Electromyography PresenterDr Sowmya

Contents IntroductionHistory Background of emg/electromyography Emg defintion Purpose of emg Uses of emg Experimental objectives of emg Emg types Emg technique

Continued ..

Emg electrodes Precautions Preparations After care Risks Normal results Abnormal results Emg in orthodontics and its applications

Introduction Electromyography is the earliest useful technique in clinical neurophysiologyEmg is a valuable diagnostic aid in recording the muscular activity under diverse functional conditionsEmg changes help in documenting the topography of diseases process by recording electrical activity evoked in a muscle by electrical stimulation of its nerve

History of emg

The most important development in history of study of muscle action potential fallowed the development of sensitive recording equipmentIn 1987 cathode ray tube was invented by braun Einthoven designed string galvanometer in1903 Cathode ray oscilloscope was invented by gasser and erlanger in 1922-most significant advances as it eliminated limitations of galvanometerAnother major advance in clinical emg came lord adrian and delton blockwho concentric needle electrode in 1929Adrian also introduced use of loud speakers in emg

Hoefer and guttaman in 1944 recorded spontaneous in patients with spinal cord injuries and found it useful in localizing lesions Denmark reported differences in neurogenic and myogenic emg changes in 1941The invest of war injury patients by herburt in canada resulted in in development of monopolar needle electrodes Interaction of jasper,gold seth and fizell paved the way for development of emg which was introduced in 1948 by goldsethIn1944 harvey and kuffer applied nerve conduction studies in patients in peripheral neuropathy

The first report of nerve conduction potential in response to median and ulnar nerve stimulation was published in 1937Sensory nerve conduction velocity became an integral part of electro diagnostic study by 1960

Emg definitionAlso called as myogramRecording and study of intrinsic electrical properties of skeletal muscle by means of surface/needle electrode in resting and contracting states which aids in diagnosis of neuromuscular diseasesElectromyograph is the instrument used in emg Eletromyogram is record obtained by emg

Back ground of emgSkeletal muscle performs mechanical work Stimulated to contract when brain or spinal cord activates motor unitsAn action potential motor neuron causes activation of muscle fiber Activation of motor units by action potential generates stochastic voltage signals in muscle

Purpose of emgdetermine -A particular muscle is responding to stimulation & whether a muscle remains inactive when not stimulatedHelp to diagnosis different diseases causing weakness a test of motor system ,may help identify abnormalities of nerves/spinal nerve roots that may be associated with pain /numbness

Continued..Distinguish b/n primary muscle diseases and dennervation myopathies from neuropathiesIdentify muscle dysfunction and be treatedAsses health of muscles and nerves that control musclesDifferentiates primary muscle conditions from muscles weakness caused by neurological diseasesEmg is a extension of clinical neurological examination

Obtaining an emg At ,rest when there is no spontaneous muscle activity During slight muscle contraction - to asses the size, duration of activity of motor units

Emg helps in diagnosis ofMuscular dystrophyCongenital myopathiesMetabolic myopathiesMyotoniasRadiculopathies Peripheral neuropathiesNerve lesionsSpinal muscular atrophymyasthenia's

Experimental objectives of emgTo observe,record and correlate motor units recruitment with increase power of skeletal muscle contractionTo record emg when inducing fatigue

Emg typesKinesiological emg

Diagnostic emg

Kinesiological emg

Used for functional anatomy force development reflex contraction of muscle

Diagnostic emg

Test the nerve and muscle integrityNerve conduction velocity for nerve damage \compressionFiring characteristics of motor units, including analysis of motor units action potential - fibrillations, fasciculation and sharp positive waves

Motor unit action potentialRepresent sum of the muscle action potentials supplied by anterior horn cell Muscle fibers discharge in a synchrony adjacent to needle electrodes MUP-has higher amplitude and longer duration than action potential produced by single muscle fiber

Nerve conduction test

Slightly different test is often performed at same time with emgspecially helpful - pain / sensory complains

Sharp positive wavesTriphasic pattern a-positive-crossing,b-negative-leaving,c-recording in a normal muscleIn abnormal muscle-a large positive sharp wave fallowed by low and prolonged negativity

Emg electrodes types-surface and needleNeedle electrodeSuperior to as quality of image betterLesser technical artifact More risks of infectionMay be painfulSurface electrodesPreferred non-invasiveness Chances of loosening of electrodes during nerve stimulationErrors Less of infection

Types of needle electrodesConcentric Monopolar Single fiberMacro electrode

Precautions no special precautions patient with the history of bleeding disorder a muscle biopsy is - of the diagnostic work , emg should not be performed at the same site

Preparations no special preparations using creams /lotions on the day of the test Doctor should give information about symptoms, medical conditions, suspected diagnosis and other test results

Emg recording It was einthoven muscle contraction gives off an idiomusclular current - action potentialStructural basis of emg is motor unit. The current generated is so small -amplified many thousands times to be recorded

