Cerebral blood flow velocity changes after ventricular taps and ventriculoperitoneal shunting

A new ultrasound sign in the diagnosis of pediatric maxillary sinusitis

Background: Computed tomography scans (CT scan) and X-rays are used to diagnose paediatric maxillary sinusitis. This study aimed at exploring the diagnostic value of the conventional and colour Doppler ultrasounds and their specific findings in cases of paediatric sinusitis. Methods: A total of 60 children diagnosed with sinusitis were included in this study. The conventional and colour Doppler ultrasounds of the sinus were performed on each of them. The symptoms that suggested increased blood flow to the sinuses were interpreted as positive findings on the colour Doppler ultrasound and were named "Ghasemi signs" for the purpose of this study. Such symptoms included unilateral artery bumps on the front artery, reduction of arterial resistive index (RI) to less than 0.5, and diameter of 2 mm or above for maxillary arteries. Sensitivity, specificity, and positive and negative predictive values, and accuracy of the conventional and colour Doppler ultrasounds were also calculated. Results: Compared to CT scan, the conventional ultrasound showed sensitivity and specificity of 73.4% and 100%, respectively. Sensitivity and specificity for the colour Doppler ultrasound were 89.36% and 100%, respectively. The maxillary artery diameter in normal and affected maxillary sinuses were, respectively, 2.4 mm (2.1-2.6, 95% CI) and 1.7 mm (1.6-1.9, 95% CI), with p<0.001. The RI of the affected sinuses were 0.47 (0.45-0.49, 95% CI), and those of the normal sinuses were 0.58 (0.54-0.61, 95% CI), with p<0.001. Conclusion: The findings of this study revealed that the conventional ultrasound agrees with the CT scans in the diagnosis of paediatric maxillary sinusitis. This diagnostic modality becomes even more valuable when the colour Doppler is used, particularly when considering the specific symptoms (Ghasemi signs) suggested by this study.

New transcranial Doppler index in infants with hydrocephalus: transsystolic time in clinical practice

Raised intracranial pressure (ICP) in infants with hydrocephalus may cause (ir)reversible damage to the brain parenchyma but can be present without clinical signs and/or symptoms. Therefore, new, favorably noninvasive, detection methods are needed to distinguish between compensated hydrocephalus with normal intracranial pressure and slowly progressive hydrocephalus with increased intracranial pressure. Because early ischemic changes in the brain parenchyma are associated with increased intracranial pressure, transcranial Doppler (TCD) indices may be useful to detect increased intracranial pressure in infants with hydrocephalus. Twenty-four infants with hydrocephalus underwent noninvasive ICP measurement, magnetic resonance imaging and TCD before and after cerebrospinal fluid (CSF) diversion. The TCD indices were paired to the anterior fontanelle pressure findings and compared for correlation. After CSF diversion, ICP decreased significantly from 21.8 cm H(2)O to 7.7 cm H(2)O (p<0.005). The transsystolic time (TST) as measured with TCD increased significantly from 176 to 221 ms (p<0.005), whereas the pulsatility index (PI) decreased significantly from 1.3 to 1.0 (p<0.05). The resistance index (RI) decreased significantly from 0.73 to 0.63 (p<0.05). Mean bloodflow velocity through the middle cerebral artery increased significantly from 55.5 to 75.8 cm/s (p<0.005). TST has a strong correlation with the ICP (p<0.005). Measuring TST with TCD can be helpful in the decision-making process about whether to perform CSF diversion in infants with hydrocephalus. Because TST is related solely to the relative changes in the flow velocity caused by intracranial physical properties, it has a closer relation to ICP than the PI and the RI.

Cerebral blood oxygenation after cerebrospinal fluid removal in hydrocephalus measured by near infrared spectroscopy

BACKGROUND

The cerebrospinal fluid (CSF) tap test has been used for the diagnosis of chronic hydrocephalus to identify the candidates for surgical CSF shunting. However, a high rate of false negative results limits it utility. The purpose of this study is to investigate whether the concomitant monitoring of cerebral hemodynamics by near infrared spectroscopy (NIRS) can improve the diagnostic accuracy of the tap test.

