Characterization of CD4 and CD8 T cell responses in MuSK myasthenia gravis

Muscle specific tyrosine kinase myasthenia gravis (MuSK MG) is a form of autoimmune MG that predominantly affects women and has unique clinical features, including prominent bulbar weakness, muscle atrophy, and excellent response to therapeutic plasma exchange. Patients with MuSK MG have predominantly IgG4 autoantibodies directed against MuSK on the postsynaptic muscle membrane. Lymphocyte functionality has not been reported in this condition. The goal of this study was to characterize T cell responses in patients with MuSK MG. Intracellular production of IFN-gamma, TNF-alpha, IL-2, IL-17, and IL-21 by CD4+ and CD8+ T cells was measured by polychromatic flow cytometry in peripheral blood samples from 11 Musk MG patients and 10 healthy controls. Only one MuSK MG patient was not receiving immunosuppressive therapy. Regulatory T cells (Treg) were also included in our analysis to determine if changes in T cell function were due to altered Treg frequencies. CD8+ T cells from MuSK MG patients had higher frequencies of polyfunctional responses than controls, and CD4+ T cells had higher IL-2, TNF-alpha, and IL-17. MuSK MG patients had a higher percentage of CD4+ T cells producing combinations of IFN-gamma/IL-2/TNF-gamma, TNF-alpha/IL-2, and IFN-gamma/TNF-alpha. Interestingly, Treg numbers and CD39 expression were not different from control values. MuSK MG patients had increased frequencies of Th1 and Th17 cytokines and were primed for polyfunctional proinflammatory responses that cannot be explained by a defect in CD39 expression or Treg number.

Trends in American Board of Psychiatry and Neurology specialties and neurologic subspecialties

OBJECTIVE

To review the current status and recent trends in the American Board of Psychiatry and Neurology (ABPN) specialties and neurologic subspecialties and discuss the implications of those trends for subspecialty viability.

METHODS

Data on numbers of residency and fellowship programs and graduates and ABPN certification candidates and diplomates were drawn from several sources, including ABPN records, Web sites of the Accreditation Council for Graduate Medical Education and the American Medical Association, and the annual medical education issues of the Journal of the American Medical Association.

RESULTS

About four-fifths of neurology graduates pursue fellowship training. While most recent neurology and child neurology graduates attempt to become certified by the ABPN, many clinical neurophysiologists elect not to do so. There appears to have been little interest in establishing fellowships in neurodevelopmental disabilities. The pass rate for fellowship graduates is equivalent to that for the "grandfathers" in clinical neurophysiology. Lower percentages of clinical neurophysiologists than specialists participate in maintenance of certification, and maintenance of certification pass rates are high.

CONCLUSION

The initial enthusiastic interest in training and certification in some of the ABPN neurologic subspecialties appears to have slowed, and the long-term viability of those subspecialties will depend upon the answers to a number of complicated social, economic, and political questions in the new health care era.

MuSK-antibody positive myasthenia gravis: Clinical and electrodiagnostic patterns

OBJECTIVE

To examine the clinical manifestations and patterns of electromyographic abnormalities in MuSK-Ab positive myasthenia gravis.

METHODS

The clinical evaluations and electrodiagnostic testing results of 20 MuSK-Ab positive myasthenia gravis patients were retrospectively reviewed and compared with matched AChR-Ab positive (N = 72) and MuSK-Ab negative/AChR-Ab negative (N = 24) patients.

RESULTS

MuSK-Ab positive patients were younger and more frequently female and African-American, and compared to the AChR-Ab positive patients, were more likely to present with respiratory symptoms or neck extension weakness. MuSK-Ab positive patients were less likely to have abnormal jitter in a limb muscle: only 59% had abnormal jitter in the extensor digitorum communis muscle, compared to 80% of the AChR-Ab negative/MuSK-negative patients and 91% of the AChR-Ab positive patients.

CONCLUSIONS

Our MuSK-Ab positive patients not only differ demographically from our MuSK-Ab negative cohort, but they also appear to have a more limited distribution of SFEMG abnormalities.

SIGNIFICANCE

The possibility that electrophysiologic abnormalities may not be widely distributed should be considered during electrodiagnostic evaluation of suspected MuSK-Ab positive MG and in selecting muscles for molecular, morphologic, or microphysiologic studies in this condition.

