ELECTRODIAGNOSIS — the method of inheritance of a functional condition of nerves and muscles based on definition of their reaction to electric irritation (electroexcitabilities).
Traditionally E. it was applied by hl. obr. for the purpose of diagnosis of motive disturbances. Later E. began to use for a research of a condition of a sensitive innervation. So, version E. the electric pulp test — definition of thresholds of excitement painful and tangoreceptors of a pulna of tooth or a periodontium at irritation is electric current (see below).
Electrodiagnosis as a method of a research of motive frustration is based on property of the neuromuscular device to come to a condition of excitement iod influence of irritation electric current. Reduction of muscles is result of excitement, character to-rogo depends on a functional condition of a nerve, a muscle and allows to judge weight of defeat of these educations.
Electrodiagnosis can be carried out by various ways. Classical E. it is based on determination of threshold power of electric irritation of the nerve or muscle causing muscular contraction and a research of qualitative characteristics of this reduction. Versions E. are hronaksimetriya (see) and determination of speed of carrying out nervous impulse (see. Electromyography ).
The simplest on technology of carrying out and interpretation of indicators is classical E. The foundation of this method was laid in 19 century by E. Du Bois-Reymond's works, and then E. Pflyuger, V. Erba, T. Cohn, E.J. Remak, etc. In development of a method works of domestic scientists N. E. Vvedensky, A. A. Ukhtomsky, V. A. Grechenin, N. I. Korotnev, P. K. Anokhin, A. N. Obrosov and N. M. Liventsev, etc. were of great importance (see. Excitability , Excitement , Lability , Muscles , Nervous impulse , Nerves ).
Classical E. allows to specify weight and level of defeat of the neuromuscular device, to track objectively dynamics of excitability of a nerve and muscle during treatment, defines the choice of parameters for carrying out electrostimulations (see). The main indications to carrying out classical E. the damages of a peripheral motor neuron proceeding with sluggish paresis and paralyzes are — poliomyelitis (see), injuries of a spinal cord, radiculitis (see), neuritis (see), plexitis (see), etc.; general diseases of muscles — a myopathy (see), a myasthenia (see), etc.; the secondary atrophies of skeletal muscles which came owing to a long immobilization (at changes) or restrictions of mobility of top and bottom extremities at diseases of a musculoskeletal system, functional (hysterical) paresis and paralyzes (see. Atrophy muscular ).
Classical E. it is contraindicated at individual intolerance of electric current, a condition of overexcitation of the neuromuscular device (a hyperexcitability of muscles, hyperkinesias, a tic, etc.), at a contracture of muscles of top and bottom extremities and persons, the expressed pain syndrome, dislocations, fractures of bones before implementation of a constant immobilization, in the early period (2 — 3 weeks) after nerve operation or a large vessel (a seam, plastics, etc.), at thrombophlebitis, acute purulent process in a zone of a research, bleeding.
For irritation of neuromuscular structures use an impulse current with a frequency of 100 Hz with impulses triangular or a rectangular shape lasting 1 — 1,5 ms — tetanizing current (see. Impulse currents ), and also direct (galvanic) current. As generators of electric currents use special devices — electrostimulators, e.g. a two-channel electroneurostimulator of ENS-01. Devices of this kind represent generators of square-wave or sawtooth pulses of positive or negative polarity with independent adjustment of temporary and amplitude parameters. The maximum value of amplitude of impulses at the exit — 100 in (200 ma), duration of impulses — 10 - 5 — 10 sec., are provided a possibility of manual adjustment of parameters of output impulses. Electrodiagnostic units provide high precision of installation of parameters of output electric impulses and their stability.
During the carrying out classical E. apply lamellar, and also bellied (unary and doubled) electrodes (see) with the push-button breaker on the handle (fig. 1).
The irritation is put in so-called motor points of nerves and muscles. A motor point of a nerve — the site where the nerve is located most superficially and available to a research. A motor point of a muscle — the place corresponding to a zone of implementation and a branching of a nerve in a muscle. Localization of motor points is approximately determined by special tables (fig. 2) and more precisely — by small trial movements of an electrode. Irritating a motor point of a nerve, define indirect electroexcitability of a muscle, and influencing a muscle, define her direct excitability. For exact judgment of a condition of electroexcitability it is necessary to check both direct, and indirect electroexcitability of a muscle.
At hemilesion the research is recommended to be begun with the «healthy» party, and then to come over to the struck side. Before a research it is recommended to tell the patient about feelings, to-rye it can test during the procedure and convince of safety of a method.