METHODS

Thirteen patients with dilated ventricular system were candidates for this study. We assessed for the patterns of cerebral blood oxygenation (CBO) change in hydrocephalus to determine whether CBO change after CSF removal is useful for selecting shunt candidates.

RESULTS

Patients who showed clinical improvement following CSF shunting had a characteristic CBO change with increases in the concentration of oxyhemoglobin (Oxy-Hb), and patients without improvement during continuous CSF drainage test showed no increase in Oxy-Hb.

CONCLUSION

The current data suggests that CBF increases after CSF removal in hydrocephalus. Although the patients utilized in the present study had secondary chronic hydrocephalus, we speculate that these data could be applied to patients with idiopathic chronic hydrocephalus. Further investigation would be of benefit.

Transcranial Doppler sonography in the early stage of critical enteroviral infection

OBJECTIVE

There is a high fatality rate in enteroviral infection with central nervous system involvement. Our aim was to investigate the change in intracranial blood flow to disclose the characteristic findings in the early stage of critical enteroviral infection.

METHODS

We examined 27 patients in critical condition with enteroviral infection in our pediatric intensive care unit. We performed transcranial Doppler sonography within 12 hours of admission to the unit. The data were compared with those of a group of 11 patients with nonenteroviral encephalitis.

RESULTS

The peak systolic, end-diastolic, and mean velocities of the critical enteroviral infection group were significantly higher than those of the control group (P < .05). Gosling pulsatility index and Pourcelot resistive index values for the right and left middle cerebral arteries (pulsatility index, [mean +/- SD], 0.68 +/- 0.22 and 0.77 +/- 0.19, respectively; resistive index, 0.48 +/- 0.01 and 0.52 +/- 0.01) in patients with critical enteroviral infection were significantly lower than those of patients with nonenteroviral encephalitis (pulsatility index, 1.10 +/- 0.30 and 0.98 +/- 0.22; resistive index, 0.62 +/- 0.01 and 0.60 +/- 0.01; P < .05).

CONCLUSIONS

Low pulsatility index and resistive index values for cerebral blood flow were observed in the early stage of critical enteroviral infection. This characteristic finding of cerebral blood flow might be associated with the increased sympathetic discharge induced by a brain stem-involved systemic inflammatory response and dysfunction of autoregulation caused by the infection or other disorders of autoregulation that might cause severe or fatal complications.

Neuron tolerance during hydrocephalus

Whether or not neuron death plays a major role in pathophysiology during hydrocephalus is not well known. The goals of this study were to determine if neural degeneration occurred during hydrocephalus, and to determine if neuron tolerance developed during this pathophysiologic procedure.Neural damage as visualized by a sensitive staining technique, silver impregnation, was observed in three experimental groups: (1) adult hydrocephalic rats induced by kaolin injection into the cisterna magna, (2) adult rats with chronic hydrocephalus for 10 weeks subjected to acute forebrain ischemia induced by four-vessel occlusion, and (3) adult rats without hydrocephalus subjected to acute forebrain ischemia. The magnitude of hydrocephalus was also evaluated during this time. In mild or moderate hydrocephalus, little cell death was found. In severe hydrocephalus, axon and neuropil degeneration was extensively distributed, but cell death was still rarely observed. Although some neuron degeneration was found after acute forebrain ischemia in hydrocephalic rats, the extensive cell death in cortical layers III and V, and in hippocampal areas CA1 and CA4 that is commonly observed in the ischemic brain without hydrocephalus, was not seen. This study suggests that neuron death was not a major pathological change in the brain during hydrocephalus, with cerebral ventricles being enlarged during the development of hydrocephalus. Less neuron death in hydrocephalic rats after acute forebrain ischemia suggests that neuronal tolerance to ischemia occurs during hydrocephalus.

Sonographic assessment of posthemorrhagic ventricular dilatation

Sonography plays a key role in the initial evaluation and monitoring of ventricular dilatation in the newborn. The use of supplemental imaging approaches by the mastoid fontanelle and foramen magnum can help identify the cause and location of obstruction. Duplex Doppler of intracranial vessels during anterior fontanelle compression is a useful indicator of altered cranial compliance in these infants. Additional views of the thoracolumbar spine can help identify which infants will likely benefit from lumbar puncture for therapy of progressive ventricular dilatation.

