3. Myasthenic disordersMyasthenic disorders
Myasthenia gravisMyasthenia gravis
reduced AChR
antibodies to AChR (85%)
Seroneg MGSeroneg MG
normal ACHR density
anti-MUSK antibodies in 2/3
LEMSLEMS
reduced release of Ach
antibodies to presynaptic Ca-channels
autonomic symptoms
malignancy in 65% Stålberg
14. ProtocolProtocol
3 Hz, 10 stimuli
immobilize the muscle
max stim strength, 125%
test at: rest after 10 sec of
act and after 1 minute
Stålberg
15. ProtocolProtocol
3 Hz, 10 stimuli
immobilize the muscle
max stim strength, 125%
test at: rest after 10 sec of
act and after 1 minute
Stålberg
Immobilize the muscle
Because shortening of the muscle will increase the
CMAP ampl
Max stim
Always important for CMAP rec, but particularly here
since small movements may cause insufficient stim
Post exercise amplitude
Gives info about number of excitable end-plates
1HZ does not give decrement
10Hz gives facilitation and will mask a decrement
10stimuli
We want to see the typical sadle shape contour, not
present in other conditions with decrement
16. ProtocolProtocol
3 Hz, 10 stimuli
immobilize the muscle
max stim strength, 125%
test at: rest after 10 sec of
act and after 1 minute
Stålberg
Max stim
Always important for CMAP rec, but particularly here
since small movements may cause insufficient stim
Post exercise amplitude
Gives info about number of excitable end-plates
Immobilize the muscle
Because shortening of the muscle will increase the
CMAP ampl
17. ProtocolProtocol
3 Hz, 10 stimuli
immobilize the muscle
max stim strength, 125%
test at: rest after 10 sec of
act and after 1 minute
Stålberg
Post exercise amplitude
Gives info about number of excitable end-plates
Post exercise decrement
Reflects safety factor, reserve of Acetylcholine
Max stim
Always important for CMAP rec, but particularly here
since small movements may cause insufficient stim
18. ProtocolProtocol
3 Hz, 10 stimuli
immobilize the muscle
max stim strength, 125%
test at: rest after 10 sec of
act and after 1 minute
Stålberg
Gives the physiological events:
•Start condition
•Post-exercise facilitation; amount of excitable end-
plates
•Post exercise exhaustion; safety factor, reserve of
Acetylcholine
33. Repetitive nerve stimulation
Anconeus muscle
after rest 0 sec after 20 s activation 1,5 min after activation
3 Hz
-2%
-6%
3 Hz
-2%
-2%
3 Hz
-4%
-7%
Stålberg
34. Repetitive nerve stimulation
in a patient with severe MG
Rest, 3 Hz 10 stim
Directly after 20 s act.
Post-act facilitation
0 sec after 20 s activation 1min after activation
3 Hz
-76%
-80%
3 Hz
-18%
-26%
3 Hz
-75%
-78%
after rest
Left ADM
Stålberg
35. LEMS, Repetitive nerve stimulation at re
Right ADM
Stålberg
Rest, 3 Hz 10 stim
Directly after 20 s
activation =
facilitation
3 Hz
-26%
-31%
3 Hz
-6%
-8%
20 Hz
30 %
35%
50 Hz
>500%
>500%
