Corticotropin and corticosteroids in generalized myasthenia gravis: comparative studies and role in management

History of Myasthenia Gravis Revisited

The first description of myasthenia gravis (MG) was given by Thomas Willis in 1672. MG was the focus of attention after mid-nineteenth century and a great amount of information has been accumulated in a span of 150 years. The aim of this review is to convey this information according to a particular systematic and to briefly relate the experience of Istanbul University. MG history was examined in four periods: 1868-1930, 1930-1960, 1960-1990, and 1990-2020. In the first period (1868-1930), all the clinical characteristics of MG were defined. Physiological/pharmacological studies on the transmission at the neuromuscular junction were initiated, and the concept of repetitive nerve stimulation emerged. A toxic agent was believed to be the cause of MG which appeared to resemble curare intoxication. Association of MG with thymus was noticed. No noteworthy progress was made in its treatment. In the second period (1930-1960), acetylcholine was discovered to be the transmitter at the neuromuscular junction. Repetitive nerve stimulation was used as a diagnostic test. The autoimmune nature of MG was suspected and experiments to this end started to give results. The hallmark of this period was the use of anticholinesterases and thymectomy in the treatment of MG. The third period (1960-1990) can probably be considered a revolutionary era for MG. Important immunological mechanisms (acetylcholine receptor isolation, discovery of anti-acetylcholine receptor antibodies) were clarified and the autoimmune nature of MG was demonstrated. Treatment modalities which completely changed the prognosis of MG, including positive pressure mechanic ventilation and corticosteroids as well as plasma exchange/IVIg and azathioprine, were put to use. In the fourth period (1990-2020), more immunological progress, including the discovery of anti-MuSK antibodies, was achieved. Videothoracoscopic thymectomy reduced the morbidity and mortality rate associated with surgery. New drugs emerged and clinical trials were performed. Valuable guidelines were published. In the last part of the review, the experience in MG of Istanbul University, a pioneer in Turkey, is related.

Maintenance immunosuppression in myasthenia gravis, an update

Therapies for myasthenia gravis (MG) include symptomatic and immunosuppressive/immunomodulatory treatment. Options for immunosuppression include corticosteroids, azathioprine, mycophenolate mofetil, cyclosporine, tacrolimus, methotrexate, rituximab, cyclophosphamide, eculizumab, intravenous immunoglobulin, subcutaneous immunoglobulin, plasmapheresis, and thymectomy. The practical aspects of long-term immunosuppressive therapy in MG are critically reviewed in this article. Application of one or more of these specific therapies is guided based on known efficacy, adverse effect profile, particular disease subtype and severity, and patient co-morbidities.

Clinical trials for myasthenia gravis: a historical perspective

Symposia dedicated to myasthenia gravis and related disorders date back to 1947 and serve as markers of the progress for the field. We provide a brief historical review of therapy development through the lens of the publications that arose from the close to quinquennial meetings that have been supported nearly since their inception by the Myasthenia Gravis Foundation of America and the New York Academy of Sciences. One can appreciate great advances, false starts, and dead ends that are found in all fields of medicine. We tally up the score card for MG and find points scored, but the win is not yet close.

Intravenous immunoglobulin as monotherapy for myasthenia gravis during pregnancy

INTRODUCTION

Pregnant women with myasthenia gravis (MG) are at increased risk of complications and adverse outcomes, including the teratogenic effects of many drugs used to treat MG women of childbearing age. The effectiveness of intravenous immunoglobulins (IVIg) on other autoimmune mediated diseases has been extensively reported in recent years, although little is known about the role of IVIg in the treatment of MG during pregnancy. We designed this study to determine the effectiveness of IVIg as monotherapy during pregnancy for women with MG.

MATERIAL AND METHODS

Five pregnant MG patients (mean age at delivery 36.4years, SD 5.8, range 29.4-45.2) were studied in 2013-14. Their treatment was switched to monthly IVIg cycles 2months before the pregnancy. Follow-up included monthly neurological QMG throughout the pregnancy and postpartum, obstetrical monitoring during monthly visits in the first two trimesters of the pregnancy, fortnightly visits between week 32 and week 36, and weekly visits after 36weeks, and neonatal follow-up after delivery.

