The Post-traumatic Vegetative State E-Book

Giuliano Dolce

• Herausgeber: Thieme
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 488

Veröffentlichungsjahr: 2002

Beschreibung

The authors have compiled into a practical text their experiences encompassing over 20 years of work in the rehabilitation of patients in a persistent vegetative state. In addition to the partial or complete recovery of mental and neurological functions, another condition has been gaining in recognition in recent years: the state of minimal responder, which they elucidate in their book. This title bridges a gap in the specialized literature by providing neurologists, emergency physicians, physiatrists, and internists, as well as therapists, with a new set of tools to aid them in obtaining more rapid progress in the treatment of these patients, whose improvement is wholly dependent upon them. A second equally relevant aspect considered is the relationship of the care-giving physician with the patient's family. Particular attention is given to the approach the physician must take towards family members of the patient lacking mental activity. A third part illustrates the structural and instrumental devices useful in planning and operating a unit specialized in the treatment of patients in the persistent vegetative state, with particular attention given to the rules governing the unit.

Leseprobe

The Post-traumatic Vegetative State

Giuliano Dolce, M.D.

Professor and Chief Neurologist Institute S. Anna for Intensive Care and Rehabilitation Crotone, Italy

Leon Sazbon, M.D.

Senior Lecturer Sackler School of Medicine Tel Aviv University Former Director Intensive Care Unit for Vegetative Patients Loewenstein Rehabilitation Center Raanana, Israel

With contributions by

M. Gil, H. Hacker, O. Keren, C. Koren, A. Pincherle, M. Quintieri, L. Rahmani, J. E. Resnik, W. G. Sannita, E. Schmutzhard, P. Scola, S. Serra, A. Shilansky, R. Weitz, M. R. Zylberman

33 Illustrations 17 Tables

ThiemeStuttgart · New York

To Inge and Nelly

- for a life of love and patience.

Library of Congress Cataloging-in-Publication Data

The post-traumatic vegetative state / [edited by]

Giuliano Dolce, Leon Sazbon ; with contributions

by M. Gil … [et al.].

  p. ; cm.

 Includes bibliographical references and index.

 ISBN 1-58890-116-5 – ISBN 313130071X

 1. Persistent vegetative state. I. Dolce, Giuliano.

 II. Sazbon, Leon.

 [DNLM: 1. Persistent Vegetative State.

 WB 182 P857 2002]

 RB 150.C6 P67 2002

 616.8'49--dc21

2002020323

© 2002 Georg Thieme Verlag,

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Cover design: Renate Stockinger, Stuttgart

Typesetting by Satzpunkt Bayreuth, Bayreuth

Printed in Germany by Gulde Druck, Tübingen

ISBN 3-13-130071-X (GTV)

ISBN 1-58890-116-5 (TNY)            1 2 3 4 5

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Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers' leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user's own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed.

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Contributors

Mali Gil, M.A. Head, Department of Speech, Language and Swallowing Disorders Loewenstein Rehabilitation Center Raanana, Israel

Hans Hacker, M.D. Professor Emeritus Johann Wolfgang Goethe Universität Frankfurt am Main, Germany

Ofer Keren, M.D. Lecturer, Tel Aviv University Sackler School of Medicine Clinical Director Clinical Neurophysiological Unit Deputy Director Traumatic Brain Injury Loewenstein Rehabilitation Center Raanana, Israel

Cecilia Koren, M.A. Deputy Head, Department of Speech, Language and Swallowing Disorders Loewenstein Rehabilitation Center Raanana, Israel

Alessandro Pincherle, M.D. Clinical Neurophysiologist Università degli Studi di Genova Genova, Italy

Maria Quintieri, M.D. Clinical Neurophysiologist Institute S. Anna for Intensive Care and Rehabilitation of Brain Injury Patients Crotone, Italy

Levy Rahmani, Ph.D. Associate Professor of Psychology Tel Aviv University, Medical School Division of Health Professions Specialist in Clinical and Rehabilitation Psychology Former Head of Psychology Loewenstein Rehabilitation Hospital Raanana, Israel

Jacqueline Elise Resnik, B. App. Sci. P.T. Director, Department of Physiotherapy Rehut Medical Center Tel Aviv, Israel

Walter G. Sannita, M.D. Professor and Director Unit of Neurophysiopathology Department of Motor Science and Rehabilitation Università degli Studi di Genova Genova, Italy Associate Professor of Psychiatry State University of New York Stony Brook, New York, USA

