Early electrodiagnostic findings in Guillain-Barré syndrome.

CONTEXT: Guillain-Barré syndrome (GBS) is the foremost cause of acute, generalized, peripheral neuropathic weakness. Although nerve conduction studies are a diagnostic aid, the characteristic electrical changes may not evolve for several weeks. Early diagnosis of GBS is important, however, because early treatment has been shown to improve outcome. OBJECTIVES: To describe the electrodiagnostic abnormalities detectable in the first week of GBS, to determine if there are early patterns suggestive of GBS, and to identify the percentage of patients whose condition can be diagnosed with reasonable certainty in the first week. DESIGN AND SETTING: We retrospectively reviewed the medical records of all patients admitted to the Cleveland Clinic Foundation, Cleveland, Ohio, having the discharge diagnosis GBS during the past 16 years. Patients who underwent nerve conduction studies within 7 days of muscle weakness were selected for this study. RESULTS: The H reflex was absent in 30 (97%) of 31 patients. Nineteen patients (61%) had low-amplitude or absent sensory nerve action potential (SNAP) in the upper extremity. Fifteen patients (48%) overall, including 21 (67%) of the 31 patients, including 14 (67%) of the 21 patients younger than 60 years, had an abnormal upper extremity SNAP combined with a normal sural SNAP. Other findings included an abnormal F wave (25 patients [84%]), reduced compound muscle action potential amplitude (22 patients [71%]), prolonged distal latency (20 patients [65%]), temporal dispersion (18 patients [58%]), slowed motor conduction velocity (16 patients [52%]), and motor conduction block (4 patients [13%]). Definite diagnosis was possible in 17 patients (55%), but not commonly until the fifth day. CONCLUSIONS: The H reflex is the most sensitive test for early GBS. Upper extremity SNAPs are also frequently abnormal in early GBS. Absent H response, abnormal F wave, and abnormal upper extremity SNAP combined with a normal sural SNAP are characteristic of early GBS. If multiple nerves are tested, definite diagnosis is possible in half the patients, but not until the fifth day after the onset of symptoms.

Peripheral nerve injuries in athletes: a case series of over 200 injuries.

We retrospectively reviewed electrodiagnostic (EDX) studies performed on 346 athletes with sports injuries who were referred to our EDX laboratory from 1974 to 1997. These injuries included 216 nerve root, plexus, or peripheral nerve injuries sustained by 180 of the athletes. Eighty-six percent of the injuries were to the upper extremity. Athletes with nerve fiber injuries participated in 27 different sports, but over one third of injuries were sustained playing football. The most common symptomatic upper extremity injury was the "burner" (N=40). Forty-three athletes had median neuropathies, many of which were asymptomatic cases of carpal tunnel syndrome. Cervical radiculopathies (N=19) and axillary (N=22), ulnar (N=19), and suprascapular (N=14) mononeuropathies were also prevalent. The most common lower extremity injuries were peroneal neuropathies (N=17) and lumbosacral radiculopathies (N=7). This is the largest reported series of sports-related nerve injuries. The mechanisms of the most common nerve injuries are discussed.

Thoracic outlet syndromes.

The term thoracic outlet syndromes, is a group designation for several distinct disorders (one of questionable validity) involving various components of the brachial plexus, the blood vessels, or both, at various points between the base of the neck and the axilla. Four of the five subgroups (true neurologic TOS, arterial vascular TOS, venous vascular TOS, and traumatic neurovascular TOS) are universally recognized to be rare lesions, with characteristic clinical and laboratory presentations; and none is particularly controversial. In contrast, disputed neurologic TOS is highly controversial. This article limits discussion to the three subgroups of TOS in which neurologic symptoms are caused, or reputedly are caused, by compromise of the brachial plexus fibers.

Clinical neurophysiology in the diagnosis of amyotrophic lateral sclerosis: the Lambert and the El Escorial criteria.

For many years, the only published criteria for the electrodiagnostic (EDX) recognition of amyotrophic lateral sclerosis (ALS) were those formulated by Lambert (1957; 1969). In 1990, different EDX guidelines were incorporated in the all-inclusive diagnostic criteria formulated by a subcommittee on ALS of the World Federation of Neurology, which met in El Escorial, Spain. Unfortunately, particularly in regard to the EDX requirements, the 'El Escorial criteria' have several flaws which compromise their usefulness. These include: (1) they ignore the fact that whenever upper and lower motor neuron disorders co-exist, as they characteristically do with ALS, the motor unit potential firing pattern is controlled by the upper motor neuron lesion; (2) they markedly devalue the usefulness of detecting fasciculations and, through presumably typographical error, state that the 'absence' rather than the 'presence' of fasciculations supports the diagnosis of ALS; this view is in direct conflict with the opinions expressed by most electromyographers; (3) they contain a statement regarding how the diagnosis of ALS is confirmed by the EDX studies which is confusing and, for two of the body regions (bulbar; thoracic), unrealistic; (4) finally, many of the EDX features they listed supporting the recognition of possible LMN degeneration appear to be mislabeled, while a few features in the EDX criteria are incorrect.

AAEM minimonograph 32: the electrodiagnostic examination in patients with radiculopathies. American Association of Electrodiagnostic Medicine.

The anatomy and pathophysiology of radiculopathies are reviewed, and the electrodiagnostic approaches used in evaluating patients with suspected root lesions are discussed. Such electrophysiologic procedures include motor and sensory nerve conduction studies, late-response studies, somatosensory and motor evoked potentials, nerve root stimulation, and needle electromyography. The value and limitations of these different procedures are considered. At the present time, needle electromyography is the single most useful approach. The findings in patients with radiculopathies at different levels are summarized.