Mycophenolate mofetil for myasthenia gravis: an analysis of efficacy, safety, and tolerability

The authors report a retrospective analysis of the use of mycophenolate mofetil (MyM) in 85 patients with autoimmune myasthenia gravis. The Myasthenia Gravis Foundation of America (MGFA) postintervention status (PIS) was used to characterize the treatment response in each patient. Sixty-two patients (73%) achieved a PIS status indicating improvement. Quantitative strength testing performed on the majority of patients before and after treatment also improved. Side effects to MyM were observed in 27% of patients but required discontinuation in only 6%.

Clinical aspects of MuSK antibody positive seronegative MG

Serum antibodies to muscle-specific receptor tyrosine kinase were detected in 12 of 32 patients with generalized seronegative MG. All were women, with onset between ages 21 and 59 years. Seven had prominent neck, shoulder, or respiratory muscle weakness and little or delayed ocular muscle involvement. The response to cholinesterase inhibitors was variable, and electromyographic findings suggested myopathy in several. None improved after thymectomy. All patients improved after plasma exchange, and most had a good response to selected immunotherapy. MuSK antibody status should help diagnose MG with atypical presentations and ensure appropriate patient treatment.

Mycophenolate mofetil for myasthenia gravis: an open-label pilot study

In an open-label study, 12 patients with refractory MG or who were taking only corticosteroids and required additional immunosuppression received mycophenolate mofetil 1 g twice daily for 6 months. A reduction of three points in a quantified MG score and two points in a manual muscle test or a reduction of 50% in corticosteroid dose defined efficacy. Eight patients improved, beginning after 2 weeks to 2 months. No major side effects were observed.

Predictive value of single-fiber electromyography in the extensor digitorum communis muscle of patients with ocular myasthenia gravis: a retrospective study

PURPOSE

To determine if the jitter in the extensor digitorum communis (EDC) muscle in patients with purely ocular myasthenia gravis (OMG) predicts the subsequent development of generalized myasthenic weakness-Methods: Included in this retrospective study were patients who initially had purely ocular manifestations and had been followed for at least 2 years after onset of myasthenic symptoms. The group consisted of 50 patients with purely ocular weakness, 26 of whom later generalized. All underwent single-fiber electromyography (SFEMG) studies in the EDC muscle at the initial examination

RESULTS

: Statistical analysis did not demonstrate that the amount of jitter in the EDC muscle predicted the development of generalized myasthenia gravis (GMG). Also, there was no threshold jitter value that predicted generalized weakness.

CONCLUSIONS

: SFEMG measurement of jitter in the EDC muscle demonstrates abnormal neuromuscular transmission in many patients with OMG but is not useful in predicting generalization in these patients.

Retrospective analysis of the use of cyclosporine in myasthenia gravis

The authors reviewed the records of patients with myasthenia gravis who took cyclosporine for at least 6 months between November 1987 and January 1999. Of 57 patients who took cyclosporine for an average of 3.5 years, 55 (96%) had clinical improvement. The median time to best clinical response was 7 months. Corticosteroids were discontinued or decreased in 95% of 38 patients taking them. Major side effects included elevated serum creatinine (28%) and malignancy (11%). Five percent could not afford or tolerate the drug.

Lambert-Eaton myasthenic syndrome: electrodiagnostic findings and response to treatment

The authors reviewed the incidence of cancer, repetitive nerve stimulation findings, and response to treatment in 73 patients with Lambert-Eaton myasthenic syndrome. Thirty-one patients (42%) had lung cancer, 29 small cell. Doubling of the compound motor action potential amplitude in three tested distal muscles was seen in only 41% of patients. Treatment with 3, 4-diaminopyridine produced moderate to marked self-reported functional improvement in 79% of the 53 treated patients.

