Myasthenia gravis management guideline
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Transcript of Myasthenia gravis management guideline
DR. SUNIL KUMAR SHARMASENIOR RESIDENT
DEPT. OF NEUROLOGY
GMC KOTA
MYASTHENIA GRAVIS-RECENT MANAGEMENT GUIDELINE
MYASTHENIA GRAVIS
• MG- an autoimmune disorder of NMJ
• AChR antibody mediated destruction of AChR.
• Impaired transmission of nerve impulse across NMJ
• Incidence -0.3 to 2.8 per 100,000
• Worldwide Prevalance- >700,000
Diagnosis - clinical and confirmed by one or morepharmacological, electrophysiological, or serological tests.
Imaging –to R/O thymoma
Response to treatments - helpful in confirming thediagnosis specially in seronegative cases
MYASTHENIA GRAVIS SUBTYPES
Generalized MG < 40 yr.
AChR AB + , non-thymoma, Thymus hyperplasia
65% of all MG.
M:F - 1:4
AChR antibodies high
HLA -DR3 B8 DR9 (in Asians)
EARLY ONSET MG
>50 yrs AChR antibody positive, non-thymoma,
generalized MG
M=F
AChR antibodies is usually lower.
≈ 50% have titin and RyR AB
HLA-A3, B7, DR2, HLA-DR4, and in titin antibody
positive patients HLA-DR7
LATE-ONSET MG
AChR + in ≈50%, non-thymoma MG with purely ocular
(non-generalized) symptoms.
More common in children and in late-onset males.
10-15% of all MG.
More common in Asia (58%)
HLA-DQ6 , BW46
OCULAR MG
MG patients with thymoma regardless of the extent of
muscular involvement.
M=F
Usually – AChR AB +
15% of MG patients
THYMOMA MG
THYMOMA MG
Peak of onset around 50 years
Frequent occurrence of titin and RyR antibodies.
Thymoma and non-thymoma MG patients have similar MG
long-term prognosis.
HLA DR2 mostly in women.
50% of GMG lacking AChR AB.
Predominantly female.
Begins from childhood through middle age.
Thymic changes are absent or minimal.
Many patients do not improve with cholinesterase inhibitors
Most improve dramatically with PLEX or corticosteroids.
MUSK- ANTIBODY MYASTHENIA GRAVIS
Double seronegative (AChR antibody and Anti-MuSK)
No evidence of thymoma.
Low affinity anti-AChR antibodies can be detected using
specialized assays.
Less severe MG than seropositive MG patients.
SERONEGATIVE MG
LAB Ix.
Anti-acetylcholine receptor antibody
Positive in 74%
80% in GMG
50% of patients with pure ocular myasthenia
Anti-striated muscle
84% of patients with thymoma <40 years
IMAGING STUDIES
Chest x-ray- Plain anteroposterior and lateral views
Chest CT scan – mandatory
MRI of the brain and orbits may help to rule out other causes of cranial nerve deficits
PHARMACOLOGICAL TESTING
Edrophonium (Tensilon test)
Edrophonium -short acting Acetylcholine Esterase Inhibitor
Onset within 30secs
Evaluate weakness (i.e. ptosis and opthalmoplegia) before and after administration
0.1ml(1-2mg) of a 10 mg/ml edrophonium solution is administered as a test
If no unwanted effects are noted (i.e. sinus bradychardia), the remainder of the drug is injected
Keep atropine ready
False positive= ALS, poliomyelitis, and some peripheral neuropathies
Neostigmine test
Longer acting
1.5 mg im or 0.5 mg iv
Action begins in 15-20 mins
Ice pack test
RNST
SFEMG
Guidance statements were developed for :
Symptomatic and immunosuppressive (IS) treatments
IV immunoglobulin (IVIg) and plasma exchange (PLEX)
Impending and manifest myasthenic crisis
Thymectomy
Juvenile MG (JMG)
MG with antibodies to muscle-specific tyrosine kinase (MuSK-MG)
MG in pregnancy
Pyridostigmine-initial treatment in most cases
Dose S/B adjusted based on symptoms.
The ability to discontinue pyridostigmine can be anindicator that the patient has met treatment goals andmay guide the tapering of other therapies.
Corticosteroids or IS therapy s/b used in all patients whohave not met Rx goals after an adequate trial ofpyridostigmine
SYMPTOMATIC AND IMMUNOSUPPRESIVE (IS) TREATMENT OF MG
A nonsteroidal IS agent should be used alone whencorticosteroids are contraindicated or refused.
A nonsteroidal IS agent s/b used initially withcorticosteroids when the risk of steroid side effects ishigh .
A nonsteroidal IS agent should be added to
corticosteroids when:
Significant steroid side effects, deemed by the pt. or thetreating physician
Inadequate response to an adequate trial of corticosteroids
Corticosteroid dose cannot be reduced d/t symptomrelapse.
