1. Disorders of the Neuromuscular Junction
Myasthenia gravis
Radim Mazanec, MD, PhD

2. Definition
An autoimmune disease due to an antibody mediated attack directed against nicotinic AchR at neuromuscular junction
10% have thymoma
70% have thymic hyperplasia

5. Synaptic antigens
nerve
muscle
VGCC
MuSK
AChR

6. Epidemiology Incidence 1 : 20 000 in USA
Women slightly higher incidence 3 : 2
Majority of the MG are young women in the third decade and middle aged men in 5th and 6th decade
Children account for 11% of all patients with MG

7. Clinical Features
Fluctuated muscle weakness and excessive fatiguability
Diplopia and ptosis
Bulbar weakness – swalloving, dysarthria
Generalized weakness of the trunk and extremities

8. Diagnostic algorhitm Electromyography AChR antibodies
MR of mediastinum – thymomas, hyperplasia

9. Low frequency stimulation - decrement

10. Treatment Thymectomy Plasma exchange in myasthenic crisis (TPE)
Human immune globuline (IvIg)
Corticosteroids + cytostatics
AChE inhibitors (pyridostigmine, distigmine)

11. Myasthenic crisis
Respiratory insuficiency – paralysis of respiratory muscles
Assisted ventilation required
Affect 15-20% myasthenic patients
Females : males = 2 : 1
Average age : 55 years

12. Clinical features Respiratory tract infection, pneumonia ( 38%)
Respiratory failure 99%
Oropharyngeal or ocular weakness 86%
Arms and legs weakness 76%

13. Complication of crisis
Ateletactic pneumonia (40%)
Hypotension
Cardio-respiratory arrest
Pneumothorax

14. Treatment ICU is required for assisted ventilation
Cardiopulmonary monitoring
Plasmapheresis ( 5 sessions) or IvIg 2g/kg in five consecutive days
Antithrombotic treatment
Antibiotics
Respiratory rehabilitation

15. Outcome Duration of intubation : 13 days
Duration of hospitalization : days
Tracheostomy cca 40%
Mortality cca 4%