Pain Dysfunction of Nervous System

The differentiation of chronic pain syndromes in relation to the participation in their formation of elements of somatic (animal) or vegetative (sympathetic) nervous system has proven to be extremely useful for practice. The existence (independently of one another) of two different systems for the conduction of nociceptive signals with the presence in each of them of substrates of the central integration of pain has been the theoretical basis of such a differentiation.

 The practical significance of the distinction of somatic and vegetative pain lies in the accentuation of physicians' attention to the need for a differentiated approach to the determination of the neurophysiologic core of pain syndromes. Various divisions of the nervous system may participate in the formation of chronic pain. This proves the need for a selective approach to the elimination of disturbances of the neural regulation of pain sensitivity of tissues at the periphery. Ignoring this fact when managing pain control therapy renders its outcome impermanent and unpredictable.

 The appearance of chronic pain syndromes can be perceived as the result of interaction between pathogenic factors acting in the periphery as pain-triggering mechanisms, with nervous processes occurring within the structures of pain transmission system in the spinal cord and the brain. Such interaction gives rise to the morphological and functional formation of pathological algesic system whose function only in its early stages is determined by the actions in the periphery of the focal pain irritant. In later stages, the pain determinant, under the influence of the incessant pathological pain impulses transmitted from the periphery, moves into the ganglia, whether somatic or vegetative, which, according to present data, represent intermediary «nerve integrators» along the route of the rising pain impulses traveling into the structures of the central nervous system (CNS). The appearance at various CNS levels of such pain determinants, which are considered generators of pathologically enhanced stimulation, makes pain especially resistant to medical treatment and requires a specialized approach for its elimination.

 What do we know about the neurophysiological specificities of the various types of chronic pain?

 There is a fairly extensive literature on this subject that mainly correlates the data of experimental morphology and physiology of the nervous system. The somatic division of the nervous system participates in the formation of tissue (ligamentous, fascial, fasciocapsular, myofascial) and arthrogenic ("synovial") pain. The vegetative division of the nervous system participates in the formation of vascular, bone marrow (osteomedullary), and particular forms of periosteal and neurogenic pain. Mainly periosteal (periosteous) pain and the majority of forms of neurogenic pain are of mixed (somatovegetative) origin.

The sensory differentiation of chronic pain in relation to its neurophysiological origin must become an indispensable element of the identification of this phenomenon. The validity of such a differentiation of peripheral pains is confirmed by the fundamental distinction between their clinical manifestations. We recommend use of the criteria of differentiation given in table 1.

Table 1. 

    Clinical Criteria for the Differentiation of Somatic and Vegetative Pain

Feature 

Somatic Pain 

Vegetative Pain

Character of pain

Any modality of sensation is possible, with the exception of burning. Pain is most often perceived as stretching, aching, or crushing 

Manifested in the form of paroxysms perceived as burning pain. Other shadings of pain (boring, shooting, pressing) are possible. A combination of several different pain sensations in a single paroxysm is often observed.

Localization

This is primarily intra-tissue, local pain, localized in the focus of development of the pathological process. Neurogenic somatic pain is manifested as "myotome," "dermatome," or "sclerotome" in type. 

This is primarily vascular or neurogenic pain. It is located either in the region of an affected vegetative ganglion or along the projection of the adjoining sympathetic trunk, or along major arteries and peripheral nerves. Only two forms of vegetative pain - periosteal and bone marrow - have an intra-tissue representation.

Constancy of pain

Constant in character in the intra-tissue type of pain or is manifested in the form of brief attacks of pain lasting up to 5 minutes in the case of neurogenic somatic pain.  

The duration of vegetative paroxysms ranges from several hours to several days. Appears either against the backdrop of already existing pain or during a clear interval of an illness. 

Boundaries

The zone of tenderness has distinct boundaries, is well localized by the patient; does not extend beyond the limits of its initial boundaries with further progression of the illness.

This is diffuse pain without distinct boundaries which, in case of progression of the illness, may extend beyond the limits of its initial boundaries (the repercussion effect).

Painful points

Located in structures relating to the stroma of the skeleton and internal organs (muscles, ligaments, fasciae, skin). 

Detected through gliding palpation of major arteries, as well as vegetative ganglia of the adjoining sympathetic trunk. Palpatory exploration is accompanied by intensification of painful sensations. 

Alteration of reflexes

Increase in muscle, tendon, or periosteal reflexes is possible. 

The appearance of white dermographism, positive white spot test (Laignel-Lavastine test), a markedly positive "Thomas goose flesh" phenomenon (pilomotor reflex) are characteristic.

Factors intensifying pain

Physical loads, impairment of the biomechanics of joints and spine, structural abnormalities of the musculoskeletal apparatus, cooling.

Diseases of neural regulation (hypertensive disease, neuroses, bronchial asthma), emotional excitement, fear, depression, change in weather.

Action of spasmolytics

Ineffective.

Have a temporary effect.

Action of analgesics

Reduce manifestations of pain syndrome.

Ineffective.

Action of narcotics

Bring about complete relief of manifestations of pain syndrome.

Reduce manifestations of pain syndrome.

Reliability criteria for the differentiation of pains

Pain-relieving effect absent after novocaine blockade of ganglia of the adjoining sympathetic trunk.

Complete arrest of pain syndrome observed after novocaine blockade of the relevant ganglia of the adjoining sympathetic trunk. 

In addition to principles of differential diagnosis of somatic and vegetative pain, we wish to draw the attention of physicians to a very important circumstance. Under the influence of the stagewise character of the pathological process and the succession of pathogenetic mechanisms at various stages of its development, the clinical manifestations of pain are frequently fundamentally altered. For this reason, the algesic picture in patients with identical pathology may vary substantially. For better understanding of the individual features of the development of algesic pathology, data reflecting the change over time of the alterations of the clinical manifestations of pain, as compared with the severity of the biomechanical and pathophysiologic shifts characteristic of the pathology in question, must be used without fail for the assessment of patients.  We felt that it was expedient to cover the particular features of the diagnosis of the various forms of tissue pain in a separate book devoted to the characterization of the methods of treating the pain syndromes.

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