Erich Schmutzhard, M.D. Professor, Univ.-Klinik für Neurologie Neurologic Intensive Care Unit Innsbruck, Austria

Paolo Scola, M.D. Otorhinolaryngologist Institute S. Anna for Intensive Care and Rehabilitation of Brain Injury Patients Crotone, Italy

Sebastiano Serra, M.D. Clinical Neurophysiologist Institute S. Anna for Intensive Care and Rehabilitation of Brain Injury Patients Crotone, Italy

Anat Shilansky, M.S.W. Head, Department of Social Work Loewenstein Rehabilitation Center Raanana, Israel

Rosemarie Weitz, B.S.W. Department of Social Work Loewenstein Rehabilitation Center Raanana, Israel

M. Rachele Zylberman, M.D. Neurology and Psychiatry Specialist Head, Department of Neuro-Rehabilitation Osp. San Gionvanni Battista Rome, Italy

Forword

In the 30 years since Plum and I described and named the vegetative state, there has been widespread interest in the medical, ethical and legal aspects of this strange condition.

It is therefore not surprising that at least three books on this topic, from different countries, are soon to be published. This one reviews the available medical data and emphasizes how much remains to be found out about the pathophysiology of the condition, and how limited is our understanding of the mechanisms underlying consciousness. Consistent with its claim to be “the first systematic presentation of a new phase in the history of neurorehabilitation,” this book is optimistic about the chances of good recovery from the vegetative state. It details in practical terms the many complexities of the medical management of these patients and will be a useful source for those dealing with patients who are temporarily vegetative. It deals with how to ensure that such patients can make the most of their capacity for recovery, and will not be further handicapped by avoidable complications. It acknowledges that various countries hold differing views about the appropriate management of patients who are permanently vegetative. In North America and several countries in Northern Europe, an ethical and legal consensus has emerged that continuing treatment that is considered to be of no benefit to such patients may not be justified.

Its withdrawal is therefore regarded as an ethically and legally acceptable option, and is claimed not to infringe the European Convention on Human Rights (B. Jennett, The vegetative state: medical facts, ethical and legal dilemmas, Cambridge: Cambridge University Press, 2002). Mediterranean countries are not part of this consensus, but little has been published about their viewpoint. It is therefore valuable to have the opposing view set out here, even if many of us from elsewhere would reject the supposed contrast between “a policy of abandonment” and “compassionate care.” We also believe that we are being compassionate, although we interpret this differently. It is therefore likely that this book, as well as providing practical guidance for rehabilitationists, will be a useful contribution to the debate that is bound to continue about the ethical and legal issues surrounding this perplexing condition.

Fortunately, survival in a permanent vegetative state is the outcome for only a few of the many patients who, thanks to the technologies of resuscitation and intensive care in the acute stage, now survive episodes of severe brain damage that would previously have proved rapidly fatal.

Bryan Jennett CBE, MD, FRCS Emeritus Professor of Neurosurgery University of Glasgow, Scotland

Preface

Traumatic brain injury is the primary cause of death in the first 45 years of life. Mortality during the early post-traumatic phase has been significantly reduced in developed countries, thanks to scientific and technological advances in emergency care and reanimation. However, severe post-traumatic disabilities are increasingly frequent. Notably, cases of “vegetative state” lasting anything from a few days to many months have been progressively increasing in frequency. Vegetative state can persist over long periods of time, or may become permanent. These terms are generally applied when the condition lasts for more than 1 year, although they are discouraged in the International Working Party's report on the vegetative state (London, 1996). The estimated incidence is five new cases per million population per year.

The diagnosis of vegetative state and, more specifically, the management of patients in such a condition, require the appropriate expertise and a multidisciplinary approach. The vegetative state requires maintenance of life in the absence of contact between the patient and the outside world, as well as procedures aimed at minimizing the impact of common yet potentially severe complications and aiming to provide the necessary conditions to promote the recovery of motor and higher brain functions. Patients in the vegetative state suffer from serious and diffuse primary and secondary brain lesions and present with deficits reflecting pathophysiological states that may be highly peculiar to the individual injury or injuries. Practical experience is therefore required in order to devise patient-specific therapeutic strategies, while defining precise rules to help the patient progress from an emergency state to a condition of controlled stability.

