Myasthenia gravis
Click here to load reader
-
Upload
drfaiza786 -
Category
Health & Medicine
-
view
680 -
download
2
Transcript of Myasthenia gravis
A 35 years old woman comes to the clinic complaining of double vision that seems to worsen near he end of the day.She also complains of difficulty in chewing meat and other hard foods.She notices that her symptoms improve following a good night’s sleep.on neurologic examination, you note a snarling appearance when the patient is asked to smile, & a nasal tone is heard in her voice.You also note the weakness in the upper extremities when the patient is asked to clench her fist around your finger repeatedly.
“It is an acquired autoimmune
neuromuscular junction disorder
characterized clinically by weakness of
skeletal muscle and rapid fatigability on
exertion”
1) Estimated annual incidence is 2 per
1,000,000 in US( from research)
2) Mortality rate: previously it was 40 to 50
% now it is 2 to 3 %
3) Sex: female:male ratio is 6:4
4) Age: presents at any age. Mean age of
onset is 28 years in females and 42 years
in males.
1)Thyroid diseases
2)SLE
3)Rheumatoid arthritis
4)Pernicious anemia
5)Various drugs can exacerbate symptoms
of myasthenia gravis which are
lithium,procainamide,verapamil,quinidin
e,propranolol,aminoglycosides,erythrom
ycin,timolol etc.
A)Type 2 hypersensitivity reaction
Antibodies target the Ach receptor
results in receptor blockage,down
regulation of receptor and compliment
mediated destruction thus reducing
the number of receptors available to
interact with the ACh released from the
presynaptic nerve terminal
B)Compliment activation attracts
activated macrophages which cause
significant damage to the syneptic
fold,loss of voltage gated sodium
channels muscle weakness and
fatigability.
According to the Myasthenia Gravis
Foundation of America (MGFA) clinical
classification was created in the year
1997 which is as follows;
CLASS 1:
a)Any ocular muscle weakness
b)May have weakness of eye closure
c)All other muscle strength is normal
CLASS II:
a)Mild weakness affecting other than ocular muscles
b)May also have ocular muscle weakness of any severity
CLASS 11 a:
a)Predominantly affecting limb, axial muscles, or both
b)May also have lesser involvement of oropharyngeal muscles
CLASS II b:
a)Predominantly affecting oropharyngeal, respiratory muscles, or both
b)May also have lesser or equal involvement of limb, axial muscles, or both
CLASS III:
a)Moderate weakness affecting other than ocular muscles
b)May also have ocular muscle weakness of any severity
CLASS III a:
a)Predominantly affecting limb, axial muscles, or both
b)May also have lesser involvement of oropharyngeal muscles
CLASS III b:
a)Predominantly affecting oropharyngeal, respiratory muscles, or both
b)May also have lesser or equal involvement of limb, axial muscles, or both
CLASS IV
a)Severe weakness affecting other than ocular muscles
b)May also have ocular muscle weakness of any severity
CLASS IV a
a)Predominantly affecting limb and/or axial muscles
b)May also have lesser involvement of oropharyngeal muscles
CLASS IV b:a)Predominantly affecting oropharyngeal,
respiratory muscles, or both
b)May also have lesser or equal involvement of limb, axial muscles, or both
CLASS V:
a)Defined by intubation, with or without mechanical ventilation, except when used during routine postoperative management.
b)The use of a feeding tube without intubation places the patient in class IVb.
1)TENSILON(edrophonium)TEST:edrophonium 10 mg is injected as iv improvement in weakness within seconds and last for 2- 3 minutes when test is positive.
2)Serum acetylcholine receptor antibodies: raised
3)CPK: Normal
4)ESR: Not raised
5)Antibodies to striated muscle: Present
5)Antinuclear antibodies & rheumatoid factor: positive
6)NERVE STIMULATION TEST: characteristic decrement in the evoked muscle action potential.following continuous stimulation of motor nerve
7)CXR: may show thymoma
1)Oral anticholinesterases like pyridostigmie is given.drug prolongs the action of Ach by inhibiting the action of cholinesterases( adverse effect can becolic,diarrhoea )
2)Immunosuppressant drugs like corticosteriods like azathioprine are used when there is incomplete response to anticholinesterases.thereis improvement in 70% of cases.Mycophenolate is a newer immunosuppressive drug having less adverse effects then steroids.
3)Thymectomy: for malignant tumor
4)Plasmapheresis and intravenous immunoglobulins:usewhen there is respiratory involvement