Leukemia inhibitory factor, oncostatin M, IL-6, and stem cell factor mRNA expression in human thymus increases with age and is associated with thymic atrophy

The roles that thymus cytokines might play in regulating thymic atrophy are not known. Reversing thymic atrophy is important for immune reconstitution in adults. We have studied cytokine mRNA steady-state levels in 45 normal human (aged 3 days to 78 years) and 34 myasthenia gravis thymuses (aged 4 to 75 years) during aging, and correlated cytokine mRNA levels with thymic signal joint (sj) TCR delta excision circle (TREC) levels, a molecular marker for active thymopoiesis. LIF, oncostatin M (OSM), IL-6, M-CSF, and stem cell factor (SCF) mRNA were elevated in normal and myasthenia gravis-aged thymuses, and correlated with decreased levels of thymopoiesis, as determined by either decreased keratin-positive thymic epithelial space or decreased thymic sjTRECs. IL-7 is a key cytokine required during the early stages of thymocyte development. Interestingly, IL-7 mRNA expression did not fall with aging in either normal or myasthenia gravis thymuses. In vivo administration of LIF, OSM, IL-6, or SCF, but not M-CSF, i.p. to mice over 3 days induced thymic atrophy with loss of CD4+, CD8+ cortical thymocytes. Taken together, these data suggest a role for thymic cytokines in the process of thymic atrophy.

A randomized trial of 3,4-diaminopyridine in Lambert-Eaton myasthenic syndrome

OBJECTIVES

The authors report the results of a prospective, placebo-controlled, randomized study to evaluate the effectiveness of 3,4-diaminopyridine (DAP) in patients with Lambert-Eaton myasthenic syndrome (LEMS) and to determine the acute and long-term side effects of DAP.

METHODS

Twenty-six patients with LEMS completed a two-arm parallel treatment protocol in which DAP, 20 mg three times daily, or placebo was given blindly for 6 days, and a quantitative examination of muscle strength (the quantitative myasthenia gravis [QMG] score) was used as the primary measure of efficacy. After the blinded study, patients were given open-label DAP and monitored for side effects as long as there was symptomatic improvement.

RESULTS

Twelve patients took DAP, and 14 took placebo. There was no difference in the age of LEMS onset, gender distribution, incidence of lung cancer, or baseline muscle strength between the patients who were randomly assigned to receive placebo and those randomly assigned to DAP. Statistical analysis using the Wilcoxon's rank sum test demonstrated that patients who received DAP had a significantly greater improvement in the QMG score and in the summated amplitude of compound muscle action potentials recorded from three sentinel limb muscles. All but one LEMS patient had significant symptomatic improvement from subsequent open-label DAP. Side effects of DAP were negligible, consisting of perioral and digital paresthesia. Laboratory measurements demonstrated no evidence of toxicity affecting liver, renal, hematologic, endocrinologic, encephalographic, or electrocardiologic function acutely or after 6 months of open-label DAP.

CONCLUSIONS

This study corroborates previous studies and many years of clinical experience showing that DAP is an effective and safe treatment for LEMS.

Changes in thymic function with age and during the treatment of HIV infection

The thymus represents the major site of the production and generation of T cells expressing alphabeta-type T-cell antigen receptors. Age-related involution may affect the ability of the thymus to reconstitute T cells expressing CD4 cell-surface antigens that are lost during HIV infection; this effect has been seen after chemotherapy and bone-marrow transplantation. Adult HIV-infected patients treated with highly active antiretroviral therapy (HAART) show a progressive increase in their number of naive CD4-positive T cells. These cells could arise through expansion of existing naive T cells in the periphery or through thymic production of new naive T cells. Here we quantify thymic output by measuring the excisional DNA products of TCR-gene rearrangement. We find that, although thymic function declines with age, substantial output is maintained into late adulthood. HIV infection leads to a decrease in thymic function that can be measured in the peripheral blood and lymphoid tissues. In adults treated with HAART, there is a rapid and sustained increase in thymic output in most subjects. These results indicate that the adult thymus can contribute to immune reconstitution following HAART.

Botulinum toxin type B: a double-blind, placebo-controlled, safety and efficacy study in cervical dystonia

We enrolled and treated 122 patients with idiopathic cervical dystonia in a double-blind, placebo-controlled safety and efficacy study of botulinum toxin type B (BotB). Both A-responsive and A-resistant patients were enrolled. Patients received intramuscular injections of either BotB (2,500 U, 5,000 U, or 10,000 U) or placebo. The primary outcome measure of efficacy was the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS)-Total score at 4 weeks following study drug administration. Secondary measures of efficacy were TWSTRS-Severity, -Disability, and -Pain subscale scores, and Analog Pain Assessment, Investigator Global Assessment, Patient Global Assessment, and Sickness Impact Profile scores. Duration of effect was estimated with an intent-to-treat analysis of responders. Safety measures included clinical parameters, laboratory tests, and adverse events. The primary and most of the secondary analyses indicated a statistically significant treatment effect and a dose response. BotB is safe, well tolerated, and efficacious in the treatment of cervical dystonia at the doses tested.

