Color-coded transcranial Duplex, a noninvasive real-time method, can be used as a pediatric bedside tool to identify compromised intracranial hemodynamics. Its utility is described to identify blood flow more reliably in specific intracranial vessel segments; allows for more detailed assignment of vascular pathologies; and offers the opportunity for angle correction, resulting in more accurate measurement of flow velocities [4].
In case 1 with color-coded transcranial duplex evaluation, it is reliable and noninvasive of patients with cerebral artery stenosis becomes feasible, avoiding the potential adverse effects of cerebral angiography. Transcranial ultrasound provides reliable assessment of cross-flow through the circle of Willis and stenosis, occlusions and vasospasm of the main basal cerebral arteries. It also identifies intracranial hemorrhage but is inferior to neuro radiological techniques [5].
In patients with traumatic brain injury with endocranial hypertension, transcranial Doppler can be a useful tool to estimate cerebral perfusion pressure in a noninvasive manner, and there are studies that show a good correlation between invasive and noninvasive determination of cerebral perfusion pressure [12]. On the other hand, attempts have also been made to estimate intracranial pressure from the pulsatility index, with a good correlation [13]. Transcranial Doppler could not only be useful in the diagnosis of increased intracranial pressure, but also in its follow-up, which is demonstrated through changes in the morphology of the spectral wave, where there is a progressive decrease mainly in the velocities at the end of diastole and a tendency to systolicization of the spectral wave, finally reaching patterns of encephalic death [12],[14],[15],[16],[17],[18].
One of the most notable advantages of CBCT over blind Doppler is that the direction of blood flow can be precisely known and thus align the ultrasound beam as close as possible to an angle of zero degrees with respect to the direction of the erythrocytes, obtaining the velocities with great precision [19],[20],[21],[23]. DCT not only has the advantage of obtaining accurate blood flow velocities in the vessels of the polygon of Willis but also provides information about any structural or pathophysiological anatomical alteration of the skull base vessels [20]. In addition, this technique allows insonation of segments of cranial vessels inaccessible by conventional Doppler through the temporal window (e.g., insonation of segment A2 of the anterior cerebral artery) [22].
In case 2 we describe TCCS as a valuable method for the detection and follow-up of hemodynamic changes of AVM in children, before and after treatment, but further studies are needed to establish the benefits of this approach, for the use of color-coded transcranial duplex ultrasound (TCCS). As mentioned above, DCT not only has the advantage of obtaining more accurate erythrocyte velocities, but also provides information about any structural anatomical alteration of the blood vessels [20].
In case 3 we describe sonographic findings of cerebral circulatory arrest. Color-coded duplex ultrasonography and CT angiography have recently been incorporated in the fourth update of the German Medical Association guidelines for the determination of irreversible cessation of brain function ("brain death"), as of July 2015 [6].
Although the diagnosis of encephalic death is clinical [24], on some occasions the clinical examination cannot be performed, as in cases of severe facial trauma or in situations where it is impossible to perform the apnea test, it is in these cases where ancillary tests become fundamental tools for making the diagnosis of encephalic death [24],[25]. Within the ancillary tests, cerebral angiography is one of the tools with the greatest diagnostic certainty and when CDCT was compared with cerebral angiography, CDCT was a sensitive tool for diagnosing brain death, offering a reliable alternative to cerebral angiography [26].
Case 4 describes TCCS signs of cerebral vasospasm and finding of cerebral aneurysm. TCCS is useful for the detection and follow-up of intracranial vasospasm, can visualize larger supratentorial hematomas with subcortical localization and hemorrhagic transformation of ischemic infarcts, and provides incidental detection of cerebral aneurysms and arteriovenous malformations [7]. Findings in cerebral occlusive disease, TCCS provides information on the location of the stenosis. An increase in flow velocity is also measured in the case of vasospasm [8]. It should be noted that the reliability to detect the real magnitude of the velocities is much more accurate with CBCT than with blind Doppler, however it should be noted that the Lindergard Index was described by this author with a 2MHz transducer, both to insonate the midbrain and to insonate the extracranial portion of the ipsilateral internal carotid [27],[28]; this frequency may vary slightly when performing CBCT.
Case 5 Intracranial hypertension is described using color Doppler can localize intracranial vessels and simplifies the acquisition of the pulsed wave Doppler spectrum. Elevation of the pulsatility index may be useful as a diagnostic support tool when very high intracranial pressure or cerebral hypoperfusion is suspected [9].
The intracranial arteriovenous index is a reliable parameter that can be used to assess vasospasm after subarachnoid hemorrhage. Its reliability in differentiating vasospasm and hyperperfusion is slightly higher than that of the established Lindegaard index, and this method has the additional advantage of a markedly lower failure rate [10].
An aneurysm is visualized as a color-coded appendage next to a normal vessel. The most typical color-coded feature is the presence of two areas with inversely directed flow: half of the aneurysm is color-coded blue and the other half is color-coded red, with the colors corresponding to the direction of blood inflow and outflow [11].
The early use of TCCS (within 24 h of admission), its status as a first line neuromonitoring tool, and the frequency of use during night shifts highlighted the immediate availability of this technique. Thus, TCCS has the potential to become an influential neuromonitoring strategy in the PICU.