Neuromuscular functions (Stålberg): The microphysiology and the microanatomy
of the human motor unit have been studied extensively at our laboratory by
Stålberg. Some of the methods will be described in detail in following
chapters of this supplement. Studies have been performed both in normal muscles
and in various neuromuscular disorders. The methods have had a large impact
both in neurophysiological research and clinical routine and have received
a great interest within the international community of clinical neurophysiologists.
The studies have dealt with the patophysiology of neuromuscular transmission
in myastenia gravis as well as neuromuscular transmission in conditions of
reinnervation. Detailed analysis of the motor unit potential (MUP) have been
performed describing the normal size variations of the motor unit, changes
in myopathy and neurogenic conditions and dynamic changes in the motor unit
over time in neurogenic conditions (ALS, polio).
The research has also included studies of single cells in the central nervous
system investigating H-reflex and flexion reflexes on single cell level and
the use of cortical stimulation together with SFEMG recordings. The project
has also encompassed the peripheral nerves studing different phenomena related
to electrical stimulation and excitability changes such as A-waves and neuromyotonia.
In parallel various computerized methods have been developed for quantitative
signal analysis such as the techniques of SFEMG, macro EMG and scanning EMG.
New motor unit parameters such as jiggle and size index have been described
and the method of decomposition of the EMG signal into individual motor units
(multi MUP analysis) is widely spread and built in to EMG equipment for automatic
EMG signal analysis.
Stålberg has also been most active in developing software for computerized
signal simulation. Two of the recent projects concerns the simulation of the
EMG signal recorded with concentric, macro or SFEMG needles (EMG Simulator).
The most sophisticated software allows the setting of several parameters.
The motor unit properties can be changed with respect to number of muscle
fibres, territory radius, fire frequency, force threshold. Fibre properties
can also be changed such as fibre diameter and diameter variation, fibre density
and distance from recording site to enplate zone. The delay and the jitter
of the neuromuscular transmission can also be changed in the set up. The program
have an option of simulating a scanning EMG in 100 ?m steps with the display
of the MUPs in raster mode or the amplitudes color coded. The Nerve Simulator
is just as detailed in the set up options. That software will simulate any
nerve conduction study. You will just decide the nerve properties such as
number of axons, length, diameter and conduction velocity (the distal slowing
will be set as a percentage of the proximal conduction velocity). F-response
probability, F-response delay, A-wave delay and stimulation threshold are
other parameters that can be varied. Both these simulating programs will be
excellent instrument both for research as well as education and training.