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.

Brachial plexopathy: recurrent cancer or radiation?

We reviewed clinical and electrodiagnostic features of 16 patients with neoplastic brachial plexopathy (NBP) and 17 patients with radiation-induced plexopathy (RBP). The groups were similar in symptom-free interval after cancer diagnosis and location of the plexus lesions. NBP patients had pain and Horner's syndrome; RBP patients had paresthesias, but rarely Horner's. NBP patients presented earlier after symptom onset and had a shorter course. RBP patients more frequently had abnormal sensory and normal motor nerve conduction studies and characteristically had fasciculations or myokymia on EMG.

Common peroneal mononeuropathy: a clinical and electrophysiologic study of 116 lesions.

We analyzed the clinical and electromyographic (EMG) findings of 116 common peroneal mononeuropathies in 103 patients (13 with bilateral lesions). Prior to the EMG examination, the diagnosis was not clinically suspected or seriously considered in 44% of the lesions. Sensory manifestations were common (79%) but pain was rare (16.5%). The onset was acute in 57 patients, gradual in 35, and indeterminate in 11. Of the 116 lesions, 64 were solely axonal loss in type, 23 manifested as conduction block, presumably secondary to focal demyelination, and 29 were a mixture of the two. Contrary to common belief, the pathophysiology was predominantly axonal loss regardless of etiology, including those that developed perioperatively. The peroneal motor nerve conduction study, recording tibialis anterior muscle, was the single most important electrophysiologic study; it localized all 52 lesions causing conduction block at the fibular head. In contrast, peroneal motor conduction velocity along the knee-to-fibular head segment was seldom abnormal, with slowing in only five of the 52 cases.

Postpartum neuralgic amyotrophy.

We report 11 women with at least one episode of neuralgic amyotrophy occurring postpartum. One woman had three episodes-two postpartum and a third occurring after minor foot surgery. Two others had a second episode, one following a first trimester spontaneous abortion and one after a viral syndrome. Pain followed delivery from as little as 1 to 2 hours to up to 2 weeks and usually lasted from a few weeks to several months. Weakness, if delayed, followed onset of pain by 2 or 3 days up to 5 weeks. Four of the episodes were bilateral. Clinical weakness and electrodiagnostic findings varied widely, from involvement of a single peripheral nerve (e.g., long thoracic, anterior interosseous) to multiple bilateral proximal and distal nerves. Functional recovery was excellent (90 to 100%) in 8 of the 10 with adequate follow-up, requiring as little as 2 weeks or up to 3 years. Two women have moderate persisting weakness (both bilateral) at 3 years and 2 years. Five patients went on to subsequent deliveries without recurrence of neuralgic amyotrophy. Only one of the 11 women had a history suggesting familial neuralgic amyotrophy, a disorder generally thought to be associated particularly with postpartum episodes. Although the etiology of postpartum neuralgic amyotrophy remains unknown, an immunologic mechanism is suspected. Focal demyelination may play a role in some, but clearly axonal degeneration is predominant in the majority.

Spinal accessory (11th) nerve palsy following carotid endarterectomy.

We report three cases of ipsilateral spinal accessory nerve palsy complicating carotid endarterectomy. Awareness of this cranial nerve injury, as a complication of this common surgical procedure, can lead to early diagnosis and avoids unnecessary investigations. This should be considered whenever such patients complain postoperatively of ipsilateral shoulder pain/weakness or "aching" about the ear, even if some time has elapsed since surgery.

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.

Compartment syndromes and compression neuropathies in coma.

Eight patients are reported who developed peripheral nerve injuries due to limb compression during unattended coma. In each patient, the site of the peripheral nerve lesion or the unique combination of peripheral nerve lesions and swollen limbs, pressure blisters, or myoglobinuria indicated that compartment syndromes caused the nerve injury. The peripheral nerve injuries were characterized by severe axonal loss with persistent and often disabling sequelae.

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.

Cervical radiculopathies: comparison of surgical and EMG localization of single-root lesions.