RESULTS

We observed no exacerbations during pregnancy, delivery or post-partum. The mean QMG score at baseline (before pregnancy) was 7.4 points in five women with generalized forms of MG. The maximum mean value reached during pregnancy was 8.6 points. The mean pregnancy duration was 38 w+5 d. No infant with transient neonatal myasthenia gravis.

CONCLUSIONS

These results suggest that monotherapy with IVIg during pregnancy in MG patients could be promising, although confirmation is required in studies with larger populations.

Treatment of Acquired Autoimmune Myasthenia Gravis: a Topic Review

We propose a new approach to staging the disease based on clinical and immunological response to treatment. We oppose clinical remission to immunological remission and define total clinical remission as the goal of therapy. We describe the use, side effects and indications of established therapies. Acetycholine esterase inhibitors are only a symptomatic treatment as is plasma exchange. Usefulness and limits of thymectomy, corticosteroids and immunosuppressants are described here. Their goal is to reduce the auto-immune process. Long-term hazards from these medications are described and methods to reduce their potential risks are suggested. We suggest the number of patients having life threatening complications while undergoing aggressive immunosuppression can be reduced by a systematic approach to follow-up. In the second part of this review article, adapting management to specific situations is emphasized in refractory disease, respiratory failure, neonatal and juvenile forms of the disease. The special situation of seronegative myasthenia is discussed.

Glucocorticoids in myasthenia gravis - if, when, how, and how much?

Glucocorticoids (GC) are the most commonly used immune-directed therapy in myasthenia gravis (MG). However, to date, GC have not proven their effectiveness in the setting of a randomized clinical trial that complies with currently accepted standards. The rationale for the use of GC in MG is the autoimmune nature of the disease, which is supported by consistent positive results from retrospective studies. Well-defined recommendations for treatment of MG with GC are lacking and further hampered by inter- and intra-individual differences in the disease course and responses to GC treatment. Uncertainties concerning GC treatment in MG encompass the indication for treatment initiation, exact dosage, dose adjustment in specific conditions (e.g., pregnancy, thymectomy), mode of tapering, and surveillance of adverse events (AE). This review illustrates the mode of action of GC in the treatment for MG, presents the currently available data on GC treatment in MG, and attempts to translate the currently available information into clinical recommendations.

Treatment Principles in the Management of Autoimmune Myasthenia Gravis

The pathogenesis of myasthenia gravis (MG) involves a T cell-directed antibody-mediated autoimmune attack on the nicotinic acetylcholine receptor (AChR) or, occasionally, on other postsynaptic antigens. The antibodies induce their effects through complement-mediated destruction of the postsynaptic endplate membrane with resultant reduction in endplate AChR, and to a lesser degree by increased turnover of endplate AChR or blockade of AChR function. Considerable progress in the treatment of MG has accrued from so-called symptomatic treatments, including improved critical care of seriously ill patients and medications (e.g., cholinesterase inhibitors) increasing the concentration of acetylcholine at the remaining endplate AChRs. Information from other autoimmune diseases and from the response of the normal immune system to invading pathogens supports the view that the course of MG is characterized by exacerbations and remissions. Therefore, the goal in MG treatment is to induce and maintain a remission. This usually involves combinations of short-term and long-term immunosuppressive agents. Selection of the particular combinations of agents in a given patient is guided by the goal of minimizing the cost/benefit ratio of the regimen in an individual patient. In general, the plan involves an initial forceful attack followed by a slow and measured withdrawal.

