Ebook Neurological rehabilitation - Spasticity and contractures in clinical practice and research: Part 1

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Neurological

Rehabilitation

Spasticity and Contractures in Clinical Practice and Research

Series Editors

Marcia J Scherer, PhD

President, Institute for Matching Person and Technology

Professor, Physical Medicine & Rehabilitation,

University of Rochester Medical Center

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Visiting Professor, University of Suffolk

Past and Founding Chair of Chamber of Commerce

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Neurological Rehabilitation: Spasticity and Contractures in Clinical Practice and

Research, edited by Anand D Pandyan, Hermie J Hermens, Bernard A Conway

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Library of Congress Cataloging‑in‑Publication Data

Names: Pandyan, Anand, editor | Hermens, Hermie J., editor | Conway,

Bernard A., editor.

Title: Neurological rehabilitation : spasticity and contractures in clinical

practice and research / [edited by] Anand Pandyan, Hermie J Hermens, and

Bernard A Conway.

Other titles: Neurological rehabilitation (Pandyan) | Rehabilitation science

in practice series.

Description: Boca Raton, FL : CRC Press/Taylor & Francis Group, 2018 |

Series: Rehabilitation science in practice series | Includes

bibliographical references and index.

Identifiers: LCCN 2017058710| ISBN 9781466565449 (hardback : alk paper) |

ISBN 9781315374369 (ebook)

Subjects: | MESH: Muscle Spasticity therapy | Contracture therapy |

Neurological Rehabilitation

Classification: LCC RC935.S64 | NLM WE 550 | DDC 616.85/6 dc23

LC record available at https://lccn.loc.gov/2017058710

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Contents

Editors viiContributors ix

1 Definition and Measurement of Spasticity and Contracture 1

Anand D Pandyan, Bernard A Conway, Hermie J Hermens

and Garth R Johnson

2 Pathophysiology of Spasticity 25

Jens Bo Nielsen, Maria Willerslev-Olsen and Jakob Lorentzen

3 Functional Problems in Spastic Patients Are Not Caused

by Spasticity but by Disordered Motor Control 59

Jakob Lorentzen, Maria Willerslev-Olsen, Thomas Sinkjær

and Jens Bo Nielsen

4 The Clinical Management of Spasticity and Contractures

in Cerebral Palsy 79

Andrew Roberts

5 Clinical Management of Spasticity and Contractures in Stroke 101

Judith F M Fleuren, Jaap H Buurke and Alexander C H Geurts

6 Clinical Management of Spasticity and Contractures in Spinal Cord Injury 135

Martin Schubert and Volker Dietz

7 Clinical Management of Spasticity and Contractures

in Multiple Sclerosis 175

Lorna Paul and Paul Mattison

8 Clinical Assessment and Management of Spasticity

and Contractures in Traumatic Brain Injury 203

Gerard E Francisco and Sheng Li

9 Hereditary Spastic Paraparesis and Other Hereditary

Myelopathies 235

Jon Marsden, Lisa Bunn, Amanda Denton

and Krishnan Padmakumari Sivaraman Nair

Index 289

Editors

Anand D Pandyan, PhD, is Professor for Rehabilitation Technology  and Head of the School of Health & Rehabilitation at Keele University He origi-nally trained as a bioengineer and has a special interest in neurological rehabilitation, clinically usable measurement and applied clinical research His interest in spasticity started during his PhD study (Bioengineering Unit, University of Strathclyde, Glasgow) and he completed a five-year postdoc-toral training period at the Centre for Rehabilitation and Engineering Studies (CREST), Newcastle upon Tyne (with Professors Garth Johnson and Michael [Mike] Barnes) exploring the phenomenon of spasticity in stroke His cur-rent portfolio of research projects, carried out in partnership with therapists and local clinicians, is aimed at: developing a better understanding of the pathophysiological basis of spasticity and its impact on people with upper motor neurone lesions; identifying the therapeutic benefits (and mecha-nisms of action) associated with treatment involving electrical stimulation; and exploring the effects of early antispasticity treatment and studying their long-term impacts Much of his current research is focussed on neurological patients with severe levels of disability

Hermie J Hermens, PhD, earned his master’s in Biomedical Engineering at the University of Twente His PhD, on surface EMG modelling, processing and clinical applications, was also undertaken at the University of Twente, and he subsequently became Professor of Neuromuscular Control at the same institution He was the initiator and coordinator of the SENIAM project, which resulted in a broadly accepted worldwide standard on surface EMG electrode properties and their placement on the muscles He was, together with Anand D Pandyan, actively involved in the European SPASM project, which resulted in important new insights into the definition of spasticity and procedures and methods for assessing spasticity in a quantitative way

Dr Hermens was co-founder of Roessingh Research and Development (RRD), originating from the Roessingh Rehabilitation Centre, which has now grown into the largest institute in the area of rehabilitation tech-nology and telemedicine in the Netherlands He gradually switched his research area from rehabilitation technology towards combining biomedi-cal engineering with ICT to enable remote monitoring and telemedicine In

2008, he became Professor of Telemedicine and Head of the Telemedicine Research Group, at UTwente; in 2010 Director of Telemedicine at RRD and,

in 2012, Director of Technology at the Centre for Care Technology Research (CCTR) and Visiting Professor at the Caledonian University in Glasgow

Bernard A Conway, PhD, is Professor in Biomedical Engineering at the University of Strathclyde, where he co-directs the Centre for Excellence in Rehabilitation Research He earned his PhD in Neurophysiology from the University of Glasgow and since then has focussed his research interests

on problems related to the loss of control of movement in patients with rological conditions including spinal cord injury, movement disorders, and limb loss Over his career he has enjoyed close collaboration with clinical colleagues, giving his research a translational perspective The multidisci-plinary nature of his research has led to its publication in a diversified group

neu-of journals He has also been actively involved in supporting funding cies in various advisory capacities linked to bioengineering, rehabilitation, health technologies, and ageing He currently is a trustee of the Institute of Physics and Engineering in Medicine and Medical Research Scotland

Contributors

Lisa Bunn

School of Health Professions

Faculty of Health and Human

Spinal Cord Injury Center

University Hospital Balgrist

Zürich, Switzerland

Amanda Denton

School of Health Professions

Faculty of Health and Human

Sciences

University of Plymouth

Plymouth, United Kingdom

Judith F M Fleuren

Roessingh Rehabilitation Centre

Roessingh Research and

Alexander C H Geurts

Radboud University Medical Centre Department of Rehabilitation Nijmegen, Netherlands

Hermie J Hermens

Roessingh Research and Development

University of TwenteEnschede, Netherlands

Garth Johnson

ADL Smartcare LtdNewcastle UniversityNewcastle, United Kingdom

School of Health Professions

Faculty of Health and Human

Sciences

University of Plymouth

Plymouth, United Kingdom

Paul Mattison

Ayrshire Multiple Sclerosis Service

Douglas Grant Rehabilitation Centre

Ayrshire Central Hospital

Irvine, United Kingdom

Krishnan Padmakumari

Sivaraman Nair

Department of Neurology

Royal Hallamshire Hospital

Sheffield Teaching Hospitals NHS

Thomas Sinkjær

Department of Health Science and Technology

Aalborg UniversityAalborg, Denmark

Maria Willerslev-Olsen

Elsass InstituteCharlottenlund, Denmark

1

Definition and Measurement

of Spasticity and Contracture

Anand D Pandyan, Bernard A Conway,

Hermie J Hermens and Garth R Johnson

1.1 Introduction

Spasticity is a clinical condition that is expected to develop following a lesion

in the descending tracts of the central nervous system (CNS), at any level (i.e., cortex, internal capsule, brain stem, or spinal cord) (Burke [1988]) It is a com-mon neurological impairment with a reported prevalence of between 20% and 80% (this will depend on the population under study and the method

of measurement), which is considered clinically important (see subsequent chapters for disease-specific data) Not all spasticity is considered trouble-some to patients; however, a significant number of patients with spasticity will require treatment Treatment of spasticity is often driven by goals aimed