To identify the various electrodiagnostic (EDX) patterns of C-5, C-6, C-7, and C-8 cervical radiculopathy, we compared 50 cases of surgically proven solitary-root lesions with their preoperative EDX patterns. We excluded patients with polyradiculopathy, myelopathy, and previous surgery. We classified EDX studies as abnormal only by the needle electrode examination, and only by the demonstration of fibrillation potentials (either the positive sharp wave or the biphasic spike form). Seven patients (14%) had C-5 radiculopathy, nine (18%) had C-6, 28 (56%) C-7, and six (12%) C-8. With C-5, C-7, and C-8 radiculopathies, changes were relatively stereotyped, with involvement of the spinati,deltoid, biceps, and brachioradialis with C-5; the pronator teres, flexor carpi radialis, triceps, and anconeus with C-7; and the first dorsal interosseous, abductor digiti minimi, abductor pollicis brevis, flexor pollicis longus, and extensor indicis proprius with C-8. The root lesion with the most variable presentation was C-6--in half the patients, the findings were similar to C-5 radiculopathies, except that the pronator teres tended to be involved, whereas in the other half, the findings were identical to those with C-7 radiculopathies.

Ischemic monomelic neuropathy.

Ischemic monomelic neuropathy (IMN) is an infrequently recognized type of ischemic neuropathy produced by the shunting of blood away from, or the acute noncompressive occlusion of, a major proximal limb artery. IMN consists of multiple axonal-loss mononeuropathies that develop acutely and simultaneously in the distal portion of a limb. We found stereotyped clinical and EMG features in 14 patients. In six the IMN was thromboembolic in nature, whereas in eight it was due to various vascular surgical procedures. Our experience with IMN suggests that distal axonal infarction can occur without significant muscle necrosis, supporting the hypothesis that in humans the distal nerve fibers are more vulnerable than muscle to acute noncompressive limb ischemia.

Amyotrophic lateral sclerosis: effects of acute intravenous and chronic subcutaneous administration of thyrotropin-releasing hormone in controlled trials.

We performed double-blind crossover trials to assess the effects of thyrotropin-releasing hormone (TRH) on amyotrophic lateral sclerosis patients. For acute intravenous trials, 500 mg TRH or placebo with norepinephrine was given at 1-week intervals (16 patients). CSF TRH concentration increased, and clinical side effects appeared with TRH. For chronic studies, 25 mg TRH and a saline placebo were given subcutaneously every day for 3 months (25 patients). CSF TRH level increased 29-fold after a single TRH injection, and mild transient side effects occurred. Vital signs, respiratory function, semiquantitative and quantitative neurologic function, muscle strength by manual and dynamometer testing, and EMG were studied. With daily TRH, 10 patients noted subjective improvement without objective evidence, and 10 patients complained of worsening of the disease with objective decline after TRH was stopped. Statistical analysis, however, showed no beneficial effects from either acute or chronic TRH trials.

Fast axonal transport in amyotrophic lateral sclerosis: an intra-axonal organelle traffic analysis.

Fast transport of intra-axonal organelles was studied in motor nerve from amyotrophic lateral sclerosis (ALS) patients. Organelle traffic in ALS nerves demonstrated a significant increase in anterograde mean speed, while retrograde mean speed was decreased compared with that of controls. Retrograde traffic density (organelles per unit time) was also significantly decreased in the ALS specimens. Anterograde transport machinery is therefore intact and may be responding to the increased physiologic demand of larger motor units. Diminished retrograde speed and organelle traffic density are consistent with a defect in retrograde transport and could impair communication between axon terminals and perikarya.

Mechanism and frequency of brachial plexus injury in open-heart surgery: a prospective analysis.

A computer-assisted prospective analysis of 531 patients undergoing open-heart operations revealed that 26 patients (5%) sustained brachial plexus injury. In 22 of the 26 patients (85%), the lesion involved the lower trunk or C8-T1 nerve roots. Electromyograms confirmed the clinical impression in 13 patients. In 19 of the 26 patients (73%), the side on which the plexus lesion was found correlated with the side of internal jugular vein cannulation. Because of the anatomical proximity of the lower trunk to the internal jugular vein and the preponderance of lower trunk lesions, we postulate that traumatic cannulation may be a major mechanism of plexus injury. Thus, the resulting syndrome of pain, dysesthesias, and hand weakness may sometimes be preventable.

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.

High sciatic lesion mimicking peroneal neuropathy at the fibular head.

We report 4 patients with severe, axon-loss, high sciatic mononeuropathies affecting exclusively the peroneal fibers: a boy with a slowly-growing nerve tumor, a woman with an injection injury, and 2 patients who had undergone proximal femur surgery. Clinically, the findings mimicked those seen with common peroneal neuropathy at the fibular head. The peroneal conduction studies were very low in amplitude/unelicitable. Conversely, the tibial studies and H-responses were normal in all; the sural responses were normal in one while low in amplitude/unelicitable in the remaining three. The biceps femoris, short-head, and all peroneal-innervated muscles showed fibrillations and profound motor unit loss. Conversely, the remaining hamstrings and all tibial-innervated muscles were normal. We conclude that a sciatic lesion can imitate a more distal peroneal lesion. Needle EMG of the biceps femoris, short head, is essential for correct diagnosis.

