1. 163-1
Myasthenia/Thymoma

2. Figure 1. Ptosis OS Pre-tensilon

3. Figure 2. Positive tensilon test

4. Figure 3. Ptosis OS Post-tensilon

5. Figure 4 CT mid-thorax thymic mass (arrows)

6. Figure 5 CT Mid-thorax thymic mass (arrows)

7. Thymic hyperplasia in AChR antibody positive MG
Mantle of B cells surrounding follicular dendritic cells,
immune complexes and plasma cells
Thymic myoid cells express
fetal type AChRs
Fluorescein-labelled troponin antibody
Rhodamine labelled AChR antibody
Schluep et al., Ann Neurol 1987

8. acetylcholine receptor antibodies are present in 85%
Neuromuscular junction in Myasthenia Gravis
acetylcholine receptor antibodies are present in 85%
of MG patients and cause AChR loss
Mechanisms
Adult AChR a b d
ACh
C’-mediated lysis
cross-linking
blocking e e
nerve
terminal C’
acetylcholine
receptors
muscle fibre

9. Neuromuscular Junction in Myasthenia Gravis
antibodies to MuSK in ~ 7% of patients
blood-brain barrier
voltage-gated
potassium channels
(VGKC)
voltage-gated
sodium channels
MuSK – an
endplate
transmembrane
protein
nerve
terminal
voltage-gated
calcium channels
(VGCC)
acetylcholine
receptors
(AChR)
muscle-specific kinase (MuSK)
rapsyn

10. MuSK antibody positive Myasthenia Gravis
aged 16 years
Electromyography:
R frontalis and orbicularis oculi
no spontaneous activity
no motor units under voluntary control
no activity on nerve stimulation
R orbicularis oris
few very small units (max ampl 50uV)
normal profile
(duration 5msec; not polyphasic)

11. MuSK antibody positive Myasthenia Gravis
aged 20 years

12. in > 90% of LEMS patients and cause VGCC loss
Neuromuscular junction in Lambert-Eaton Myasthenic Syndrome Antibodies to voltage-gated Ca++ channels (VGCCs) present
in > 90% of LEMS patients and cause VGCC loss α 2 g
out a 1 in d
nerve
terminal
nerve
terminal b
P/Q-type
voltage-gated
calcium channels
(VGCCs)
Mechanism
Cross-linking of
VGCCs by antibody
acetylcholine receptors
muscle fibre