entities throughout the paediatric age have been evaluated. The potential of 3D US, including 3D US of the cerebral vessels based on colour Doppler data, is discussed based on comparison with conventional 2D US or other imaging (as available), and with regard to the literature. In our experience, 3D US is feasible in neonatal and paediatric neurosonography. It reduces imaging time, improves demonstration of complex anatomy and vasculature, and allows for evaluation of anatomy/pathology in any plane. The 3D US furthermore improves volume assessment (e.g. in hydrocephalus), and comparison with CT, MRI and during follow-up, with a potentially improved standardisation and documentation. The 3D US additionally offers an ideal modality for training and education, as the brain and the neonatal spine can be virtually rescanned at the workstation. Yet, limitations such as areas inaccessible to 2D US, limited resolution and motion artefacts have to be acknowledged. Three-dimensional US has the potential to become a valuable additional imaging tool in paediatric neurosonography.

Neonatal cerebral Doppler: arterial and venous flow velocity measurements using color and pulsed Doppler system

OBJECTIVE

To contribute to the establishment of reference values of blood flow velocity assessed by cerebral Doppler in healthy infants related to gestational age and birth weight during the first week of life.

METHODS

Five arteries and three veins were evaluated respectively in 120 (74 premature) newborns and in 100 (70 preterm) infants. In a quarter of the latter three recordings at 5-minute intervals were made to assess reproducibility. The relation between flow measurements and gestational age was assessed by linear regression, means by analysis of variance (or Kruskall-Wallis test) and paired samples by Student's t test.

RESULTS

There was a significant increase of arterial velocities with increasing gestational age and birth weight, but not for venous velocities. Significant higher values were found in the internal carotid artery followed by the medium cerebral artery. The venous velocities were highly reproducible and the main patterns observed were bandlike and sinusoid type.

CONCLUSION

The knowledge of normal cerebrovascular physiology is essential to understand the pathogenesis of neonatal brain damage and can help pediatricians in an accurate interpretation of the flow profile in neurological pathology.

Neonatal focal temporal lobe or atrial wall haemorrhagic infarction

AIMS

To describe two variants of infarction within the temporal lobe, associated with local matrix bleeding and mild to moderate intraventricular haemorrhage.

METHODS

The files of 10 neonates, extracted from a sonographic study of 560 very low birthweight infants conducted between 1993 and 1997, were retrospectively examined.

RESULTS

Seven lesions were located in the middle to posterior area of the temporal lobe, three others faced the atrium. All except two of those with a temporal site were VLBW infants with hyaline membrane disease. Except for one fatal case, intraventricular bleeding was mild to moderate. Computed tomograms or magnetic resonance imaging were used to illustrate the haemorrhagic nature of three lesions. Survivors of this so far undescribed entity who were followed up for more than 18 months did not have a uniform type of cerebral palsy but some scored in the low normal range on the Bayley Mental Development Index. One girl developed temporal lobe epilepsy.

CONCLUSIONS

This pattern of injury seems to be one of venous infarction associated with temporal or para-atrial matrix haemorrhage. The temporal site fits the picture of venous infarction within the area drained by the inferior ventricular vein. A less constant lateral atrial vein, either draining into the basal or internal cerebral vein, is probably involved in the para-atrial lesion. Sonography may be the only practical tool currently available for detection in life.

A device for applying postsurgical pressure to the lateral face

OBJECTIVE

The purpose of this study was to improve the effect of pressure applied on the lateral face after operations, particularly after parotid surgery for prevention of complications, especially the formation of salivary fistula.

STUDY DESIGN

A pressure instrument (face pad) was designed to fit all types of facial morphology. The blood flow velocity of the superficial temporal artery was measured by means of a Doppler detector in 30 healthy volunteers under 2 different conditions, with and without the face pad. Values for 2 parameters, peak velocity and average peak velocity, were determined for the purpose of selecting an appropriate pressure. Each of 47 patients who had undergone regional parotidectomy received pressure with the face pad for 3 days; the results were compared with those in a control group of 44 patients who had undergone similar operations but received traditional packing dressings.

