Aspects of treatment of crisis in myasthenia gravis

Clinical profile and outcome of myasthenic crisis in a tertiary care hospital: A prospective study

Background:

The present understanding of the clinical course, complications, and outcome of myasthenic crisis (MC) is based chiefly on observational studies and retrospective case series.

Aim:

To study the baseline demographic and clinical variables, risk factors, complications, outcome, and mortality in patients of MC.

Materials and Methods:

All patients of myasthenia gravis (MG) who presented with myasthenic crisis between July 2009 and December 2010 were included.

Results:

Ten patients of MC were included in this study. The median age of the patients was 40.5 years (range 14-71 years). Seven were females and three were males. Nine had generalized MG and one patient had oculobulbar involvement only. Median duration of disease was 3 years (range 1 month to17 years). Two patients had thymoma. Two patients had history of thymectomy in the past. Infection was the most common triggering factor accounting for five cases (50%) followed by inadequate treatment/drug withdrawal in three (30%) and steroid initiation and hypokalemia in the remaining two patients (20%). Median duration of MC was 12 days (range 3-28 days). Mortality was in 3 out of 10 (30%) during MC. Management in the intensive care unit (ICU) and treatment with plasma exchange/intravenous immunoglobulins were associated with good outcome.

Conclusions:

Ventilator support and management in intensive care unit are the most important components in the management of MC. The high mortality rate seen in present study may be more reflective of the actual ground reality in resource constrained developing countries, however, larger prospective studies are needed to confirm these findings.

[Drugs that may trigger or exacerbate myasthenia gravis]

Myasthenia gravis (MG) is an autoimmune disease causing muscle weakness due to impaired transmission at the neuromuscular junction. MG or a MG-like condition may be triggered or exacerbated by several drugs used for treatment of other diseases. Drugs may interfere with the neuromuscular transmission through several mechanisms, either by affecting pre- or postsynaptic ion channels or by affecting acetylcholinesterase. Based on a literature search in PubMed and the authors' own clinical experiences, we provide an overview focusing on the most frequently used drugs that may exacerbate weakness in patients with MG. In our experience, symptomatic MG-patients who have a generalised disease are especially vulnerable to drug-induced exacerbations, while stable MG patients with few symptoms more seldom are. Nevertheless, patients with MG must receive treatment for co-existing conditions. It is important to be aware of a possible increase in muscle weakness when introducing a new drug. If the patient deteriorates, the new treatment must be withdrawn or the dose reduced.

On the concept of myasthenic crisis

This article reviews controversies surrounding the concept of myasthenic crisis. Literature review and our own experience demonstrate that there is disagreement about how a crisis should be defined, what the implications of a crisis are, whether crises are preventable, and how crisis incidence should be calculated. We propose that crisis be defined as weakness from acquired myasthenia gravis that is severe enough to necessitate intubation or delayed extubation following surgery. We argue that crisis need not "doom" a myasthenic patient to a different prognosis or response to therapy compared with myasthenic patients with severe generalized weakness. Finally, we argue that crisis is preventable and that crisis incidence, calculated in a standardized fashion, could be a useful outcome measure.

Therapy of myasthenic crisis

OBJECTIVES

To investigate the frequency, causes, and characteristic features of the course of isolated myasthenic crisis (defined as acute respiratory failure with the need for mechanical ventilation). To compare the effectiveness of three different therapeutic regimens (i.e., continuous intravenous infusion of pyridostigmine, pyridostigmine plus prednisolone, and plasma exchange) in terms of duration of ventilation and outcome of patients with myasthenic crisis.

DESIGN

Population-based retrospective study covering the period 1970 to 1995.

SETTING

University hospital, center for myasthenia gravis in Saxony, Germany.

PATIENTS

Of 235 patients with myasthenia gravis treated at our institution, 44 patients developed a total of 63 myasthenic crises (average annual incidence 2.5%).

INTERVENTIONS

Myasthenic crises were treated with pyridostigmine (n = 24), pyridostigmine plus prednisolone (n = 18), and plasma exchange (n = 21).

MEASUREMENTS AND MAIN RESULTS

There were no significant differences between the three treatment groups with respect to clinical characteristics, duration of mechanical ventilation, complications, and outcome on release from intensive care and after 3 months. Eleven (17%) patients had severe cardiac arrhythmia, which ended fatally for six patients.

CONCLUSIONS

None of the therapeutic regimens applied demonstrated any advantage over the others. All three regimens used were found to be effective and should be applied depending on the circumstances prevailing. Patients with myasthenic crisis must undergo careful cardiac monitoring, and temporary pace-making should be provided where clinically indicated.

Antibody response to pneumococcal polysaccharide vaccine in myasthenia gravis: effect of therapeutic plasmapheresis

The removal of specific antibody in experimental animals has been reported to result in a subsequent increase in antibody to levels equal to (rebound) or exceeding those existing prior to removal (overshoot). Anecdotal reports suggest that rebound antibody synthesis after plasmapheresis may occur in humans with autoimmune disorders. We measured the antibody response to 12 pneumococcal polysaccharide antigens in patients with myasthenia gravis (MG) receiving a variety of therapies in order to determine whether the T-cell-independent IgG response to these antigens was augmented by plasmapheresis. MG patients receiving no immunotherapy or receiving prednisone had pre- and post-immunization titers similar to those of control patients. MG patients receiving prednisone and chronic plasmapheresis had higher pre-immunization titers than did other patient groups and had significantly higher post-immunization titers against multiple pneumococcal serogroups. Aggregate post-immunization geometric mean titers were more than three-fold higher in the plasmapheresis group as compared with other MG treatment groups. Enhancement of antibody response by plasmapheresis was abolished by the concomitant administration of azathioprine. Antibody rebound and overshoot after antibody removal may have important implications for the therapy of immune disorders by plasmapheresis.

Staphylococcal carriage and infection in myasthenia gravis patients receiving therapeutic apheresis

Populations exposed to repetitive needle puncture (such as hemodialysis patients, insulin-dependent diabetics, and parenteral drug abusers) are at increased risk for nasal carriage of Staphylococcus aureus. These groups appear to have increased susceptibility to serious staphylococcal infection as well. We performed a microbiologic survey on a group of patients receiving regular, long-term therapeutic apheresis for myasthenia gravis (MG), and compared the rate of nasal staphylococcal carriage with that found in control groups of MG patients not receiving apheresis and ambulatory general medical patients without known risk factors for staphylococcal carriage. Medical records were reviewed for episodes of significant staphylococcal infection occurring since commencement of apheresis. Nasal S. aureus carriage was found in 9/29 (31%) apheresis patients, 8/30 (27%) MG controls, and 8/30 (27%) general medical controls. No significant difference in frequency of apheresis was noted between carriers and noncarriers. A single episode of S. aureus bacteremia occurred in 95 patient-years of apheresis therapy. We conclude that therapeutic apheresis for MG does not increase the risk of staphylococcal carriage, and that serious infection is infrequent.

Drugs that may exacerbate myasthenia gravis

Myasthenia gravis is an uncommon disease. The emergency physician should be cautious when prescribing medications to myasthenics for problems not related to myasthenia gravis. We have discussed some of those agents (Figure 3) that are recognized to cause exacerbation of MG or that may have the potential to exacerbate MG. We recommend that management of any medical or surgical problem of the myasthenic be done in consultation with a managing neurologist, and that either early follow-up or admission is necessary when these agents are used in the patient with myasthenia gravis.