ﾊ
ﾊ2. Characteristics of motor disorders
ﾊﾊ In the previous section, the background of the orthopaedic
selective spasticity-control surgery concept was documented in
detail. Now, to establish the effective spasticity-control surgery,
analysis of the characteristics of the motor disorder in cerebral
palsy is indispensable.
Hypertonicity of the muscles
ﾊ The most characteristic feature of the cerebral palsy is
hypertonicity of the muscles. This hypertonicity includes all
hypertonic conditions of the muscles, such as spasticity, rigidity
and involuntary movements as in athetosis and tremor.
Hypertonicity not only inhibits alternate movements of the
extremities and body-supporting activities of the antigravity
muscles, but also causes various deformities in different parts of
the body. In the cervical region, hyperextension and involuntary
movements of the neck are characteristic and consequently cervical
radiculopathy and myelopathy are induced. In the thoracolumbar
region, lordosis and scoliosis of the trunk due to hypertonicity are
often seen. In the upper extremity, shoulder retraction, flexion or
extension of the elbow, pronation of the forearm, flexion of the
wrist, flexion or swan-neck deformity of the finger, and adduction
and flexion deformity of the thumb are common. In the lower
extremity, dislocation, and subluxation of the hip,
flexion-adduction deformity and extension deformity of the hip,
extension or flexion deformity of the knee, and various kinds of
deformities of the foot and ankle are seen. Thus, hypertonicity of
multiarticular muscles causes deformity, contracture and hypertonic
posture in different parts of the body.
The most important point to be considered is that this
hypertonicity inhibits activities of the monoarticular muscles that
are located in antagonistic position. For example, hypertonicity of
the psoas muscle inhibits activities of the gluteus maximus muscle,
which is an antigravity hip-extensor. Also, hypertonicity of muscles
in various parts of the body can result in a hypertonic condition in
whole body such as tonic neck reflex or tonic labyrinthine reflex.
Simultaneous co-contraction of hypertonic extensors and flexors
(Rigidity)
Another important characteristic feature of the motor disorders
in cerebral palsy is rigidity. In cerebral palsy, rigidity is usually
combined with spasticity and athetoid movement to some extent,
and causes serious problems, such as limitation of range of joint
motion and shortening in the stride length, resulting in interference
with smooth body motion. Rigidity also decreases the effectiveness
of the activities of daily living. Motor-function-wise, rigidity is the
result of simultaneous co-contraction of the hyperactive flexors and
extensors. In cerebral palsy, the multiarticular muscles of the
flexors and extensors are contracting continuously, and
simultaneously (Fig. 1C.[p1.ch1.1. Introduction]). These concomitant
contractions inhibit smooth reciprocal movements to flexion and
extension and decrease speed of movement.
In the quadriplegic patients with athetosis, we can see that
electromyography shows simultaneous co-contraction of the
multiarticular extensors and flexors, during crawling (Fig. 8B
[p1.ch1.3]). This simultaneous co-contraction of the flexors and
extensors causes rigidity and results in deformities with loss of fine
motor skills of the fingers (Fig. 8A). Postoperatively, the electrical
discharge of these multiarticular muscles is decreased (Fig. 8D),
thereby resulting in facilitation of the skills and restoration of
dexterity in the fingers (Fig. 8C). These co-contractions of the
multiarticular muscles can also be seen in the proximal joints, such
as the trunk, shoulder, elbow, hip and knee, with inhibition of their
smooth movements. In normal individuals, the flexors and
extensors act separately in different phases of flexion and extension
and are not hypertonic, and hence the smooth reciprocal
flexion-extension movements are possible (Fig. 9[p1.ch1.3]).
ﾊWeakening of the antigravity muscles
Another feature of cerebral palsy is the weakness of muscles.
Existence of the weakened muscles has not been mentioned and not
been measured in cerebral palsy, although the difficulties in keeping
the head and body upright in sitting and standing suggest their
existence (Fig. 14A, 15, 17).
Now, we have to come back again to our working concept that
the monoarticular muscles are acting as antigravity muscles, by
keeping the body upright. It seems logical to consider that the
decrease of antigravity stability in cerebral palsy is due to
weakening of the monoarticular muscles. The aim of our treatment
is therefore to restore the activities of the weakened antigravity
muscles. However, unfortunately, it is impossible to reactivate the
weakened muscles by any means, if they are actually paralyzed due
to impairment of the central nervous system.
In cerebral palsy, we can notice and become aware of the fact
that the activities of the monoarticular muscles are depressed by the
hypertonicity of the multiarticular muscles in the opposite
antagonistic side, resulting in the paralysis or weakness of the
antigravity muscles. Here, we also need to be aware of the
capability of regaining the activities of the antigravity muscles, by
relieving the hypertonicity of the antagonistic muscles
(Fig. 1ABCD)
The damage of central nervous system and paralysis caused by
damage of brain cells cannot be restored. But, by careful control of
hypertonicity and by facilitation of latent potentials of the
remaining muscles, spasticity-control surgery enabled us to reduce
hypertonicity, to facilitate activities of antigravity muscles, and to
promise various improvements in the cerebral palsy patients.
Disturbance of the alternate movement (Difficulty in alternation)
Difficulty in alternate movements in cerebral palsy patients is
also a notable feature. This difficulty interferes with crossed
pattern movements, thereby, causing a symmetric posture in spastic
diplegia. Difficulty in alternation is observed at various motor
levels of cerebral palsy.
The most typical pattern due to difficulty in alternate
movements of upper and lower extremities is seen in the symmetric
tonic neck reflex (Fig. 13A, 21A [p .ch . ]). Difficulty in alternation
is also seen in symmetrical crawling on the abdomen (Fig. 19A,
40A[p .ch . ]). Another example is the symmetrical four-point crawl,
the so-called bunny hopping (Fig. 16A[p .ch . ]). You could also see
the difficulty in crossed alternate movements in the lower
extremities in diplegic patients at standing level (Fig. 6A, 82A
[p .ch . ]). So to achieve smooth alternate movements in these
patients, restoration of individual movement of each lower
extremity by blocking the symmetrical position is needed. After the
symmetric position is broken, the alternate position and movements
can be restored (Fig. 6B, 13B, 16B, 19B, 40B, 82B).
Difficulty in alternate movements is also seen in totally involved
patients, as in the asymmetric tonic neck reflex (Fig. 17, 18A), and
windswept deformity of the trunk and lower extremities (Fig. 22A
[p .ch . ]). Fixed asymmetric deformities also present a very serious
problem, inhibiting alternate movements in turnover and crawling.
Clinically, we have been able to overcome this difficulty in
alternate movements by the use of OSSCS. With concomitant
release of the multiarticular muscles on the flexor and extensor
sides of both extremities, reciprocal and alternate movements could
be facilitated (Fig. 6B, 13B, 16B, 19, 40B, 82B). These clinical
observations led us to a conclusion that difficulty in alternate
movements is due to hypertonicity of the multiarticular muscles on
both flexor and extensor sides. It is also concluded that the
monoarticular muscle is closely related to the separate, individual
movements of the extremity, and contributes to alternate movements.
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