Immunoglobulin treatment in refractory Myasthenia gravis

Failure to induce and maintain remission in severe exacerbations of myasthenia gravis (MG), despite optimal care, is a common problem. We evaluated the efficacy and safety of high-dose intravenous immunoglobulin (IVIg) therapy in an open-label study of 10 patients with severe generalized myasthenia and an acute deterioration unresponsive to conventional therapy including high-dose corticosteroids, cyclosporine, and azathioprine. Intravenous Ig at a loading dose of 400 mg/kg was administered daily for 5 consecutive days, with maintenance IVIg treatment at a dose of 400 mg/kg, once every 6 weeks. Significant improvement occurred in all patients, beginning at 6 +/- 2 days of treatment as measured by the Osserman scale, fatigue variables, muscle strength, and respiratory function tests. No side effects were observed during induction of remission. Further IVIg treatments were highly efficacious in maintaining the remission. The severity of the disease decreased by 2.5 +/- 0.8 grades of the Osserman scale over a period of 1 year (P <0.001), in parallel with reduction of immunosuppressive therapy as well as a decrease in acetylcholine receptor antibody titers (P < 0.01). Intravenous Ig therapy seems to be highly potent for inducing rapid improvement in refractory myasthenia during acute deterioration as well as for maintaining remission.

Seronegative myasthenia gravis and human immunodeficiency virus infection: response to intravenous gamma globulin and prednisone

BACKGROUND

There are only rare reports of myasthenia gravis complicating human immunodeficiency virus infection. The role of immunomodulatory therapy is unknown.

METHODS

Case report and literature review.

RESULTS

The diagnosis of human immunodeficiency virus infection followed that of myasthenia gravis in a 35-year-old man. Clinical and electrophysiological features were diagnostic of generalized myasthenia gravis but two edrophonium chloride tests and acetylcholine receptor antibodies were negative. Prednisone therapy and intravenous gamma globulin were associated with rapid clinical recovery.

CONCLUSIONS

Prednisone therapy and intravenous gamma globulin may be helpful in patients with generalized myasthenia gravis complicating HIV infection.

The management and outcome of patients with myasthenia gravis treated acutely in a neurological intensive care unit

The management and clinical course of patients with myasthenia gravis admitted to a neurological intensive therapy unit (ITU) over a 66 month period were reviewed. Twenty-seven patients were admitted in myasthenic crisis, eight of whom had multiple admissions. One patient had a cholinergic crisis and a further patient an acute myocardial infarction. A specific aetiological factor precipitating myasthenic crisis was identified in 19 instances: infection (8), reduction in medication (5), menstruation (4), and steroid administration (2). Thirteen patients with crisis had had a previous thymectomy, six with thymoma. Twenty-three out of 35 (66%) patients admitted in crisis required intubation; nine subsequently needed a tracheostomy. Twenty-nine patients received plasma exchange and seven intravenous immunoglobulin. Four patients in myasthenic crisis died in ITU [adult respiratory distress syndrome (1), disseminated intravascular coagulation and cytomegalovirus (CMV) pneumonitis (1), cardiac failure (1) and multiple organ failure (1)]. Appropriate management of myasthenia gravis requires the easy availability of specialised neuro-intensive care facilities. Copyright Rapid Science Ltd

Thymectomy: its role in the management of myasthenia gravis

The management and clinical course of patients with myasthenia gravis admitted to a neurological intensive therapy unit (ITU) for thymectomy over a 66 month period were reviewed. There were 53 patients, 20 male and 33 female, mean age 35.2 years (18-74) and median ITU stay of 5 days (2-30). Indications for thymectomy were thymic enlargement on computed tomography (34%), persistence of generalized symptoms (38%), a combination of both (20%), steroid side effects or dependency (4%) and progressive bulbar symptoms (4%). Following thymectomy, thymic histology revealed thymic follicular hyperplasia (26/53; 49%), atrophy (11/53; 21%), thymoma (12/53; 23%) and normal thymus (4/53; 8%). Post-operatively 23% required prolonged intubation (> 48 hrs); two patients required a tracheostomy 10 and 13 days post-operatively. Plasma exchange was required for two patients (3.8%) due to persistent severe myasthenic weakness. Three patients (6%) developed a post-operative chest infection and one pseudomembranous colitis. There were no post-operative mortalities during the study period. After 2 years, 35% of patients were in remission and 46% had ocular or mild generalized symptoms only. Thymectomy for myasthenia gravis is followed by sustained clinical improvement in the majority of patients. The appropriate post-operative management of these patients is best undertaken in a specialized neuro-intensive care setting. Copyright Rapid Science Ltd

