Neuromuscular electrodiagnosis.

The electrodiagnostic (EDX) study is an extension of the clinical examination, which means that the clinical features dictate the initial nerve conduction studies (NCS) performed. However, once the EDX study is started, it continues in an independent manner, meaning that the initial NCS findings dictate the subsequent studies performed. Because competent EDX study performance requires considerable knowledge (and special training), it is not possible to convey all of the basic and advanced concepts in a single chapter. Nonetheless, the most important concepts are easily conveyed by a discussion limited to EDX-pertinent anatomical, physiological, pathological, pathophysiological, and basic electrical concepts. The focus of this chapter will be on the standard NCS and needle EMG measurements made during EDX studies and their significance with regard to lesion localization and characterization. Because the most challenging portion of EDX study is motor unit action potential analysis, this topic is more extensively reviewed. The utility of the sensory NCS for identifying focal axon loss, the utility of the motor NCS for screening long nerve segments for focal demyelination and for determining lesion severity, and the utility of the needle EMG for confirming the NCS findings, better defining lesion localization, and identifying the temporal features (e.g., chronicity) and rate of progression of the lesion are also reviewed.

The Assessment and Management of Peripheral Nerve Trauma.

PURPOSE OF REVIEW: The purpose of this review is to discuss the therapeutic options available in the treatment of traumatic injuries involving peripheral nerves. RECENT FINDINGS: For nerve gap repair, synthetic nerve tubes are limited to gaps below 3 cm in length and to small-diameter nerve repairs, whereas the dependency on proliferating host Schwann cell limits the size of acellularized autografts. Thus, in most situations, nerve autografts remain superior for nerve gap correction. When conservative treatment is either not indicated or ineffective, surgical intervention may be employed. The ideal timing of surgical intervention is often unclear and determined by a number of factors, including the circumstances surrounding the injury, the timing of the symptoms, the type and severity of the injury, the completeness of the lesion, the required regenerative distance, the degree of fascicular disruption, and the degree of concomitant tissue trauma and contamination, as well as the morbidity and mortality of the procedure, and the age and comorbidities of the patient. The most common nonsurgical error is unnecessary surgical delay. To avoid losing the opportunity to achieve successful motor recovery, it is important to involve a peripheral nerve surgeon early.

The thoracic outlet syndromes: Part 1. Overview of the thoracic outlet syndromes and review of true neurogenic thoracic outlet syndrome.

The thoracic outlet syndromes (TOSs) are a group of etiologically and clinically distinct disorders with 1 feature in common: compression of 1 or more neurovascular elements as they traverse the thoracic outlet. The medical literature reflects 5 TOSs: arterial; venous; traumatic neurovascular; true neurogenic; and disputed. Of these, the first 4 demonstrate all of the features expected of a syndrome, whereas disputed TOS does not, causing many experts to doubt its existence altogether. Thus, some categorize disputed TOS as a cervicoscapular pain syndrome rather than as a type of TOS. To better understand these disorders, their distinctions, and the reasoning underlying the categorical change of disputed TOS from a form of TOS to a cervicoscapular pain syndrome, a thorough understanding of the pertinent anatomy, pathology, pathophysiology, and the electrodiagnostic manifestations of their pathophysiologies is required. This review of the TOSs is provided in 2 parts. In this first part we address information pertinent to all 5 TOSs and reviews true neurogenic TOS. In part 2 we review the other 4 TOSs. Muscle Nerve 55: 782-793, 2017.

The thoracic outlet syndromes: Part 2. The arterial, venous, neurovascular, and disputed thoracic outlet syndromes.

The thoracic outlet syndromes (TOSs) are a group of etiologically and clinically distinct disorders with 1 feature in common: compression of 1 or more neurovascular elements as they traverse the thoracic outlet. The medical literature reflects 5 TOSs: arterial; venous; traumatic neurovascular; true neurogenic; and disputed. Of these, the first 4 demonstrate all of the features expected of a syndrome, whereas disputed TOS does not, causing many experts to doubt its existence altogether. Thus, some categorize disputed TOSs as cervicoscapular pain syndrome rather than as a type of TOS. To better understand these disorders, their distinctions, and the reasoning underlying the categorical change of disputed TOS from a form of TOS to a cervicoscapular pain syndrome, a thorough understanding of the pertinent anatomy, pathology, pathophysiology, and electrodiagnostic manifestations of these pathophysiologies is required. This review of the TOSs is provided in 2 parts. In part 1 we covered general information pertinent to all 5 TOSs and reviewed true neurogenic TOS in detail. In part 2, we review the arterial, venous, traumatic neurovascular, and disputed forms of TOS. Muscle Nerve 56: 663-673, 2017.

