Normal and sonographic anatomy of selected peripheral nerves. Part I: Sonohistology and general principles of examination, following the example of the median nerve

Abstract

Ultrasonography is an established method for imaging peripheral nerves. It serves to supplement the physical examination, electromyography, and magnetic resonance imaging. It enables the identification of post-traumatic changes of nerves, neuropathies secondary to compression syndromes, inflammatory or neoplastic nerve lesions as well as the evaluation of postoperative complications. In certain situations, this technique is the imaging method of choice. It is increasingly used in anesthesiology for regional anesthesia. As in the case of other ultrasound imaging studies, the examination of peripheral nerves is non-invasive, well-tolerated by patients, and relatively inexpensive. This article presents the histological structure of peripheral nerves and their appearance in ultrasonography. It also presents the examination technique, following the example of the median nerve, and includes a series of diagrams and ultrasound images. The interpretation of the shape, echogenicity, thickness and vascularity of nerves is described, as well as their relation to the surrounding tissues. The “elevator technique”, which consists of locating a set nerve at a characteristic anatomic point, and following it proximally or distally, has been explained. The undisputed benefits of the ultrasound examination have been presented, including its advantages over other diagnostic methods. These advantages include the dynamic component of the ultrasound examination and the possibility of correlating the patient's symptoms with the ultrasound images. As an example, the proper anatomy and the ultrasonographic appearance of the median nerve were described. This nerve's course is presented, its divisions, and characteristic reference points, so as to facilitate its location and identification, and enable subsequent use of the aforementioned “elevator technique”. This article opens a series of publications concerning anatomy, technique of examination and pathologies of peripheral nerves.

Anatomical landmarks for tibial nerve motor branches in the management of spastic equinovarus foot after stroke: An ultrasonographic study

“…This, so-called "elevator technique", enables assessment of nerve shape, echogenicity, thickness and its relation with surrounding tissues (e.g. skin, muscles or vessels) (17). The correct identification of tibial motor nerve branches to the gastrocnemii, soleus and tibialis posterior muscles was checked by means of needle (70-mm, echogenic-coated, 22-gauge needle with length graduation) electrical stimulation (1 Hz frequency and 100 μs duration).…”

Echogenicity and ultrasound visibility of peripheral nerves of the upper extremity

“…The nerve can be located, but visualization is poor and using this image for performing a nerve block would be very difficult. 3 An adequate view was obtained but a better image of the nerve might be desired for a nerve block. 4 A good view was obtained and the reviewer would feel comfortable performing a nerve block.…”

“…Nerves that are difficult to visualize makes the procedure more challenging to perform and could potentially lead to complications, failure to perform the procedure, or decreased success. Prior research documents the common anatomical appearance of the target nerves by ultrasound in healthy subjects and in states of pathology such as neuropathy, nerve damage or disease [1][2][3][4]. These studies have identified that the echogenicity of nerves changes based on ratio of total fascicular area to whole nerve area and fascicle pattern [5].…”

New imaging techniques in reumathology: MRI, scintigraphy and PET

“…Thanks to dynamic technological advances, ultrasound scans became one of the leading methods for diagnosing motor organs [4–7]. The advantage of MRI as compared to other techniques is the ability to assess bone marrow.…”