6. Initial aim
• To find a method for the assessment of
fatigue (Ekstedt and Stålberg)
• We used:
force (Merton, Morton)
twitch
surface EMG
wire electrodes
7. Inspired by Buchthal
• His multi-electrodes were too large (1 mm
cannula, 14 electrodes, each 1 mm), we needed
miniaturization
• We spend years in making smaller electrodes
8.
9. Multielectrodes to record electrical activity
from human muscle
Buchthal
1957
......... 14 recording surfaces
Ekstedt, Stålberg
1960
10. Brief signals of constant shapeBrief signals of constant shape
What is this?What is this?
Stålberg
1 msec
11. What do the spikes
represent
• tank-experiments
• multi-electrode experiments
• Na-citrate activation to get single fibre
activation
• curare and ischemia experiments
• presentation in -63 in Copenhagen, -67
in Glasgow - SINGLE FIBERS
14. Lost and found during the trip
• Technical
– General for EMG
– Specifically for SFEMG
• Physiological
– MU organisation
– Propagation velocity
– Jitter in various synapses
– Understanding MU physiology
15. Technical
Electrode type and size
Wall effect
Reference electrode
Filter
Trigger, no delay
Delay line 14 km cable = 168 µs
Variable sweep speed
Sweller
Wobbler
Jittermeters
Cable transmission
the x
16. Buchthal´s hypothesis: the signals are
generated from groups of 10-30 muscle
fibres, subunits
MU organization
Physiological findings
17. SFEMG suggested random organization
• Multielectrode studies
• FD measurements
• Scanning SFEMG
MU organization
18. Struggle with the motor unit
• SFEMG led to new ideas on the
organization of fibres in the motor unit,
not in subunits, but fibres separated
randomly
MU org.
20. ”proof” of random distribution from
Kugelberg,Edström glucogen depletion
studies, 1968-70
Bild v kugel
Dense groups in reinnervation but
random fibre distribution in normal muscle
EKugelberg et al 1970Reinnervated
tibial anterior muscle
SADH
PAS
Control rat
Randomdistribution
of fibres in normal muscle
MU organization
34. The jitter phenomenon,
where does it arise?
• technical problems excluded
• probably in the n-m junction
• tested on MG, YES!
• Lambert,Elmqvist intracellular
recordings 1964 helped to show the
details
itter
35. Intracellular recording of EPPIntracellular recording of EPP
Normal Myasthenia gravis
• Elmqvist et al, 1964
itter
37. Jitter in routine
• analysis was standardized, MCD
• many EMG equipment have a “jittermeter”
• new features (spike detection) facilitate
procedure
• other electrodes
38. Jitter, where?
• Neuromuscular transmission
• Anterior horn cell
• Multi-synapses
• Node of Ranvier
• Stimulation point
itter
39. Further understanding of the MU,
some phenomena
• split fibre
• dual innervation
• neurogenic blocking
• ephaptic transmisssion, CRD
• myogenic decrement
• F-H wave differences
• reflex jitter
40. New developments
• Reflex studies
• Post stimulus time histogram
• TMS, single pathway study
• Spike triggered averaging
– Study other parts of one MU
– MUNE
– Macro EMG
– Scanning EMG
41. SFEMG INDICATIONS
•Neuromuscular transmission in diseases
•Experimental studies of n-m transmission
•Spatial organisation of MUs in diseases
•Firing pattern
•Spike triggering
•Propagation velocity
Stålberg
44. What to do with SFAP?
• Volume conduction; understanding of EMG
• Jitter; neuromuscular transm.; diseases, drugs
• Propag. velocity; fatigue, membrane function (event memory)
• MU organisation; microanatomy of the MU
• Single MU physiology;
single axonal cond;
H and F studies (single AHC)
cortical stimulation,
corticopyramidal pathways, PSTH
• Markers for trigger; surface MU, Macro EMG, Scanning EMG
45. What did we learn?
• News on the motor unit
• Understanding of EMG
• Technical spin-off
• Value of open-minded collaboration
• Value of friendship
Thank you all!
61. A
NMJ-1 NMJ-2
Two NMJs from different neurons
Strong stim
B
NMJ-2 NMJ-1
Recording
NMJ-1 (Block at NMJ-2 or collision)
NMJ-2 (Block at NMJ-1)
Block at NMJ-1 and NMJ-2)
Dual innnervation
seen in MG
