Ultrasound assessment on selected peripheral nerve pathologies. Part I: Entrapment neuropathies of the upper limb - excluding carpal tunnel syndrome

Abstract

Ultrasound (US) is one of the methods for imaging entrapment neuropathies, post-traumatic changes to nerves, nerve tumors and postoperative complications to nerves. This type of examination is becoming more and more popular, not only for economic reasons, but also due to its value in making accurate diagnosis. It provides a very precise assessment of peripheral nerve trunk pathology - both in terms of morphology and localization. During examination there are several options available to the specialist: the making of a dynamic assessment, observation of pain radiation through the application of precise palpation and the comparison of resultant images with the contra lateral limb. Entrapment neuropathies of the upper limb are discussed in this study, with the omission of median nerve neuropathy at the level of the carpal canal, as extensive literature on this subject exists. The following pathologies are presented: pronator teres muscle syndrome, anterior interosseus nerve neuropathy, ulnar nerve groove syndrome and cubital tunnel syndrome, Guyon's canal syndrome, radial nerve neuropathy, posterior interosseous nerve neuropathy, Wartenberg's disease, suprascapular nerve neuropathy and thoracic outlet syndrome. Peripheral nerve examination technique has been presented in previous articles presenting information about peripheral nerve anatomy [Journal of Ultrasonography 2012; 12 (49): 120-163 - Normal and sonographic anatomy of selected peripheral nerves. Part I: Sonohistology and general principles of examination, following the example of the median nerve; Part II: Peripheral nerves of the upper limb; Part III: Peripheral nerves of the lower limb]. In this article potential compression sites of particular nerves are discussed, taking into account pathomechanisms of damage, including predisposing anatomical variants (accessory muscles). The parameters of ultrasound assessment have been established - echogenicity and echostructure, thickness (edema and related increase in the cross sectional area of the nerve trunk), vascularization and the reciprocal relationship with adjacent tissue.

Keywords: Guyon's canal syndrome; Kiloh-Nevin syndrome; Wartenberg's disease; entrapment neuropathies; pronator teres muscle syndrome; supinator muscle syndrome; thoracic outlet syndrome; ultrasound.

Figures

Fig. 1

A. Chronic neuropathy of the median nerve at the level of the carpal canal: compression site (arrow), cephalad nerve hyperemia symptoms. B. Effusive inflammation of the tendinous sheath of extensors (asterisk – effusion, arrow – median nerve). C. Intraoperative image of the synovial membrane hypertrophy. D. Swollen branch of thenar of the thumb (arrows), shaped by tumor (in histopathological examination – lipoma; asterisks)

Fig. 2

Pronator quadratus muscle (P.Q.) atrophy on the right side, normal image in the contralateral limb on the left side; radial bone (R), ulna (U)

Fig. 3

A. Anconeus epitrochlearis muscle (AE), compressing ulnar nerve (arrows). B. Ulnar nerve cross section at the level of the corpus of humerus bone (cross sectional area 5 mm2) and at the level of the groove for ulnar nerve (cross sectional area 17 mm2). C. Intraoperative image of chronic pressure neuropathy of ulnar nerve – the nerve with a clear narrowing site separated by the surgical tool. D. Longitudinal section of ulnar nerve (between the cross-hair pointers) as an example of a primary neuropathy at the level of the entry between the FCU heads (FCU c.h. – ulnar head, FCU c.u. – humeral head, Hum. – humerus bone). E. Ultrasound image of the atrophic lesions in hand muscles due to chronic ulnar nerve neuropathy (L – lumbricales muscles, IO – interossei)

Fig. 4

Ulnar nerve at the level of Guyon's canal (arrow), accessory abductor digiti minimi muscle (asterisks), OP – pisiform bone

Fig. 5

A. Intraoperative image of PIN, exit from supinator muscle (asterisk) with a visible branch to ECRB (arrow). B. Acute bending angle (large arrow) along PIN (small arrows), at the level of the entry between profound (Sup2) and superficial part (Sup1) of the supinator muscle. C. Smooth physiological nerve bending angle at the same level

Fig. 6

Cervical rib with a clear acoustic shadow (asterisk), brachial plexus trunks (arrows)