CONTENTS

1.1 Introduction 1

1.2 Definition of Spasticity 2

1.2.1 Can the Words Increased Tone/Hypertonia and Spasticity Be Used Interchangeably? 3

1.2.2 Developing the Framework for Defining Spasticity 6

1.2.2.1 Increased (Hyper-Excitable/Exaggerated) Reflexes 8

1.2.2.2 Spasms and Clonus 8

1.2.2.3 Altered Tone or the Response of a Relaxed Muscle to an Externally Imposed Stretch 9

1.2.2.4 Abnormal Movement Patterns and Co-Contraction 12

1.2.3 The Classification and Definition of Spasticity in Upper Motoneuron Syndrome 13

1.2.4 Contractures in Patients with Upper Motoneuron Syndrome 14

1.2.5 The Measurement of Spasticity and Contracture 17

1.2.6 Concluding Thoughts 19

References 21

at improving function or preventing significant secondary complication such

as pain, pressure sores, limb deformities, etc

At a pathophysiological level this condition has been studied in reasonable detail since the 1880s and our current understanding of the pathophysiologi-cal basis of this condition and its impact on function has been summarised in Chapters 2 and 3 Unfortunately, the literature related to treatment is scanty and the quality is predominantly poor (and the team found this to be a sig-nificant challenge in the compilation of this book) The two main barriers to

good science have been the lack of a proper definition of the term spasticity

and the use of invalid methods of measurement

Attempting to provide a universally acceptable definition that is both entifically valid and clinically usable is probably too much of a challenge for now; however, an attempt will be made to present a framework that may help in this process It may help for readers to have an understanding of this framework before reading the individual disease-specific chapters The measurement of spasticity is a much easier problem to deal with as there are a range of valid measures that are available This chapter will, therefore, summarise the state-of-the-art approaches to the measurement of spasticity, both directly or indirectly

sci-1.2 Definition of Spasticity

The observations of Landau (1974) that the term spasticity has become such

a habitual part of neurological jargon that no one is expected to define it remains true today in practice (Landau [1974]) What is more challenging is that this behaviour appears also to have permeated the published research! In his editorial, Landau (1974) provides six variations to the definition of spasticity found in the literature Unfortunately, since then, many more have appeared (e.g Lance [1980a,b,c]; Sanger et al [2003]; Pandyan et al [2005]; Malhotra et

al [2009])

Currently, there is agreement that spasticity is a condition that can develop following an upper motoneuron lesion Most texts would suggest that the sensory motor problems following an upper motoneuron lesion, of any

origin, can be classified as having positive features and negative features

(Pandyan et al [2009]) This particular approach to classification can be traced back to the work of Hughlings Jackson (York and Steinberg [2007]), who con-sidered that the positive features were associated the exposure of activity that was previously inhibited by the nervous system and the negative fea-tures result from the loss of higher-level excitatory control This classification was based on Jackson’s thinking of the nervous system as being hierarchical, with the higher levels having modulatory control over the lower levels Table 1.1 summarises the features of the upper motor syndrome as commonly

Definition and Measurement of Spasticity and Contracture

reported in the literature and the text, and it is important to note that ity was only considered as one feature of the upper motoneuron syndrome

spastic-Spasticity is derived from the Greek root word spastikos, which means

draw-ing or tuggdraw-ing If one reads the literature from the time of 1830 (see Chapter 4),

it appears that the term spasticity is often associated with a ‘resistance one feels when passively moving/mobilising a limb segment’ and was also associated

with the terms tone and rigidity (Siegel [1988]) Although a variety of

descrip-tions exist in the literature, the first formal definition appears in the works of

Denny Brown, where he defines spasticity in capsular hemiplegia as the

pres-ence of a soft yielding resistance that appears only towards the end of a passive stretch, and is associated with increased amplitude stretch reflex (Denny-Brown [1966]) Two decades later, in a series of post-conference discussions and a presentation, Lance (1980a,b,c) put forward a series of definitions for the term spasticity Of the three definitions, the one that is most commonly cited defines spasticity as

a motor disorder characterised by a velocity dependent increase in tonic stretch reflexes (muscle tone) and increased tendon jerks resulting from disinhibition of the stretch reflex, as one component of an upper motoneuron lesion (Lance [1980b])

However, the literature still appears not to have any form of consensus with respect to a definition (Pandyan et al [2005]; Malhotra et al [2009]) When the literature was last reviewed, approximately a third of the litera-

ture equated spasticity with increased or altered muscle tone or hypertonia

(and this will be discussed in Section 1.2.1) A third of the literature defined spasticity according to the Lance (1980b) definition (as cited above) or some

minor variation A third of the literature did not define the term spasticity at

all, suggesting that not much has been learnt since Landau (1974) or the more recent article from Thilmann (1993) Accordingly, and before we progress to discussing a framework for defining spasticity, it is important to first deal

with use of the term (high) tone as a synonym for spasticity.

1.2.1 Can the Words Increased Tone/Hypertonia

and Spasticity Be Used Interchangeably?

The term tonus was originally introduced in 1838 to describe the slight

con-tractile tension in the muscles when at rest (Rushworth [1960] citing Mueller

Spasm & clonus

Abnormal movement patterns & co-contraction

Weakness Fatigueability Loss of dexterity (motor control)

[1838]) It is fascinating to read the summary of Cobb and Wolf (1932) ing the First International Congress of Neurology:

follow-Confusion of thought has occurred throughout the diverse use of the term tonus However carefully defined it now carries with an incubus

of vague connotation which seems to cloud the issue Its place as term applied to striated muscle can be more accurately taken over by such specific terms as ‘standing reflex’, ‘postural reflex’, and ‘righting reflex’ The state of the striated muscle at any moment can be described by adjectives such as slack or taut Better still the amount of tension can

be measured and stated in quantitative terms We make a plea that the term tone be either discarded or returned to its former home in smooth muscle and kept there.