Acquired myasthenia gravis

Myasthenia gravis, an antibody-mediated disorder of neuromuscular transmission that produces clinical weakness, may be ocular or generalized. Clinical diagnostic evaluation may be supplemented by electrophysiologic studies and antibody testing. Therapeutic options, including anticholinesterase inhibitors, immunosuppressive agents, plasmapheresis and thymectomy, are tailored for the individual patient. This article emphasizes the key aspects of the clinical evaluation, diagnosis, and therapy.

Treatment of spasmodic torticollis with intramuscular phenol injection

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Race, sex, and puberty influence onset, severity, and outcome in juvenile myasthenia gravis

We assessed the influence of race, sex, and puberty upon clinical features and outcome in 115 patients with autoimmune juvenile myasthenia gravis (JMG). These demographic variables influenced not only disease incidence but also disease severity, response to therapy, and outcome, despite comparable therapeutic strategies. Among white patients, those with prepubertal onset had low incidence and equal sex ratio; the incidence in females increased during and after puberty; males had lesser disease severity than females during and after puberty (p < 0.05); spontaneous remissions were most frequent (44%, p = 0.001) and persistence of active JMG for more than 10 years was least frequent (p = 0.05) in patients with prepubertal onset; remissions were more frequent after early than late thymectomy (p = 0.03); and final disease severity was less after early than late thymectomy. Black patients had similar incidence, disease severity, and sex ratio (F:M = 2:1) with pre-, peri-, or postpubertal disease onset; infrequent spontaneous or treatment-induced remissions; and the same final disease severity after early or late thymectomy. These observations imply that race and sex hormones modify the clinical features and outcome of JMG; spontaneous remissions are common in white patients with prepubertal disease onset; early thymectomy may be more beneficial than late thymectomy in white patients; and the role of thymectomy in the youngest patients is uncertain. We suggest that demographic factors should be considered when evaluating past and future therapeutic strategies for JMG.

The electrodiagnosis of myasthenia gravis and the Lambert-Eaton myasthenic syndrome

Electrodiagnostic studies are valuable in confirming the diagnosis of a disorder of neuromuscular transmission. They are used to distinguish presynaptic and postsynaptic abnormalities. These studies provide an objective measure of the severity of the illness and may be useful in assessing the response to therapy. This article reviews the electrodiagnostic techniques that are commonly used today and highlights their specificity, sensitivity, and pitfalls.

Single fiber EMG and repetitive stimulation of the same muscle in myasthenia gravis

We performed RNS and SFEMG studies of the same muscle in 46 patients with myasthenia gravis. Maximum decrement to 3-5-Hz stimulation before and after maximum voluntary exercise, percentage of action potential pairs with increased jitter and blocking, and mean MCD in each study were compared. A significant decrement (> 10% decrease in CMAP area or amplitude between the first and fourth response) was never found without increased jitter and impulse blocking on SFEMG. Increased jitter, blocking, and mean MCD were each correlated with maximum decrement (r > 0.61, P < 0.0001). We conclude that decrement to RNS and impulse blocking on SFEMG result from the same physiologic phenomenon, and that SFEMG is more sensitive at detecting disordered neuromuscular transmission given its ability to detect impulse blocking at levels below the resolution of RNS and increased neuromuscular jitter when there is not blocking.

Single fiber electromyography in myasthenia gravis during pregnancy

We report the use of single fiber electromyography (SFEMG) to demonstrate changes in the physiologic abnormality of myasthenia gravis (MG) during pregnancy. A 23-year-old became pregnant 15 months after the onset of mild ocular weakness. On initial evaluation, SFEMG jitter measurements demonstrated a slight abnormality of neuromuscular transmission. There was no change in severity of clinical disease or jitter measurements until the third trimester, when she improved. Jitter measurements at that time were normal. Labor was normal and she delivered a normal male. Three days postpartum, myasthenic weakness recurred temporarily and jitter measurements showed worsening. At 16 days and 6 weeks postpartum, she had only minimal medial rectus weakness and jitter studies were normal. Three months postpartum, ocular symptoms recurred and jitter measurements were slightly abnormal. She continued to worsen, developing limb muscle and severe ocular muscle weakness at 4 months postpartum. She was treated with plasma exchange and thymectomy. Prednisone was added 2 months after thymectomy due to continued worsening and development of oropharyngeal weakness. Three years postpartum she was taking prednisone 10 mg every other day and had only slight weakness of neck flexors, and jitter studies were again normal.