Azathioprine
Mycophenolate mofetil
Cyclosporine
Methotrexate
Tacrolimus
NONSTEROIDAL IMMUNOSUPPRESIVE AGENTS
The following factors should be considered inselecting among these agents:
There is widespread variation in practice with respectto choice of IS agent d/t paucity of literature comparingthem.
Expert consensus and some RCT evidence support theuse of azathioprine as a first-line IS agent in MG.
Evidence from RCTs supports the use of cyclo-sporine inMG, but potential serious adverse effects and druginteractions limit its use.
RCT evidence does not support the use of mycophenolateand tacrolimus but one or both are recommended in severalnational MG treatment guidelines.
Def.-PIS is unchanged or worse after corticosteroids and at least 2 other IS agents, used in adequate doses for an adequate duration, with persistent symptoms or side effects that limit functioning, as defined by patient and physician.
Patients with refractory MG should be referredto physician or a center with expertise in management ofMG.
REFRACTORY MG
Following IS agents may also be used in refractory
MG.
Chronic IVIg and chronic PLEX
Cyclophosphamide
Rituximab, for which evidence of efficacy is building, butfor which formal consensus could not be reached
Once patients achieve treatment goals, the corticosteroiddose should be gradually tapered.
In many patients, continuing a low dose of corticosteroidslong-term can help to maintain the treatment goal.
For nonsteroidal IS agents, once treatment goals have beenachieved and maintained for 6 months to 2 years, the ISdose should be tapered slowly to the minimal effectiveamount.
IS AGENT DOSAGE AND DURATION OF TREATMENT
Dosage adjustments should be made no more frequentlythan every 3–6 months
Tapering of IS drugs is associated with risk of relapse,which may necessitate upward adjustments in dose.
The risk of relapse is higher in patients who aresymptomatic, or after rapid taper.
Usually some maintainance immunosuppression is neededfor many years, sometimes for life.
Patients must be monitored for potential adverse effectsand complications from IS drugs.
Changing to an alternative IS agent should be considered ifadverse effects and complications are medically significantor create undue hardship for the patient.
PLEX and IVIg -used as short-term treatments in patientswith MG with life-threatening signs such as respiratoryinsufficiency or dysphagia
In preparation for surgery in patients with significantbulbar dysfunction
When a rapid response to treatment is needed; whenother treatments are insufficiently effective
Prior to beginning corticosteroids if deemed necessary toprevent or minimize exacerbations
INDICATIONS FOR IVIG AND PLEX
The choice between PLEX and IVIg depends onindividual patient factors and the availability of each.
IVIg and PLEX are probably equally effective in thetreatment of severe generalized MG.
The efficacy of IVIg is less certain in milder MG or inocular MG.
PLEX may be more effective than IVIg in MuSK-MG
The use of IVIg as maintenance therapy can beconsidered for patients with refractory MG or forthose in whom IS agents are relativelycontraindicated.
Impending and manifest myasthenic crisis-emergentsituations - aggressive management and supportive care.
Although cholinergic crises are rare, excessive ChEI cannotbe completely excluded as a cause of clinical worsening.
ChEIs increase airway secretions, which may exacerbatebreathing difficulties.
IMPENDING AND MANIFEST MYASTHENIC CRISIS
PLEX and IVIg are the mainstay of management inmyasthenic crisis.
Impending crisis requires hospital admission and closeobservation of respiratory and bulbar function, with theability to transfer to an ICU if it progresses to manifestcrisis.
PLEX and IVIg are used as short-term treatment forimpending and manifest myasthenic crisis and in patientswith significant respiratory or bulbar dysfunction.
MYASTHENIC CRISIS
Corticosteroids or other IS agents are often started atthe same time to achieve a sustained clinicalresponse.
Because corticosteroids may cause transientworsening of myasthenic weakness, it may beappropriate to wait several days for PLEX or IVIg tohave a beneficial effect before startingcorticosteroids.
Clinical trials - IVIg= PLEX
Expert consensus –PLEX> IVIg
The choice between the 2 therapies depends onpatient comorbidity and other factors, includingavailability.
A greater risk of hemodynamic and venous accesscomplications with PLEX may be minimized byusing peripheral rather than central venous access.
In non-thymomatous MG, thymectomy is performedas an option to potentially avoid or minimize thedose or duration of immunotherapy,
If patients fail to respond to an initial trial ofimmunotherapy or have intolerable side-effects fromthat therapy.
Thymectomy in MG
Thymectomy for MG is an elective procedure-longdelay.
It should be performed when the patient is stableand deemed safe to undergo a procedure wherepostoperative pain and mechanical factors can limitrespiratory function.
The value of thymectomy in the treatment ofprepubertal patients with MG is unclear.