It is frustrating that we appear not to have learnt very much from the sion in the literature of the past There is now clear evidence that in a state

preci-of rest skeletal muscles are electrically silent and that there is good reason to believe that the advice of Cobb and Wolf (1932) is just as appropriate today

as it was then However, asking for people to change entrenched behaviour

• The second equates tone with the readiness to act

The term hypertonia (or high tone) is related to the first definition of tone (i.e.,

an increased resistance that one encounters during passive limb displacement) The assumption being made is that any resistance encountered to an exter-nally imposed passive movement is due to an increased activation of muscles (e.g Sanger et al [2003]) There is now ample evidence that such an assumption cannot be made (Malhotra et al [2008]) The resistance that one encounters is often associated with changes in the biomechanical properties of soft tissues and joint structures (Figure 1.1) In certain circumstances, increased muscle activity can contribute to this increased resistance in the absence of any form

of soft tissue and joint changes, but this is rare (Figure 1.1)

The term hypotonia is often related to both definitions of tone If one considers the argument in support of a condition of hypotonia against the

first definition of tone then the hypothesis one has to consider is that the

resistance to passive movement in people with hypotonia is lower than

nor-mal This does make the assumption there is ‘normal tone’ The evidence is clear: in a relaxed state there is no electrical activity in muscles The stiffness measured in patients with a dense flaccid paralysis is also not very different

to people who have no neurological deficits (Barnaby et al [2002]); Kumar

Definition and Measurement of Spasticity and Contracture

et al [2006]) In the circumstances, the argument that people with low tone have lower-than-normal resistance to an externally imposed movement is

untenable The other argument links the definition of hypotonia to the

sec-ond definition of tone (i.e., the muscles can be activated with a normal stimulus or the muscle is not in a state of readiness to act) This is a more complex problem to deal with In some patients with an upper moto-neuron lesion there is evidence that a smaller-than-normal stimulus (proprio-ceptive, cutaneous, etc.) can trigger the activation of an involuntary response

smaller-than-of either an isolated muscle or a group smaller-than-of muscles (see Chapter 2) However,

such patients are often treated, contradictorily, as hypertonic not hypotonic One then has to consider whether patients with hypotonia have a lower-than-

normal ‘readiness to act’ and the only interpretation left is that such a person does not have an ability to act, i.e., they are paralyzed It is important to high-light that the original articles on rigidity and spasticity use two specific terms:

hypertonic paralysis and hypertonicity in paralysis The former term is used to

describe patients who were unable to voluntarily activate muscles (paralysis) and whose muscles are in a state of contraction The latter term is used to describe patients who are unable to activate muscles voluntarily (paralysis) but

an examiner is able to elicit or observe reflex muscle activation (Bennett [1887])

FIGURE 1.1

Recording of stiffness at the elbow (the slope of the force angle curve) measured before and after injection of Botulinum Toxin – A (BoNT-A) The trace in gray is before injections and the trace in black is four weeks after injections Both patients are responders to treatment of botulinum toxin, i.e., the injections suppressed the stretch-induced activation of muscles In the patient with no contractures (left-hand pane [a]; discussed in Section 2.3) the stiffness was influenced by the abnormal muscle activity associated with spasticity (stiffness pre-injection was 0.4 N/deg and post-injection was 0.2 N/deg) Note also that in this patient a catch fol- lowed by a release can be seen However, in the patient with the established contractures (b) there was no change in stiffness, suggesting that the spasticity had no contribution to the resistance to passive movement (stiffness pre-injection was 1.1 N/deg and post-injection was

1.0 N/deg) (With permission from Pandyan AD et al [2009] Spasticity, The New Encyclopedia

of Neuroscience. Squire LR, ed Vol 9 Oxford: Academic Press, pp 153–163.)

In summary, the words hypertonia and spasticity cannot be used

inter-changeably From a first-principles argument, if there was a choice the authors would probably want to support the position taken by Cobb and Wolf (1932) and Rushworth (1960), i.e., not to use these terms within the context of neu-rological rehabilitation These terms, however, have been extensively used already and such a recommendation would not be adopted However, it is important that readers reflect on this discussion when they interpret the

term tone, both within this book and in the general literature Furthermore, for the future, if people choose to use the word tone then it is important that

the term is explicitly defined whenever it is used The challenges of not viding such definitions can be seen with the chapters of this book, in particu-lar the chapters on cerebral palsy and multiple sclerosis (Chapters 4 and 7,

pro-respectively), where the authors have struggled to interpret the term tone as

the literature has not defined this for them

1.2.2 Developing the Framework for Defining Spasticity

Having accepted that the term spasticity is likely to remain in common use,

one then needs to consider a framework that will help with articulating a clinically meaningful definition of this term for routine clinical and research use More importantly, a valid definition and description is an essential first step in measurement The remainder of this section will therefore focus on

developing a framework for the definition and description of the term

spas-ticity Two teams, in the early part of 2000, explored ways to develop a

uni-versally acceptable definition for spasticity The first of these teams, the Task

Force on Childhood Motor Disorders, took the approach of splitting existing

def-initions to provide a series of sub-defdef-initions The second of these teams, A

European Thematic Network to Develop Standardised Measures of Spasticity, took

a diametrically opposite approach of lumping existing definitions into a versal definition The two approaches are chronologically described below.Sanger et al (2003) provide a series of definition linked to both spasticity and hypertonia Their definition for hypertonia will not be discussed further

uni-in this section as the arguments as to why such a defuni-inition will not work have already been presented in Section 2.1 Sanger et al (2003) defined hyper-

tonia as a case in which one or both of the following signs are present: (1) resistance

to externally imposed movement increase with increasing speed of stretch and varies with the direction of joint movement and/or (2) resistance to externally imposed move- ment rises rapidly above a threshold speed or joint angle Such a definition does not add much clarity to the definition originally proposed by Lance (1980b); in fact, one could argue that it confuses the measurement a lot more At a fun-damental level, there are two major problems with the above definition: (i) a velocity-dependent increase in resistance to passive movement is an inherent viscoelastic behaviour of muscles and tendons (Figure 1.2); and (ii) the thresh-old speed or joint angle are not defined per se Under these circumstances one would argue that the approach to splitting lacks adequate precision

Definition and Measurement of Spasticity and Contracture

The SPASM Consortium (Pandyan et al [2005]), after reviewing the ture came to the conclusion that the term spasticity was being used to refer

litera-to a range of signs and symplitera-toms associated with the upper molitera-toneuron lesion This is probably true of clinical practice too, and anecdotal evidence from discussions with students, researchers and clinical practitioners con-firms that this is the case If one were to ensure that all of the relevant lit-

erature associated with the term spasticity was to be reviewed, then there

was a need to develop a definition that was sufficiently broad so as to be inclusive of all of the clinical manifestation but adequately specific to focus

on the neurological basis of the phenomenon The consensus definition that

was agreed defined spasticity as disordered sensori-motor control, resulting from

an upper motoneuron lesion, presenting as intermittent or sustained involuntary activation of muscles This definition then meant that spasticity was no longer

a term used to denote one component of the upper motoneuron syndrome (as described in Table 1.1) but all of the positive features upper motoneuron syndrome (Table 1.2)

0 4 8 12 16 20

FIGURE 1.2

Stiffness measured at the knee joint using two different velocities The authors Singer et al (2003) have clearly demonstrated that changes in velocity-dependent stiffness can be inde- pendent of spasticity (With permission from Singer B et al [2003] Velocity dependent passive

flexor resistive torque in patients with acquired brain injury Clinical Biomechanics 18:157–165.)

