Methodology of functional tests

The sensor is placed in the projection of the supratrochlear artery and records a clear antegrade physiological arterial signal with normal systolic-diastolic flow parameters corresponding to the patient’s age.

• Compression (5-10 sec) of the common carotid artery homolateral to the sensor. In this case, the signal from the supratrochlear artery normally stops or is sharply weakened.
• Compression (5-10 sec) of the branches of the homolateral external carotid artery - the superficial temporal artery and the mandibular artery. The compression of these vessels can be performed either sequentially or simultaneously - in this case, the operator applies synchronous pressure in the area of the mandibular fossa (at the exit point of the mandibular branch of the external carotid artery) and the tragus of the auricle (at the source of the superficial temporal artery) with the first and second fingers of the hand free from the sensor. In this case, under normal conditions, the specified compression of the branches of the homolateral external carotid artery either increases the signal intensity from the supratrochlear artery or does not change it. The possibility of increasing circulation through the ophthalmic artery at the moment of compression of the branch of the homolateral external carotid artery reflects the natural redistribution of blood flow, when an unexpected obstacle to the passage of blood through the external carotid artery sharply changes the pressure gradient between the systems of the internal and external carotid arteries. In this case, the entire volume of blood delivered by the common carotid artery rushes through the internal carotid artery, which is reflected in the increased sound of its periorbital branches. A sharp weakening or disappearance of the blood flow signal from the ophthalmic artery during compression of the branches of the homolateral external carotid artery is characteristic of subtotal stenosis or occlusion of the internal carotid artery on the same side with collateral compensation along the branches of the ipsilateral external carotid artery. An even more typical (if not pathognomonic) phenomenon for occlusion of the internal carotid artery is the registration of a change in the direction of circulation along the ophthalmic artery on the side of the suspected occlusion of the internal carotid artery, especially in combination with a complete cessation of the periorbital circulation signal during compression of the temporal branch of the homolateral external carotid artery.
• Compression (5-10 s) of the common carotid artery contralateral to the sensor. Normally, this either does not change the linear velocity of blood flow in the supratrochlear artery, or increases its circulation, probably due to the flow of blood from the opposite carotid artery through the anterior communicating artery (competence of the anterior part of the circle of Willis). If the said compression causes a noticeable decrease in the amplitude of circulation in the sounded supratrochlear artery, it is necessary to exclude stenotic/occlusive lesion of the carotid artery on the side of the altered blood flow in the ophthalmic artery. With such a picture of periorbital ultrasound Dopplerography, it is quite legitimate to assume the presence of intracerebral steal syndrome with the flow of blood from the unaffected hemisphere "to help" the ischemic hemisphere through the anterior communicating artery.

Next, the sensor is placed at the point of sounding of the vertebral artery and the following tests are performed.

• Compression (5 s) of the homolateral common carotid artery. Normally, this manipulation either does not affect the intensity of circulation through the vertebral artery or increases the linear velocity of blood flow through it, which indirectly indicates good functioning of the unilateral posterior communicating artery (competence of the vascular potential of the posterior part of the circle of Willis).
• The cuff test, or reactive hyperemia test, involves significant compression of the brachial artery of the homolaterally examined vertebral artery, where continuous monitoring of the linear velocity of blood flow and its direction is performed before, during and after the end of compression. Normally, the systolic-diastolic parameters and the direction of blood flow along the vertebral artery do not change at any stage of the cuff test. Any change in the specified parameters of circulation along the vertebral artery at the height of compression or immediately after decompression is very characteristic of the subclavian steal syndrome due to blood flow from the brain to the upper limb with proximal occlusion of the homolateral subclavian artery.
• Functional test with intensive head turns (10-15 times).

The values of the initial linear velocity of blood flow and circulation in the vertebral arteries are assessed at the end of the movements. Normally, a uniform increase in the linear velocity of blood flow by 5-10% is usually recorded compared to the initial values. In cases of moderate initial asymmetry (about 20%), physiological or caused by extravascular influences, a head rotation test most often leads to equalization of the velocity indicators at a slightly higher flow level. In stenotic/occlusive lesions, as well as congenital hypoplasia, the initial difference in the linear velocity of blood flow not only does not equalize, but sometimes even increases. At the same time, the indicated changes in the linear velocity of blood flow in the vertebral artery cannot be considered reliable signs of its stenosis or gross extravasal compression, in particular, they can reflect a change in the angle of location of the vertebral artery.

It should be noted that although the location of extracranial segments of the carotid, vertebral and peripheral arteries and veins is absolutely safe in itself, compression, even very short-term, of the carotid arteries is not always asymptomatic. In particular, in patients with carotid sinus hypersensitivity, compression of the carotid artery causes pronounced vagal reactions - nausea, hypersalivation, pre-syncope and, most importantly, a sharp slowdown in heart rate. In such situations, the examination should be stopped immediately, it is advisable to let the patient inhale ammonia vapors, and seat the patient on the couch. Even more risky, and according to some experts, absolutely unacceptable, are compressions of the carotid artery in patients with acute cerebrovascular accident, which can lead to iatrogenic cerebral embolism (this does not apply to compression of the branches of the external carotid artery, which are absolutely safe for any patient).

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