The H-reflex test as Delwaide., and Fisher., explained can be useful for the objective measure of motor neuron hyperex-citability Although various techniques for this study have been introduced, the ratio of the maximum amplitude of H-reflex to maximum M-amplitude (H/M ratio) is most practical because of the easier technique. H/M ratios tend to be increased in patients with CNS lesions and upper motor neuron signs, and recruitment curves are altered in a manner consistent with increased excitability of the central motor neuron pool. Conversely, H reflexes during cataplexy are depressed. H-reflex studies in patients with CNS dysfunction have been helpful for understanding the pathophysiology of these disorders.
Many Potential benefits could derive from RSWT, compared with ESWT, because it is less painful effect and thus can be administered without anesthesia, thereby reducing the risks of treatment for patients. Furthermore, due to the radial emission of RSWT, the calcification, once located radiographically, is surely included inside the wave propagation area. Contrarily, when the shock wave is focused, as occurs in the ESWT, refocusing of the applicator is periodically necessary to be certain that the waves hit the calcification. [37] Moreover, no ultrasound guide is needed to perform therapeutic applications of RSWT. [13]
A direct effect of shock waves on fibrosis and on the rheological properties of the chronic hypertonic muscles in CP should be considered together with the documented therapeutic effect on bone and tendon diseases. [15-19, 38-39]
Possible inhibitory effects of shock waves on hypertonic muscles and tendons might be attributed to the effect of mechanical stimuli of shock waves on the muscle fibres next to the tendon that cannot be excluded as suggested by (Leone and Kukulka. [40] Also continuous or intermittent tendon pressure produced by shock wave could decrease the spinal excitability without long-lasting clinical or neurophysiological effects. Another possible mechanism was the mechanical vibratory stimulation, which reduces excitability of motor neurons and induces the change of F wave. [40] Despite transitory and short lasting inhibitory duration of mechanical vibratory stimulation on muscle, the clinical results of this study continued for weeks and assisted in inhibition of monosynaptic excitability of tendoachillis as revealed by lowering of the H/M ratio in the study group .This finding suggesting a different mechanism of action need further investigation and explanation.
Geldard [41] in his work found that Pressure technique has been therapeutically effective to alter motor response and when pressure is continuously applied, there is a decline in sensitivity. Tuttle and Mc Clearly [42] added that mechanical pressure (force), provided continuously is inhibitory, perhaps because of pressure adaptation. It is hypothesized that this deep pressure activates pacinian corpuscles, which are rapidly adapted receptor; however, the adaptation may vary with the intensity of stimulus and with the area of the body being stimulated. This pressure seemed most effective on tendinous insertions. [42]
Pacinian Corpuscles as Quillin [43] explained are located deep in The dermis of the skin: in viscera, mesenteries, and ligaments and near blood vessels. Interestingly. they are most plentiful in the soles of the feet, where they seem to exert some influence on posture, position, and ambulation. The pacinian corpuscles adapt quickly and they are activated by deep pressure and quick stretch of tissues. [43]
Umphred et al., [43] reported that Because of the rapid adaptation, a maintained stimulus will effectively cause inhibition by preventing further stimuli from entering the system . The technique of deep pressure is applied to hypersensitive areas to normalize skin responses. Also, they recommended that constant pressure applied over the tendons of the wrist flexors may dampen flexor hypertonicity as well as elongate the tight fascia over the tendinous insertion. The pressure is applied across the tendon with increasing pressure until muscles relax. [43]
Pierson [45] recommended that the maintained pressure is effective in reducing spasticity if it is applied to the tendon than the muscle belly. It is thought to act as a counter irritant that overwhelms sensory ability to mediate other types of stimuli. H-reflex testing has shown that the motor neuron is inhibited in the tendon being pressed. [45]