Whilst such an all-encompassing definition has some benefit, it is of ited clinical and research value as this does not provide an unambiguous framework to inform the measurement process In order to develop this defi-nition further it is important the lumped definition can be split or stratified

lim-in a way that could lim-inform the measurement process This would require the examination of the individual components and explore if the components could be classified as spasticity This process is described below It is impor-tant to note that pathophysiology is discussed comprehensively in Chapter 2,

so this chapter will not review pathophysiology

1.2.2.1 Increased (Hyper-Excitable/Exaggerated) Reflexes

The term increased reflexes will very specifically be equated to the response

observed following a clinical testing of reflexes, i.e., where an examiner taps a tendon to produce a transient stretch of the muscle that then leads to a subsequent contraction Although not formally studied, the literature seems to suggest that the sensitivity* and specificity† of the stretch reflex response as currently mea-sured is a poor indicator of spasticity in both acute and chronic populations The literature also remains unclear on what constitutes the signature of an increased reflex: do these terms mean the reflex has a lower threshold, greater magnitude, longer duration or a combination of all The reflex response, when tested clini-cally using a tendon tap, normally will involve mono- and polysynaptic path-ways, meaning that the observation of a change in reflex cannot in itself be a sub-classification of spasticity but rather is a reflection of changed excitability Furthermore, as this discussion develops (Sections 1.2.2.2 and 1.2.2.3) it will become more apparent that many of the other signs and symptoms that can be classified under the umbrella definition of spasticity is predominantly associ-ated with changes in excitability within a variety of motor pathways

1.2.2.2 Spasms and Clonus

A spasm can be defined as a transient but continuous muscular contraction which

can be triggered by a combination of cutaneous and/or visceral triggers and a

clo-nus is defined as a transient but intermittent rhythmic muscle contraction with

proprioceptive and/or cutaneous triggers Both of these signs are commonly reported in patients with spasticity Both of these phenomena are common

in patients with upper motoneuron lesions Exact prevalence and incidence cannot be reported as these are not systematically documented Spasms can affect both the flexor and extensor muscle groups of patients and can

be influenced by changes in ambient temperature Anecdotal reports gest that an increase in spasms is normally associated with a decrease in temperature Cutaneous stimuli that are noxious can trigger spasms There

Definition and Measurement of Spasticity and Contracture

is some anecdotal evidence that spasms can be influenced by changes in activity within the autonomic nervous system However, this association has not been systematically studied in any depth It is important to note that spasms can occur due to reasons other than spasticity, i.e., there is a lack

of specificity Despite this, if a person has spasms subsequent to the upper motoneuron lesion one could conclude that this is an indicator of spasticity Clonus is also documented to occur, predominantly at the ankle joint, in the later stages following an upper motoneuron lesion In studies conducted on stroke patients, upper limb clonus is very rarely observed at the elbow joint (<1%) and its prevalence in the lower limb is most likely a consequence of excitability changes facilitating interactions between neurogenic networks, reflex loops, and the biomechanics of the muscle/joint system At this stage, there is adequate theoretical evidence to consider both spasms and clonus as sub-classifications under the umbrella term of spasticity

1.2.2.3 Altered Tone or the Response of a Relaxed Muscle

to an Externally Imposed Stretch

The research underpinning the response of a relaxed muscle to an externally imposed stretch has probably been studied the most extensively in the litera-ture Some of the earliest clinicians and researchers measured spasticity by studying the muscle response to an externally imposed stretch using either fine wire or surface electromyography (EMG) It is a pity that somewhere along the way this approach to studying spasticity has for all practical pur-poses disappeared in clinical practice

In neurologically healthy subjects, when a relaxed muscle is passively stretched no EMG responses are normally observed below velocities of 200 deg/s However, in patients with an upper motoneuron syndrome a range

of EMG responses can be seen (Figure 1.3) These can be classified as (a) a velocity-dependent response, (b) a position-dependent response, a combina-tion of (a) and (b), and (c) a clasp-knife-type response

Whilst the muscles of most patients will be in a state of rest prior to the start

of the test, there are some patients in whom residual EMG activity at rest is observed The literature describes these patients as having ‘spastic dystonia’‡

(Figure 1.4) However, what is important to also note in such patients is the phenomenon of position dependency, and possibly a combination of velocity and position dependency can be observed

Recordings such as those above have been widely observed (by, e.g., Tardieu et al [1954]; Lance [1980a,b,c] and Rymer and Katz [1994]) Readers are encouraged (after reading Chapter 2 of this publication) to explore the literature produced by notable authors such as Sherrington, Matthews, Denny-Brown, Tardieu, Pierrot-Deseilligny, Hultborn, Burke, Lance, etc.,

be found (this is unlikely to happen!).

Slow vs fast (Vel & EMG)

EMG during slow movement

EMG during fast movement 300

200 100

–100 –80 –64.139 –60 –40 –20

4.406 × 10 –3

0 0

0.02 0.04 0.06 0.08

20 40 36.153 –1.818

Slow velocity Slow_flexor EMG Fast_flexor EMG

60 40 20

–20

–80 –100 –97.38

–60 –40 –20

4.309 × 10 –3

0 0.1 0.2

0 –10.003 –5.31

Slow velocity Slow_flexor EMG Fast_flexor EMG

Fast velocity

(b)

EMG during fast movement

EMG during slow movement

FIGURE 1.3

Images recorded from the Biceps Brachii muscle of stroke patients The elbow joint was fully flexed and then extended using a ‘ramp and hold’ method (Rymer and Katz [1994]) The hold was <5 sec- onds in duration Two velocities were used to stretch the joint (an uncontrolled slow velocity and

an uncontrolled fast velocity as annotated on the respective graphs) The EMG during movement was also collected and the corresponding EMG traces are annotated on the respective graphs The EMG activity was notch-filtered (50 Hz) and then smoothed using an RMS procedure as described

in the source article (a) This graph shows a velocity-dependent response to an externally imposed

movement There is very little EMG activity during the slow movement; however, there is a large burst of activity during the fast movement The EMG activity starts to drop off towards zero at the

end of the stretching movement (b) This graph shows a position-dependent response to an

exter-nally imposed movement The EMG activity increase as the muscle is stretched and the activity remains elevated during the hold phase It is also important to note the EMG activity during the

Definition and Measurement of Spasticity and Contracture

Slow vs fast (Vel & EMG)

–100 –60 –48.161 –40 –20 0

9.557 × 10 –3

20 0

0.05

0.15 0.1

0.2 0.25

40 60 40.704 –5.04

Slow velocity Slow_flexor EMG Fast_flexor EMG

Fast velocity

(c)

EMG during slow movement

EMG during fast movement

Slow vs fast (Vel & EMG)

EMG during fast movement

Velocity during fast movement

Velocity during slow movement

150 100 50

–50

–80 –100 –120 –140 –122.589

–60 –40 –20

–27.948

0.012 0 0.02 0.04 0.06 0.08 0.1

Slow velocity Slow_flexor EMG Fast_flexor EMG

in the source article (c) This graph shows a combination of velocity- and position-dependent

responses to an externally imposed movement The EMG activity increase as the muscle is stretched and the activity remains elevated during the hold phase It is also important to note the EMG activity during the quick stretch starts earlier in the range of movement and is of a greater

magnitude (d) This graph shows the clasp-knife response to an externally imposed movement

The EMG activity increases rapidly as the muscle is stretched and this slows the movement down

If the examiner continues with the stretch the EMG activity then reduces This response occurs during both the slow and fast stretch and is triggered at relatively slow velocities.

all of whom employed direct measures of muscle electrical activity to gain

an understanding of spasticity

What is obvious is that the stretch-induced response (i.e., velocity-dependent response, position-dependent response, the velocity- and position-dependent response and the ‘clasp-knife’ phenomenon) results from an afferent input

to the central nervous system However, the abnormal muscle activity at rest (i.e., spastic dystonia) appears to be independent of an afferent input to the CNS (e.g., loss of cortical inhibition to the brainstem pathways/nuclei) Within the context of a SPASM definition all of these conditions can be con-sidered a sub-classification of spasticity

1.2.2.4 Abnormal Movement Patterns and Co-Contraction

The abnormal movement patterns and co-contractions that are commonly seen after an upper motoneuron lesion are currently classified under the term spasticity However, it is possible that the abnormal patterns of move-ment and co-contraction one observes during voluntary movement may result from the compensation to the weakness that co-exists (Chapters 2 and 3 discuss this possibility in greater detail) Furthermore, if one were to test individuals with no known impairments, enhanced tremor-like oscilla-tions and co-contractions can be provoked in cases of fatigue or peripheral

EMG triceps brachii

FIGURE 1.4

A figure illustrating the phenomenon of spastic dystonia A patient demonstrating EMG of the Biceps Brachii at rest When the muscle is stretched the EMG activity increases as the stretch on the muscle is increased and as the stretch is carried out using a quicker speed the magnitude

of the activity increases It is important to note that in this patient stretching of the extensors lead to activation of the Triceps Brachii When the Triceps were active the activity in the Biceps reduced.

