Classification and Definition of Disorders Causing Hypertonia in Childhood
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Classification and Definition of Disorders Causing Hypertonia in Childhood Terence D. Sanger, MD, PhD*; Mauricio R. Delgado, MD‡; Deborah Gaebler-Spira, MD§; Mark Hallett, MDʈ; Jonathan W. Mink, MD, PhD¶; and the Task Force on Childhood Motor Disorders ABSTRACT. Objective. This report describes the con- disorders. Pediatrics 2003;111:e89–e97. URL: http://www. sensus outcome of an interdisciplinary workshop that pediatrics.org/cgi/content/full/111/1/e89; spasticity, dys- was held at the National Institutes of Health in April tonia, rigidity, movement disorders, hypertonia, pediatric, 2001. The purpose of the workshop and this article are to childhood. define the terms “spasticity,” “dystonia,” and “rigidity” as they are used to describe clinical features of hyperto- nia in children. The definitions presented here are de- ABBREVIATION. CP, cerebral palsy. signed to allow differentiation of clinical features even when more than 1 is present simultaneously. bnormalities of tone are an integral compo- Methods. A consensus agreement was obtained on the best current definitions and their application in clin- nent of many chronic motor disorders of ical situations. Achildhood. These disorders result from dys- Results. “Spasticity” is defined as hypertonia in genesis or injury to developing motor pathways in which 1 or both of the following signs are present: 1) the cortex, basal ganglia, thalamus, cerebellum, resistance to externally imposed movement increases brainstem, central white matter, or spinal cord. with increasing speed of stretch and varies with the When the injury occurs in children before 2 years of direction of joint movement, and/or 2) resistance to ex- age, the term cerebral palsy (CP) is often used1; when ternally imposed movement rises rapidly above a thresh- it occurs in older children, a variety of descriptive old speed or joint angle. “Dystonia” is defined as a labels have been applied, depending on the cause. movement disorder in which involuntary sustained or Childhood motor disorders are commonly classified intermittent muscle contractions cause twisting and re- petitive movements, abnormal postures, or both. “Rigid- into hypertonic or hypotonic groups on the basis of ity” is defined as hypertonia in which all of the follow- the abnormality of muscle tone. ing are true: 1) the resistance to externally imposed joint At least 3 descriptive terms are associated with movement is present at very low speeds of movement, different forms of childhood hypertonia: “spastici- does not depend on imposed speed, and does not exhibit ty,” “dystonia,” and “rigidity.” Although some re- a speed or angle threshold; 2) simultaneous co-contrac- search laboratories have developed precise defini- tion of agonists and antagonists may occur, and this is tions for these terms, there has not been general reflected in an immediate resistance to a reversal of the agreement on the definitions as used in clinical situ- direction of movement about a joint; 3) the limb does not ations.2 Current definitions have been based on adult tend to return toward a particular fixed posture or ex- treme joint angle; and 4) voluntary activity in distant disorders and the manifestations of spinal cord in- muscle groups does not lead to involuntary movements jury and therefore have not always led to consistent about the rigid joints, although rigidity may worsen. labeling of pediatric signs and symptoms by clini- Conclusion. We have provided a set of definitions for cians and researchers in different fields. Studies of the purpose of identifying different components of appropriate rehabilitative interventions in chronic childhood hypertonia. We encourage the development of motor disorders of childhood have been hampered clinical rating scales that are based on these definitions, by the difficulty in establishing homogeneous co- and we encourage research to relate the degree of hyper- horts for study as a result of varying classification tonia to the degree of functional ability, change over systems. This is in large measure attributable to im- time, and societal participation in children with motor precision in the classification of abnormalities in tone as well as in categorizing the severity of functional impairments.3 There is therefore a need for a clear From the *Department of Neurology and Neurological Sciences, Stanford University Medical Center, Stanford, California; ‡Department of Neurology and consistent set of definitions that will allow accu- and Neurosciences, Texas Scottish Rite Hospital for Children, Dallas, Texas; rate communication between clinicians as well as §Department of Pediatrics, Rehabilitation Institute of Chicago, Chicago, appropriate selection of