Craniocervical vessels Doppler ultrasonography
Doppler ultrasonography - method of investigating linear blood flow velocity (LBFV), based on the Doppler effect (the analysis of changes in the frequency of returning ultrasonic signals in comparison with the originally sent, depending on the speed of the scanned vascular flow and the angle between it and the ultrasound beam).
Other factors affecting the linear blood flow velocity in the vessels of the neck and brain, are the hematocrit, fibrinogen and other indicators measuring the viscosity of the blood. The method allows to estimate the linear blood flow velocity in cm/sec in the carotid and vertebral arteries in severe traumatic brain injury, especially combined with a neck injury. Doppler ultrasound is also used when head injury, combined with damage to the adjacent arteries (in acute and residual periods).
Craniocervical vessels Doppler ultrasonography - method of investigating linear velocity of blood flow in the brain through the intact skull, based on the Doppler effect. Use pulsating sensor with a frequency of 2 MHz. For the best of its contact with the skin of the head used gel.
Scans of brain vessels performed through a kind of "ultrasound window", located at 2-3 cm above the zygomatic arch. Thin squama of the temporal bone absorbs the least ultrasonic signals. At the specified position of the sensor investigate the linear blood flow velocity in the anterior, middle, posterior cerebral artery. Directing the probe to the base of the skull, estimate the linear blood flow velocity in the artery segment of the cranial base.
At ultrasonic diagnostics to the vessels differentiation helps:
- blood flow direction indicator (to the sensor or away from it) on the screen in ultrasonography
- knowledge of the estimated depth of the scanned portion of the artery
- age characteristics of linear blood flow velocity
- images of pulse waves above and / or below the axis of abscissas
Basilar artery examined through the foramen magnum (the head is given to the sternum, the sensor is strictly in the midline). It requires a certain caution, because of neck flexion may have a negative effect on intracranial pressure (ICP).
Normal linear velocity of blood flow in the middle cerebral artery (80% of hemispheric volume of blood flow) - 30-80 cm / sec (higher blood flow in children and its decline in the elderly).
Iindications for Doppler ultrasonography
Doppler ultrasonography craniocervical vessels used by our physicians in the diagnosis of the following diseases:
- Ischemic stroke, cerebral ischemia
- Vertebrobasilar insufficiency (VBI) with vertigo symptom
- Somatoform autonomic dysfunction
- Ischemic brain disease
- Dizziness, stuffiness in ear and tinnitus
- Increased intracranial pressure and hydrocephalus
- Headache, migraine
- Traumatic brain injury (concussion, contusion, brain hemorrhage, axonal shearing lesions)
- Cervicocranial syndrome and whiplash neck injury
- Parkinson's disease
- Pituitary microadenoma, macroadenoma and nonfunctioning adenomas (NFPAs), hyperprolactinemia syndrome
The procedure of craniocervical vessels Doppler ultrasonography is performed on special equipment using sensors with a frequency of 2-10 MHz. Data evaluation can be done in absolute terms or in comparison with similar parameters of the opposite side artery.
Contraindications to the use of Doppler ultrasonography - are extensive wounds of soft tissues in the area of research, which prevents the application of the sensor.
In severe TBI method ultrasonography cerebrovascular allowed to use as an extra for the diagnosis of brain death, in which the first marked progressive increase in systolic blood flow velocity while reducing diastolic pulsation, followed by a decrease in the amplitude of the systolic peak, the advent of reverse flow and a gradual fading pulsation. From that moment until biological death of the victim usually takes 1-3 days.
Shown above dynamics usually reflects the development of intracranial hypertension. On autopsy in this case there may be a generalized edema and swelling of the brain with the temporal-tentorial herniation or axial brainstem structures.
At diffuse brain lesions figures the average linear velocity of blood flow ultrasonography may be symmetrical and close to normal values of age. Focal trauma (with marked mass effect on CT) followed by the asymmetry of the average linear velocity of blood flow to the predominance of its increasingly on the side of lesion volume (due to unilateral ischemic hemisphere of the brain). Perhaps the absence of complete ipsilateral dopplerographic signal with ultrasonographywith its further identification after surgical removal of the substrate.
An increase in the average linear blood flow velocity at vessels ultrasonography over 100 cm/s must be understood, that it is based on:
- uncontrolled rise of intracranial pressure (ICP)
- brains compensatory hyperperfusion
- combination of the mentioned factors
Currently, there are large reserves of diagnostic opportunities for vessels ultrasonography method. There are not contraindications for using of cerebral blood vessels ultrasonography, excluding soft tissue rough damage in the temporal region.