Functional Electrical Functional Electrical StimulationStimulation

With your hosts: With your hosts: Robin Engel and Agnes Robin Engel and Agnes LeitnerLeitner

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What is Functional Electrical What is Functional Electrical Stimulation?Stimulation?

Functional electrical stimulation (FES) is the application Functional electrical stimulation (FES) is the application of electrical current to excitable tissue to supplement or of electrical current to excitable tissue to supplement or replace function that is lost in neurologically impaired replace function that is lost in neurologically impaired individuals.individuals.

It is a developing field that addresses both motor and It is a developing field that addresses both motor and sensory problems including MS, Cerebral Palsy, sensory problems including MS, Cerebral Palsy, Orthopaedic Healing, Muscle Atrophy, Treatment of Orthopaedic Healing, Muscle Atrophy, Treatment of Chronic Pain, Spinal Cord or Peripheral Nerve injury, Chronic Pain, Spinal Cord or Peripheral Nerve injury, hearing and vision loss etc.hearing and vision loss etc.

FES systems used to substitute lost neurological FES systems used to substitute lost neurological function are often referred to as function are often referred to as neuroprosthesesneuroprostheses..

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FES Regarding Neuromuscular FES Regarding Neuromuscular ActivationActivation

Often the goal is to restore voluntary control over a Often the goal is to restore voluntary control over a muscle or group of muscles by electrically stimulating in muscle or group of muscles by electrically stimulating in tact lower motor neurons.tact lower motor neurons.

As a result of this approach FES can only be used when As a result of this approach FES can only be used when lower motor neurons are excitable and neuromuscular lower motor neurons are excitable and neuromuscular junctions are in tact.junctions are in tact.

There are many problems associated with FES There are many problems associated with FES including timing and sites of stimulation to cause a including timing and sites of stimulation to cause a complex movement like walking, voltage, frequency, complex movement like walking, voltage, frequency, and current used to generate impulse, and current used to generate impulse, biocompatabilitybiocompatability

(immune response, tissue damage), portability, power, (immune response, tissue damage), portability, power, and aesthetics.and aesthetics.

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LetLet’’s Talk Nervess Talk Nerves

Two segments of the nervous system:Two segments of the nervous system:

--The Central Nervous SystemThe Central Nervous System--The Peripheral Nervous SystemThe Peripheral Nervous System

Two Major Cell Types:Two Major Cell Types:

--Neurons Neurons ––

signallingsignalling--GlialGlial

––

SupportSupport

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Central Nervous SystemCentral Nervous System

The CNS consists of the brain and the spinal The CNS consists of the brain and the spinal cord and is the starting point for all motor cord and is the starting point for all motor impulses and ideally the endpoint for all sensory impulses and ideally the endpoint for all sensory impulses.impulses.

The CNS is made up of both grey matter and The CNS is made up of both grey matter and white matter. White matter is made up of two white matter. White matter is made up of two cell type: Astrocytes, and Neurons. Grey matter cell type: Astrocytes, and Neurons. Grey matter is made up of two cell types: Oligodendrocytes, is made up of two cell types: Oligodendrocytes, Microglia.Microglia.

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Peripheral Nervous SystemPeripheral Nervous System

The peripheral nerves The peripheral nerves branch off the spinal cord branch off the spinal cord and are responsible for the and are responsible for the innervations throughout the innervations throughout the body.body.

Cranial Nerves that connect Cranial Nerves that connect the spinal cord to the rest of the spinal cord to the rest of the body include C1the body include C1--C8, T1C8, T1--

T12, L1T12, L1--L5, S1L5, S1--S5.S5.

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PNS Continued PNS Continued ……

Cells that make up the PNS are Neurons and Cells that make up the PNS are Neurons and Schwann Cells. Immune defence for the PNS is Schwann Cells. Immune defence for the PNS is provided by the immune cells found in the provided by the immune cells found in the blood, including Tblood, including T--cells and Macrophages.cells and Macrophages.

Two types of neurons that exist in both the Two types of neurons that exist in both the CNS and PNS are sensory and motor. In the CNS and PNS are sensory and motor. In the PNS the sensory neurons are referred to as PNS the sensory neurons are referred to as afferents, and the motor neuron are referred to afferents, and the motor neuron are referred to as as efferentsefferents..

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Key Differences Between CNS and Key Differences Between CNS and PNSPNS

Neurons in the CNS are postNeurons in the CNS are post--mitotic and the mitotic and the gliaglia

inhibit axon growth and regeneration.inhibit axon growth and regeneration.