Unlike long-term coma in steady conditions and with no chances of recovery, patients in the vegetative state show a great many signs and signals which the therapist must identify, help elicit, and then interpret. Besides partial or complete recovery of mental and neurological functions, on the one hand, or outcome as a chronic condition, on the other, another development of the vegetative state has attracted interest in recent years: the state of the minimal responder. This form of life represents a new condition in human existence about which little is yet known, but which needs to be discussed in order to assist those involved in the care of patients in post-traumatic vegetative state.

In the present handbook, combining theoretical and practical approaches, the authors summarize three decades of experience in recuperative care for patients in the vegetative state. The goals are to help bridge a gap in the specialist literature; to provide anesthesiologists, neurologists, physiatricians, internists, and therapists with the expertise they need; and to assist them in improving the treatment of these patients. A second but equally relevant aspect – the relationship between the attending physician and the patient's family during many months of personal contact – is also considered, with the focus on how the physician should relate to the families of patients who lack mental activity and for whom a definite prognosis is not easy to establish. The organization and the structural/technological facilities required when planning and operating a unit dedicated to the treatment of patients in the vegetative state are also discussed, with particular attention being given to the meeting of regulatory requirements.

Giuliano Dolce and Leon Sazbon

Acknowledgements

The Authors wish to thank Dr. and Mrs. G. Pugliese for their warm and friendly support and encouragement to review a full 40-years of work and experience in a book. This project would have never been accomplished without Mrs. Rossella Casciaro's patience and dedication.

Contents

1 Introduction

History of the Concept of Vegetative State

2 Preliminary Concepts

Leon Sazbon, Giuliano Dolce

Etiology

Epidemiology

Age and Gender

Season and Time of Day

Circumstances of VS

Recovery

Neuropathological Basis of the Vegetative State

3 Neurophysiopathology

Giuliano Dolce, Leon Sazbon

Relationship with the Outer World

Relationship with the Inner World

Working Hypothesis on the Brain's Functional Organization in the Vegetative State

4 Clinical Picture

Leon Sazbon, Giuliano Dolce

General Considerations

Medical Aspects and Complications

Cardiovascular Effects

Respiratory Complications

Urinary Complications

Gastrointestinal Complications

Motor Problems

Periarticular New Bone Formation

Seizures

Ventricular Enlargement

Undernutrition

Water and Electrolyte Balance

Hematological Alterations

Hormonal Disorders

Immunologic Disorders

Infections

Deep Vein Thrombosis

Autonomic Disturbances

Dermatological Changes and Bedsores

Complications of Medications

Other

Neurological Aspects

Neurological Examination

Posture

Spontaneous and Pathological Movements

Passive Movements and Muscular Tone

Behavioral Responses

Ocular Motility

Oral Reflexes and Automatism

Oculocephalic Reflex

Trunk and Limbs

Reflexes

Recovery of Conscious Activity

Prognostic Value of Neurological Signs

Giuliano Dolce, Leon Sazbon

Basic Glossary and Definitions of Relevant Signs

Differential Diagnosis

Erich Schmutzhard

Introduction

Locked-in Syndrome

Akinetic Mutism

Paramedian Diencephalic Syndrome (Hypersomnia)

Prognosis and Outcome

Leon Sazbon, Giuliano Dolce

Survival

Recovery of Consciousness

Recovery of Function

Assessment of the Vegetative State

Ceclia Koren, Mali Gil, Leon Sazbon

The Glasgow Coma Scale

The Rancho Los Amigos Levels of Cognitive Functioning Scale

The Disability Rating Scale

The Western Neuro-Sensory Stimulation Profile

The Coma/Near Coma Scale

The Coma Recovery Scale

The Sensory Stimulation Assessment Measure

Prognostic Model of Emergence from Vegetative States

The Coma Exit Chart

The Sensory Modality Assessment and Rehabilitation Technique

The Preliminary Neuropsychological Battery

Loewenstein Communication Scale for the Minimally Responsive Patient

5 Ancillary Examination

Leon Sazbon

Laboratory Findings

Neuroimaging in the Vegetative State

Hans Hacker

Neurophysiological Assessment of Brain Function in the Persistent Vegetative State