Acetylcholine receptor antibodies in juvenile myasthenia gravis

We analyzed relationships among pubertal stage at disease onset, sex, disease severity, and acetylcholine receptor antibody (AChR Ab) levels in 46 patients with autoimmune juvenile myasthenia gravis (JMG). Female predominance was least in children with prepubertal disease onset (F:M = 1.3:1) and increased in patients with peripubertal (F:M = 1.8:1) and postpubertal (F:M = 14:1) onset. Seronegative JMG was most common in children with early disease onset: 4 of 9 (44%) with prepubertal, 4 of 22 (18%) with peripubertal, and 0 of 15 (0%) with postpubertal onset were seronegative. The rapid therapeutic response to plasmapheresis was useful in distinguishing some patients with seronegative JMG from those with congenital myasthenia gravis (CMG). The high frequency of seronegative JMG in patients with prepubertal onset indicates that AChR Ab assays do not adequately discriminate between JMG and CMG in young children. Furthermore, the different sex distribution in patients with different pubertal stages at disease onset suggests that sex hormones play an important modulating role in JMG.

Botulinum toxin therapy for neurologic disorders

In the last 20 years, the therapeutic uses of botulinum toxin, a potent neurotoxin, have been investigated. The agent produces chemical denervation of muscle, thereby causing atrophy and weakness. Studies have shown that injection of this agent is an effective therapy for focal dystonias, particularly blepharospasm, hemifacial spasm, and torticollis. Investigation continues into the role of botulinum toxin in the treatment of anismus, detrusor-sphincter dyssynergia, writers' cramp, and other disorders in which focal weakening of selected muscles could be useful.

Single-fiber EMG demonstrates reinnervation dynamics after nerve injury

Serial single-fiber EMG (SF-EMG) studies in the frontalis muscle showed increased jitter with normal fiber density 15 days after facial nerve trauma. Both measurements were increased thereafter. The maximum increases occurred at 37 days, coincident with the initial return of function, and persisted until 67 days, when function had returned to normal. Thereafter, both features returned toward normal values, but were still elevated 34 months after injury.

Extubation after transsternal thymectomy for myasthenia gravis: a prospective analysis

Recommendations concerning postoperative extubation after thymectomy for myasthenia gravis are presently based upon retrospective chart reviews. We present the results of a prospective investigation of time to extubation after thymectomy for 14 patients over a 12-month period based upon a protocol that included preoperative immunologic therapy, combined epidural and general anesthesia, postoperative epidural narcotic analgesia, and a standardized approach to discontinuation of ventilatory support. After a neurologist took measures to optimize preoperative neuromuscular function, all 14 patients received agents to produce lumbar epidural anesthesia and light general anesthesia. Muscle relaxants were avoided in all but one patient. Postoperative analgesia was initially maintained with epidural hydromorphone, then therapy was switched to patient-controlled intravenous morphine sulfate. Criteria for weaning from mechanical ventilation, first measured at the end of anesthesia, were partial pressure of oxygen (arterial) greater than or equal to 90 mm Hg (fraction of inspired oxygen = 0.40), partial pressure of carbon dioxide (arterial) less than or equal to 50 mm Hg, pH greater than or equal to 7.30, and respiratory rate less than or equal to 30 breaths/min. If these criteria were not met, ventilatory support was continued postoperatively with intermittent mandatory ventilation, and the patient was weaned gradually from this support. Criteria for extubation included meeting the criteria for weaning, vital capacity greater than or equal to 10 mL/kg, and inspiratory pressure better than -30 cm H2O. Criteria for reintubation included tachypnea (respiratory rate greater than 40 breaths/min), respiratory acidosis not due to narcotics, or vital capacity less than or equal to 8 mL/kg. The mean time to extubation was 9 hours (range, 0.75 to 25 hours). Mean preoperative vital capacity was 2.59 +/- 0.64 L (range, 1.90 to 4.20), which decreased approximately 50% to 1.19 +/- 0.39 L (range, 0.70 to 2.0) at the time of extubation. No patient required reintubation. Half of the patients required postoperative anticholinesterase therapy based upon serial neurologic examinations; there were no instances of cholinergic crisis. Thirteen patients returned to the ward on the first postoperative day, and one on the second day. Thirteen patients preferred epidural analgesia to patient-controlled analgesia. The time to extubation and average length of stay in an intensive care setting were markedly reduced compared to those reported in previous retrospective studies. We conclude that a multidisciplinary approach that optimizes neuromuscular function and decreases poststernotomy pulmonary insult will shorten the time to extubation and decrease the length of stay in the intensive care or recovery room after thymectomy.