[Transfontanellar Doppler ultrasound measurement of cerebral blood velocity before and after surgical treatment of hydrocephalus]

Twenty-seven children with hydrocephalus of different etiologies diagnosed by clinical examination, neurosonography and computerized brain tomography were submitted to transfontanellar US-Doppler evaluation for measurement of blood flow velocity and for the calculation of resistance index (RI) in the anterior and middle cerebral arteries and internal carotids. All children were submitted to evaluation before surgery and on the 1st, 30th and 60th postoperative days. We conclude that neurosonography and US-Doppler technique is useful for determination of hydrocephalus, indication and control of cerebrospinal fluid shunts and monitoring of changes in RI, comparing data obtained immediately before and after surgery and during the late postoperative period. The results obtained when comparing the RI values for the various arteries during the different stages of the study also permitted us to conclude that the anterior cerebral arteries are representative of the maximal alterations that occur in cerebral vascular resistance in pediatric patients with hydrocephalus.

Reduced local cerebral blood flow in periventricular white matter in experimental neonatal hydrocephalus-restoration with CSF shunting

The extent to which the reduction in CBF occurring in hydrocephalus is a primary or secondary event in the pathogenesis of the brain injury that ensues has not been clearly established. This is particularly true in neonatal hydrocephalus, where the disorder is most common, and where timing of the treatment of the developing nervous system is so important. We investigated the changes in local CBF (lCBF) in an animal model of severe progressive neonatal hydrocephalus before and after CSF shunting. Hydrocephalus was induced in 27 1-week-old kittens by percutaneous injection of 0.05 ml of 25% kaolin into the cisterna magna. Fourteen littermates acted as controls. The lCBF was measured by 14C-iodoantipyrine quantitative autoradiography after 1 week in 15 animals (8 hydrocephalic, 7 controls) and after 3 weeks in 26 animals (19 hydrocephalic, 7 controls) following induction of hydrocephalus. Twelve of the 3-week hydrocephalic group received a ventriculoperitoneal shunt 10 days following kaolin injection. At 1 week following induction of hydrocephalus, lCBF was globally reduced in cortical gray matter and white matter as well as deep subcortical structures. The maximum reduction was in the parietal white matter, to 37% of control levels. At 3 weeks a significant reduction in lCBF persisted only in the white matter (parietal, occipital, and corpus callosum; average, 42% of control levels), whereas cortical gray and deep subcortical structures had returned to normal levels spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of transcranial Doppler indices in predicting raised ICP in infantile hydrocephalus. A study with review of the literature

Cerebral hemodynamic changes in infants with progressive hydrocephalus have been studied with the transcranial Doppler (TCD) technique. Several authors have referred to the correlation between the hemodynamic changes and increased intracranial pressure (ICP). Despite conflicting conclusions on the value of pulsatility index (PI) and resistance index (RI) measurements for monitoring infantile hydrocephalus, these pulsatility indices are the most commonly used for this purpose. Although clinical signs of raised ICP are highly variable and unreliable in infants, assumptions have been made in most of the studies about the presence of elevated ICP on the basis of the patient's clinical state. Few studies have reported on actual ICP values, however, and a direct relationship between ICP and TCD changes has never been adequately demonstrated. In the present study, this relationship was investigated in long-term simultaneous TCD/ICP measurements, in an attempt to develop a noninvasive method of monitoring the effect of ICP on intracranial hemodynamics. Two groups of data sets were established. Group I consisted of pre- and postoperative (shunt implantation) TCD/ICP measurements. Group II were long-term simultaneous TCD/ICP recordings showing significant ICP variations. In most of the postoperative measurements there was a decrease in the average PI and RI values. The correlation between PI or RI and ICP in the long-term simultaneous recordings, however, was generally poor. The risk of obtaining false positive or false negative PI or RI values in short-term measurements was also demonstrated. It can be concluded from our results, besides the wide range of reference values for the Doppler indices and extracranial influences upon them, that the present Doppler indices are inadequate for monitoring the complex intracranial dynamic responses in patients with raised ICP.