Emg accessoriesElectrode hand setHand dynamometer

Disposable electrodes

Emg recording techniqueA needle electrode is inserted through skin into muscle.Recordings -while muscle is at rest contraction . displayed as electrical waves on the cathode ray oscilloscope At same time activity is reproduced as sound over a speaker the pressure ,size,shape of wave form-action potential-produced

EMG-raw signal-voltage difference in electrical potential measured b/n record electrodes Origin-electrical activity tissuesImportant guideline Confirm needle positionEmg alone cannot confirm-antagonistic muscle-synergistically

NerveMuscleTendonRaw EMG SignalElectrodeElectrodeTendonSkin

After careMinor pain &bleedingMuscle-tender Risks no significant risks-needle insertionNormal results some brief action increased in nerve diseases reduced in long standing muscle disordersAbnormal results electrical activity at rest nerve lesions myotonia/inflammatory myopathies

EMG in orthodonticsHistory 1 st effort apply emg by robert e moyers observed normal relations of teeth to each other in same jaw and with those of opposite jaw influenced by muscular balanceMuscles relevant mandibular elevators masseter, temporalis, medial pterygoid mandibular depressor lateral pterygoid Genioglossus role in facial morphologyMentalis orbicularis -important

Allen Brodie-if we could learn to control the musculature through critical period of growth, we might be able to expect that in at least a proportion of patients,there would be spontaneous unfolding of development ,that we thought previously must be managed with orthodontic force

EMG its application-orthodonticsDiagnosis-habits-tongue thrusting lip &cheek activity,sucking habits swallowing palsy Malocclusions-class1 class2 class3

Treatment aspects- myofunctional appliances activator twin blockorthognathic surgeryRetention and relapseCleft and palate

EMG activity in class 2 malocclusion patientsGraber in contrast to cl 1, cl 2 patients-abnormal muscle activity,especially,cl 2div 1In cl 2div 2-compensatory muscle activity-posterior fiber temporalis&masseter He also added-in cl 3 and cl 2div1maloclussion-problem is dominant bone dysplasia with adaptive muscle function and tooth irregularity reflecting a severe basal dysplasia

Pancherz analyzed-emg activity in masticatory muscles cl 2div1 and normal occlusion-maximal biting in centric occlusion and chewingMaximal biting in centric occlusionCl 2-less emg in masseter and temporal than controlReduction more in masseterDuring chewingCl 2 less emg in masseter than controlsTemporalis no difference

High positive-b/n emg activity maximal biting and chewing for both muscles of 2 groupsImpaired muscle activity in cl2 a diverging dentofacial morphology and unstable occlusal contact conditionsMoyers emg in children with cl2 div1-dysfunction of temporal in habitual occlusion and rest may be etiological factor-post normal occlusion

Emg on cl 3It is believed-correction of anterior cross bite-cl3-increased emg of masseter and temporalis/bilateral improvement of bothStudy-deguchi and iwahara-chin cup reduced masseter activity with no improvement of bilateral co-ordination of both Reported-integrated emg activity-in cl3 reduced than in normal occlusion

Emg on functional appliance therapy Neuromuscular reaction seen in patients wearing appliance on full time-as pterygoid response;by james.mc namara.jr-begins after few monthsDuring 1 few hrs no changeDistinct change in muscle activity-few days/weeks-

Decrease post temporalis increase-masseter significant increase-function-lateral pterygoid As expt-progressed pterygoid response decreased gradually-pr -appliance levelResults treatment with oral shields caused a decrease in oro-facial activity during oral function

Lacouture,et,al-action of 3 types functional appliance on activity of masticatory musclesUsed-herbst,twin block,frankel applianceStudy done to lateral pterygoid hypothesis-functional and postural activity of sup and inf heads of lateral pterygoid-increases-appliance placementEmg activity-decreased-placement of appliance more lateral pterygoidStudy-did not support hypothesis

Sessle bj,wood side dg.-univer toronto,canadaStudied functional appliance-change in postural emg activity of muscle Showed decrease in postural activity of sup inf heads of pterygoid,sup masseter and ant digastric-more-lateral pterygoid

Emg activity-swallowingShowed characteristic differences-normal and abnormal swallowingIn mature swallow-During teeth apart swallow-Winders-study force exerted on dentition by perioral and lingual musculature-swallowingConcluded during swallowing buccal and labial musculature do not contract In tongue thrust swallowing-tongue muscle hypertrophies-,emg activity increasesEmg activity-returns to normal after correction

Emg in cerebral palsy Useful in children with cerebral palsy patients Paralysis/hyper kinetic activity of muscle associated with stomatognathic system

Effect of pain orthodontic treatmentEffect from archwire jaw muscle is unclearGoldrich et al evaluated effect-on masseter emg activity emg activity during function reduced-significantly after treatment startedShows that orthodontic pain on teeth tend to reduce muscle activity during function

Negan assessed muscle pain and emg activity before and after treatment with orthopedic retraction head gear800 gm force and 75% of force transmitted to tmj via mandibleNo significant increase in muscle activity/muscle pain associated with orthopedic treatment

Emg activity in cleft lip and palate patientsLi et al evaluated-muscle activity in operated unilateral cleft lip and palateActivity masseter higher activation in rest positionLower potential function