Definition and Measurement of Spasticity and Contracture

loading, the latter being the interia-sensitive mechanical-reflex oscillation component of tremor (Elble and Koller [1990]) In normal movement, patterns

of co-contraction and the synergetic activation and de-activation of muscles are the norm and are an essential feature of successful movement execu-tion in both simple and complex actions For example, the ability to grip and transport an object will be severely compromised if one is unable to stabilise the wrist and simultaneously coordinate the co-contraction of muscles of the shoulder and elbow joint during this action Under these conditions classify-ing abnormal movement patterns and co-contraction as a sub-classification

of spasticity is not appropriate and, collectively, more appropriately reflects

a deficit of control

1.2.3 The Classification and Definition of Spasticity

in Upper Motoneuron Syndrome

Based on our current understanding, and extending the work of the SPASM

consortium, it is possible to first define spasticity as an emergent feature of

disordered sensori-motor control, resulting from an upper motoneuron lesion, senting as intermittent or sustained involuntary activation of muscles Spasticity can present as:

pre-• Spasms (A transient but continuous muscular contraction which can be

triggered by a combination of cutaneous and/or visceral triggers)

• Clonus (A transient but intermittent rhythmic muscle contraction with

proprioceptive and/or cutaneous triggers)

• Abnormal activation of muscles to an externally imposed stretch, which can present as a combination of:

affer-a lesion the centraffer-al nervous system goes into affer-a period of shock affer-and recovery during which time the system will start to present with varying responses and time delays The time course of development of spasticity is likely to be disease-specific In stroke, traumatic/hypoxic brain injury, and spinal cord injury the evidence is that spasticity onset can be rapid (i.e., within 48 hours

or earlier) but often the onset time course is highly variable The natural

history and time course of onset in many disease populations needs to be established.

A significant limitation to the proposed definition is the narrow focus on patients with an acquired upper motoneuron lesion There are large popula-tion of patients with acquired/degenerative disease of the nervous system who present with signs that are similar to those described under spasticity

or spastic dystonia In particular, patients with Parkinsonism who present with rigidity and/or cog-wheel rigidity, patients with movement disorders such as Huntington’s disease, Blepharospasm, and Cervical Dystonia, all of whom can present with spasms (often termed dystonia) affecting different parts of the body, and patients with motoneuron disease Maybe discussion

of this is for a second edition; however, there is much work that needs to be done to produce such a unifying framework for definition and measurement

1.2.4 Contractures in Patients with Upper Motoneuron Syndrome

A contracture has been defined as a pathological condition of soft tissues characterised by stiffness and is usually associated with loss of elasticity and fixed shortening of the involved tissues (muscle, tendon, ligament, subcuta-neous tissue, skin, blood vessels, and nerves) and results in loss of movement around a joint (Botte et al [1988]; Lehmann et al [1989]; Harburn and Potter [1993]; Teasell and Gillen [1993]) Contractures normally occur as a result of

a joint being fixed in a shortened position with a lack of loading to the soft tissue structures In the following paragraphs, we will briefly discuss factors that can contribute to contractures following an upper motoneuron lesion.Following an upper motoneuron lesion a patient will present with paralysis or paresis and as a result the muscle and joint structures of the affected periphery become unloaded In particular, if a patient does not regain functionally useful movement then the patient will present with muscle atrophy, i.e., a decrease in the size of the muscle fibres and there-fore the muscle itself, a decrease in the force generation capacity within the muscle, and an increase in the fatiguability of muscles The increase

in fatiguability probably arises from decreasing glycogen stores and ATP levels within a muscle (Lieber [2009]) The loss of muscle mass could in part be explained by an increase in the catabolic enzyme levels within these muscles that have been paralyzed (Lieber [2009]) The loss of load-ing, on the soft tissues, may also contribute to an increase in the collagen crosslinks that occur within the tendon and soft tissue structures and this can contribute to an increase in stiffness However, it is important to note that a patient presenting with no symptoms other than paralysis rarely presents with contractures in the acute and subacute stages following the neurological injury (Figure 1.5)

If a patient were to develop contractures, as defined above, in addition to the lack of loading and motion, the joints should also be held in a shortened position Based on the evidence collected by Pandyan and co-workers there

Definition and Measurement of Spasticity and Contracture

0 1 2 3

0 0.01 0.02

Angle vs Force (slow) Angle vs Flex or EMG Angle (deg)

– 50 0 50

Force (N) EMG (mV) Force (N) EMG (mV) Force (N) Force (N) EMG (mV)

4 3 2

2 1

Angle (deg)

Angle vs Force (slow)

Angle vs Flex or EMG

Angle (deg) Angle vs Force (slow) Angle vs Flex or EMG

Angle (deg) Angle vs Force (slow) Angle vs Flex or EMG

5

0 1 2 3 4

0 0.01 0.02 0.03 0.04

4

Angle (deg)

1 1

Angle (deg) –50 0 50

Angle (deg)

Angle vs Force (slow)

Angle vs Flex or EMG

4 3 2 1 –1000 –50 0 50 1000

0.02 0.04

Angle (deg) Angle vs Force (slow) Angle vs Flex or EMG

4 3 2 1 –1000 –50 0 Angle (deg) Angle vs Force (slow) Angle vs Flex or EMG

5

4 3 2 1 –1000 –50 50 0

0.02

Angle (deg) Angle vs Force (slow) Angle vs Flex or EMG

50 0

0.02 0.01 0.04

0

0.04 0.03

FIGURE 1.5

The relationship between spasticity, contractures, and function Graphs illustrating the observation that the person most prone to developing a contracture is a patient who has not regained functional

is indicated in gray and stretch-induced muscle activity from the forearm flexors (a plot of angle vs

Measurements were taken at the forearm flexors of the wrist less than two weeks after the stroke (subscript of I and ii) and repeated six months after stroke (subscripts iii and iv) A patient present-

NIHSS score of 18 and an action research arm test (ARAT) score of 1 At six months after stroke the patient had a Barthel index of 15 and an ARAT score of 57 Contractures were assessed during slow movement (i.e., the range of movement at the wrist had not changed and the stiffness at baseline and at six months was 0.014 N/deg and at six months was 0.011 N/deg) and there was no evidence

on admission after stroke, had an NIHSS score of 17 and an ARAT score of 0 At six months after stroke the patient had a Barthel index of 18 and an ARAT score of 0 Contractures were assessed during slow movement (i.e., the range of movement at the wrist had not changed and the stiffness

at baseline and six months were both 0.009 N/deg) and there was no evidence that contractures had occurred A patient presenting with a combination of velocity and position-dependent spasticity

13 and an ARAT score of 0 At six months after stroke the patient had a Barthel index of 3 and an ARAT score of 1 Contractures were assessed during slow movement (i.e., the range of movement

at the wrist had reduced by about 50% at the six-month measurement; the stiffness had increased from 0.007 N/deg at baseline to 0.047 N/deg at six-months) and there was unambiguous evidence that contractures were established.

are three possible factors that can contribute to a person holding a limb in a shortened position: (a) spasticity, (b) pain and (c) reduced cognitive ability.