Intracranial pressure and cerebral arterial flow velocity indices in childhood hydrocephalus: current review

Because of its noninvasive and repeatable nature, Doppler ultrasound has been increasingly used to assess changes in cerebral haemodynamics in infants and children with hydrocephalus. There is general agreement that a direct correlation exists between the intracranial pressure (from experimental, fontanometric and direct measurement evidence) and the resistance index. In addition, this increasing index has been predominantly due to a reduction in the end-diastolic velocity. Stable ventriculomegaly is associated with normal pulsatility. The cerebral blood flow velocity parameters change significantly following CSF drainage by tapping or shunting. The measurement of intracranial pressure and cerebral blood flow velocity are currently the best ways of assessing the need for CSF diversion and monitoring subsequent shunt function.

Monitoring intracranial dynamics by transcranial Doppler--a new Doppler index: trans systolic time

Since the introduction of transcranial Doppler sonography (TCD) several investigators have described the relationship between raised intracranial pressure (ICP) and Doppler waveform. This waveform has been expressed by several indices, such as the pulsatility index (PI) and the resistance index (RI). These indices are used to demonstrate the presence of raised ICP. In childhood hydrocephalus this information can be used to indicate the need for shunt implantation. However, PI and RI do prove to have certain disadvantages as both are strongly influenced by the heart rate. Moreover, both indices have a broad range of reference values, especially in children. Therefore, they are not very reliable for detecting insidious changes in the ICP. These drawbacks are due to the fact that these indices are composed of blood flow velocity measurements and do not embody the slope of the TCD waveform itself. An ideal TCD waveform analysis should be performed concerning the time-related changes of the velocities. We present a hydrodynamic model, with its electrical analogue, which shows the effects of raised ICP on the intracranial hemodynamic system. Based on these physical findings we define a new Doppler index, the Trans Systolic Time, reflecting specific changes in the TCD waveform induced by changes in the mean ICP. The applicability of this index, compared with PI and RI, is illustrated by consecutive simultaneous TCD and AFP measurements in three children with hydrocephalus.

Cerebral blood flow velocity monitoring in pyogenic meningitis

Transcranial Doppler ultrasound monitoring of cerebral blood flow velocity (CBFV) was performed on 17 children (age range 8 days to 6 years) with pyogenic meningitis. Serial measurements of the peak systolic, end diastolic, mean flow velocity, and resistance index (equal to peak systolic velocity minus end diastolic velocity divided by peak systolic velocity) were obtained over the period of their hospital admission. In all 16 survivors there was a significant decrease in the final resistance index compared with the initial resistance index due to a significant increase in the end diastolic velocity. There was a significant increase in the final mean flow velocity. In four patients the decrease in intracranial pressure and increase in cerebral perfusion pressure after mannitol infusions was accompanied by a corresponding decrease in resistance index and increase in mean flow velocity. A pressure passive CBFV response with a significant linear correlation for resistance index/mean arterial pressure may suggest a loss of cerebrovascular autoregulation. These results suggest that in the early phase increased cerebrovascular resistance may contribute to a relative impairment of cerebral perfusion. Non-invasive monitoring by transcranial Doppler ultrasound may be helpful for early detection of deterioration in cerebral haemodynamic trends.

Cerebrovascular resistive index assessed by duplex Doppler sonography and its relationship to intracranial pressure in infantile hydrocephalus

Duplex Doppler sonography and direct intracranial pressure (ICP) measurement were performed on 18 patients with infantile hydrocephalus. ICP was measured through a frontal reservoir or ventricular tap using a nondisplacement pressure transducer. The Pourcelot Resistive Index, RI = (peak systolic-end diastolic)/peak systolic velocity was obtained from pulsed-wave Doppler measurements of blood flow velocity in the anterior (ACA) and/or the middle cerebral (MCA) arteries. There was a statistically significant positive correlation between ICP and RIs in the MCA and ACA. Paired RI measurements in 7 patients with raised ICP decreased significantly from a mean of 0.90 pre-tap to 0.75 post-tap. Our results suggest that the RI provides a reliable measure of cerebrovascular resistance in hydrocephalus. Duplex Doppler ultrasonography thus is a useful noninvasive means of monitoring cerebrohaemodynamic change with simultaneous imaging of ventricular size in infantile hydrocephalus.