RESULTS

The peak velocities of the superficial temporal artery with and without the face pad were not significantly different (t = 1.541, P = .132) when a pressure value of 4 to 5 N was applied. However, the average peak velocity of the superficial temporal artery increased significantly (t = 3.678, P = .001) with the face pad. The 47 patients with the face pad had no postoperative parotid fistula; in contrast, salivary fistula developed in 5 of the 44 control cases, for an overall fistula rate of 11.36%. A significant difference existed between the 2 groups (P = .023).

CONCLUSIONS

The face pad worked quantitatively and was stable and comfortable. A pressure of 4 to 5 N on the lateral face did not influence the blood flow of the superficial temporal artery. The higher peak velocity was correlated with regional stenosis of the temporal vein caused by pressure. Evidently, the face pad can reduce postoperative complications after parotidectomy; moreover, it makes pressure dressing easy and shortens the in-hospital days of the patient as well.

Assessment of normal flow velocity in basal cerebral veins. A transcranial doppler ultrasound study

BACKGROUND AND PURPOSE

Transcranial Doppler ultrasound has not yet been applied systematically to the analysis of the venous system and cerebrovenous disorders. Assessment of the intracranial venous system, however, would contribute to the understanding of cerebral hemodynamics and thus allow new possibilities for clinical application of the Doppler technique. Therefore, we demonstrated the validity of the transcranial Doppler technique in analyzing the basal cerebral veins.

METHODS

Venous transcranial Doppler ultrasound was performed with a range-gated 2-MHz transducer in 60 healthy volunteers in patients without central nervous disorders ranging in age from 10 to 71 years (mean +/- SD, 41.9 +/- 15 years).

RESULTS

A venous signal away from the probe and adjacent to the posterior cerebral artery, considered to correspond to the basal vein of Rosenthal, was found in all subjects on at least one side. Mean blood flow velocity ranged from 4 to 17 cm/s (mean +/- SD, 10.1 +/- 2.3 cm/s). Analysis for age dependency revealed a trend of decreasing values with increasing age, exclusively caused by a significant reduction of velocity in men aged 40 years or older. No significant intraindividual side-to-side differences were found. A venous signal away from the probe and paralleling the middle cerebral artery, interpreted as corresponding to the deep middle cerebral vein, was found in 21.7% of the subjects with similar velocities.

CONCLUSIONS

We have shown that transcranial Doppler methods can also be used for evaluation of the basal cerebral veins in both sexes, in differing age groups, and without major difficulty. The cerebral basal veins could be identified on the basis of their anatomic relation to specific arteries.

Characterization of superior sagittal sinus blood flow velocity using color flow Doppler in neonates and infants

The objective of the investigation was to determine what effect intracranial pathology has on alterations of superior sagittal sinus blood flow, and to determine the role of color flow Doppler imaging of the superior sagittal sinus in the diagnosis of intracranial pathology in the neonate and infant. One hundred examinations were performed prospectively in 96 patients. The velocity was determined with an angle correction at 30-60 degrees and was obtained with and without gentle transducer compression. Superior sagittal sinus thrombosis was identified in two patients by the absence of flow. Multiple t-tests for independent measures showed no clinically significant differences between flow velocities with regard to intracranial hemorrhage, ventriculomegaly, extracorporeal membrane oxygenation therapy or prematurity. The authors conclude that color flow Doppler can accurately diagnose superior sagittal sinus thrombosis and may be used to screen high risk neonates such as those with thrombosis elsewhere or those treated with extracorporeal membrane oxygenation. No clinically significant associations were found between superior sagittal sinus flow velocity and any of the parameters evaluated in this study.