• Does spasticity contribute to contractures?

Of the various forms of spasticity presented in Figure 1.3, it can be hypothesised, in patients who have no return of useful function, that any form of position-dependent spasticity, the ‘clasp-knife’ response, and ‘spastic dystonia’ can all contribute to a limb being held in a short-ened positon If one were to extrapolate from the animal models then it

is possible that the rate of contracture formation is likely to be quicker

in patients with ‘spastic dystonia’ than in patients  with  a  form  of position-dependent spasticity or the ‘clasp-knife’ response (Lieber [2009]) A general rule appears to be that joints that are held in a short-ened position through muscle activity develop contractures more rap-idly than in active muscles held in shortened position The evidence from clinical studies reinforce these observations, i.e., people who have

no function and develop spasticity develop contractures more rapidly than those who do not (Figure 1.4) (Pandyan et al [2003]; Malhotra et

al [2011]) People who regain limb function and present with signs

of spasticity do not develop contractures A general confounder in the literature is that most people who have studied the relationship between spasticity and contractures have often used invalid clinical scales, making interpretation of the results difficult

• Does pain and cognitive dysfunction contribute to contractures? Anecdotal evidence from data generated form a recently completed study (unpublished observations from Cameron et al [2014]) suggests that patients with a combination of pain and/or congnitive dysfunc-tion tend to be more prone to contractures Many of these patients were capable of functional movement but were often unable to use their limbs due the nature of the pain and/or cognitive dysfunction The most plausible explanation for this is likely to be the individual protecting the limb in a shortened positon in an attempt to alleviate pain However, these anecdotal associations need to studied more sys-tematically before any firm conclusion can be made

The literature seems to suggest that contractures, when they occur, are more common at the ankle and the wrist when than at other proximal joints (Sackley et al [2008])

If one were to explore the data from animal models and the few dinal data in adult patients with acquired brain injuries, including stroke,

longitu-it can be found that contractures can develop quiet rapidly, i.e., wlongitu-ithin 4 to

6 weeks after a stroke (Malhotra et al [2011]) This is also the time window within which spasticity is expected to develop This is an important consid-eration when one has to start measuring or treating patients

Definition and Measurement of Spasticity and Contracture

1.2.5 The Measurement of Spasticity and Contracture

When you can measure you know something about it – but when you cannot measure your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge but you have scarcely, in your thought, advanced to the

Both spasticity and contractures would come under the classification of

impairments under the ICF classification From a first-principle basis one needs to consider spasticity an impairment of the central nervous system and contractures as an impairment of the musculoskeletal system Both of these impairments are likely to have an impact on activity, societal partic-ipation, and possibly carer burden From a clinical perspective, it may be advantageous to measure spasticity indirectly, i.e., measuring the effects of treatment on activity, societal participation, or carer burden as appropriate

to the needs of an individual patient The disease-specific chapters have cussed approaches to measurement as appropriate Within the context of this chapter, however, the primary focus will remain on the measurement of the primary impairments of spasticity and contractures

dis-The current methods of measurement or assessment can be classified as clinical scales, biomechanical methods, and neurophysiological methods The most direct approach to measuring spasticity and the associated patho-physiology is by using neurophysiological methods The biomechanical methods have the greatest potential to measure contractures These three approaches are briefly examined in this section and the relative merits are discussed

• Clinical scales to measure spasticity and contractures

There are two scales that can be used to measure spasms: the Penn Spasm Frequency Scale and the Spasm Frequency Score (Penn

et al [1989]; Snow et al [1990]; Biering-Sørensen et al [2005]) Both these scales are patient reported scales and quantify the severity of spasms at an ordinal level of measurement The reliability is limited

as this does depend on patient memory of events (Biering-Sørensen

et al [2005])

There are a variety of scales that measure the resistance to an externally imposed passive movement and use these to indirectly quantify spasticity (e.g., the Ashworth Score and its variations – the Tardieu Score, the Composite Spasticity Index, etc.) (Platz et al [2005]) These scales are the most commonly used measures of spasticity, and are also the measures that are endorsed by many of the regulatory authorities (e.g., FDA) Unfortunately, none of these measures are useful measures of spasticity as these are all signifi-cantly confounded The research evidence proving that these scales,

and the general principle of measuring resistance to an externally imposed movement, are not fit for purpose have originated from multiple research groups carrying out work on different conti-nents and will not be rehashed here If readers are interested, please see the relevant papers (Pandyan et al [1999]; Haugh et al [2006]; Fleuren et al [2010]) It is a source of regret that many of the more direct neurophysiological and relatively simple measures that have underpinned our understanding of spasticity (Rymer and Katz [1994]) have been replaced by inadequate clinical scales for purposes

of clinical expediency

• Biomechanical methods to measure spasticity and contractures

A range of biomechanical methods have been described to sure spasticity These can be classified as manual methods (e.g., Pandyan et al [2001]); controlled displacement methods using ramp-and-hold perturbations (Rymer and Katz [1994]), sinusoidal pertur-bations (Zhang and Rymer [1997]), or random perturbations (Andersen and Sinkjaer [1996]); controlled torque methods (Walshe [1992]); or the gravitational method (Bajd and Bowman [1982]) All

mea-of the above methods attempt to measure spasticity by measuring the resistance to an externally imposed perturbation The evidence would suggest that these biomechanical measures are more often measuring concomitant biomechanical changes in the soft tissue structures as opposed to measuring spasticity Furthermore, whilst attempting to measure spasticity, most methods measure stiffness eccentrically; under these conditions it is not possible to delineate the components of stiffness (i.e., that arising from muscle activity, the intrinsic stiffness within the muscle due the residual actin and myosin cross bridges, and the contribution from the mechanical properties of the associated soft tissue structures) The biomechani-cal methods of measurement have been reviewed previously (Wood

et al [2005]; Pandyan et al [2009]) All of the biomechanical methods have limited clinical applicability when used as measures of spastic-ity; however, they have a significant role to play in the measurement

of contractures

Although not commonly used, accelerometers have the potential

to contribute to the measurement of spasms and clonus in a relevant way (Granat and Edmonds [1999]) While in the past such technology was expensive, the size and costs of these sensors have significantly reduced and there is the potential for such technologies to play an important role in the measurement and management of spasms (e.g., 24-hour monitoring systems for patients) In addition, it is also now possible to additionally measure muscle activity data concomitantly Whilst such technology is available, there is a need for additional research to make it accessible to clinicians

