Myasthenia gravis (MG)

2017-07-26  Summaried by Debby

defination:

myasthenia gravis is a disease of skeletal muscle acetylcholine receptors;

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Occurance;

MG occurs at any age ,involves either men or women;women get it earlier; men get it later.

begin 20-30 commonst age of onset  in women;

60-70 commonst in men.

mechanism:

In patients with MG, the antibodies block,alter destroy the receptors for acetylcholine at the neuromuscular junction ,preventing muscle contraction.

factors that aggravates MG:

emotional stress;

sysmetic illness;

thyroid disease;

pregnancy;

menstrual cycle;

fever;

drug.

clinical manifestations:

1.diplopia;

2.blurry vision,difficulty in focus on something;

3.drooping eyelids;

4. dysphagia:difficulty to chew or swallow;

5.dysphonia:voice impairment;

6.cessation of activities that requres prolonged use   of muscles;

most of patints with myathenia gravis present with ocular manifestation.

65% patients :ptosis or diplopia;

17% :patients:oropharygeal  muscle weakness; (difficulty in chewing and swallowing)

10% limb weakness.

(from harvard PPT)

Myopathy                        Myasthenia
Symmetric  Appearance   Asymmetric
No   Ptosis on fatigue  Yes
No   Lid twitch   Yes
No   Recovery w/ eye closure Yes
Constant  Range lev. function  Varies
Yes   Weak orb. oculi  Yes
Negative  Tensilon test   Positive
50%   Family history  Rare
Slowly Progressive Course   Fluctuates

severity of weakness fluctuates during the day:

least in the moring ,worsening as the day progress ,especally after prolonged use of affected  muscles.

classfication:

1.ocular alone;

2.mild generalized;????

3.moderately severe generalized plus  usually bulbar involvement;

4.acute severe over weeks-months with severe bulbar involvement;

5.late severe with marked bulbar involvement.

MG is associated with other diseases:

hyperthroidism;

rheumatoid arthritis

sysmetic lupus erythematosus;

diabete millitus.

diagnositics:

EMG

treatment goals:

1.control symptoms;

2.maitain functional ability;

3.prevent complications.

treatment:

Mestinon (Pyridostigmine bromide) first choice, dose 30-60 mg q 6-8 h/daily

Prostigmine (Neostigmine bromide) 7.5 – 15.0 mg q 6-8 h/daily