Neurons in the PNS, however, can regenerate. Neurons in the PNS, however, can regenerate. GliaGlia

produce growth factors and macrophages produce growth factors and macrophages

remove debris. Axons can grow up to 1mm/day.remove debris. Axons can grow up to 1mm/day.

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Nerve ConductionNerve Conduction

An action potential is initiated by a stimulus that depolarizes An action potential is initiated by a stimulus that depolarizes the the local membrane of a neuron, allowing Na+ to enter the cell.local membrane of a neuron, allowing Na+ to enter the cell.

The inside of the cell membrane becomes briefly positive which The inside of the cell membrane becomes briefly positive which causes depolarization at the next node of causes depolarization at the next node of RanvierRanvier

propagating propagating

the signal along the nerve.the signal along the nerve.

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Muscle ContractionMuscle Contraction

Contraction occurs Contraction occurs when the myosin when the myosin heads attach and heads attach and walk along the thin walk along the thin filaments. As a filaments. As a result the thin result the thin filaments slide filaments slide inward and meet at inward and meet at the centre of the the centre of the sarcomere.sarcomere.

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InnervationInnervation

of a Muscle Fibreof a Muscle Fibre

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Summation of StimulationSummation of Stimulation

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History of electrical StimulationHistory of electrical Stimulation

46 A.D.: 46 A.D.: ScriboniusScribonius

LargusLargus

(Roman physician) (Roman physician) recommends treating pain recommends treating pain (headache and gout) by (headache and gout) by using electrical discharge of using electrical discharge of the torpedo fishthe torpedo fish

Application of torpedo fish until 17Application of torpedo fish until 17thth

centurycentury

also for treating migraine, melancholy and also for treating migraine, melancholy and epilepsyepilepsy

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History of electrical StimulationHistory of electrical Stimulation

1672: Otto von Guericke constructs first 1672: Otto von Guericke constructs first electrostatic generatorelectrostatic generator

1791: Galvani produces muscle contraction in 1791: Galvani produces muscle contraction in frog legsfrog legs

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History of ESHistory of ES

1855: G. 1855: G. B.DuchenneB.Duchenne

established electrotherapy established electrotherapy as a separate discipline.as a separate discipline.

By 1900: plenty of machines had been invented:By 1900: plenty of machines had been invented:

Pain treatment (rheumatism, fractures, ...)Pain treatment (rheumatism, fractures, ...)

Treatment of Treatment of CardiocirculatoryCardiocirculatory

problemsproblems

Treatment of diseasesTreatment of diseases

Devices Devices ““for the cure of weak, nervous and debilitated for the cure of weak, nervous and debilitated conditions of the generative organsconditions of the generative organs””

ExorcismExorcism

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First serious efforts in ESFirst serious efforts in ES

1931: success in resuscitating animals and 1931: success in resuscitating animals and humans after cardiac arresthumans after cardiac arrest

1952: first cardiac pacemaker was implanted1952: first cardiac pacemaker was implanted

1961: first FES application for treatment of 1961: first FES application for treatment of footdropfootdrop

Until today: many different applications of ESUntil today: many different applications of ES

Restoring sensory functionRestoring sensory function

Restoring motor functionRestoring motor function

Therapeutic electrical stimulationTherapeutic electrical stimulation

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FES to the neuromuscular systemFES to the neuromuscular system

Electrical pulses applied to nerve elicit action Electrical pulses applied to nerve elicit action potentialpotential

Potential propagates away from the site of Potential propagates away from the site of stimulation (in both directions)stimulation (in both directions)

AP that propagate distally are transmitted across AP that propagate distally are transmitted across the neuromuscular junctionthe neuromuscular junction

Muscle fibres contractMuscle fibres contract

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Activation of nerve easier than Activation of nerve easier than activation of muscle directlyactivation of muscle directly

Threshold charge Threshold charge for producing for producing activation is in activation is in neurons lower neurons lower than in muscle than in muscle

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NeuroprostheticNeuroprosthetic

SystemsSystems

Surface systems (Surface systems (transcutaneoustranscutaneous))

Percutaneous systemsPercutaneous systems

Implanted systemsImplanted systems

S = stimulator, A = anode (reference electrode), C = cathode (active electrode), 

ECU = external control unit

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Surface SystemsSurface Systems