Sports and peripheral nerve injuries: report of 190 injuries evaluated in a single electromyography laboratory.

We retrospectively reviewed electrodiagnostic studies performed on 169 athletes with 190 sports injuries to nerve fibers. Eighty-eight percent of the injuries were to the upper extremity. Athletes participated in 27 sports, but over one third of injuries were sustained playing football. The most common injuries were burners (n = 38) and cervical radiculopathies (n = 18), followed by median (n = 28), axillary (n = 22), ulnar (n = 19), suprascapular (n = 14), and peroneal (n = 11) mononeuropathies. This is the largest reported series of sports-related nerve injuries.

Cervical rib and median sternotomy-related brachial plexopathies: a reassessment.

OBJECTIVE: The objective of this study was to identify electrodiagnostic and anatomic distinctions between true neurogenic thoracic outlet syndrome and median sternotomy-related brachial plexopathy, in reference to the pattern of abnormality of the medial antebrachial cutaneous sensory nerve conduction study (NCS) response. BACKGROUND: Neurogenic thoracic outlet syndrome and sternotomy-related brachial plexopathy are both lower trunk brachial plexopathies, but their clinical and electrodiagnostic presentations are distinct. The anatomic differences distinguishing these disorders from each other, and from other lower trunk brachial plexopathies, have not been defined. METHODS: We compared the medial antebrachial cutaneous sensory nerve action potential amplitude with the median motor, ulnar motor, and ulnar sensory NCS amplitudes in 10 patients with neurogenic thoracic outlet syndrome and in 14 patients with sternotomy-related brachial plexopathy. RESULTS: In the 10 patients with neurogenic thoracic outlet syndrome, the medial antebrachial cutaneous amplitude was most affected, followed in decreasing order of involvement by the median motor, ulnar sensory, and ulnar motor amplitudes. Conversely, in the 14 patients with sternotomy-related brachial plexopathy, the ulnar sensory and motor amplitudes were the most affected responses. Medial antebrachial cutaneous NCS changes closely paralleled median motor response changes. CONCLUSIONS: The medial antebrachial cutaneous sensory response is sensitive in the diagnosis of neurogenic thoracic outlet syndrome. Our data suggest that medial antebrachial cutaneous nerve fibers are closely associated anatomically at the T1 root level with median motor fibers innervating the thenar muscles. Neurogenic thoracic outlet syndrome shows predominant damage in the T1 distribution, whereas sternotomy-related brachial plexopathy shows predominant damage in the C8 distribution, suggesting that these lesions are localized at the level of the anterior primary rami of the cervical roots, and not in the lower trunk of the brachial plexus.

Iatrogenic nerve injuries.

Iatrogenic nerve injuries are an undesired byproduct of the practice of medicine and have been so since antiquity. The majority of such injuries occur perioperatively, and are, therefore, attributed to surgeons and anesthesiologists. Nonetheless, the members of almost every clinical specialty are at risk to some degree. Iatrogenic nerve injuries can affect almost any portion of the peripheral nervous system, and can result from many different causes. This article reviews many of the more common iatrogenic nerve lesions.

Cervical radiculopathy and coexisting distal entrapment neuropathies: double-crush syndromes?

The double-crush hypothesis (DCH) proposes that a proximal lesion along an axon predisposes it to injury at a more distal site along its course through impaired axoplasmic flow. Although this hypothesis has been accepted, it has anatomic and pathophysiologic restrictions that limit its application as an explanation for coexisting cervical root lesions (CRLs) and carpal tunnel syndrome (CTS) or ulnar neuropathy at the elbow (UN-E). We retrospectively surveyed all electrodiagnostic (EDX) reports of coexisting CTS or UN-E and CRL for anatomic correlation, if any, between the proximal root lesion and the distal entrapment neuropathy. In the period between January 1982 and August 1995 there were 12,736 limbs with CTS or UN-E. In 435 of these limbs (3.4%) there was a coexisting CRL, but only 98 (0.8%) had an association that was anatomically appropriate. Moreover, only 69 (0.5%) of the 98 cases demonstrated axon loss at the distal lesion site on EDX examination. Therefore, cumulatively, only 69 of our 12,736 cases of CTS and UN-E satisfied the pathophysiologic and one of the anatomic requirements of the DCH. Our data thus suggest that a CRL can seldom serve as the proximal lesion with these entrapment neuropathies in the DCH.

International proficiency testing of analytical laboratories for foods and feeds from 1990 to 1996: the experiences of the United Kingdom Food Analysis Performance Assessment Scheme.

The Food Analysis Performance Assessment Scheme (FAPAS) organized by a Secretariat of the UK Ministry of Agriculture, Fisheries, and Food has checked the proficiency of analytical laboratories for foods and feeds from 1990 to 1996. FAPAS was started for UK laboratories but was expanded worldwide at the request of analysts in other countries who did not have a home-based scheme. Thirteen thousand homogeneity-checked test materials were issued, covering a very wide range of analytes, including pesticides, toxins, veterinary drug residues, trace and nutritional elements, food colors, preservatives, sweeteners, alcohol congeners, fatty acids, nitrate, and proximate analysis. Participants returned 85% of requested data, and 47,000 z-score proficiency assessments were made, of which 81% were satisfactory. Evidence is presented of improvements in overall analytical ability with increased participation in proficiency testing in the areas of proximate analysis; organochlorine pesticide analysis; and lead, mercury, and acesulfame-K analyses. Little improvement was shown in other analytical areas such as calcium analysis. Overall accuracies for analysis of specific pesticides and specific trace elements in the circulated test materials were compared.