Study of polysynaptic reflex excitability and somatosensory evoked potentials in patients with myofascial pain syndrome

Introduction. Myofascial pain syndrome (MFPS) is one of the most common pathologies of the musculoskeletal system that causes chronic pain. This type of pain reaches its peak in middle-aged people; women get sick 2,5 times more often than men. The disease leads to significant disability; it is not only a medical but also a social problem. Atthe same time, a number of authors still note the low clinical efficacy of the applied therapy regimens. In this situation there is in demand the further study of the MFPS pathogenesis, in particular, the clinical and electroneurophysiological characteristics of this pathology, in order to search for new, including pathogenetically proved, treatment methods.The aim of the research was to study the relationship between the indicators of the blinking reflex and somatosensory evoked potentials in patients with active and latent forms of MFPS.Materials and methods. In order to study the neurophysiological aspects of MFPS, a comprehensive clinical and electroneurophysiological examination was carried out in 92 patients of working age, including 78 women and 14 men, whose average age was 48,1±9,3) years, suffering from MFPS of the scapular area. The patients were subdivided into subgroups depending on the prevalence and severity of pain manifestations: the first subgroup — with an active form (58 people, 63 %), the second subgroup — with a latent form of MFPS (34 people, 37 %). The control group was formed from conditionally healthy volunteers in the amount of 35 people, comparable to the main group by age and sex.Results. The comparing of the study results, taking into account polysynaptic reflex excitability and the data of somatosensory evoked potentials, revealed the significant positive correlations of the indicators. The obtained results allowed to assess the excitability of spinal cord motor neurons as well as suprasegmental structures in MFPS, involved in the implementation of pain syndrome.Conclusion. The use of clinical electroneurophysiology methods makes it possible to assess the functional state of the CNS structures involved in the analysis of nociceptive afferentation. In the active form of MFPS, an increase in the excitability of stem and thalamic structures was mainly determined, which could potentially indicate the activation of adaptive processes on the one hand, and on the other hand, the predisposition of neuronal networks to a state of arousal. In the latent form of MFPS, a multidirectional change in reflex excitability was observed.

The use of neurophysiological tests in integrated diagnostics of the myofascial pain syndrome in athletes

<em>The aim of the study</em>: to study of electroneurophysiological characteristics of myofascial pain syndrome in athletes. <em>Material and methods.</em> 40 sportsmen, representatives of the 4 sports at the age from 17 to 24 years and 25 healthy volunteers have participated in the study. The global electromyography and the study of the blink reflex have been included in the program of electroneurop hysiological studies in order to assess the polysynaptic reflex excitability of the brainstem. <em>Results</em>. If there is a myofascial trigger point in a muscle, the increased rest activity typе its pathogenic influence on the structures of the central nervous system, and this indicant can be used for objective assessment of the pathological process. The study of the blink reflex data allows to determine the connection of polysynaptic reflex excitability level with the myofascial pain severity in athletes. <em>Conclusions</em>: it has been determined that the global electromyography allows to objectively evaluate the pathogenesis of myofascial pain, and the blink reflex study can serve as an adequate neurophysiological test that reflects the performance peculiarities of the central nervous system suprasegmental parts to assess the blink reflex severity in athletes.

Serotonergic Modulation in Aplysia. II. Cellular and Behavioral Consequences of Increased Serotonergic Tone

Serotonin (5-HT) plays an important role in sensitization of defensive reflexes in Aplysia and is also involved in several aspects of arousal, such as the control of locomotion and of cardiovascular tone. In the preceding paper, we showed that tail-nerve shock, a noxious stimulus that readily induces sensitization, increases the firing rate of a large number of serotonergic neurons throughout the CNS. However, the functional consequences of such an increase in serotonergic tone are still poorly understood. In this study, we examined this question by using the 5-HT precursor 5-hydroxytryptophan (5-HTP) to specifically increase 5-HT release in the CNS. Increased tonic 5-HT release after 5-HTP treatment was manifested by facilitation of sensorimotor (SN-MN) synapses, increased firing rate of serotonergic neurons in the pedal and abdominal ganglia, and enhanced 5-HT release evoked by tail-nerve shock. When 5-HTP was administered to freely moving animals, it produced a strong arousal response characterized by increased locomotion and heart rate, which was reminiscent of the defensive arousal reaction triggered by noxious stimulation such as tail-shock. In contrast, 5-HTP actually inhibited the tail-induced siphon-withdrawal reflex. It is possible that 5-HT-induced facilitation of SN-MN synapses was counteracted by inhibition of polysynaptic reflex pathways between SNs and MNs, resulting in transient behavioral inhibition of the reflex, which could favor escape locomotion and/or respiration shortly after an aversive stimulus. We conclude that a major function associated with the activation of the Aplysia serotonergic system evoked by noxious stimuli is the triggering of a defensive arousal response. It is known that tail-shock-induced serotonergic activation contributes to memory encoding at least in part by facilitating SN-MN synapses. However, this effect in isolation might not be sufficient for the behavioral expression of sensitization.