Question

Acquired myasthenia gravis is associated with muscle weakness. This muscle weakness is caused by:

1 pt Breakdown of skeletal muscle fibers.

2 Damage to the CNS control of muscle movements.

3 Disturbed neuromuscular junction transmission.

4 Loss of functional motor units.

5 Loss of skeletal muscle nerve supply.

Answer 1

Answer is 3) Disturbed Neuromuscular junction transmission

Myasthenia gravis is a severe attack by antibody mediated T cells on the Acetylcholine receptors on postsynaptic membrane which is symptomatic after more than 80 % receptors are damaged .
Characteristics features
1. Fatigue
2.Extraocular muscle weakness
3. Bulbar weakness
4.Proximal limb muscle weakness
5.Opthalmoplegia plus ptosis
6.Respiratory muscle weakness
7.Expresionless face
8.Dropped posture
Cardinal features are Muscle fatiguability plus flucutuating weakness .

Investigations :
1. Icepack test
2. Edrophonium test only if antibody is positive
3. Most specific - Acetylcholine receptor antibody
4.Most sensitive - Single nerve fibre electromyography
5..Rapid nerve stimulation test - Decremental response seen

Treatment :
1 Cholinesterase inhibitor
Pyridostigmine 60 mg x 4 times
Plus steroids and Azathioprine
2.)Plasmapheresis (plasma exchange PLEX) is plamsa compartment of blood is exchanged with subatitute and thereby removing circulating humoral factors (ie, anti-AChR antibodies and immune complexes) from the circulation. It is used for myasthenia crisis management. Like IVIg, plasmapheresis is generally reserved for myasthenic crisis and refractory cases. Improvement seen in few days, but it does not last for more than 2 months.
Plasmapheresis is an effective therapy for MG and is often the initial treatment of choice in myasthenic crisis given for 2 weeks .
3) Thymectomy