ProsPros

NonNon--invasiveinvasive

Relatively technologically simpleRelatively technologically simple

Easily reversibleEasily reversible

Relatively inexpensiveRelatively inexpensive

ConsCons

Repeated placement of the electrodes needs skill and Repeated placement of the electrodes needs skill and is timeis time--consumingconsuming

Difficult to achieve isolated contraction or activate Difficult to achieve isolated contraction or activate deep musclesdeep muscles

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PercutaneousPercutaneous

systemssystems

Intramuscular electrodes, implanted into the muscle, Intramuscular electrodes, implanted into the muscle, pass through the skinpass through the skin

ProsPros

Activation of deep muscles possibleActivation of deep muscles possible

Isolated muscle contractionsIsolated muscle contractions

Less likely to cause pain (less effect on sensory afferents in Less likely to cause pain (less effect on sensory afferents in the skin)the skin)

Minimal invasiveMinimal invasive

ConsCons

Minimal invasiveMinimal invasive

Care of skin at electrode site to reduce risk of complicationCare of skin at electrode site to reduce risk of complication

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Implanted systemsImplanted systems

Stimulator is implanted (chest, abdomen)Stimulator is implanted (chest, abdomen)

Electrodes are connected to stimulator by leads Electrodes are connected to stimulator by leads under skinunder skin

Pros:Pros:•• Leads can be larger and more durable Leads can be larger and more durable do not do not

have to pass through skinhave to pass through skin

Cons:Cons:•• SurgerySurgery

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Implanted systemsImplanted systems

12‐channel implanted upper extremity 

neuroprosthesis

with myoelectric

control capability

High power demands no implanted batteries

Stimulator receives power and command instructions through a radio-frequency (RF) link to an external control unit (ECU)

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ElectrodesElectrodes

At least two electrodesAt least two electrodes

1 active electrode1 active electrode

1 reference electrode1 reference electrode

Multichannel systemsMultichannel systems

Stimulation of more Stimulation of more than one musclethan one muscle

Different motion Different motion patternspatterns

Smith et al

Mulcahey et al.

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Electrical StimulationElectrical Stimulation

Electrical current pulsesElectrical current pulses

Characterized byCharacterized by

Pulse frequencyPulse frequency

AmplitudeAmplitude

DurationDuration

These parameters control strength of muscle These parameters control strength of muscle contractioncontraction

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Pulse frequencyPulse frequency

Low frequency leads to a series of twitchesLow frequency leads to a series of twitches

Above Above ““fusion frequencyfusion frequency””

smooth contractionsmooth contraction

Higher frequencies produce stronger contractionHigher frequencies produce stronger contraction

Increased rate of muscle fatigue at high Increased rate of muscle fatigue at high frequenciesfrequencies

Typically, the frequency is set constant and Typically, the frequency is set constant and as low as possibleas low as possible

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Control of strength of contractionControl of strength of contraction

Activation of more motor units Activation of more motor units higher higher strength of muscle contraction (spatial strength of muscle contraction (spatial summation)summation)

Increase pulse amplitudeIncrease pulse amplitude

Increase pulse durationIncrease pulse duration

Increased electric charge injected leads toIncreased electric charge injected leads to

Larger electric field, which leads to aLarger electric field, which leads to a

Broader region of activationBroader region of activation

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Restoration of Upper Extremity Restoration of Upper Extremity FunctionFunction

Primarily for individuals with spinal cord injury Primarily for individuals with spinal cord injury (SCI)(SCI)

But also for individuals with stroke and But also for individuals with stroke and traumatic brain injurytraumatic brain injury

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The handThe hand

The wide number of possible motions that the The wide number of possible motions that the hand can makehand can make

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Hand muscles and motionHand muscles and motion

Large muscles in forearm generate most of the Large muscles in forearm generate most of the power of the hand, force is transmitted by the power of the hand, force is transmitted by the tendons to the fingerstendons to the fingers

Fine movements are controlled by small muscles Fine movements are controlled by small muscles in the handin the hand

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The handThe hand

Individual finger Individual finger movements movements require selective require selective activation of activation of particular sets of particular sets of musclesmuscles

Long et al., 1970

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Hand muscles and motionHand muscles and motion

Most important Hand motions:Most important Hand motions:

Lateral or keyLateral or key--pinch grasp pinch grasp (handling small objects, spoon, (handling small objects, spoon, pen)pen)

PalmarPalmar

grasp (holding glass, grasp (holding glass, book)book)