children for medical therapy ʈ Illinois; Human Motor Control Section, Medical Neurology Branch, Na- and clinical research trials. The ultimate purpose is to tional Institute of Neurological Disorders and Stroke, Bethesda, Maryland; ¶Department of Child Neurology, University of Rochester Medical Center, minimize disability and promote independence and Rochester, New York. full participation in society for children with motor Received for publication Jul 2, 2002; accepted Oct 3, 2002. disorders. Reprint requests to (T.D.S.) Department of Child Neurology, Stanford Uni- The goal of treatment of children with motor dis- versity Medical Center, 300 Pasteur Dr, MS 5235, Stanford, CA 94305-5235. E-mail: [email protected] orders mirrors the management of other forms of PEDIATRICS (ISSN 0031 4005). Copyright © 2003 by the American Acad- chronic disease and disability. The World Health emy of Pediatrics. Organization separates the issues of chronic diseases http://www.pediatrics.org/cgi/content/full/111/1/Downloaded from www.aappublications.org/newse89 byPEDIATRICS guest on October Vol. 1, 2021 111 No. 1 January 2003 e89 into 3 categories: impairment, functional ability, and possible anatomic localization, such as the “upper societal participation.4 The National Center for Med- motor neuron syndrome,” or related clinical obser- ical Rehabilitation Research model encourages those vations, such as a “spastic catch,”“clasp-knife re- who evaluate outcome for disabling conditions to sponse,” or clonus. Furthermore, the term “spastici- use a model of outcome that encompasses 5 axes: ty” is often used interchangeably with the term pathophysiology (underlying disease), impairment “upper motor neuron syndrome.” Current defini- (clinically observable abnormality), functional limi- tions of dystonia are based on the observation of tations (effect on task performance), disability (effect particular abnormal postures or movements with on daily living), and societal limitations (effect on sustained twisting qualities that are often associated lifetime opportunities).5 Major obstacles to evalua- with injury to the basal ganglia. Current definitions tion of outcomes within this model include limita- of rigidity are based on a constant resistance to pas- tions of measurement tools and a lack of objective sive motion that has a “plastic,”“malleable,” or criteria.6 In this context, this article provides specific “lead-pipe” quality. Although the current definitions clinical definitions of 3 types of hypertonia that are provide a set of useful guidelines, we believe that thought to cause specific impairment of movement. they are insufficiently specific to distinguish between This article presents a set of classifications and different findings, particularly when more than 1 is operational definitions that are designed to build the present simultaneously. foundation for understanding how childhood hyper- We use the term “motor disorder” to include dis- tonia relates to other impairments and how it has an orders of multiple neural components, including impact on function, disability, and societal participa- basal ganglia, cerebellum, cerebral cortex, brainstem, tion. We consider definitions of 3 important types of and descending spinal tracts, because the term hypertonia. The immediate goals of these definitions “movement disorder” is often used specifically to are 1) reliable communication between clinicians, 2) refer to disorders associated with presumed basal accurate distinction of diagnostic groups for clinical ganglia or cerebellar dysfunction. Hypertonia is a research, and 3) appropriate selection of patients for component of many motor disorders. In common medical or surgical interventions. On the basis of clinical usage, motor disorders are often divided into these goals, the definitions must meet the following pyramidal and extrapyramidal types. These terms criteria: have strong historical bases and have proved to have clinical utility, but it is increasingly recognized that • Utility: the ability to test a child easily in a routine the pyramidal and extrapyramidal motor systems clinical setting and assign appropriate labels that are highly interconnected and interdependent. Pyra- differentiate between spasticity, dystonia, and ri- midal motor disorders result from injury to the cor- gidity even when more than 1 feature is present ticofugal projections to the brainstem (corticobulbar) simultaneously, as well as the eventual ability to and spinal cord (corticospinal) at any point along confirm the findings by quantitative methods their course. The corticospinal tracts were previously • Reliability: the likelihood that different examiners believed to be responsible for all aspects of the motor will assign the same label to the manifestations of dysfunction, but recent evidence suggests that other any