Lesion distribution among 281 patients with sporadic neuralgic amyotrophy.

INTRODUCTION: The muscles commonly affected by neuralgic amyotrophy (NA) are well known, but the location of the responsible lesions is less clear (plexus versus extraplexus). METHODS: We report the lesion locations in 281 NA patients as determined by extensive electrodiagnostic (EDX) testing. RESULTS: Our 281 patients had 322 bouts of NA, 57 of which were bilateral, for a total of 379 assessable events. A single nerve was involved in 174 (46%), and 205 (54%) were multifocal. EDX testing identified 703 individual lesions: 699 neuropathies and 4 supraclavicular radiculoplexus lesions. CONCLUSIONS: The frequency of nerve involvement reflects the motor predilection of NA. Involvement of pure motor nerves exceeded that of predominantly motor nerves, both of which far exceeded involvement of more evenly mixed sensorimotor nerves. Cutaneous sensory nerves were least commonly involved. Because of the common C5-C6 innervation, NA often mimics an upper plexus lesion. Extraplexus nerve involvement far exceeded plexus involvement. Distal motor branch involvement explains the severe single-muscle wasting and weakness often observed. Muscle Nerve 55: 858-861, 2017.

The Relationship Between Sustained Gripping and the Development of Carpal Tunnel Syndrome.

An examination of clinical and electrodiagnostic assessments and fully characterized individual hand usage patterns finds a relationship between sustained gripping and the development of carpal tunnel syndrome in the nondominant hand.

Brachial plexopathies.

PURPOSE OF REVIEW: The main objective of this article is to offer a regional approach to brachial plexus assessment because, although the brachial plexus is the largest and most complex peripheral nervous system structure, most of its disorders involve only a portion of it. Consequently, regional assessment typically localizes and characterizes the lesion. RECENT FINDINGS: The sensory axons traversing each region are known and provide localizing information. SUMMARY: Because localization dictates the differential diagnosis and the resulting initial clinical management, examining physicians must first localize the lesion. Localization of a brachial plexus lesion requires an appreciation of brachial plexus anatomy, lesion classification, and the routes traversed by the various axons composing the brachial plexus, especially the sensory axons. This information is reviewed in this article and followed by discussions of several brachial plexus disorders, especially those with regional predilections.

Electrodiagnostic features of true neurogenic thoracic outlet syndrome.

INTRODUCTION: We report the electrodiagnostic (EDX) features of 32 patients with surgically verified true neurogenic thoracic outlet syndrome (TN-TOS). METHODS: Retrospective record review. RESULTS: We found uniform EDX evidence of a chronic axon loss process that affected the lower portion of the brachial plexus and disproportionately involved the T1 more than the C8 sensory and motor fibers. Because of this relationship, the medial antebrachial cutaneous sensory nerve (T1) and median motor (T1 > C8) study combination was abnormal in 89%, whereas response combinations that primarily assessed the C8 fibers were less frequently affected. CONCLUSIONS: The characteristic EDX features of TN-TOS are T1 > C8 nerve fiber involvement. A comprehensive EDX examination of the lower plexus with contralateral comparison studies is imperative to diagnose this disorder accurately.

The thoracic outlet syndromes.

The term thoracic outlet syndrome (TOS) refers to a heterogeneous group of disorders, all of which have in common compression of one or more neurovascular elements at some point within the thoracic outlet. Of the five disorders comprising this group, four have all of the features expected of a syndrome-a recognized constellation of clinical features; an anatomic derangement accounting for these features; and a method of testing that identifies the anatomic derangement. Consequently, their recognition and management are relatively straightforward. Conversely, one of these five disorders (nonspecific TOS) lacks these correlations, which has generated considerable debate in the literature and caused some experts to doubt its existence altogether. The primary focus in this study is on the neurologic forms of TOS. However, for completeness and a better understanding of these neurologic manifestations, the vascular forms are also reviewed.