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StimulatedStimulated musclesmuscles

extensorextensor

pollicispollicis

longuslongus

(EPL)(EPL)

flexorflexor

pollicispollicis

longuslongus

(FPL)(FPL)

adductor adductor pollicispollicis

(ADP)(ADP)

abductor abductor pollicispollicis

brevisbrevis

((AbPBAbPB))

extensor extensor digitorumdigitorum

(EDC)(EDC)

flexor flexor digitorumdigitorum

superficialis superficialis (FDS)(FDS)

flexor digitorum profundus flexor digitorum profundus (FDP)(FDP)

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Physical requirements Physical requirements for FES in the handfor FES in the hand

Hand and forearm muscles must be sufficiently Hand and forearm muscles must be sufficiently innervatedinnervated

Upper arm muscle (bicep), shoulder muscles Upper arm muscle (bicep), shoulder muscles (deltoid, rotator cuff) must have enough (deltoid, rotator cuff) must have enough strength to control hand placementstrength to control hand placement

Patient must be able to see well enough (hand Patient must be able to see well enough (hand lacks sensation) lacks sensation)

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Command sourcesCommand sources

Pushing a buttonPushing a button

Measuring wrist movementsMeasuring wrist movements

VoiceVoice

Shoulder motionShoulder motion

EMGEMG

BrainBrain--ComputerComputer--Interface (BCI) Interface (BCI) ––

detection of detection of

specific EEGspecific EEG--patternspatterns

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FreehandFreehand®®

Implanted system, developed at Case Western Implanted system, developed at Case Western Reserve University (CWRU)Reserve University (CWRU)

38Mulcahey et al. 1997

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FES controlled by BCIFES controlled by BCI

Pfurtscheller et al. 2003

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Gait AnalysisGait Analysis

Gait is the manner of walking, stepping or Gait is the manner of walking, stepping or running.running.

The main goal of walking is to move oneself The main goal of walking is to move oneself forward and the most efficient way to do so is forward and the most efficient way to do so is alternates ones body weight from one foot to alternates ones body weight from one foot to the other while propelling oneself forward and the other while propelling oneself forward and limiting unnecessary body movements.limiting unnecessary body movements.

Able bodied individuals produce a cyclic and Able bodied individuals produce a cyclic and symmetric gait pattern.symmetric gait pattern.

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Cerebral PalsyCerebral Palsy

CP patients have difficulty with gait as a result of CP patients have difficulty with gait as a result of spasticity or abnormal muscle tone, and gait problems spasticity or abnormal muscle tone, and gait problems will persist if not treated.will persist if not treated.

Currently it is the trend for CP patients to undergo a Currently it is the trend for CP patients to undergo a thorough evaluation including a complete patient thorough evaluation including a complete patient history, a comprehensive physical exam, consultation history, a comprehensive physical exam, consultation with other specialists, and a gait analysis.with other specialists, and a gait analysis.

Instrumented Gait Analysis (IGA) has the capability Instrumented Gait Analysis (IGA) has the capability helping to identify gait abnormalities. By putting helping to identify gait abnormalities. By putting together information about the 3D position of the together information about the 3D position of the pelvis, hip, femur, knee, tibia, ankle and foot at any pelvis, hip, femur, knee, tibia, ankle and foot at any point in the gait cycle with dynamic electromyography point in the gait cycle with dynamic electromyography (D(D--EMG), more is understood about that individuals EMG), more is understood about that individuals gait cycle allowing treatment options to emerge.gait cycle allowing treatment options to emerge.

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Stiff Knee Gait in CP PatientsStiff Knee Gait in CP Patients

Stiff knee gait is one of the most common Stiff knee gait is one of the most common patterns found in CP patients, seen in 80% of patterns found in CP patients, seen in 80% of cases in a 2005 study.cases in a 2005 study.

Notice the lack of left knee flexion in CP patientNotice the lack of left knee flexion in CP patient

The reduction of swing and The reduction of swing and phase in knee flexion makes foot phase in knee flexion makes foot clearance and the task of advance clearance and the task of advance difficult. It can result in tripping difficult. It can result in tripping and use of another less efficient and use of another less efficient motion to compensate.motion to compensate.

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More On IGAMore On IGA

IGA is a tool that had been used in a clinical IGA is a tool that had been used in a clinical setting for more than 40 years and assists in setting for more than 40 years and assists in finding the best possible solution to improve the finding the best possible solution to improve the gait of an individual.gait of an individual.

Big thing to watch out for when interpreting Big thing to watch out for when interpreting information obtained from IGA is the information obtained from IGA is the difference between the primary gait difference between the primary gait abnormalities and the compensatory deformities.abnormalities and the compensatory deformities.