Randomized trial of azathioprine or prednisone for initial immunosuppressive treatment of myasthenia gravis

Ten patients with myasthenia gravis were randomized to azathioprine or prednisone as the initial immunomodulating drug and followed for over one year. Of five patients randomized to azathioprine, two had idiosyncratic reactions and were immediately crossed over to prednisone. Two patients completed one year on azathioprine with little or no change in level of function and were crossed over to prednisone and showed greater improvement. The fifth patient on azathioprine had a satisfactory improvement and continued on it during the second year. All patients initially randomized to prednisone improved, but the degree varied among patients. The side effects of azathioprine were idiosyncratic reactions. The side effects of prednisone were manageable.

Corticosteroid therapy in Duchenne muscular dystrophy

In recent years, various clinical trials have documented the benefit of glucocorticoid therapy in the palliation of Duchenne muscular dystrophy (DMD). Prednisone therapy, daily or on alternate days, has been confirmed to be of value in enhancing muscle strength and function in DMD for up to two years. However, there is evidence that corticosteroid treatment results in muscle weakness and degeneration. This review, therefore, examines the available studies and addresses various possible mechanisms involved in the efficacy of prednisone therapy and amelioration of DMD. The progression of DMD is known to be associated with profound changes in structure, biochemistry and physiology of the affected muscles. It is hypothesized, therefore, that these very changes offer a fortunate set of circumstances, and it is owing to these alterations, as well as the well known anti-inflammatory/immunosuppressive action of steroid, that muscles in DMD are rendered responsive resulting in significant improvement of muscle bulk and function.

Myasthenia gravis

Myasthenia Gravis is a disorder of neuromuscular function resulting from an immunologically based premature destruction of acetylcholine receptors. The disease is characterized clinically by variable weakness accentuated by repetitive muscular activity and usually responding to the administration of acetylcholinesterase inhibitors. Myasthenia Gravis is a complex disease and requires understanding of the many facets of its natural history and immunological basis to ensure optimal individual patient management. The long-term goal is control of the immunological imbalance; treatment regimens include thymectomy, corticosteroids, azathioprine, and plasmapheresis. The common use of acetylcholinesterase inhibitors provides symptomatic relief during variable daily muscular activity. Disability due to myasthenia gravis is to a large extent reversible and death is preventable. Early recognition of myasthenia gravis and appropriate treatment are often rewarded by remission that may be permanent.

Steroids induce acetylcholine receptors on cultured human muscle: implications for myasthenia gravis

Antibodies to the acetylcholine receptor (AChR), which are diagnostic of the human autoimmune disease myasthenia gravis, block AChR function and increase the rate of AChR degradation leading to impaired neuromuscular transmission. Steroids are frequently used to alleviate symptoms of muscle fatigue and weakness in patients with myasthenia gravis because of their well-documented immunosuppressive effects. We show here that the steroid dexamethasone significantly increases total surface AChRs on cultured human muscle exposed to myasthenia gravis sera. Our results suggest that the clinical improvement observed in myasthenic patients treated with steroids is due not only to an effect on the immune system but also to a direct effect on muscle. We propose that the identification and development of pharmacologic agents that augment receptors and other proteins that are reduced by human genetic or autoimmune disease will have broad therapeutic applications.

Experience with intravenous immunoglobulin in myasthenia gravis

Myasthenia gravis (MG) is an acquired autoimmune disorder of neuromuscular transmission associated with a deficiency of acetylcholine receptor at the neuromuscular junction. Current therapeutic strategies are aimed at increasing the amount of acetylcholine at the neuromuscular junction or at addressing the abnormal immune response. Therapies influencing the immune response include thymectomy, corticosteroids, nonsteroidal immunosuppression, and plasmapheresis. Unfortunately, whether used alone or in combination the toxicities of these agents can be quite significant; thus, an agent with a distinct and more favorable side effect profile might be useful in MG. Intravenous immunoglobulin has such potential.