Diabetic proximal neuropathy. Clinical and electromyographic studies.

Clinical and electromyographic findings in 27 diabetics with proximal lower extremity weakness were analyzed. Two groups could be distinguished: patients in whom electromyographic findings were restricted to the clinically involved parts of the lower extremity (group A) and those in whom an associated distal symmetric, peripheral neuropathy could be proved on clinical and electromyographic grounds (group B). Patients in group B had significantly greater incidence of the following features: gradual onset of symptoms, bilateral proximal lower extremity weakness, insulin dependency, recent weight loss, EMG evidence of bilateral disease and paraspinal fibrillations. These findings concur with recent reports describing heterogeneity in the syndrome of "diabetic proximal neuropathy".

Solitary primary lymphoma of the sciatic nerve: case report.

An unusual case of a solitary extranodal primary lymphoma of the sciatic nerve in a patient presenting with sciatica and a left footdrop is described. Magnetic resonance imaging was successful in identifying a fusiform lesion in the sciatic nerve in the left infragluteal region. Surgical exploration and biopsy confirmed this as a B cell lymphoma. An extensive metastatic work-up has not identified other sites of lymphomatous involvement.

Sensory nerve conduction studies.

Sensory nerve conduction studies (NCS) are an indispensable component of the electrodiagnostic examination. They evolved from mixed NCS, and were initially described by Dawson in 1950. Gilliatt and Sears first reported their clinical value in 1958. Compared to motor NCS, sensory NCS are much less standardized. Variables regarding them include: (a) bipolar vs. monopolar recording; (b) antidromic vs. orthodromic technique; (c) needle vs. surface stimulating electrode(s); (d) needle vs. surface recording electrodes; (e) fixed vs. variable distances between cathode and active recording electrode; (f) measuring latencies to onset vs. to peak; and (g) measuring amplitudes baseline to peak vs. peak to peak. The value of sensory NCS with various peripheral nerve fiber lesions, including plexopathies, mononeuropathies, and polyneuropathies, is discussed.

The electrodiagnostic examination with myopathies.

The values and limitations of the electrodiagnostic examination in assessing patients with possible myopathies are discussed. Limitations include: (1) no findings are specific for muscle disease; (2) the particular changes may be quite diverse; (3) myopathies of different etiologies may have the same presentation, whereas the same myopathy may have different presentations at different times; (4) a specific myopathy cannot be diagnosed; and (5) the ability to diagnose myopathy may be seriously compromised by the presence of certain disorders. Benefits include: (1) widespread muscle sampling; (2) help in determining most appropriate muscle for biopsy; (3) ascertaining, to some extent, the type of myopathy present, depending on the particular findings; (4) distinguishing entities often confused clinically with myopathies; (5) recognizing abnormalities (e.g., myotonic discharges) otherwise undetectable. Both the clinical and electrodiagnostic presentations of myopathies are discussed. Regarding the latter, the potential or actual changes seen with each component of the electrodiagnostic assessment (nerve conduction studies, late responses, repetitive stimulation studies, needle electrode examination, quantitative electromyographic studies) is reviewed.

Causes and diagnosis of sensory neuropathies: a review.

Sensory neuropathies are rare but unique peripheral neuropathies that involve only the peripheral sensory system. The diagnosis is made by both clinical and electrophysiological findings. Sensory neuropathies occur predominantly in women. The symptoms begin in the arms more often than the legs and occur asymmetrically. Pain and severe sensory ataxia in varying degrees are the main presenting symptoms. Definable causes of sensory neuropathies are hereditary, paraneoplastic, immunological, metabolic, infectious, and drug-induced disorders. In our experience, however, nearly half of all sensory neuropathies have been idiopathic. The clinical course of these sensory neuropathies is variable. The symptoms clearly worsened in 25% of our patients, but in the rest remained unchanged for many years, resulting in a poor functional prognosis because of intractable pain and ataxia. Most sensory neuropathies are resistant to any treatment. We review the electrophysiological features, laboratory findings, and nerve biopsy results in our patients and discuss in detail the potential underlying diseases included in the differential diagnosis.