Alessandro Pincherle, Walter G. Sannita

Electroencephalography

Sleep EEG

Stimulus-Related Evoked Potentials

6 Therapy

Leon Sazbon, Giuliano Dolce

Medical Therapy

Types of Drug Used in the Vegetative State

Deep Brain Electrical Stimulation

Surgical Therapy

Incidence of Hydrocephalus

Diagnosis and Treatment

Outcome of Surgery

Stimulation Techniques

Types and Techniques of Sensory Stimulation

Assessment and Outcome

Other Potential Advantages

Conclusions

7 Practical Guide to the Management of Patients in the Vegetative State

Maria Quintieri, Sebastiano Serra

General Considerations

Observation of the General State

Survey of Vital Parameters

Pharmacological Therapy and Drug Administration Modes

Procedure: before Drug Administration

Treatment Program

Hygiene

Evaluation of Nutritional Aspects and Methods

Procedure for Body Weight Monitoring

Feeding: Routes of Administration

Treatment in the Gym

Respiratory Treatment

Verticalization

Hydrotherapy

Positioning the Patient on the Wheelchair

Treatment of Swallowing Disturbances

Evaluation and Treatment of Spasticity

Management of Tracheostomy Patients in the Vegetative State

Paolo Scola

Countercannula Disinfection

Inhalation

Swallowing

Fibrotracheal Bronchoscopy

Complications

Cannula Removal

8 Minimal Response Syndrome

Ofer Keren, Jacqueline Resnik

What is Minimal Response Syndrome?

Significance of the Syndrome

Implications for Health Policy

Diagnosis and Assessment Tools

Incidence and Prevalence

Practical Management Recommendations

Clinical Management

Objectives of Treatment

Treatment Aimed at “Care”

Treatment Aimed at “Therapy”

Clinical Treatment Providers

Policy and Ethics Related to the Minimally Responsive Patient

Conclusions

9 Ethical Aspects

Giuliano Dolce, Leon Sazbon

10 Treating Families of Patients in Vegetative State: Adjustment and Interaction with Hospital Staff

Anat Shilansky, Rosemarie Weitz

Focusing on the Families

Family Assessment

Typical Psychological Reactions of the Family Members

Focusing on the Staff: Emotional Stress and Sources of Tension

Recommendations and Suggested Strategies

11 Covert Cognitive Abilities of a Person with Altered Consciousness

Levy Rahmani

12 Intensive-Care Unit for Vegetative State: Management Guidelines

M. Rachele Zylberman

General Organizing Criteria

Admission Criteria

Discharge Criteria

The Department

Structural Organization

Building Materials

Equipment and Biotechnology

Lying-in Period

Gymnasium

Sanitary Rooms

Human Resources

Epilogue and Future Prospects

Giuliano Dolce, Leon Sazbon

Index

1 Introduction

The progression from unconsciousness and coma to recovered wakefulness – either direct or with a transition through a condition such as the vegetative state – is often characterized by a very complex clinical picture, which is determined by pathophysiological mechanisms that are only known in part. The treatment of patients in this phase – in relation to total or partial recovery of higher brain functions/mental functions – implies detailed procedures, while nursing practices and the many measures required to avoid secondary complications follow precise rules. The recovery of higher brain functions and mental activity requires individualized treatment and relies on an empirical approach, which is usually also based on the creativity, collaboration, and drive of the therapists and family members concerned. Such care cannot replace rehabilitative procedures conceived as part of a scientific plan of treatment. When there are deficits for which detailed identification of the physiopathological basis is lacking, a thoroughly scientifically based therapeutic model must be followed. Experimentation should never be justified in patients who are not in a position to choose treatment or discuss the risks with the attending physician. Although often underestimated, this aspect may generate moral dilemmas for those who are in charge of patients in vegetative state, as these patients present with the most serious of all deficits: the loss of identity. It is also for this reason that, after many years of work with such patients, we have felt the need to carry out close scrutiny and critical evaluation of our experience in order to revise the available clinical outline of the vegetative state and to try characterize the world in which patients in this condition live. This rationale has allowed us to elaborate a new approach to the diagnosis, prognosis, and treatment of patients in the vegetative state.

The driving force behind the preparation of this manual has been not only our immense curiosity and interest in this pathology and its mysterious features, which involve the most highly evolved function of the human being – awareness – but also the love we have felt for those individuals who, through their illness, have contributed to the growth in the quality of our own awareness.

History of the Concept of Vegetative State

The Oxford American Dictionary defines “vegetative state” as a condition of living “a merely physical life, devoid of intellectual activity or social intercourse” that is characteristic of “an organic body capable of growth and development but devoid of sensation and thought” [1]. The term “vegetative” is used in the scientific terminology of several languages to signify an “autonomous being.”

