BRACHIAL PLEXOPATHY in Objective-C

Create DataMatrix in Objective-C BRACHIAL PLEXOPATHY

Brachial plexopathies can be classi ed on the basis of the nature of the injury (ie, an open or closed brachial plexopathy), the anatomic location of the lesion, or the mechanism of injury (Table 21 2)1 3 From a clinical perspective, the way we approach patients is to rst localizing the site of the lesion and then trying to identify the etiology (although in cases of trauma the cause is often obvious) Therefore, we will begin by reviewing clinical and electrodiagnostic features that one may expect to see with lesions affecting various trunks and cords of the brachial plexus

Upper Trunk (Fig 21 3)

Individuals with upper trunk lesions have weakness in the deltoid and biceps brachii muscles Therefore, they

commonly complain of dif culty lifting their arms Sensory loss involves the lateral arm and forearm down to the lateral aspect of the hand and ngers The biceps brachii and brachioradialis re exes are typically reduced Injuries in isolation are relatively common when compared to lone middle or lower trunk lesions EMG and NCS are useful in differentiating an upper trunk lesion from a C5 or C6 radiculopathy Remember that upper trunk lesions are distinguished from C5 6 injuries in that the posterior primary rami are spared, as are the nerve branches to the rhomboid and serratus anterior muscles Also, trunk lesions are distal to the dorsal root ganglion Therefore, if the nature of upper trunk injury is axonal damage and not just neuropraxia (ie, conduction block and/or demyelination), the radial, median, and lateral antibrachial cutaneous SNAPs may have reduced amplitudes, particularly when compared to an asymptomatic contralateral arm (Table 21 3) These SNAPs would be normal in a cervical radiculopathy or in a neuropraxic or demyelinating process affecting the trunk Routine median and ulnar CMAPs are not particularly helpful other than excluding involvement of other trunks or nerves A musculocutaneous CMAP can be done by recording from the biceps brachii, but this is usually not useful in distinguishing a C5 or C6 radiculopathy from an upper trunk lesion However, the EMG can be localizing in combination with the sensory studies Recall that the posterior primary rami to the paraspinal muscles, the dorsal scapular nerve to the rhomboid, and long thoracic nerve to the serratus anterior come off the cervical roots before the formation of the upper trunk So EMG of these muscles may show evidence of denervation in a C5 or C6 radiculopathy but would be spared if the lesion only involved the upper trunk One should do extensive EMG to ensure that abnormalities are restricted to muscles innervated by the upper trunk, with sparing of muscles innervated by the middle and lower trunk (Table 21 3)

ber that the middle trunk contains the C7 spinal nerves and after passing through the middle trunk these diverge and traverse the posterior and lateral cords (Table 21 1, Fig 21 3) Thus, all the muscles innervated by the radial nerve would be affected in addition to some medianinnervated forearm muscles (eg, those muscles with C6 and C7 and lateral cord innervation) Additionally, EMG abnormalities may be appreciated in the pectoralis major, latissimus dorsi, and teres major muscles, as these muscles are, in part, innervated by the C7 spinal nerves and middle trunk via the medial and posterior cords However, the serratus anterior muscle, which has C7 innervation in common but not the middle trunk, would be spared with a middle trunk lesion (recall the long thoracic nerve branches directly off the roots) There are no nerve branches arising directly from the middle trunk, and so it can be dif cult to distinguish a lesion involving the middle trunk from those affecting portions of the lateral and posterior cords

Lower Trunk (Fig 21 3)

Lesions affecting the lower trunk present symptoms similar to a C8/T1 radiculopathy, medial cord, and ulnar neuropathy Individuals who are affected often have sensory loss on the medial aspect of the forearm (more extensive than that seen with an ulnar neuropathy) and hand along with weakness of ulnar-, median-, and radialnerve-innervated wrist/hand muscles Involvement of radial-nerve and posterior cord innervated C8/T1 muscles puts the lesion more proximal than a medial cord NCS are valuable in localizing the lesion (Table 21 3) With axonal lesions, one would expect to see reduced amplitudes of ulnar and medial antebrachial cutaneous SNAPs in both lateral trunk and medial cord lesions but not in a C8 or T1 radiculopathy A reduction in the amplitude of the median and ulnar CMAPs may be seen in a severe radiculopathy, lower trunk, or medial cord axonopathies EMG should show signs of denervation in radial-, median-, and ulnar-innervated distal arm muscles, as the nerves supplying these muscles all course through the upper trunk (Table 21 1) However, the lower cervical paraspinal muscles should be spared in lower trunk lesions Compared to other plexus nerve injuries, the prognosis for recovery is comparatively poor because of the long distance a regenerating nerve must cover to reinnervate the muscles in the distal arm1,51

Middle Trunk (Fig 3)

Isolation of middle trunk lesions is extremely rare and is most often affected in combination with other lesions in the plexus Symptoms and signs would resemble a C7 radiculopathy Affected people may experience weakness of elbow, wrist, and nger extension and sensory loss or pain in the posterior forearm and the dorsal and palmar aspect of the middle nger The triceps re ex may be reduced Provided the injury is axonal in nature, a diminished amplitude of the median SNAP to the third digit may be evident as the cutaneous bers that supply this nger usually traverse the middle trunk (Table 21 3) Also, the radial CMAP recorded from the extensor indicis proprius may have a reduced amplitude, if there is suf cient axon loss However, the EMG is most important in delineating the extent of motor involvement Remem-

Posterior Cord (Fig 21 3)

The nerves originating from the posterior cord include the thoracodorsal, the upper and lower subscapular, axillary, and radial nerves Depending on where the lesion is in the cord, individuals who are affected may have weakness of shoulder abduction, shoulder extension, supination of the wrist, and elbow/wrist/ nger