Colour-coded echographic flow imaging and spectral analysis of cerebrospinal fluid (CSF) in infants. Part II. CSF-dynamics

41 comprehensive colour Doppler studies (including spectral analysis) of the ventricular system were performed in 6 infants with CSF-flow (age range: 2 to 27 days). Two premature infants showed no evidence of disease related to the central nervous system (CNS). Overt intraventricular hemorrhage or CNS-infection were present in the other infants. All children were examined several times until CSF-flow was no longer visible. The entire ventricular system, including the fourth ventricular outlet, was investigated for the presence of CSF-flow signals. Dynamic CSF-flow studies consisted of scanning during typical infant activity (crying, sucking, leg movement) and with external manoeuvres (abdominal or fontanellar palpation). CSF-flow was found to be: 1. synchronous with respiration 2. induced by rising intraabdominal (retrograde CSF-pulse) and transfontanellar pressure (orthograde CSF-pulse) 3. predominantly within the cerebral aqueduct, but also found at the foramina of Monro, within the third and fourth ventricles and at the foramen of Magendie. CSF-flow was not detected at the foramina of Luschka or within the lateral ventricles, except adjacent to the foramina of Monro. Dynamic CSF-flow as observed in infants may have important clinical and scientific implications. Examples of this are activity-related ventricular "reflux" of bacteria, erythrocytes, drugs, radionuclides or contrast; the importance of CSF-flow pulses for the development or progression of hydrocephalus; flow dynamics at the fourth ventricular outlet foramina and the study of CSF-pulse wave velocity and regional compliance. These issues are discussed and the new diagnostic approach is compared with other methods of CSF-investigation.

Major pitfalls in Doppler investigations. Part II. Low flow velocities and colour Doppler applications

Many pitfalls result from the limited ability of Doppler instruments to record low flow velocities. These include a misleading resistance or pulsatility index due to diastolic cut-off and taking no signal to equal no flow assuming that no signal means no flow. Comparison of actual flow velocities as measured in an in-vitro system (range: 0.8 to 3.4 cm/s) with the lowest recordable spectral or colour signals in 3 Duplexscanners showed that reduced sensitivity to low flow velocities is not only dependent on the high pass ("wall") filter setting, Doppler frequency or angle of incidence, but also on factors such as vessel diameter, impairing the signal to noise ratio. Characteristic errors of colour flow mapping (misleading vascular anatomy, imitation of pathological findings, erroneous exclusion of flow) are due to partial volume effect, limited temporal and velocity resolution, changing angle of incidence, aliasing and failure to detect low flow velocities.

Major pitfalls in Doppler investigations with particular reference to the cerebral vascular system. Part I. Sources of error, resulting pitfalls and measures to prevent errors

Major pitfalls in Doppler investigations are presented based on 340 evaluated cerebral Doppler examinations in infants. Substantial pitfalls may result from: A. Physics of sound waves and Doppler instruments (errors due to high pass filter cut off, aliasing, rapid image update). B. Quality and adjustment of the Doppler instrument (errors due to low sensitivity, inappropriate adjustment of Doppler controls, inadequate wall filter). C. Examination technique (errors due to an unfavourable angle of incidence or due to transducer-induced pressure: decrease predominantly in diastolic flow velocity-increase in maximum flow velocity in the straight sinus). D. Hemodynamics (errors due to spatial or temporal variations of the flow profile, pulsatility, non-uniform distribution of cerebral blood flow/CBF). E. Cerebral vascular anatomy (errors due to an unfavourable probe position as related to the three-dimensional arrangement of vessels, inadequate separation of closely adjacent vessels). F. Interpretation (flow velocity or Resistance Index/RI is taken to equal CBF, RI is taken to equal peripheral vascular resistance, one artery is taken to represent the cerebral circulation). Pitfalls may be avoided by using adequate means (low wall filter adjustment, high Doppler frequency, critical assessment of velocity spectra) to reduce the likelihood of errors occurring.