In their work about the effect of soleus muscle pressure on alpha motoneuron reflex excitability in subjects with spinal cord injury(SCI) Robichaud and Agostinucci [46] found that Circumferential pressure applied to the lower leg decreased soleus muscle alpha motoneuron reflex excitability in subjects with SCI. [46]
The results of study tested the effectiveness of intermittent tendon pressure on the depression of alpha motoneuron excitability. Kukulkaet al., [] showed that the application of intermittent pressure to a tendon produced a statistically significant decrease in the amplitude of the H reflex, indicating a depression in alpha motoneuron excitability. This depression was sustained over a 30-second period of intermittent pressure application. These findings support those reported earlier by KuKulka et al., [47] in which sustained tendon pressure was found to produce a transient inhibition of motoneuron excitability. Intermittent tendon pressure, therefore, may be useful for patients who require a sustained reduction in muscle activity, and sustained tendon pressure may prove most useful for transient reductions in muscle tone. [47]
Regarding to the inhibitory effect of vibration, Maisden [48] in their studies showed that Because its ability to decrease hypersensitive tactile receptors through supraspinal regulation, local vibration is considered an inhibitory technique.. Vibration also stimulates cuteaneous receptors, specifically the pacinian corpuscles, and thus can also be classified an extroceptive modalities. Vibrators function with frequency below 75 Hz is thought to have an inhibitory effect on normal muscle. [48]
Umphred et al., [44] concluded that low-frequency vibration used alternately with pressure can be highly effective. It should be remembered that these combined inputs use different neurophysiological mechanisms. [44]
Vibration is an effective way to suppress the H-reflex as stated by Delwaide., [49] and Braddom & Johnson.[50] Somerville and Ashby [51] added that Applying a vibrating stimulus to the Achilles tendon in the limb under investigation results in depression of the H-reflex that may outlast the duration of the vibration by several hundred milliseconds. The mechanism of H-reflex suppression as explained by Taylor et al ., [52] is unknown but may involve presynaptic inhibition through primary spindle afferent firing or neurotransmitter depletion.
The results of this study agreed with the finding of the work done by Manganotti and Amelio [53] who used 1,500 shots of shock wave to treat flexor muscles of the forearm and 800 shots for each interosseus muscle of the hand with 0.030 mJ/mm2 intensity. They reported that ESWT on the flexor hypertonic muscles of the forearm and the interosseus muscles of the hand was effective for the improvement of upper limb spasticity in stroke patients for more than12 weeks.
Also the finding of Yoo et al. [29] proved significant reduction of spasticity on the elbow flexor and wrist pronator for 1 to 4 weeks after 1,000 shots of ESWT with 0.069 mJ/mm2 intensity.
In their study aimed for evaluating the spasticity and electrophysiologic effects of applying extracorporeal shock wave therapy (ESWT) to the gastrocnemius by studying F wave and H-reflex. Sohn et al., [30] concluded that after applying ESWT on the gastrocnemius in stroke patients, the spasticity of the ankle plantarflexor was significantly improved, with no changes of F wave or H-reflex parameters. They recommended that further studies are needed to evaluate the mechanisms of the antispastic effect of ESWT.
The significant improvement in the development of walking skill in the participant children in the study group might be due to the application of traditional neurodevelopmental intervention technique in addition to the long lasting reduction of spasticity produced by shock wave therapy and its role in lowering calf muscle spasticity .This inhibitory effect on tendoachillis hypertonia assist the children in the study group to develop their motor function and walking abilities which was positively reflected on the gross motor function measure score in the walking part following post treatment period
The modulation of Achilles tendon hypertonicity and its influence on improving motor functional and walking abilities for hypertonic CP children is concomitant with the view of Natarajan and Ribbans [54] who strongly affirmed on that “Achilles tendon is involved in a variety of padiatric conditions†.So its shortening or weakness is a feature of many neurological conditions affecting the central or peripheral nervous system such as cerebral palsy. And Achilles tendon spasticity, weakness or contractures in these conditions lead to delaying of walking and gait abnormalities.
