One of the leading neurological manifestations of dyscalgia, radiculo- and neuropathies is pain. The fight against it implies that the doctor has not only clinical knowledge, but also modern ideas about the neurophysiological, neurochemical and psychophysiological basis of this syndrome.
Pain is a kind of psychophysiological state of a person that occurs as a result of exposure to superstrong or destructive stimuli that cause organic or functional disorders in the body. This is not only a sensation, but also an integrative function of the body, which mobilizes a wide variety of functional systems to protect the body from exposure to a harmful factor. The biological meaning of pain, according to I.P. Pavlov, is to discard and discard everything that interferes (threatens) the life process, which would upset the balance of the body with the environment. Pain is a signal of danger.
According to the most common opinion, one of the components of the pain syndrome – sensation – occurs when unencapsulated nerve endings are excited, which in essence are chemoreceptors. Under the action of damaging agents, kinins and some ions (calcium, normally located inside the cells) enter the intercellular spaces and irritate nerve endings with a low threshold of excitability. Further, nociceptive irritation is carried out mainly along the bezmyelinovy and thin myelin fibers.
It is known that two types of pain are distinguished: fast local or epicritical pain and slow, delayed, protopathic (evolutionarily older). They are carried out in different ways. The process of transmission and processing of excitations that form pain is ensured by structures located at different levels of the nervous system. It should be noted that pain impulses are transmitted along the pathways of the autonomic nervous system, in particular, through the borderline trunk.
The receipt of pain impulses in the central nervous system and its processing occur by feedback mechanisms. The first level is localized in the gelatinous substance of the posterior horns of the spinal cord, where the influx of impulses to the cells of the posterior horns is regulated. Melzak and Wall (1965) based on their research put forward the theory of “controlling the afferent flow at the output.” The excitation reaches the specific nuclei of the visual tubercle along the spinothalamic tract (especially its ventrolateral group). Nociceptive signals of protopathic sensitivity are carried out along extra-lemniscal systems – spinoreticular, spinotectal and spinobulbar pathways. At the stem level, the suture nuclei (midbrain) are of great importance for conducting and integrating nociceptive signals, and then the impulses go to the ventrolateral nuclei of the visual tubercle.
The leading role of the thalamus in the formation of pain is confirmed by modern data. In it, the nociceptive irritation that came from the periphery acquires the character of a primary sensation. Further, the limbic system of the brain, related to memory and emotions, takes part in pain integration. Pain as an integrative function also includes components such as consciousness, sensation, memory, motivation, autonomic, somatic and behavioral reactions. In the design of the pain impulse, the circulation of pulses along the thalamocortical circular orbits plays a role. In the process of reversal, the incoming excitation is read with the available genetic information.
The process of awareness of pain as a sensation, its localization in relation to a certain area of the body and the entire complex of behavior associated with pain are performed with the mandatory participation of the cerebral cortex and, above all, the somatosensory zone. The activation that occurs with nociceptive stimulation is formed with the participation of the reticular formation of the trunk, especially the mesencephalic region.
According to Melzak (1965), one of the modulators of pain irritation is the posterior cords of the spinal cord, in which the paths of deep sensitivity are located. It is these paths that contain rapidly conducting myelinated fibers that allow the brain to quickly receive information about the nature and localization of external influences. Increased activity of the posterior cords reduces the transmission of pain from the cells of the posterior horn. That is why, with selective damage to the former, sharply expressed pain occurs.
The formation of pain with discogenic radiculopathy can be represented as follows. Under the influence of mechanical and hypoxic factors, myelinated fibers are primarily damaged (Khmara N.F., Ivashina E.N., 1970), which leads to a decrease in the blocking of nociceptive impulses at the level of the gelatinous substance of the spinal cord and to activation of bezmyelinovye conductors. The existence of the notion of reciprocity in pain between thick (fast conducting) and thin (including myelin-free) fibers (slowly conducting) formed the basis of electrical stimulation methods of treatment – percutaneous electrical stimulation (BSEC). Electrical stimulation provides the creation of an additional stream of impulses along the thick fibers of the nerve trunks and pathways, which leads to a reciprocal decrease in the flow of pain impulses along the thin fibers.
In the early 70s, receptors with a high affinity for endogenous opiates were isolated and described in the central nervous system. Most of them were found in the gelatinous substance of the posterior horns of the spinal cord, in the gray matter around the sylvian aqueduct, in the thalamus, hypothalamus, and limbic system. Electrical stimulation of these formations causes the development of analgesia,
due to humoral factors. Indeed, peptides with morphine-like properties, endorphins, have been discovered. They are divided into small endorphins (enkephalins) and large. Enkephalins are formed from the pituitary hormone peptide (alpha-lipotropin), which consists of many amino acids. Most of them are in the intermediate lobe of the pituitary gland. They are in the peripheral nervous system. Endorphins, like serotonin, adrenaline, histamine, are in granules inside the cells. Obviously, under stress and pain, they are secreted and regulate synaptic transmission and perception of nociceptive irritation, inhibiting the secretion of adrenaline, norepinephrine and acetylcholine and thereby inhibit synaptic transmission along nociceptive pathways. Large endorphins are slightly different in structure from enkephalins. All have a high affinity for opiate receptors. The described peptides are able to significantly change the electrophysiological properties of nociceptive neurons and their antalgic effect can be explained by a change in the energy status of the cell and the state of neural membranes.