More than a century ago, in 1899, Rosemblath described the first case of a long-term “chronic” coma in which the patient survived for 8 months on artificial nutrition [2]. The very specific clinical picture of a patient lying passively, akinetic, unresponsive, and with eyes open was described by Kretchmer in 1940 as an “apallic” syndrome, with the term “apallic” being meant to describe the loss of complex functions of the cerebral cortex (pallium) [3]. To the author, this functional decortication signified a “mesencephalic” existence. According to Kretchmer, the loss of cortical function, due either to cortical (and white matter) or brain-stem lesions, presents a typical picture of a condition in which there is no contact with the outside world, lack of reaction and recognition, and an attentive look. Kretchmer described this syndrome as an expression of panagnosis and panapraxis. In 1972, Jennett and Plum described this clinical picture in terms of a global disturbance in cognitive function [4].

Following the efforts of several authors, this clinical condition was described in progressively greater detail, and various definitions of it were suggested, including the term “vegetative state” originally proposed by Jennett in 1972 and accepted by the London workshop [5]. Publications by the American Task Force on the vegetative state in 1994 and by the London conference marked a milestone in the study of this serious cerebral pathology, by defining the vegetative state in terms that still apply today. In spite of its negative connotations, the term “vegetative state” does in fact fulfill two requirements in defining the condition: it is universally broad and etymologically correct. The heading “vegetative state” now also includes several syndromes that are often confused with other conditions in the relevant literature, due to the lack of a precise definition based on clinical or anatomical-pathological criteria.

Irrespective of whether its origin is post-traumatic or vascular, a vegetative state may develop after 3–4 weeks of coma, or can occur as a result of progressive, degenerative, or congenital neurological disease. According to the American Task Force, a vegetative state is characterized by concomitant findings of:

• Absence of awareness of self or environment and inability to interact with others

• Absence of sustained or reproducible behavioral or voluntary responses; absence of responses to auditory, visual, tactile, or noxious stimuli

• No comprehension or verbal expression

• Intermittent wakefulness, occasionally observed in the presence of a sleep-wake cycle

• Sufficiently preserved autonomic functions of the hypothalamus and brain stem, allowing survival with medical and nursing care

• Sphincteral incontinence

• Preserved spinal and cranial nerve reflexes (pupillary, oculocephalic, corneal, oculovestibular, and gag)

According to Sazbon, the condition referred to as “vegetative state” is characterized by two cardinal signs – wakefulness and unawareness. Any condition included within this framework is to be considered as a vegetative state, regardless of origin, etiology, duration, course, or outcome. All authors agree with the American Task Force in accepting that two cardinal features characterize the clinical picture: that the vegetative state is one of three possible progressions of coma (although it represents a special condition), and that it manifests a loss of the contents of consciousness even after the recovery of vigilance – as distinct from coma. “Contents of consciousness” is meant to describe both the ability to relate to the outer world (awareness) and the awareness of self. It is apparent that the contents of consciousness are lacking in the vegetative state, as also are sensory functions, attentiveness, and spatiotemporal orientation – that is, all of the functions that make up a conscious experience of the outer world.

We do not regard this point of view as correct, and wish to discuss it from a different angle, based on observations that are expounded in greater detail in Chapter 3, page 16 below. Specifically:

• The vegetative state is an expression of a direct primary brain pathology, and is not an extension of coma. Although existing from the outset of the brain pathology, the vegetative state may be masked by a state of coma, thus hindering a proper diagnosis.

• We believe inappropriate attention has been given to those functions that allow the patient to relate with the inner world, including in addition to imagination, ideas, and will, feelings and memory as well – all functions that allow the continuation of mental life.

References

1. Oxford American Dictionary, ed. Ehrlich E. New York: Oxford University Press, 1980.

2. Rosenblath W. Über einen bemerkenswerten Fall von Hirnerschütterung. Dtch Arch Klein Med 1899; 64: 406–420.

3. Kretchmer E. Das apallische Syndrom. Z ges Neurol Psychiat 1940; 169: 576–579.

4. Jennett B, Plum F. Persistent vegetative state after brain damage: a syndrome in search of a name. Lancet 1972; i: 734–6.

5. Andrews K, Beaumont JG, Danze F, et al. International Working Party report on the vegetative state. London: Royal Hospital for Neurodisability, 1996 (http://www.comarecovery.org/pvs.htm).

