Application of Stork Ultrasound in Peripheral Nerve
Ultrasound examination is one of the most timely and effective imaging methods for diagnosing peripheral neurological diseases. Ali and others from the University of Pennsylvania in the United States published an article in the 10th issue of World Neurosurgery in 2015 to introduce it in detail.
In the past, due to the low resolution of the handheld ultrasound probe, its value in diagnosing nerve injury was limited. However, with the improvement of ultrasound equipment and inspection technology (including the application of high-frequency probes and the improvement of scanning methods), the high-resolution images on the current advanced ultrasound equipment can show relatively small peripheral nerves. Its resolution is even higher than the most commonly used MRI inspection technology. Neuroelectrophysiological examinations can provide important diagnostic data such as the location and extent of neurological dysfunction. However, due to its own limitations, it is impossible to determine the morphological changes of nerves and the detailed types of nerve damage. Ultrasound examination can make up for this defect of neuroelectric physiological examination, and it will not cause pain to the patient.
The resolution of clinical MRI images is generally about 450 microns, while ultrasound images can reach higher resolutions. The axial resolution of the 10MHz probe can be close to 150 microns, while the current commonly used clinical 18MHz probe will have a higher resolution. Therefore, ultrasound can show the ultrastructure of each nerve more clearly and evaluate smaller nerves (such as peripheral nerves). In addition, ultrasound can also evaluate nerves near artificial implants, and MRI may be limited in the field.
Application of Stork Ultrasound in Peripheral Nerve
Stork's handheld wireless ultrasound probe
Stork ultrasonogram manifestations of normal peripheral nerves
Ultrasound examination should be carried out according to its anatomical shape. For example, the examination of the brachial plexus should start from the spinal nerve and the brachial plexus nerve trunk and extend to the end of the finger nerve. The operator's local anatomy knowledge and the shape of the examination site can affect the examination effect. Therefore, the operator must have anatomical knowledge of muscles, tendons, and blood vessels. At the same time, it is easier to find the location of nerves based on certain anatomical landmarks.
Ultrasound examinations of nerves mostly use a high frequency linear probe (8-18MHz), and different internal anatomical structures can show different echoes.
Stork'S Wireless High-Frequency Linear Array Probe
Stork's wireless high-frequency linear array probe
On the cross-sectional sonogram, the nerves appear as a hypoechoic structure, and small circular or oval hypoechoic areas can be seen inside, which are "honeycomb". The anatomical basis for this appearance is that hypoechoic tracts are separated by hyperechoic fascicles. The nerve gradually narrows into small branches as it travels from the proximal end to the distal end, and the perineurium also changes in different ways. Cross-sectional images are the most valuable for describing neuroanatomy and discovering lesions. The cross-sectional area of nerves is often used as an important parameter for the diagnosis of various neurological diseases.
On the ultrasonogram of the longitudinal section, the nerves run in a bundle. That means a linear high-level echo of the fascicular membrane can be seen within the hypoechoic tubular structure. Because the peripheral nerves are not straight and their diameter is relatively small, it is technically difficult to display the nerves through the longitudinal section. The cross-section perpendicular to the longitudinal section is especially helpful for finding abnormalities or changes in nerve contours.
Longitudinal section of Ulnar nerve
Nerves should be distinguished from the surrounding muscle tissue, which has lower echo than nerves. Comparing the thickness of the muscle around the nerve with the contralateral side can determine whether the muscle is normal and whether there is muscle atrophy due to obvious neuropathy. Tendons are different from muscles. Their echoes are higher than those of surrounding nerves, and they have a dense fiber shape. The dynamic examination of limbs can also help distinguish nerves from tendons. Color Doppler ultrasound can be used to identify nerves and blood vessels and detect increased blood flow signals and congestion caused by nerve compression or infectious neuropathy. Under normal circumstances, ultrasound shows that there is no blood flow signal distribution in the nerve bundle.
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