Thymectomy should be considered in children withgeneralized AChR antibody–positive MG-
-If the response to pyridostigmine and IS
therapy is unsatisfactory
-In order to avoid potential complications of
IS therapy.
For children diagnosed with seronegativegeneralized MG, the possibility of a congenitalmyasthenic syndrome or other neuromuscularcondition should be entertained, and evaluation at acenter specializing in neuromuscular diseases is ofvalue prior to thymectomy.
With rare exceptions, all patients with MG withthymoma should undergo surgery to remove thetumor.
Removal of the thymoma is performed to rid thepatient of the tumor and may not produceimprovement in MG
All thymus tissue should be removed along with thetumor.
Further treatment of thymoma will be dictated byhistologic classification and degree of surgicalexcision.
Incompletely resected thymomas should bemanaged after surgery with an interdisciplinarytreatment approach (radiotherapy, chemotherapy).
In elderly or multimorbid patients with thymoma,palliative radiation therapy can be considered in theappropriate clinical setting.
Small thymomas may be followed without treatmentunless they are enlarging or become symptomatic.
Endoscopic and robotic approaches to thymectomy -have a good track record for safety in experiencedcenters.
Thymectomy may be considered in patients withgeneralized MG without detectable AChR antibodiesif they fail to respond adequately to IS therapy, or toavoid/minimize intolerable adverse effects from IStherapy.
Current evidence does not support an indication forthymectomy in patients with MuSK, LRP4, or agrinantibodies.
Children with acquired autoimmune ocular MG aremore likely than adults to go into spontaneousremission.
Thus, young children with only ocular symptoms ofMG can be treated initially with pyridostigmine.
Immunotherapy can be initiated if goals of therapyare not met.
Juvenile MG
Children are at particular risk of steroid side effects-
Eg. - Growth failure, poor bone mineralization, andsusceptibility to infection, due in part to a delay in livevaccinations
Longterm treatment with corticosteroids should use the lowest effective dose to minimize side effects
Maintenance PLEX or IVIg are alternatives to IS drugs in JMG.
Many MuSK-MG pt -respond poorly to ChEIs, andconventional doses frequently induce side effects.
Respond well to corticosteroids and to many steroid-sparing IS agents.
They tend to remain dependent on prednisonedespite concomitant treatment with steroid-sparingagents
MG WITH MuSK ANTIBODIES
MuSK-MG responds well to PLEX, while IVIg seems to be less effective
Rituximab should be considered as an early therapeutic option in patients with MuSK-MG who have an unsatisfactory response to initial immunotherapy
Planning for pregnancy should be instituted well in advanceto allow time for optimization of myasthenic clinical statusand to minimize risks to the fetus
Multidisciplinary communication among relevantspecialists should occur throughout pregnancy, duringdelivery, and in the postpartum period
MG IN PREGNANCY
Provided that their myasthenia is under good control beforepregnancy, the majority of women can be reassured thatthey will remain stable throughout pregnancy.
If worsening occurs, it may be more likely during the firstfew months after delivery.
Oral pyridostigmine is the first-line treatment duringpregnancy.
IV ChEIs may produce uterine contractions and shouldnot be used during pregnancy.
Thymectomy should be postponed until after prenancy , as benefit is unlikely to occur during pregnancy.
Prednisone is the IS agent of choice during pregnancy
Azathioprine and cyclosporine are relatively safe inexpectant mothers who are not satisfactorilycontrolled with or cannot tolerate corticosteroids.
Current evidence indicates that mycophenolatemofetil and methorexate increase the risk ofteratogenicity and are contraindicated duringpregnancy.
There was a strong minority opinion against the useof azathioprine in pregnancy.
Azathioprine is the nonsteroidal IS of choice for MGin pregnancy in Europe but is considered high risk inthe United States.
This difference is based on a small number of animalstudies and case reports.
PLEX or IVIg are useful when a prompt, althoughtemporary, response is required during pregnancy.
Careful consideration of both maternal and fetalissues, weighing the risks of these treatments againstthe requirement for use during pregnancy and theirpotential benefits, is required.
Spontaneous vaginal delivery should be the objectiveand is actively encouraged.
Magnesium sulfate is not recommended
Barbiturates or phenytoin usually provide adequatetreatment.
All babies born to myasthenic mothers should beexamined for evidence of transient myasthenicweakness, even if the mother’s myasthenia is well-controlled, and should have rapid access to neonatalcritical care support.
PHARMACOLOGICAL MANAGEMENT OF MG
Bradley’s Neurology In Clinical Practice;7th Edition.
International Consensus Guidance For Management Of Myasthenia Gravis- Executive Summary; Donald B. Sanders, MD Et. Al. ; Neurology® 2016;87:419–425
Myasthenia gravis: clinical, immunological, and therapeutic advances; Acta Neurol Scand 2005: 111: 134–141 DOI: 10.1111
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