Electromyography in disorders of neuromuscular transmission

Electrophysiologic tests in neuromuscular transmission disorders are valuable aids in the clinical assessment of patients with suspected disease. The techniques of RNS and SFEMG are most reliable when the electromyographer is aware of their pitfalls and when they are interpreted in relation to the overall clinical setting. RNS is the most widely used technique to assess the integrity of neuromuscular transmission but may be normal in many patients. Among the techniques used to assess abnormality of neuromuscular transmission, SFEMG is the most sensitive.

Vascular headache from extracranial venous malformation

Headache associated with intracranial venous anomalies is well described but headache associated with extracranial venous malformation previously has not been recognized. A case of extracranial venous malformation producing vascular headache is presented.

Moyamoya disease associated with polycystic kidney disease and eosinophilic granuloma

Moyamoya disease has been associated with renal artery stenosis, cerebral hemorrhage, and multiple cranial traumas. We report a unique case of moyamoya disease associated with polycystic kidney disease and eosinophilic granuloma. Although the etiology of moyamoya disease is unknown, a familial pattern of occurrence has been documented. Of particular importance is its presentation with polycystic kidney disease, an autosomal dominant disease, suggesting a hereditary component to the etiology of this unusual vasculitic disease.

Reproductive performance in mares subjected to examination by diagnostic ultrasound

Mares were subjected to frequent examination by diagnostic ultrasound and data were compiled with respect to reproductive efficiency. The data were collected over a 3-yr period on 1032 light horse mares. The cummulative pregnancy rate at 35 d post-ovulation was 96.8% and the pregnancy rate per cycle was 76.0% as determined by ultrasound examination. The average number of cycles per conception was 1.43, with an average of 2.29 inseminations per cycle. The incidence of early embryonic death was 7.8%. Mares were subjected to an average of 5.04 scans during the follicular phase of the cycle. The average number of ultrasound examinations per mare (including pregnancy examinations) was 9.99. Although these data were obtained from an experiment that did not use both control and treated mares, there was no indication that preovulatory oocytes or embryos were damaged by routine ultrasound examination. Comparisons with existing data from commercial facilities are difficult to make concerning any improvement in reproductive efficiency resulting from the routine use of ultrasonography, but these data do suggest relative safety in equine reproductive management when ultrasound examinations are conscientiously used.

Evaluation of an automatic method of measuring features of motor unit action potentials

This study was performed to evaluate an automatic method of motor unit action potential (MUAP) analysis developed in our laboratory. MUAPs were recorded from the biceps brachii muscle of 68 normal subjects and 122 patients with nerve or muscle disease. The values of mean MUAP durations from normal subjects obtained by automatic analysis were similar to those reported in the literature. However, the normal range of MUAP amplitude and the incidence of polyphasic MUAPs were much higher. Normal ranges of mean MUAP area, area/amplitude ratio, and the number of turns were also defined. Automatic analysis demonstrated an abnormality of at least one MUAP feature in 70% of patients. There was concordance between automated analysis and visual assessment of MUAPs in 76% of patients with neuropathy but in only 50% of patients with myopathy. The relationships between different MUAP features seen in neuropathy and myopathy are explained in physiologic terms.

The effect of cholinesterase inhibitors of SFEMG in myasthenia gravis

We report four patients with myasthenia gravis (MG) in whom single-fiber electromyography (SFEMG) jitter measurements were normal in some muslces while they were taking pyridostigmine and became abnormal 2-14 days after the medication was discontinued. When the abnormality of neuromuscular transmission in MG is mild, cholinesterase inhibitors may mask the findings of increased jitter on SFEMG.