Definition and Measurement of Spasticity and Contracture

• Neurophysiological methods to measure spasticity

A range of neurophysiological methods have been described

to measure spasticity or the pathophysiological basis of spasticity These methods have previously been comprehensively reviewed (Voerman et al [2005]; Pandyan et al [2009]) The methods of rel-evance are as follows: the efferent response to an electrical stimulus (The H-reflex and F-wave); and the efferent response to a mechani-cal perturbation (tendon tap, manual perturbation, or controlled dis-placement perturbation – normally a ramp-and-hold stretch) While most of these methods of measurement are relatively easy to per-form, in particular the efferent response to a mechanical perturba-tion, the reliability of these methods of measurement needs to be better understood Current experimental evidence would suggest that H-reflex and F-wave measurements show a large degree of vari-ability Furthermore, in patients with an upper motoneuron lesion, developing a method of standardisation in measuring the muscle response to a mechanical perturbation is not possible

Despite the poor levels of reliability, many of these methods surement provide far more useful information to inform the manage-ment of spasticity than any of the clinical scales or the biomechanical measures used in isolation For example, when selecting patients for implantation of an intrathecal baclofen pump, an effective way to identify a suitable patient will be to study the H-reflex response to

of mea-a bolus injection of introf mea-athecof mea-al bof mea-aclofen (Mof mea-acdonell et of mea-al [1989]) In order to either select patients for treatment with botulinum toxin (or phenol or a motor nerve dissection) or study the response to treatment

it would make sense to ensure that the muscle/nerve being treated has an overactive efferent response associated with spasticity (Figures 1.3 and 1.5) as measured using manual neurophysiological methods

1.2.6 Concluding Thoughts

Spasticity appears to be an inevitable sequela following a lesion in the upper motoneuron pathways Within this chapter we provide a framework to clas-sify spasticity in a way that makes measurement possible We have also pro-vided an argument to suggest that patients who have spasticity and who do not recover useful functional movement are at risk of contractures The con-tractures can develop rapidly and often co-exist with spasticity The options

to treat spasticity are limited:

• Reduce the afferent input to the nervous system (selective dorsal rhyzotomy)

• Reduce the gain/threshold within the nervous system logical treatments that tend to depress the nervous system)

(pharmaco-• Reduce the efferent drive to the muscle (botulinum toxin, phenol, and neurectomies).

• Use muscle relaxants

The options to treat contractures are even more limited:

• Cyclical Passive Movement (using ergometers or electrical stimulation)

• Stretching using splints, serial casts, or progressive stretching devices

• Loading the tendons using electrical stimulation

In order to identify the most useful treatment combination it is essential that not only the right treatment is selected but that the response to the treatment

is effectively monitored This chapter will hopefully give some pointers in ensuring that the right definitions and measurements can inform the meth-ods of treatment

Then there is the issue of linking our understanding of spasticity to the recovery potential of patients Many of the current first-line treatments for spasticity have the potential to inhibit the learning that is essential for recov-ering functionally useful movement (e.g., pharmacological agents routinely used in clinical practice) (Cameron et al [2016]) Current practice will need

to be carefully re-examined; however, doing this in the absence of a precise framework is not appropriate This chapter hopefully provides such a frame-work to both clinicians and researchers

Finally, one must also consider the possibility that spasticity is an nomenon, although this may not be the case in all patients The literature and our own work provides evidence that patients who have recovered useful arm function continue to demonstrate signs of spasticity Identifying such patients is important as it is possible that spasticity may be an inevitable first step in the recovery pathway The framework may have a role to play in this classification process

epiphe-This book is the first attempt at bringing together a volume of work from a range of professionals with an interest in spasticity The framework for the defi-nition was developed in part by the authors reading the chapters that make up this volume There are likely to be some anomalies between the framework and the summaries within respective chapters This was expected as the literature that the respective authors have had to draw upon is imprecise One would hope that the framework within this chapter will help guide the research that follows

so that future reviews will be able to coherently summarise the literature with

no ambiguity As pointed out in Section 2.3, this framework has currently been developed for patients with upper motoneuron lesions, as identified within this book There is a significant volume of work that now needs to be done to provide

a framework that will include a range of other disease conditions where patients present with signs and symptoms similar to those described in this chapter (e.g., Parkinsonism, the various forms of dystonia, and other motoneuron diseases)

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from Surviving Fibres 352.5.3.1 Presynaptic Inhibition 362.5.3.2 Post-Activation Depression 372.5.4 Transmission in Group II Pathways 392.5.5 Pathophysiological Role of Changes in Postsynaptic

Inhibition of Motoneurons 402.5.5.1 Disynaptic Reciprocal Ia Inhibition 402.5.5.2 Recurrent Inhibition 412.5.5.3 Autogenetic Ib Inhibition 432.5.5.4 Fusimotor Drive, Gamma-Spasticity 432.6 How Is Clonus Related to Spasticity? 442.7 What Causes a Spasm? 452.8 Spastic Dystonia Is Not Caused by Increased Stretch Reflex Activity 452.9 Concluding Remarks 46References 47

2.1 How to Measure Spasticity – From Clinical

Evaluation to Biomechanical Techniques

The clinical evaluation of spasticity currently rests on the eyes and hands of the clinician Clinically, spasticity is often inappropriately equated to muscle tone and is essentially determined by sensing the resistance to passive move-ment around a joint with the patient in a position that is as relaxed as possible

By making movements at different velocities the clinician may get a feeling

of whether the resistance is present at all velocities or only during fastest stretching of the muscles Sometimes a distinct brief resistance – a catch – may be determined with quick stretches at specific positions of the joint Backed up by other signs such as large – and especially non-symmetrical – tendon tap reflexes and the presence of clonus, the clinician may perceive that the resistance is velocity-dependent and may possibly be related to hyperex-citable stretch reflexes; i.e., that the muscle resistance is caused by spastic-ity according to Lance’s definition In many cases the determination of the presence of spasticity is relatively straightforward and unproblematic (this may especially be the case when the clinician has knowledge of the underly-ing disorder, e.g., stroke or spinal cord, but may not necessarily be the case without this prior knowledge) However, if the patient is not fully relaxed, if the changes in reflex excitability are not very large, or if other mechanisms also contribute to increased muscle resistance, it may be very difficult to accurately determine the nature of the muscle resistance The presence of alterations in the elastic properties of the muscle, connective tissue, and/or tendons especially makes it difficult to perform the evaluation sufficiently fast and powerfully and it therefore becomes a challenge to determine the pres-ence of spasticity The presence of involuntary static muscle activity (spastic dystonia) and an associated inability of the patient to fully relax the muscle also make the evaluation difficult Clinical evaluation of spasticity has con-sequently been shown to have variable reproducibility within and between raters (Bhimani et al 2011, Biering-Sorensen et al 2006, Haugh et al 2006, Mutlu et al 2008) and to be unrelated to objective biomechanical measures of spasticity (Lorentzen et al 2010, Willerslev-Olsen et al 2013) The Ashworth scale was introduced in 1964 (Ashworth 1964) as a simple 5-point scale rang-ing from normal muscle tone (0) to rigidity (4) in order to quantify spasticity

in multiple sclerosis before and after treatment An additional grade (1+) was introduced in 1987 to designate slight resistance with a clear catch (Bohannon and Smith 1987) This modified Ashworth Scale (MAS) is now the most com-monly used clinical scale, although it is confounded by the same limitations

as the original scale, except for the additional grade Furthermore, the duction of this additional grade seems not to have improved the reliability of the scoring (Bhimani et al 2011, Biering-Sorensen et al 2006, Burridge et al 2005) and a conspicuous over-representation of scores 1 and 2 (Fleuren et al 2010) suggests that what is scored in most patients is ‘some resistance but not