Activity temporalisHigher activationLower potential of action

In harmonious activity masticatory muscles during mandibular border movementHigher asymmetry index of masseter and temporalis

Emg on buccinator activity

In cl 2 div 1 buccinator contracts excessively and hyper active mentalis muscle Post fibers of temporalis exerts a greater influence in cl2 div 1 than normalEmg identifies this abnormality

Influence of activator on emg activity of mandibular elevator Mirallis r burger faculty of medicine-univ of chile Emg activity record-15 children-cl 2 div1Records-anterior temporal and masseter with or without activator in postural rest position during saliva swallowing and maximal clenchingSaliva swallowing-both muscle increased with activator Negative correlations-age of children-change of masseter

Muscle response-twin blockAggarwal p aims .delhiSignificant increase in activity of masseter and temporalis Enhanced stretch reflex of activator muscleMain force-twin block appears through increased active tension in stretched muscle and from initiation of myotactic reflex activityImportance of full time wear of appliance

Emg study on mand movement unilateral cleft lip and palate patients-Saksmoto t ohtsuakak dept of ortho tokoyo japanInvestigate masticatory muscle functionImprovement in masticatory muscle and jaw reflexes after ortho treatmentInfluence plastic surgery- causes maxillary retrusion- results skeletal malocclusionOrtho treatment-designed to compensate malocclusion

Emg Herbst appliance

Dept of ortho tokoyo medical and dental univ japanExamine functional muscular adaptation to changes in saggital jaw relation by emgActivity of lateral pterygoid-increased after wearing appliance remarkably reduced after 4to 6 hrs These findings indicate multifactorial effect of adaptation of muscle functionConcluded that functional adaptation were not dependent only on only on intensity and functional stimulation

Emg on post orthodontic stabilityJ adwt ortodontic orthognathic surgery 2002.17[4]307-13To prevent relapse after ortho treat-retention is often considered indispensableTo quantify influence of masticatory muscle on post treatment relapse study was done Result-emg assessment help in detection of patients who might need a post orthodontic retention

Muscular equilibrium and orthognathic surgeryEvaluate modifications of muscular activity b/n pre surgical and during year after surgeryDecrease in lower facial height-appears to indicate that at rest masseter activity tends to normalize ,temporal increasesMaximal contraction reduced temporal and masseter activityIncrease in vertical dimension causes a change in muscular tonus depending on associated osteotomy

Existence of significant modification after surgery often reveals a craniomandibular dysfunctionEmg activity during treatment enables a perfect re evaluation of these major vertical discrepancies

Surface emg on TMJMore specifically delineate and define hypertronic musculature in the compromised TMJ patientsSeries of test necessary differentiate diagnosis b/n intra capsular and extra capsularSurface electrodes Summary-several studies conducted shows unequivocal evidence to support use of emg for diagnosis of tmj disorders-robert jankelson

Emg on lip and cheek activity in sucking habitsAhlgeren study on lip and cheek activity in sucking habitsProfound lip[perioral] activity-thumb and dummy suckingCheek;buccinator] less evidentLip and cheek activity more during dummy sucking than thumb suckingActivity at rest in perioral muscle-pronounced among thumb suckingLip and cheek activity was Less among control group-both at rest and during sucking

conclusionRole of musculature in malocclusion is very important Facial muscles have various functions that are equally importantAn emg studies have shown ,even at postural rest position muscles are apparently at function,maintaining a status quo soft tissue and bony elementsPremature occlusal contacts and compensatory muscle activity during active function produces a departure from normal such activities can change bony morphology accentuating the malocclusion

Emg helps to identify impaired muscle activity in malocclusion patients compared to normal and also muscle activity during various treatment periods and helps to overcome these abnormalities

References A text book of clinical neuro physilogy by U K mishraElectromyography and its applications in orthodontics by meenaskhi iyer and ashima valiathanAm J orthod Dentofacial Orthop 1988 Aug 94 [2] 97-103Kokubyo gakki zassgi 1996 mar 63 [1] 18-30Dr.joseph f .smith medical libraryAm J Orthod dentofacialOrthopedic 1990 sep 98 [3] 222-30

Int j adult orthodon orthognathic surg 2002 17[4] 307-13Orth fr 2000 jan 71 [1] 37-48Am j ortho dentofacial orth 1988 aug 94[2] 97-103am j orthod dentofacial orthp 200 apr 117[4]25aMedical encyclopedia

Thank you

An electrical signal is produced in the nerve through a series of chemical eventsThe signal propagates along the nerve fiber to the muscleAnother series of chemical events occur allowing the signal to transfer to the muscleThe electrical signal commands the muscle to contractMuscles are attached to bone via tendons, and thus when the muscle contracts, the bones move through their joints and movement occurs

Electrodesact as sensors to the electrical activityCan be surface electrodes, as I have drawn here, or indwelling electrodes are like needles and are inserted into the muscleThe result is a raw EMG signal that can be processed further into linear envelopes, or used to estimate muscle tension, or undergo fourier analyses to determine frequency information