Automatic analysis of the electromyographic interference pattern using the turns: amplitude ratio

This study was performed to compare different techniques of analyzing the electromyographic interference pattern (IP). Recordings were made from the biceps muscle with a concentric needle electrode at different sites and at different constant levels of voluntary contraction. The number of turns per second (NT), the mean amplitude change between successive turns (MA) and NT:MA ratio were determined for epochs of 1 sec duration. Normal limits of individual epoch NT:MA ratios and the mean value of NT:MA ratio obtained from all epochs in each muscle were determined. The mean NT:MA ratio was less in normal males than in females. IP recordings were made in the biceps muscle of 69 patients with neuropathy and 54 patients with myopathy, though this muscle was not necessarily affected by the disease in all patients. The IP was abnormal by visual inspection in 82% of patients compared to 61% based on NT:MA ratio and 74% using a technique that automatically quantitates some features of the IP that are assessed subjectively by an electromyographer. All techniques demonstrated IP abnormalities in more than 80% of the muscles that were moderately to severely weak. Though measuring the NT:MA ratio without monitoring the force of contraction is not as sensitive as other IP analysis techniques, it may be useful in quantitating abnormalities when other techniques are not available.

Single fiber electromyography in chronic progressive external ophthalmoplegia

We have reviewed the electromyographic (EMG) studies of 17 patients with chronic progressive external ophthalmoplegia (CPEO). In 13 of 17 patients, conventional concentric needle EMG demonstrated a "myopathic" pattern, usually predominating in the shoulder muscles. Single-fiber EMG showed increased jitter and/or blocking in at least one muscle in 13 of 16 patients. Jitter was increased in the frontalis muscle in 10 of 13 patients and in an arm muscle in 5 of 12. When both muscles were tested, jitter was greater in the frontalis muscle in 5 patients and in the arm muscle in 2. These observations demonstrate that it may be difficult to distinguish myasthenia gravis from CPEO by EMG. The frequency with which abnormal jitter is found in CPEO suggests that, in addition to a mild generalized myopathy, a primary defect in neuromuscular transmission may be present.

Facial diplegia due to amyloidosis

In a 61-year-old man with facial diplegia and new onset of congestive heart failure (CHF), electroneuromyography indicated diffuse axonal degeneration, but sural nerve biopsy showed mild changes and no amyloid. Four months later, after the onset of diplopia and increasing CHF, rectal biopsy demonstrated amyloid.

Forearm neuropathy and pruritus

Five adult patients (four of them men) had episodic brachioradial pruritus associated with forearm paresthesia and hypalgesia. No cervical, shoulder, or forearm trauma was known. Onset was variable, but two had had the condition for more than ten years. In each, sensory alteration was detectable by pinprick and temperature in the distribution of the posterior cutaneous nerve of the forearm supplying the skin over the proximal portion of the brachioradial muscle. This seems to be a benign neuropathy.

Ergot, the "jerks," and revivals

Epidemics of epilepsy, a form of mass hysteria, were known in Eastern and Western cultures in the 17th and 18th centuries. A unique situation in the United States during the 19th centurey was the frontier religious movement, the setting in which the "jerks" occurred. The "falling exercise," "dancing exercise," "barking exercise," "laughing exercise," and the "running exercise" centered around the excitement involved in the religious revival. During some exercises, people saw "visions," and exhibited bizarre behavior and sudden jerking motions. During the summers of 1801-1803 on the Kentucky frontier, some pioneers who attended the religious revival camp meetings had convulsions, hallucinations, tremors, jerks, compulsive dancing and "epileptic trances." Although these have been assumed to be psychological in origin, the epidemiology of the symptoms may correlate with the diagnosis of ergotism. Those affected were usually children and young adults. Symptoms of ergotism include giddiness, fatigue, depression, formications, muscle twitching, tonic spasms, convulsions, delirium, and loss of speech.

L-glucosylceramide: synthesis, properties, and resistance to catabolism by glucocerebrosidase in vitro

Procedures for the synthesis and radioactive labeling of L-glucosylceramide are described. This compound is a stereoisomeric analogue of D-glucosylceramide which occurs in nature and accumulates in pathological quantity in the organs and tissues of patients with Gaucher disease. The properties of L-glucosylceramide that have been examined so far have been found to be indistinguishable from those of the naturally occurring glycolipid. However, L-glucosylceramide is completely refractory to enzymatic hydrolysis by purified placental glucocerebrosidase and enzyme(s) present in whole tissue extracts. It is anticipated that L-glucosylceramide will be a uniquely useful substance for exploring pathogenetic processes in animal analogues of Gaucher disease.