Acquired immune-mediated myasthenia gravis in a cat

Acquired myasthenia gravis was diagnosed in a four‐year‐old castrated male Somali in which the presenting signs consisted of progressive lameness, weakness, generalised muscle tremors, an inability to blink and voice loss. Clinical testing with edrophonium chloride, electrophysiology, immunocytochemistry and serum immunological techniques confirmed the diagnosis of myasthenia gravis and proved its immune‐mediated nature. Clinical remission was achieved following long term immunosuppression with corticosteroids.

Effects of repeated doses of intravenous immunoglobulin in myasthenia gravis

The authors administered repeated courses of intravenous immunoglobulin (IVIg) to nine patients at the onset of an exacerbation of generalized myasthenia gravis (MG). Anticholinesterase medication (nine patients) and corticosteroid dosage (six patients) had been kept constant for a 2-month period. Six patients received two courses, two patients received three courses, and one patient received five courses. Twenty of 23 courses resulted in satisfactory improvement beginning 4.3 +/- 1.2 days after start of IVIg and becoming maximal 8.2 +/- 2.0 days, with sustained improvement lasting 106.6 +/- 49.1 days. Vital capacity increased from an average of 1845.1 +/- 489 cc to 2894 +/- 762 cc (p less than 0.01) at peak effect. Four of nine patients had a decrease in strength before improvement. There was no significant change in acetylcholine receptor antibody titers before or after therapy. Side effects were minimal. Of the three patients who had nonsatisfactory course, two responded well to additional IVIg. IVIg can produce repeated beneficial effects in patients with MG and may be useful as an adjunct in the management of MG.

Autoimmunity and pregnancy

The general effect of pregnancy on autoimmunity remains controversial. In the majority of cases, pregnancy may have no effect on the disease, while on other occasions, pregnancy induces exacerbations that may be especially pronounced in the immediate post-partum period. The reasons for this preponderance are still unclear. Another important aspect of autoimmune diseases during pregnancy entails the passive transfer of the disease into the fetal compartment. It seems that until the pathogenesis and a better specific therapy for autoimmune diseases are clearly defined, careful clinical and immunologic observation of each mother-infant pair will be invaluable.

Immunosuppression with corticosteroids and thymectomy in myasthenia gravis: an evaluation of immediate and short term results in 20 patients

A comparative study was conducted on two groups of patients with the generalized severe form of myasthenia gravis. The first group of 20 patients received oral daily doses of 60-100 mg of prednisone prior to thymectomy. The control group of 20 were submitted to surgery without prior corticosteroid treatment. The study included statistical analysis of the clinical results and surgical complications for both groups. The authors concluded that the use of steroids preoperatively is beneficial.

The effect of glucocorticoid treatment on denervated rat hemidiaphragm

The degenerative process in phrenic nerve motor nerve terminals following nerve section was analyzed in rats that had previously been subjected to an intensive short term regimen of the steroid preparation triamcinolone. Morphological studies indicated that the onset time of degeneration was similar to that of untreated rats but less severe, and the time for maximal degenerative changes was increased. Concurrent to the preservation of motor nerve terminal structure under conditions of denervation, triamcinolone also induced myopathies in the diaphragm, the white muscle fibers being predominantly affected. Due to the structural aberrations of muscle, the indirect and direct twitch response of hemidiaphragms in triamcinolone treated rats was depressed. Data obtained from indirect post-tetanic potentiation (PTP) responses, however, did express the anatomical preservation of motor nerve terminals. These findings may add support to previous observations for the basis of effectiveness of the glucocorticoids in the treatment of neuromuscular disorders.

