Neurosonology

Neurological ultrasonography allows the analysis of all major brain supplying arteries by means of Doppler- and duplex sonography. These are extracranially the carotid and the vertebral arteries, intracranially the carotid siphon, the ophthalmic arteries, the vertebral arteries, the basilar artery, the circle of Willis with the anterior, middle and posterior cerebral arteries.

Hemodynamic parameters like the blood flow velocity, flow disturbances or resistancy indices can be analysed in all of these vessels. In addition, the extracranial duplex technique allows the assessment of atherosclerotic plaques, changes of the vessel wall thickness or vessel dissections.

Further routine transcranial Doppler investigations are:

– Registration of clinically "silent" microemboli in both middle cerebral arteries

– Detection of cardiac right-to-left shunts by intravenous application of ultrasound signal enhancers, not passing the pulmonary circulation

– Analysis of the cerebral reserve capacity and collateral pathways in patients with vessel stenosis or occlusion.

The use of ultrasound contrast enhancers in transcranial Doppler and duplex sonography facilitates the assessment of intracranial vessels in patients with insufficient bone windows. The ultrasound laboratory focuses especially on patients with stroke, haemorrhage, vasospasm, arteriovenous malformations, elevated intracranial pressure or vasculitis.
Currently we are implementing the technique into the acute diagnostic procedures of stroke patients in the A&E department. With a special “fast track” approach we assess, whether ultrasound is able to reliably detect or exclude arterial vascular pathology in the hyperacute phase of stroke and compare results with “conventional” vascular diagnostics like MRA and CTA.

Our main scientific interest is to study physiological and pathological aspects of the human cerebral hemodynamics. Our aim is to increase applicability and indications of ultrasonographic methods, which are in comparison to other diagnostic techniques simple, cost effective, and not distressing for the patient. Therefore, we developed new ultrasonographic approaches for the assessment of brain supplying arteries and in particular the cerebral veins to transfer the results to different vascular diseases.

Our research group established normal values of blood flow velocity in different intra- and extracranial veins and sinuses e.g. the basal vein of Rosenthal, the vertebral veins, the inferior petrosal sinus and the cavernous sinus and reported the changes of these values in patients with cerebral venous disease (1-7).
Based on our special knowledge of the venous cerebral ultrasound anatomy we developed a method to analyse the global cerebral circulation time. This is the time interval, the blood needs to pass the brain from the internal carotid artery to the internal jugular vein, assessed by echo-contrast bolus tracking. This method can for instance be used to detect cerebral arteriovenous malformations (angiomas or dural fistulas) or to monitor the patients treatment progress (8,9). However, the method has the potential to be applied in a variety of other human cerebral vascular diseases. For instance we were able to demonstrate, that the global cerebral circulation time is prolonged in patients with different types of dementia (10,11).
Combining cerebral blood volume flow and circulation time we recently described for the first time an ultrasonographic method to calculate the global cerebral blood volume (12). This new physiological value might be a valuable information in patients with raised intracranial pressure (e.g. following head injury). Currently we are extending our diagnostic abilities towards direct ultrasonographic brain perfusion imaging techniques. Also, we are studying the potential prognostic relevance of early ultrasound assessment in global cerebral hypoxia.
A further clinical application of cerebral ultrasound and field of our research interest is the transcranial parenchymal B-mode imaging. Modern ultrasound techniques allow the imaging of different brain structures (ventricle, basal ganglia) which show sonographic alterations in different neurological diseases. Especially the echogenicity of certain brain structures can be used for differentiation between different types of movement disorders (13).

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Selected Publications

1. Valdueza JM, Schmierer K, Mehraein S, Einhäupl KM (1996)

Assessment of normal flow velocity in basal cerebral veins. A transcranial Doppler ultrasound study.
Stroke 27:1221-1225.

2. Valdueza JM, Hoffmann O, Doepp F, Lehmann R, Einhäupl KM (1998)

Venous Doppler ultrasound assessment of the parasellar region. Cerebrovasc Dis 8:113-117.

3. Doepp F, Hoffmann O, Lehmann R, Einhäupl KM, Valdueza JM (1999)

The inferior petrosal sinus: Assessment by transcranial Doppler ultrasound using the suboccipital approach.
J Neuroimaging 9:193-197.

4. Hoffmann O, Weih M, von Münster T, Schreiber S, Einhäupl KM, Valdueza JM (1999)

Blood flow velocities in the vertebral veins of healthy subjects:
A duplex sonography study.
J Neuroimaging 9:198-200.

5. Valdueza JM, von Münster T, Hoffmann O, Schreiber S, Einhäupl KM (2000)

Postural dependency of the cerebral venous outflow.
Lancet 355:200-201.

6. Doepp F, Hoffmann O, Schreiber S, Lammert I, Einhäupl KM, Valdueza JM (2001)

Venous collateral blood flow assessed by Doppler ultrasound after unilateral radical neck dissection.
Ann Otol Rhinol Laryngol 110:1055-8.

7. Schreiber S, Lürtzing F, Götze R, Doepp F, Klingebiel R,
Valdueza JM (2003)

Extrajugular pathways of human cerebral venous blood drainage – assessed by duplex ultrasound.
J Appl Physiol Jan 10.

8. Schreiber SJ, Franke U, Doepp F, Staccioli E, Valdueza JM (2002)

Dopplersonographic measurement of global cerebral circulation time using echo contrast enhanced ultrasound in normal individuals and patients with arteriovenous malformations.
Ultrasound Med Biol 28:453-458.

9. Schreiber SJ, Kauert A, Doepp F, Valdueza JM (2003)

Measurement of global cerebral circulation time using power duplex echo-contrast bolus tracking.
Cerebrovasc Dis 15:129-132.

10. Doepp F, Valdueza JM, Schreiber SJ (2006)

Transcranial and extracranial ultrasound assessment of cerebral hemodynamics in vascular and Alzheimer`s dementia. Neurol Res. 28:645-649.

11. Schreiber SJ und Doepp F, Spruth E, Kopp UA, Valdueza JM (2005)

Ultrasonographic measurement of cerebral blood flow, cerebral circulation time and cerebral blood volume in vascular and Alzheimer`s dementia. J Neurol. 252:1171-1177.

12. Doepp F, Schreiber SJ, Brunecker P, Valdueza JM (2003)

Ultrasonographic assessment of global cerebral blood volume in healthy adults.
J Cereb Blood Flow Metab 1.J Cereb Blood Flow Metab 23:972-977.

13. Doepp F, Plotkin M, Siegel L, Kivi A, Gruber D, Lobsien E, Kupsch A, Schreiber SJ (2007)

Brain parenchyma sonography and 123 I-FP-CIT SPECT in Parkinson´s disease and essential tremor. Movement Dis.23:405-410.

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