To select methods of therapeutic anesthesia, in particular therapeutic drug blockade (LMB), an assessment of the intensity of the pain syndrome is important:
I degree – moderate severe pain syndrome; pain appears during a sharp transition from one body position to another, with physical exertion, especially in uncomfortable poses. The pain is absent in a calm lying position and with moderate movements in bed, with a short stay on the legs;
II degree – severe pain syndrome: pain appears with the slightest movement of the patient in bed and disappears when the patient is lying;
III – pronounced pain syndrome: pain is experienced not only when moving, but also at rest, disrupts sleep, and only sometimes subsides in a forced position.
About a third of patients have paresthesia, which are paroxysmal or permanent in nature and combined with pain. The intensity of paresthesia can also be divided into three degrees:
I degree – appear with static-dynamic loads on the spine and disappear at rest;
II degree – arises at rest and amplifies at stato-dynamic loads;
III degree – permanent, slightly decreasing when kneading, rubbing and other influences on the paresthesia zone or lumbar spine.
In the treatment of pain by blockades, it is advisable to take into account the presence of muscle-tonic pain reactions. To assess muscle soreness during palpation, you can use the classification proposed by V.P. Veselovsky (1980):
I degree – moderate soreness without motor reactions (judged by the verbal report);
II degree – severe pain,
accompanied by a mimic reaction of the patient;
III degree – pronounced soreness, accompanied by a general motor reaction of the patient.
In addition to vertebrogenic pain syndromes, an important place in the work of a practical doctor is the relief of pain and paresthesias in tunnel neuropathies.
The problem of pain and its relief is very complex and requires independent discussion. Since the pain factor in itself is a brake in the regeneration of the nerve fascicles, the relief of pain must be regarded not only as a symptomatic treatment.
The mechanism of development of peripheral localization pain syndrome in our works (V. Lobzin, 1973, 1990) is considered as a multi-neuronal pathological reflex that is realized at various levels of pain integration with the involvement of sensory and motor structures. We have indicated several fundamentally important areas that determine the effectiveness of analgesic treatment. The first is the effect on the local algogenic source (various types of blockades with the use of novocaine, hydrocortisone, anticholinergics, ganglion blockers). The second is the effect on the hypothalamic-limbic-reticular complex due to drugs such as chlorpromazine, trioxazine and other phenothiazine antipsychotics, as well as tranquilizers. The third direction takes into account the vasomotor-biochemical component of pain, including excessive accumulation of histamine and histamine-like substances in the tissues. To correct these disorders, antihistamines are prescribed (diphenhydramine, suprastin, pipolfen, etc.). The fourth direction refers to endocrine-homonal shifts and changes in electrolyte balance, which determines the purpose of calcium salts, hormones and some other drugs (Wilson RW Et al., 1974; Oh SJ 1978). The fifth direction is aimed at influencing the cortical level of perception and analysis of pain (sedatives, hypnotics, antidepressants, psychotherapy). The sixth direction in the fight against pain can be stimulation of the opiate-like endorphin system, in particular using various methods of reflexology.
With a number of diseases of the peripheral nervous system for the relief of pain, the shortest and most effective way to achieve the goal is medication blockade. The blockade can be especially effective in combination with other medical and rehabilitation measures.
When conducting therapeutic novocaine blockades, in addition to relieving pain, in some cases a distinct vasodilation and decongestant (“swelling”) effect and an improvement in neuro-trophic function are obtained.
Depending on the specific tasks facing the doctor, medical-medical blockade can play the role of a diagnostic procedure – for example, the disappearance of the phenomena of neuro- and (or) angiopathy with the introduction of a local analgesic into the muscle,
under which the corresponding vascular-neural bundle is located, confirms the correct diagnosis reflex-compression syndrome of a particular muscle (anterior scalene, inferior oblique muscles of the head, piriform, etc.). The immediate effect of a single LMB can also have prognostic significance – for example, the complete elimination of all occurrences of the disease for a certain period of time will make it possible to predict a quick and lasting effect on the course of LMB. Preventive tasks can also be solved with the help of LMB : timely use of LMB with an adequate selection of drugs for stage I neurological syndromes of osteochondrosis of the spine helps to prevent the development of dystrophic processes in dystonically or aseptically inflammatory tissues, as well as prevent stabilization of the process with the possibility of achieving complete remission.
It is well known that pain not only has a signaling value, but also negatively affects the course of the pathological process,