NEUROPHYSIOLOGY
OF THE FES FOR RESTORATION OF GAIT
We shall review development of FES for restoration of gait in parallel to neurophysiological studies of the FES in order to discuss putative underlying mechanisms.
Three categories of potential users of people with altered/or an impaired locomotion will be discussed:
1. Subjects in whom FES procedure should be integrated to established remaining functional motor control in order to improve overall functional motor performance output (ambulatory subjects with altered locomotion)
2. Subjects with present volitional motor control but unable to walk (wheelchair bound).
3. Subjects with intact brain functions and connected to the proximal spinal cord which is completely disconnected from distal lumbar portion by accidental injury.
While describing
early period of the FES development (between 1950-1975) we shall present also
parallel neurophysiological studies in order to show that external FES
stimulation of the mixed peripheral nerve fibers can modify state of excitation
and inhibition of spinal reflex activity.In the neurophysiological studies
after 1980 of effectiveness of FES for restoration of locomotion we become
aware in the subjects with identical clinical sign for impaired gait can have
different features of underlying motor control. This will be shown by
illustration of results of a EMG polielectromyographic study in a group of
ambulatory hemiplegic subject with drop foot after stroke. Thus, when these
subjects are exposed to the corrective measure for drop foot by FES, they can
have different beneficial effects. Therefore, when FES is applied for clinical
purposes it is imperative to carry not only a clinical evaluation of motor
deficit but also to assess how this clinical findings respond to a protocol of
stimulation of FES on immediate and clinically obvious modification of impaired
motor function.
Category 2
In this category of patients it is essential to be able to assess
how much present volitional movements are result of full capacity of brain
control for initiation, maintaining and ending volitional motor task to the
contrast of volitional control of components of motor task or present brain
control is result of initiation of movement and the rest is generated by motor
structures of brain stem or spinal cord. Moreover, we shall provide examples of
features of motor control within this category 2 by presentation of
neurophysiological classification of spinal cord injury people and explain how
assessment of residual profile of brain control to the lumbar pattern
generators for standing and locomotion can assist in the development of FES
stimulation protocol. We shall also provide information under what condition
will be necessary to add to FES program for restoration of locomotion another
available intervention modalities for restoration of locomotion as there are
locomotor training with reduced weight, intrathecal substances and spinal cord
stimulation and robotic systems.
Category 3
This is category of subjects who have preserved function of lumbar
neuronal network generators but complete absence of brain control or any kind
of influence to these interneuronal networks. Under intact conditions of
functions of the nervous system those network of pattern generators is
controlled by brain stem and brain motor structures. During the last forty
years this category of spinal cord injury subject with total separation of the
caudal, lumbar spinal cord, from more rostral, cranial segments of the spinal
cord has been challenge for many research groups around the world. There have
been successful demonstrations of controlled, standing, some control of the
posture and ambulation by FES multisite surface or implanted systems, hybrid
system combine with FES and exoskeletons, FES and robots and we reached at
present possibility to add to those previous efforts a combined approach with
active control of lumbar pattern generator by "mimicking" absent
brain control to the lumbar network by external stimulation control.