Last Updated: Friday, March 10, 2006
Coma stimulation is a popular term used to describe virtually any treatment applied to individuals with disorders of consciousness (DOC). It is a misnomer in the sense that most individuals who receive traditional stimulation-based treatments are not comatose. (The neurosurgical definition of coma is: no eye opening, no recognizable speech, no following motor commands.) Disorders of consciousness are among the least understood and most widely misdiagnosed conditions in medicine.1, 2 Before considering coma stimulation and other interventions designed for individuals with DOC, it is important to recognize the distinctions that exist among these conditions since these may impact treatment decisions.
Disorders of Consciousness
Coma refers to a state of complete unresponsiveness in which the eyes remain continuously closed. The individual in coma cannot be aroused even when vigorously stimulated.3 Coma rarely lasts longer than two to four weeks and its end-point is marked by the reemergence of spontaneous or stimulus-induced eye opening. The vegetative state (VS) typically follows a period of coma. Individuals in VS demonstrate periods of wakefulness (i.e., eye-opening) but are completely unable to follow instructions, communicate in any way or move in a purposeful manner.4 The term, vegetative state, is viewed as pejorative by many because of its association with the word vegetable. The term was originally intended to emphasize the return of the vegetative functions of the body (e.g., blood pressure, heart rate) in those recovering from coma.5 Some have advocated use of the term persistent VS when this condition lasts more than one month6, although broad agreement concerning the appropriateness of this term is lacking.7 VS is often considered permanent after 12 months following traumatic brain injury and after 3 months in individuals with non-traumatic brain injury.
The minimally conscious state (MCS) is characterized by inconsistent but clearly recognizable behavioral signs of consciousness.8 These signs commonly include command-following, intelligible speech or gestures, reliable yes/no responses and appropriate use of objects. Although similar in appearance to coma, VS and MCS, the locked-in syndrome (LIS) is a condition in which there is loss of speech and movement caused by severe injury to the motor systems of the brain. In LIS, consciousness is generally preserved and communication is possible through control of eye-blinking or vertical eye movements.9
Stimulation-Based Approaches to Treatment
A wide range of treatment procedures have been utilized in individuals with DOC. Despite considerable variability in method, accessibility and cost, no treatment has been clearly shown to promote recovery of consciousness or improve functional outcome. Treatment strategies can be broadly grouped into three categories: 1) sensory stimulation (SS), 2) physical management (PM) and 3) neuromodulation (NM).
Environmental enrichment strategies and structured sensory stimulation represent examples of SS. In environmental enrichment, the individual is exposed to naturally-occurring (e.g., TV/radio broadcasts) or contrived (e.g., family pictures/audiotapes) environmental stimuli in an effort to increase brain activation and consequently, behavioral responsiveness. There is some evidence that this strategy may be cognitively overwhelming to an individual recovering from severe brain injury.10 Structured sensory stimulation attempts to tailor the intensity and frequency of applied stimuli to the individuals specific tolerance level in each sensory channel. There are a number of favorable reports concerning the effectiveness of structured SS but the majority of studies in this area are methodologically weak.11
Physical management strategies include a variety of techniques designed to promote physical health, reduce medical complications and maintain comfort. Range of motion exercises, positioning protocols and nutritional supplementation constitute examples of PM strategies and are considered essential in the treatment of DOC by most rehabilitation professionals.12 (Giacino, Zasler, Katz 97)
Neuromodulation procedures aim to improve cognition and behavioral responsiveness by directly altering cerebral function. Medications that influence the central nervous system, hyperbaric oxygen therapy (HBOT) and deep brain stimulation (DBS) are included in this category. There is no convincing evidence that medication can facilitate recovery in individuals with VS, although these agents may improve basic arousal.12, 13 (Reinhard, Whyte) There is some evidence that stimulants and other medication classes may improve verbal and behavioral initiation and persistence in individuals with MCS.14, 15 (Barrett, Powell) HBOT increases blood oxygenation via use of a pressurized oxygen chamber. This improves cerebral blood flow and metabolism and is believed to restore function in damaged brain cells. Studies suggest that HBOT may improve the probability of survival if implemented early after injury but there is little evidence that it can improve functional outcome in survivors.16
DBS was first utilized to treat individuals in VS in Japan.17, 18 Initial reports described significant improvements in many of those treated but careful analysis of the findings showed major shortcomings in the methods used to study the effects of DBS.19 (STAR) Recently, there has been renewed interest in a novel use of DBS that capitalizes on recent advances in knowledge of brain-behavior relationships and technology.20 Research findings evaluating the effectiveness of DBS will likely be available within the next five years.
Educated consumerism is essential in this era of rapidly increasing (and increasingly confusing) information about brain injury. A strong partnership between family members and the health care team remains the top priority in ensuring optimal care throughout the continuum of recovery.
Joseph T. Giacino, Ph.D. is the Associate Director of Neuropsychology at the JFK Johnson Rehabilitation Institute Center for Head Injuries and the New Jersey Neuroscience Institute at JFK Medical Center. Dr. Giacino holds academic appointments in the Department of Neuroscience at the Seton Hall University School of Graduate Medical Education, the Department of Physical Medicine at the University of Medicine and Dentistry of New Jersey and the Graduate School of Applied and Professional Psychology at Rutgers University. He is on the editorial board of the Journal of Head Trauma Rehabilitation and serves as an ad hoc reviewer for the Archives of Physical Medicine and Rehabilitation. He is a Fellow in the National Academy of Neuropsychology. In 2002, he received the Distinguished Member award from the American Congress of Rehabilitation Medicine (ACRM).
Dr. Giacino's clinical and research interests include diagnostic assessment, outcome prediction and treatment efficacy in disorders of consciousness, awareness and executive function. He is the primary author of the JFK Coma Recovery Scale which is currently being used in brain injury facilities throughout the United States and Europe. He has published and lectured extensively on topics pertaining to neuropsychological and neurobehavioral sequelae of severe brain injury and is actively engaged in federal and privately-funded research on disorders of consciousness.
Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that. Hate multiplies hate, violence multiplies violence, and toughness multiplies toughness, in a descending spiral of destruction. The chain reaction of evil must be broken, or we shall be plunged into the dark abyss of annihilation.- Dr. Martin Luther King Jr.
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