The research is started from consecutive irritation currents anew of a nervous trunk, and then the muscles innervated by it. The technique can be single-pole or bipolar. At a single-pole technique an active bellied electrode (cathode) of 1-1,5 cm 2 with the push-button breaker on the handle establish on a motor point, the second plate electrode (anode) of 100 — 150 cm 2 fix on a back midline of a body in interscapular (at a research of the person and upper extremities) or in lumbar (at a research of the lower extremities) areas. Resort to a bipolar technique less often, generally at considerable decrease in electroexcitability. At the same time use the doubled electrode with the push-button breaker. One electrode serves as the cathode, another — the anode, the area of both electrodes is identical. Electrodes have along the studied muscle.
From each motor point determine threshold reaction to influence by a tetanizing, and then galvanic current. The nature of muscular contractions is estimated visually or palpatorno. Impact on a nerve or a muscle tetanizing current of threshold force is normal causes the tetanic muscular contraction lasting during the whole time of passing of current. Galvanic current of threshold force the nerve and a muscle answer irritation with the single reductions arising at the time of short circuit and disconnection of an electric chain. At threshold current irritant action of the cathode is normal stronger, than operation of the anode, and reduction of a muscle at closing of the circuit stronger, than at disconnection. This dependence is reflected in a so-called polar formula:>>> KZS gas Station ARS KRS, where KZS — katodozamykatelny reduction, i.e. force of reduction of a muscle under the cathode at closing of the circuit, gas station — anodozamykatelny reduction, APC and KPC — respectively anodorazmykatelny and katodorazmykatelny reductions.
Depending on extent of defeat of the neuromuscular device of change of electroexcitability can have quantitative or qualitative character. Quantitative changes are characterized by changes of threshold size of current. Increase in this indicator indicates decrease in electroexcitability and is observed at nek-ry forms of a myopathy, secondary atrophies of muscles and at easy extent of damage of a peripheral motor neuron. Decrease in threshold current demonstrates increase in electroexcitability and takes place, e.g., at the forming muscular contractures, spastic paresis and paralyzes, at a writer's cramp (see. Writer's cramp ). Qualitative changes of electroexcitability are observed at severe damage of a peripheral motor neuron. At the same time a peculiar reaction of a nerve and muscles to electric current — reaction of degeneration, or degenerations is noted.
Reaction of degeneration is characterized by irregularity of falling of electroexcitability of a nerve and muscles (excitability of a nerve decreases and disappears quicker, than excitability of muscles, to them innervated), galvanotetaniziruyushchy dissociation (excitability of muscles in response to influence by tetanizing current falls, and on influence by a galvanic current — raises). Along with it the nature of muscular contraction qualitatively changes — the live reduction observed normal becomes sluggish, worm-shaped, relationship of poles in a formula of muscular contraction is broken. Shift of motor points, bystry falling of force of muscular contraction in process of numerous irritation (reaction of exhaustion), delay of reduction in response to irritation (reaction of delay) is at the same time noted. However from all specified signs the sluggish nature of muscular contraction is recognized as the main indicator of reaction of degeneration.
On degree of manifestation distinguish partial (type A or B) and full reaction of degeneration. Diagnostic and predictive value of these reactions variously. Partial reaction of regeneration is more favorable, it testifies to a possibility of involution of process.
Partial reaction of type A is shown by reduced excitability of a nerve and muscle on both types of current, slackness of reduction and equalizing of a polar formula. Partial reaction of type B is characterized by lack of excitability of a nerve and muscle at influence by tetanizing current and its preservation at influence by a galvanic current at substantial increase or decrease in current. Reduction of a muscle sluggish, worm-shaped, formulas la of muscular contraction is perverted or balanced. Full reaction of degeneration is characterized by preservation of excitability of muscles only on influence by a galvanic current, excitability of a nerve is lost on both types of current. Reduction is worm-shaped, the formula of muscular contraction is perverted. An end-stage is full loss of electroexcitability — a state when neither the nerve, nor a muscle answer influence with any type of current. It is observed at the fibrosis of a muscle caused by its full denervation.
Except reaction of degeneration reveal miotonichesky and myasthenic reactions. Miotonichesky reaction is characterized by the sluggish tetanic reduction of a muscle continuing and after disconnection of current, against the background of a hyperexcitability and a perversion of a polar formula. This reaction is observed at myatonias (see). Myasthenic reaction is characterized by the fact that at long irritation of a nerve or muscle tetanizing current, the reduction of a muscle which occurred in the beginning stops, and rest is necessary for its recovery. It is observed at myasthenias (see), and also is one of manifestations of reaction of degeneration.