3 Neurophysiopathology

Giuliano Dolce and Leon Sazbon

Relationship with the Outer World

From a neurophysiological point of view, the brain structures and functional organization regulating conscious activity and allowing awake humans to express the contents of consciousness (that is to say, awareness of oneself and of the environment) only subsist when four specific conditions are met simultaneously:

• Presence of specific sensory inputs

• Presence of nonspecific, diffuse input from the ascending reticulothalamic activating systems diffusely projecting to the cortex

• Cortical activity with neuronal discharge in the medium–frequency range

• Activation of the primitive ipsilateral and contralateral motor systems, which stabilize spatial relationships and orient the system toward the source, thereby allowing for perception

These functional conditions must have a certain degree of interaction (the “theory of coherence”), and it is therefore insufficient for a certain cerebral area to be activated unless activation occurs to a degree that is appropriate to the activity of the interacting structures or functions. Information processing in the nervous system (which lacks a central pacemaker) becomes comprehensible only when the functional interaction between the activated cortical areas or brain systems is taken into account. This interaction is largely mediated through the thalamocortical system; another example elucidating the theory of coherence is given by the functional relationship between cortex, hippocampus and limbic system. Cortical information processing appears optimal when a theta rhythm of around 5 Hz is established in the hippocampus. This mechanism is considered to be the neurophysiological correlate for the phenomenon occurring (for instance during tests at school) when a strong emotional charge interferes with cortical information recall and causes a black–out of memory functions. It is therefore to no avail to activate a single cerebral structure in order to obtain improvement in performance. It would be necessary to determine the optimal coherence between the various structures to attain the best performance.

For many years, neurologists adhered to the concept that any given clinical picture would reflect the dysfunction (almost invariably a deficit, seldom hyperfunction or malfunction) of a particular structure or system. This induced Plum and Posner [1] to outline a number of different syndromes, characterized by their complex clinical picture and referred to as direct or indirect lesions of the encephalic brain stem, i.e. the syndrome of rostrocaudal deterioration responsible for coma.

The vegetative state, by contrast, results from a great variety of etiologies and pathophysiological mechanisms, in comparison with the relatively uniform clinical picture which, for instance, synthetically represents the “locked–out” syndrome [2]. Laminar encephalitis, selective damage to cortical neurons induced by insulin, several metabolic disturbances, anoxia, multiple or isolated lesions of the hemispheric structures, diencephalon, or brain stem, and lesions of the connections both between or within brain hemispheres, are all pathophysiological mechanisms capable of inducing a vegetative state.

The location, extent, and nature of the pathological anatomic lesions that determine the vegetative state do not correlate with the clinical progression. The fact that the deficit causing the vegetative state does not involve a single functional area alone, but depends on a reduction of the reciprocal connections among several brain structures, explains the lack of a definite anatomical correlate as a reference for recuperation. In our personal experience, we have often observed that patients with relatively inconspicuous morphological damage on brain computed tomography (CT) or magnetic resonance imaging (MRI) scans did not recover awareness, in contrast to unexpected recuperations in post-traumatic patients with multiple extensive lesions characterizing a severe postacute encephalopathy.

This discrepancy is most likely due to a single factor, represented by the degree of functional residual plasticity (very powerful at an age when maturation is incomplete, e.g. before 25 years), which allows a new postlesional organization to form (in general by the sixth month, but most often between the third and fourth months after brain injury), thereby establishing a certain degree of reciprocal activation among the major functional systems regulating the mechanisms needed for awareness to exist.

Following a certain functional hierarchy, the first of these major mechanisms is related to medium–frequency cortical neuronal discharge. Consciousness is not manifested at maximal discharge frequencies, during metabolic coma (e.g. in case of very high insulinemia), or when there are interfering physical factors such as low temperatures. Second, consciousness is almost completely lacking in the absence of specific input, as is seen for instance when sensory deprivation is induced experimentally. Also, conscious activity is not seen with reduced function of the ascending nonspecific activating systems (e. g. in barbiturate coma) or of the reticulothalamic system projecting diffusely to the cortex.

Although the functional anatomy and pathophysiology of these systems have been described and extensively covered in the literature, the motor component, which intervenes in mechanisms permitting contact with the outer world, has not. This contact is completely interrupted in the vegetative state.

The primitive motor systems are responsible for ipsilateral and contralateral movements, described in detail in the German literature [3,4]. We wish to describe these motor systems at this point, because the functional role they play in the pathophysiology of vegetative state is poorly known, although it is as relevant as that of the other systems described above.

Movements toward the right or left determine the spatial displacement of the body. Two distinct systems exist in each hemisphere to execute movements toward the same side (the ipsilateral system) or toward the opposite side (the contralateral system) (Fig. 3.1