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TranscutaneousTranscutaneous

Electrical Nerve Electrical Nerve Stimulation on Children with CPStimulation on Children with CP

Case StudyCase Study

This case study was specifically done to explore the possibilityThis case study was specifically done to explore the possibility

of of using TENS to reduce spasticity in hip adductors which has been using TENS to reduce spasticity in hip adductors which has been reported to improve gait. Surgical and medical managements are reported to improve gait. Surgical and medical managements are currently the most common intervention to reduce hip adductor currently the most common intervention to reduce hip adductor spasticity. TENS has been used to reduce spasticity in various spasticity. TENS has been used to reduce spasticity in various distal muscles but not proximal muscles.distal muscles but not proximal muscles.

Two TENS management programs were used the oneTwo TENS management programs were used the one--time trial time trial program and the oneprogram and the one--week trial program.week trial program.

The one time trail program involved the application of The one time trail program involved the application of conventional mode TENS to the bilateral hip abductors during conventional mode TENS to the bilateral hip abductors during passive hip abduction and walking 300cm of the total length of passive hip abduction and walking 300cm of the total length of the balance master platform.the balance master platform.

The oneThe one--week trail program involved the ongoing application of week trail program involved the ongoing application of TENS to the bilateral hip adductors while walking for 15 TENS to the bilateral hip adductors while walking for 15 minutes 3 times a day for a week.minutes 3 times a day for a week.

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Case Study Continued Case Study Continued ……

The TENS were used with a pulse duration of The TENS were used with a pulse duration of 0.25ms at a frequency of 100Hz and an intensity 0.25ms at a frequency of 100Hz and an intensity to cause just a tingling sensation. Four standard to cause just a tingling sensation. Four standard adhesive electrodes were used to transmit adhesive electrodes were used to transmit TENS.TENS.

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Balance Master PlatformBalance Master Platform

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Results of StudyResults of Study

The study results showed that the TENS programs significantly improved the step length and speed, but not the step width of the experimental group.

Hip adductor spasticity was significantly reduced in both the one-time and one-week trial.

Results show that TENS can be used to reduce spasticity in more proximal muscles and improve gait.

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ConclusionConclusion

NeuroprosthesesNeuroprostheses

have already provided hundreds of have already provided hundreds of individuals the capability to move and regain essential individuals the capability to move and regain essential functions lost after their paralysisfunctions lost after their paralysis

FESFES--based devices have proven safe and effectivebased devices have proven safe and effective

Users continue to use them on a nearly daily basisUsers continue to use them on a nearly daily basis

Control must be made more natural Control must be made more natural to the userto the user

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Bruce Bruce WainmanWainman. (2009). . (2009). Neurotransmission. Neurotransmission. Unpublished manuscript. Unpublished manuscript.

Dr. Vickie Dr. Vickie GaleaGalea. (2009). . (2009). Muscle physiology. Muscle physiology. Unpublished manuscript. Unpublished manuscript.

Frank M Chang, Jason T Rhodes, Katherine M Flynn, & James J Frank M Chang, Jason T Rhodes, Katherine M Flynn, & James J CarolloCarollo. . (2010). The role of gait analysis in treating gait abnormalities(2010). The role of gait analysis in treating gait abnormalities

in cerebral palsy. in cerebral palsy.

Organization of the muscular system. Organization of the muscular system. (2009). Unpublished manuscript. (2009). Unpublished manuscript.

P Hunter P Hunter PeckhamPeckham, & Jayme S Knutson. (2005). Functional electrical , & Jayme S Knutson. (2005). Functional electrical stimulation for neuromuscular applications. stimulation for neuromuscular applications.

Principles of anatomy and physiologyPrinciples of anatomy and physiology(2009). (12th ed.). United States of America: (2009). (12th ed.). United States of America: John Wiley & Sons. John Wiley & Sons.

Sami S Sami S AlAbdulwahabAlAbdulwahab, & , & MahaMaha

AlAl--GabbaniGabbani. (2010). . (2010). TranscutaneousTranscutaneous

electrical electrical nerve stimulation of hip adductors improves gait parameters nerve stimulation of hip adductors improves gait parameters ofchildrenofchildren

with with spastic spastic diplegicdiplegic

cerebral palsycerebral palsy

http://www.neurosurvival.ca/ClinicalAssistant/scales/ashworth.hthttp://www.neurosurvival.ca/ClinicalAssistant/scales/ashworth.htmlml

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