The electric pulp test is based on definition of threshold excitement painful and tangoreceptors of a pulp of tooth or a periodontium at irritation by electric current. Electric current, overcoming the high resistivity of the mineralized tissues of tooth, enamel and dentine, reaches a pulp, causing response in the form of feeling of a weak prick, burning or a push. Thanks to the fact that the size of current can be dosed precisely even the repeated irritation of a pulp has no the damaging effect on its fabrics. At patol. processes in tooth and peridental fabrics the excitation threshold of receptors of a pulp of tooth changes.
These electric pulp tests can be used for diagnosis, differential diagnosis and control of efficiency of the carried-out treatment at diseases of teeth and a periodontium, injuries, tumors of jaws, antritis, osteomyelitis of a jaw, an actinomycosis, neuritis and neuralgia of facial or trigeminal nerves.
Children have a close connection between a stage of development of tooth, growth of its roots and electroexcitability of a pulp. During an initial stage of eruption reaction to electric current either is absent, or is sharply reduced. In process of growth of fangs of an elektrovozbuda the bridge raises and reaches norm by the period of completion of their formation. This pattern is connected with the development of the neuroreceptor device of a pulp of tooth happening to growth of fangs.
The research is conducted by means of special electrostimulators — elektroodontometr, e.g. domestic EOM-1 and EOM-3 devices (see fig. 6 to St. Dental equipment ). These devices provide a rectangular shape of output impulses. The size of output current does not exceed, as a rule, 200 mk, the frequency of following of impulses used in various devices fluctuates from units and even shares of hertz to several tens hertz.
The teeth subjected to a research isolate from the neighboring sites of an oral cavity tampons, dry up wadded balls. The indifferent electrode is placed on a hand of the patient, and active in the form of a metal needle — on the middle of a cutting edge (cutters and canines) or on top of a buccal hillock (premolar tooths and painters). In the presence of a carious cavity the active electrode is placed on its bottom consistently in several points. As a reference point of excitability serves the minimum current causing a feeling of a weak prick in a pulp of tooth. If on site a sensitive point the seal is located, then the electrode is placed or on a seal, or nearby, but the obtained data can be indicative only. For exact definition of an excitation threshold delete a seal and conduct a research, placing an active electrode on a bottom of a carious cavity. Normal the threshold size of current makes 2 — 6 mk.
At diseases of teeth and peridental fabrics increase in an excitation threshold of receptors of a pulp is, as a rule, noted. Increase in threshold current within 7 — 60 mk demonstrates preferential defeat of a pulp of a crown, within 60 — 100 mk — pulps of a root. Increase in threshold current indicates St. 100 mk full death of a pulp, and emergence of subjective feelings in this case is caused by excitement of tangoreceptors of a periodontium; and in the presence patol. changes in a periodontium response can arise only on current from 200 to 400 mk. At nek-ry diseases (an initial stage of periodontosis, neuritis of a facial nerve) reduction of the threshold of excitability to 1,5 — 0,5 mk is sometimes noted that is a precursory diagnostic character of these processes.
Because electroexcitability of a pulp of tooth widely varies at various diseases, quantitative indices at an electric pulp test need to be considered not separately, and in combination with results of other methods of inspection.
Bibliography: Antropova M. I. Classical electrodiagnosis at neuritis of a facial nerve, M., 1971, bibliogr.; Baykushev Sr., Manovich 3. X. and Novikova V. P. A stimulation electromyography and an elektroneyrografiya in clinic of nervous diseases, M., 1974; Efanov O. I. and Dzanagova of T. F. Fizioterapiya of dental diseases, M., 1980; Kliniko-elektroneyromiografichesky studying of neuromuscular diseases and syndromes, under the editorship of L. O. Badalyan and I. A. Skvortsov, M., 1982; Korotnev N. I. Bases of an electrotherapy and electrodiagnosis, t. 1, century 1 — 2, M., 1926 — 1927; Cowen of X. L. and Brooklyn J. The guide to an electromyography and electrodiagnosis, the lane with English, M., 1975, bibliogr.; The multivolume guide to neurology, under the editorship of S. N. Davidenkov, t. 2, page 355, M., 1962; Obrosov A. N. and Liventsev of N. M. Elektrodiagnostik and electrostimulation of muscles at defeat of peripheral nerves. M, 1953, bibliogr.; Ruby of L. P. Electric pulp test, M., 1976; The Reference book on physical therapy, under the editorship of A. N. Obrosov, M., 1976.
M. I. Antropova; O. I. Efanov (electric pulp test); V. A. Mikhaylov, R. I. Utyamyshev (tekhn.).