Myasthenia gravis. A survey

Myasthenia gravis is a chronic disease characterized by a fluctuating weakness of voluntary muscle, with a preference for the muscles innervated by cranial nerves. The pathophysiological mechanism is a loss of postsynaptic acetylcholine receptors to less than 20-30% so that the safety margin of neuromuscular transmission is lost. It is probable that the function of the remaining acetylcholine receptors is impaired by antibodies against receptor proteïn, which can be demonstrated in the serum in 80-90% of the patients, and which are highly specific for the disease. An experimental autoimmune myasthenia can be induced in many animal species by immunization with purified receptor proteïn and this disease is remarkably similar to the human myasthenia with exception of the fluctuating course. The human disease has to be considered as an autoimmune disease, although the initiating mechanism is unknown. The occurrence of tumors of the thymus in 10-15% and the presence of germinal centres in about 70% of the thymus glands removed by operation are highly suggestive of the importance of the thymus in the pathogenesis, but the definite mechanism (harbouring of an abnormal antigen in myoid cells, or/and false instruction of thymocytes with lack of suppressor cells) is essentially unknown. In most patients the disease tends ot have a favourable course from 5-10 years after onset and complete remission occur in about 20% after 10-20 years. Therapy with anticholinesterases, providing an increase in acetylcholine, is of partial benefit in most patients. Thymectomy has an excellent effect in about 30% of the patients without thymoma under the age of 40 during the first three years of the disease, and is of benefit in still another 30-40%. The use of prednisone and immuno-suppressive drugs has improved the prognosis of the 20% of the patients with severe life threatening symptoms, half of whom have a thymoma.

Controversies about the treatment of myasthenia gravis

Clinicians treating patients with myasthenia gravis must choose cholinergic drugs, corticosteroids, immunosuppressive drugs, thymectomy, or plasmapheresis. Clinicians must decide the sequence or combination of these therapies and when to deem lack of improvement a sign for a different therapeutic approach. Because controlled trials have not been done to evaluate therapies that may require months or years before benefit is evident, controversy abounds.

Current trends in the management of myasthenia gravis: plasmapheresis and immunosuppressive therapy

In recent years a considerable body of evidence has accumulated to demonstrate autoimmune mechanisms in myasthenia gravis. This evidence has important implications for the aetiology, diagnosis and management of the disease. The primary abnormality in myasthenia gravis is related to the presence of antibody which reacts with the acetylcholine receptor. Measurement of this IgG antibody in the serum has become the most reliable diagnostic adjunct to the edrophonium test, and in an individual patient, the level of the serum antibody relates closely to the clinical indices. In cases of myasthenia where control with anticholinesterase drugs is unsatisfactory, methods to lower the antiacetylcholine receptor antibody are indicated: these may include thymectomy, immunosuppressive therapy of plasmapheresis. Two patients with very severe disease are described in whom all types of therapy were used and in whom survival depended ultimately on the use of plasmapheresis. These patients illustrate the importance of receptor antibody in the clinical manifestations of myasthenia gravis and in its management.

Vocal cord paralysis in myasthenia gravis following anesthesia

Our patient demonstrated two unusual features: (1) severe upper airway obstruction due to bilateral vocal cord paralysis at first manifestation of a myasthenic syndrome; and (2) precipitation of this syndrome following surgery and anesthesia with succinylcholine. In addition, this case illustrates use of ventilatory measurements through an endotracheal tube for documenting the patient's progress and response to medications, most dramatically during performance of an edrophonium test.

Treatment of myasthenia gravis. Report on 139 patients

In the treatment of myasthenia gravis (MG) considerable progress has recently been achieved. Our experience is based on the observation of 139 patients with an average follow-up of 3 years and 4 months. A treatment plan and results are presented. Indications for thymectomy: all cases of MG in adult life, apart from ocular myasthenia without radiological thymoma and without electrophysiological and pharmacological signs of generalization; before puberty only cases with radiological thymoma and severely incapacitating or life-threatening signs. Median sternotomy is preferable for thymoma, the transcervical approach with a sternal split for non-neoplastic thymus. Mediastinal radiotherapy is indicated after removal of an invasive or adhesive thymoma. Indications for corticosteroids: 1) before thymectomy: respiratory weakness; 2) soon after thymectomy: life-threatening signs; 3) later after thymectomy: incapacitating or life-threatening signs; 4) as an alternative to thymectomy: when surgery cannot be performed or it is not indicated. Oral Prednisone was nearly always preferred: alternate-day high single dose (75 to 115 mg) has given good results in most cases even if in some cases a small dose was required in the "off day"; inversely a lower alternate-day or daily dose was often sufficient. Long-term results: following this schedule for adult patients good results were scored in 67% of thymomas, in 94% of hyperplasias, and in 62% of unthymectomized patients: in prepuberal life the few cases of severe MG have all shown a favorable evolution.