Electrodiagnostic assessment of the brachial plexus.

The brachial plexus is one of the largest and most complex structures of the peripheral nervous system and, as such, cannot be studied by a single nerve conduction study (NCS) or muscle sampled by needle electrode examination (NEE). Typically, the screening sensory NCS is used and expanded to identify the region of involvement, the motor NCS is applied to determine the severity of the process, and the NEE is used to further characterize the lesion. Our approach to the electrodiagnostic assessment of the brachial plexus is the focus of this article; 3 electrodiagnostic cases with discussion follow this article.

Utility of electrodiagnostic testing in evaluating patients with lumbosacral radiculopathy: An evidence-based review.

This is an evidence-based review of electrodiagnostic (EDX) testing of patients with suspected lumbosacral radiculopathy to determine its utility in diagnosis and prognosis. Literature searches were performed to identify articles applying EDX techniques to patients with suspected lumbosacral radiculopathy. From the 355 articles initially discovered, 119 articles describing nerve conduction studies, electromyography (EMG), or evoked potentials in adequate detail were reviewed further. Fifty-three studies met inclusion criteria and were graded using predetermined criteria for classification of evidence for diagnostic studies. Two class II, 7 class III, and 34 class IV studies described the diagnostic use of EDX. One class II and three class III articles described H-reflexes with acceptable statistical significance for use in the diagnosis and confirmation of suspected S1 lumbosacral radiculopathy. Two class II and two class III studies demonstrated a range of sensitivities for use of muscle paraspinal mapping. Two class II studies demonstrated the utility of peripheral myotomal limb electromyography in radiculopathies.

Brachial plexopathies: classification, causes, and consequences.

The brachial plexus, which is the most complex structure of the peripheral nervous system, supplies most of the upper extremity and shoulder. The high incidence of brachial plexopathies reflects its vulnerability to trauma and the tendency of disorders involving adjacent structures to affect it secondarily. The combination of anatomic, pathophysiologic, and neuromuscular knowledge with detailed clinical and ancillary study evaluations provides diagnostic and prognostic information that is important to clinical management. Since most brachial plexus disorders do not involve the entire brachial plexus but, rather, show a regional predilection, a regional approach to assessment of plexopathies is necessary.

Electrodiagnostic approach to the patient with suspected brachial plexopathy.

Of the four major PNS plexuses, disorders of the brachial plexus are encountered far more frequently than those of the others. The EDX examination is probably the best procedure available by which to evaluate brachial plexus lesions. It provides localizing, pathologic, pathophysiologic, severity, and prognostic information. By localizing the lesion and identifying the underlying pathophysiology, it often predicts the underlying etiologic process; for example, (1) major T1 APR involvement with true neurogenic thoracic outlet syndrome; (2) C8 APR involvement with postmedian sternotomy brachial plexopathies; (3) supraclavicular demyelinating conduction block with classic postoperative paralysis (often confined to the upper plexus); (4) widespread infraclavicular demyelinating conduction blocks with radiation plexopathy; (5) severe progressive axon loss with neoplastic processes; (6) motor NCS abnormalities exceeding sensory NCS abnormalities for the same peripheral nervous system segment with intraspinal canal lesions (e.g., avulsions); (7) demyelinating conduction block with sparing of the pertinent sensory NCS study with multifocal motor neuropathy; and (8) lack of EDX abnormalities with hysteria, conversion reactions, and malingering, as well as with disputed neurogenic thoracic outlet syndrome. In addition, incorrect clinical considerations may be excluded (e.g., when abnormal SNAPs are identified, an isolated radiculopathy is excluded). Among the various EDX study components, the sensory NCS are the most useful for brachial plexus element localization. One drawback of the sensory NCS for localization occurs in the setting of concomitant carpal tunnel syndrome; the latter negates the utility of the median sensory NCS for brachial plexus localization. The motor NCS and NEE often overcome this drawback and, regardless of sensory NCS findings, are always performed.