Transcranial Doppler (TCD) and neurosonography
Methods for ultrasound evaluation of intracranial hemodynamics depend on the patient's age and skull bone density.
Neurosonography is used in newborns. The fontanelles serve as acoustic windows. Key indications for infants include prematurity, low Apgar score, dysmorphic features, seizures, craniosynostosis, and suspected intracranial or intraventricular hemorrhage.
In adult patients, TCD is technically more challenging due to the bone barrier, so the study is typically performed through the temporal or mastoid regions. This specialized method allows for:
- Detecting cerebral vasospasm (especially after subarachnoid hemorrhage).
- Diagnosing intracranial arterial stenoses and arteriovenous malformations (AVMs).
- Detecting microembolism during carotid endarterectomy.
- Assessing cerebrovascular reserve in significant internal carotid artery (ICA) stenosis to determine the need for surgical intervention.
- Experimentally monitoring the efficacy of thrombolysis.
Prolonged ultrasound monitoring makes it possible to assess cerebrovascular reactivity and detect sources of embolism. Emboli can be artery-to-artery (resulting from large-artery atherosclerosis) or cardiac (thrombi from the heart chambers). A reduction or complete disappearance of emboli on repeat monitoring is the main criterion for successful treatment.
Duplex scanning of neck vessels
In neurological practice, this is the most sought-after instrumental method for evaluating patients with cerebrovascular disorders (CVD). It is used both for targeted diagnostics and for screening individuals at high risk for CVD, helping to detect asymptomatic stenoses and occlusions of extracranial and intracranial vessels.
The method carries no radiation burden or risk of complications, yet in many respects, it is comparable to standard angiography. The physician can quantitatively assess the degree of stenosis at the common carotid artery (CCA) bifurcation and the proximal ICA, as well as study the morphological characteristics of the atherosclerotic plaque.
Of particular importance is the ultrasound semiotics of internal carotid artery occlusion:
- Color duplex scanning clearly demonstrates the occlusion zone—blood flow in the ICA lumen is completely absent.
- Spectral dopplerography records the hemodynamic consequence of the blockage: a marked decrease in blood flow in the common carotid artery.
Blood flow assessment in systemic pathologies
Blood flow ultrasound is critically important for managing complications not only in neurology but also in other severe diseases.
Paroxysmal nocturnal hemoglobinuria (PNH). Newly diagnosed patients routinely undergo lower extremity venous ultrasound. When thrombosis of other localizations is suspected, mesenteric Doppler ultrasound, duplex scanning of the inferior vena cava, and portal system veins are performed. It is important to remember that contrast-enhanced magnetic resonance angiography in such patients must be strictly justified, as there is a high risk of acute kidney injury and nephropathy against the background of active intravascular hemolysis.
Cystic fibrosis (CF). Comprehensive abdominal ultrasound in such patients necessarily includes Doppler ultrasound of the portal system vessels. The physician specifically assesses the liver blood flow pattern and performs duplex scanning of hepatic vessels to identify specific changes and monitor their dynamics.
Class and exam questions
What is prolonged TCD monitoring used for?
The method allows for assessing cerebrovascular reactivity parameters, detecting signs of cerebral vessel embolism (artery-to-artery or cardiac), and monitoring the efficacy of therapy aimed at reducing the emboli count.
What is visible on ultrasound in internal carotid artery occlusion?
Color duplex scanning visualizes a complete absence of blood flow in the ICA. Meanwhile, spectral dopplerography records a compensatory decrease in blood flow in the common carotid artery.
Which vessels are examined when thrombosis is suspected in PNH patients?
Lower extremity venous Doppler ultrasound, mesenteric vessel ultrasound, as well as duplex scanning of the inferior vena cava and portal system veins are performed.
What else to study on this topic
- Anatomy of cerebral venous drainage (sinuses, Trolard and Labbe veins, superior sagittal sinus).
- Comparison of CT and radiography capabilities in emergency neuroradiology.
- Indications for orbital ultrasound in ocular trauma and emergencies.
- Cerebrospinal fluid examination technique and lumbar puncture guidelines.
- Assessment of external respiration function (spirometry, body plethysmography) and blood gas composition.
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