Plasma-exchange combined with immunosuppressive therapy in myasthenia gravis

Twenty-one patients with myasthenia gravis underwent a course of plasma exchange combined with immunosuppressive therapy. In fifteen there was dramatic clinical improvement which has been maintained for periods up to 19 months. Nine of these patients now take no anticholinesterase drugs. Six patients had a recurrence 3--9 months after the first course but in the three given a second course remissions were again obtained.

Corticosteroids and neuromuscular transmission: electrophysiological investigation of the effects of prednisolone on normal and anticholinesterase-treated neuromuscular junction

The effect of prednisolone on indirectly stimulated rat muscle twitch was investigated at normal and prostigmine-treated neuromuscular junctions. In vivo, predenisolone up to 150 mg/kg body weight did not affect twitch contraction in normal animals. In neostigmine-pretreated animals, however, doses between 12.5 and 90 mg/kg could entirely abolish the anticholinesterase-induced twitch augmentation. In vitro, prednisolone produced a depressant effect on the twitch of a normal phrenic nerve diaphragm preparation which could amount to 20%. When the preparation was pretreated with neostigmine the augmented twitch could be depressed by 10(-3) to 10(-6) mol/l prednisolone to levels below the untreated control. Part of this effect is owing to a suppression of the neostigmine-induced, stimulus-bound repetitive firing of the motor nerve terminals, but to explain the full effect a further inhibitory action on neuromuscular transmission must be assumed. The latter could be accounted for by a depolarizing interaction of prednisolone and neostigmine on the nerve terminals resulting in conduction block. An action of prednisolone on postsynaptic receptors could also be considered. Such effects of the glucocorticoid might contribute to the exacerbation of muscular weakness occasionally observed in patients with myasthenia gravis at the beginning of steroid therapy.

Myasthenia gravis: review of diagnosis and management

Although the cause of myasthenia gravis is still unknown, its pathogenesis appears clear: immunologic attack on synaptic receptors in muscle causes receptor deficiency, decreased miniature endplate potentials, and decrements in the compound action potentials evoked from muscles on repetitive stimulation of peripheral nerves. In addition to the involvement of skeletal muscle, some MG patients may manifest subtle alterations of the function of heart, lung, smooth muscle, and CNS, indicating that this is truly a systemic disorder. Modern therapy involves adjusting treatment to the needs of individual patients. Anticholinesterases, calcium, ephedrine, potassium, and germine partially correct the defect in neuromuscular transmission; prednisone, ACTH, cytotoxic drugs, antilymphocyte serums, gamma globulin, thoracic duct drainage, plasmapheresis, and thymectomy partially modify the abnormalities of the immune system.

Effect of prednisolone on motor end-plate fine structure: a morphometric study in hamsters

The fine structure of quadriceps motor end-plates in hamsters was analyzed quantitatively one, two, four, seven, and thirty-two weeks following intraperitoneal injections of prednisolone. Except for transient increases in postsynaptic length and membrane profile concentration after prednisolone administration at dosages of 4 mgper kilogram of body weight for one week and 2 mg per kilogram for four weeks, mean values for various measurable profiles in the presynaptic and postsynaptic regions showed no significant differences between control and treated animals.

Plasmapheresis and immunosuppressive drug therapy in myasthenia gravis

Plasmapheresis combined with prednisone and azathioprine therapy produced striking clinical improvement in five patients with myasthenia gravis who still had moderate to severe disability despite thymectomy, high-dose prednisone therapy and optimal doses of cholinesterase inhibitors. Serial determinations of titers of serum antibody toward the acetylcholine receptor demonstrated a fall to 21 +/- 5 per cent (mean +/- S.D.) of the original levels concurrently with the patients' increasing strength. Clinically improved patients maintained lowered titers, whereas clinical relapses were associated with a rebound in titer. Our results suggest that plasmapheresis will find a place in the management of patients with myasthenia gravis, and they implicate antibodies to acetylcholine receptor as a pathogenic factor in this disease.