Pathophysiology of Spasticity

too much’ (Biering-Sorensen et al 2006) The scale has consequently shown low validity and sensitivity in studies in which it has been related to biome-chanical measures of stiffness (Biering-Sorensen et al 2006, Burridge et al

2005, Lorentzen et al 2010, Malhotra et al 2008, Sehgal and McGuire 1998)

It is surprising given these drawbacks that the scale has become the scale of choice in the clinic, rather than the older Tardieu scale The Tardieu method was originally introduced in 1954 (Tardieu et al 1954) and has been modi-fied significantly to become the Tardieu scale that is in use today (Haugh

et al 2006, Held 1969) The essence of the scale is that the examiner has to move the examined limb at three different velocities (slow, moderate, and as fast as possible) in order to estimate range of movement, presence of passive resistance, and presence of spasticity The scoring of spasticity is based on the presence of a catch and clonus Although the Tardieu scale theoretically should more adequately distinguish passive and active components of mus-cle resistance than the Ashworth scale, it has not gained as wide a use in the clinic as the Ashworth scale Part of the reason for this is that the technique

is more demanding for the examiner and is therefore less easy to perform in

a similar way for two raters The scale also lacks sufficient dimensionality to cover patients with very severe spasticity that prevents elicitation of stretch reflexes and clonus The focus on the presence of clonus is also problematic given the uncertainty regarding the mechanisms of clonus and its relation to spasticity (Mukherjee and Chakravarty 2010)

Biomechanical evaluation of spasticity was introduced in the 1950s by Tardieu (Tardieu et al 1954) and later developed by Knutsson (Knutsson and Martensson 1976) Since then, various devices and techniques have been developed and tested (Mirbagheri et al 2005, Mirbagheri et al 2009, Mirbagheri et al 2004, Sinkjaer 1997, Sinkjaer et al 1992, Sinkjaer and Magnussen 1994, Sinkjaer et al 1995, Sinkjaer et al 1988, Toft et al 1989b, Toft et al 1989c, Wood et al 2005) The main advantage of these techniques

is that they provide an objective and quantitative assessment of resistance about a joint With the addition of EMG measurements from the stretched muscles, they may provide an objective and precise way of distinguish-ing reflex-mediated from passive muscle resistance (Lorentzen et al 2010, Sinkjaer et al 1993, Toft et al 1989b, Willerslev-Olsen et al 2013) From this point of view, biomechanical evaluation combined with electrophysiological measures might be considered a ‘gold standard’ for a combined evaluation

of spasticity and contractures with which other measures may be compared However, the expertise and technology involved is too demanding for rou-tine clinical use Handheld dynamometers and other simplified biomechani-cal devices may provide sufficiently reliable and consistent measures, but none of the commercially available devices have so far shown sufficiently promising results to be used more widely in the clinic for spasticity evalua-tion (Barden et al 2012, Benard et al 2010, Calota et al 2008, Kim et al 2011, Lee et al 2004, Lorentzen et al 2012, Waldman et al 2013) Only few of the existing devices claim to provide a distinction between reflex-mediated and

passive muscle stiffness and there is therefore a clear need to develop more optimal easy-to-use devices that can help the clinician in the routine clinical diagnosis.

2.2 The Nature of the Muscle Response to Stretch

In order to understand the pathophysiology of spasticity it is useful initially

to consider the responses of a muscle to stretch (1) At velocities below the threshold of the stretch reflex the resistance against the movement is caused solely by the passive elastic properties of the muscle, connective tissue, ten-don, and joint (Lorentzen et al 2010, Mirbagheri et al 2005, Mirbagheri et al

2004, Toft et al 1989a, Toft et al 1989b) This resistance is usually called sive stiffness (Toft et al 1989a, Toft et al 1989b) and is far less sensitive to the velocity of the stretch than the stretch reflex-mediated resistance (Lorentzen

pas-et al 2010) However, the resistance varies with the position of the joint and thus the degree of stretch of the muscle (Mirbagheri et al 2005, Mirbagheri

et al 2009, Mirbagheri et al 2004) If the subject is not fully relaxed, neural activation of the muscle will result in formation of cross-bridges between myosin and actin filaments that will impede the stretch and add very sig-nificantly to the stiffness (Figure 2.1) This stiffness is usually called intrin-sic stiffness, to distinguish it from passive and reflex-mediated stiffness

Motoneurone Motoneurone

Motoneurone

Descending

Descending drive Sensory

Sensory input

Output from

spinal cord

Output from spinal cord

Output from spinal cord

FIGURE 2.1

Theoretical changes in sensory and descending input to spinal motoneurons in the acute and chronic phase following central motor lesion The figure illustrates sensory and descending input to spinal motor neurons in the intact state (Normal), and following a central motor lesion

in both the acute state (Lesion), and in the chronic phase (Adaptation, spasticity) The numbers and thickness of the arrows represent the power and intensity of the input and outputs.

Pathophysiology of Spasticity

(Sinkjaer et al 1993), but it should be emphasised that it is caused by an (extrinsic) neural signal and may be very difficult to distinguish in practice from reflex-mediated stiffness given the integration between descending motor commands and reflexes (Nielsen 2004) When stretches above a cer-tain threshold (which is determined individually by the sensitivity of muscle spindles, transmitter release from central synapses, and the excitability of motoneurons) are applied, a stretch reflex response will be evoked and add

to the resistance against the movement (Figure 2.1) This reflex- mediated stiffness is, at least in theory, equivalent to the catch that is assessed as part

of the clinical evaluation of spasticity The mechanical response evoked by the stretch conceals that there are at least two separate reflex responses in most muscles (Christensen et al 2000) These responses may be demon-strated by EMG measurement from the muscle (Toft et al 1989b, Toft et al 1991) The initial (short-latency or M1) response is mediated by the spinal monosynaptic Ia pathway and is equivalent to the reflex response elicited by

a tendon tap (Morita et al 1998) The response is generally strongly ated in spastic patients (Ibrahim et al 1993, Sinkjaer and Magnussen 1994, Sinkjaer et al 1993) In lower limb muscles the initial response is followed

exagger-by a second (medium-latency or M2) and sometimes a third (long-latency

or M3) response (Christensen et al 2000) The M2 response has been shown

in all likelihood to be mediated by gr II afferents from the muscle spindles (Christensen et al 2000, Grey et al 2001) Similar to the M1 response, it is gen-erally exaggerated in spastic patients (Sinkjaer and Magnussen 1994, Sinkjaer

et al 1993, Willerslev-Olsen et al 2014) The third response, on the other hand, is generally reduced or abolished in spastic patients consistent with the idea that it is mediated by a transcortical pathway that is involved in the lesion (Christensen et al 2000) Similar mechanisms probably also contrib-ute to the stretch response observed at longer latency than the M1 response (generally called long-latency or M2 response) in upper limb muscles, but due to the short difference in conduction time for spinal and transcortical responses, the responses appear to be difficult to separate (Christensen et al 2000) These later responses in upper limb muscles may therefore be reduced, unchanged, or exaggerated in the individual patient

Since the mechanical resistance sensed either by a clinical examiner or a biomechanical device is the sum of these different reflex responses, trans-mission in all the involved pathways should be taken into account when con-sidering the cause of an exaggeration of the muscle resistance

2.3 Is Spasticity Caused by Lesion of the Pyramidal Tract?

Spasticity is observed following both spinal and cortical lesions and is in the clinic commonly associated to lesion of the corticospinal tract, but studies in