Question: What is coma stimulation? How effective is this unique therapeutic technique? Should facilities offer this kind of treatment?
Answer: Brain Injury Source, Volume 1, Issue 1, Ask the Doctor
by Nathan D. Zasler, MD, FAAPM&R, FAADEP
In this day and age, of high technology and aggressive medical care, coma stimulation programs seem to have come and gone as an integral part of most continuums of rehabilitative care for persons with severe brain injury, regardless of the specific etiology. There are obviously major issues regarding how coma stimulation, probably more appropriately called sensory stimulation, may have a beneficial effect on a brain that is other-wise "unaware" of its environment.
For purposes of this discussion, it is important to differentiate between environmental and structured sensory stimulation from both a clinical and research perspective. Environmental stimulation simply implies that the individual is subjected to ongoing environmental stimuli of various types in an unpredictable, uncontrolled fashion. Structured sensory stimulation implies that stimuli are presented in a systematic fashion; whereby, the person is subjected to multisensory stimulation typically including tactile, visual, vestibular, auditory, olfactory and gustatory stimuli.
Most coma stimulation is not really coma stimulation at all but rather vegetative or low level stimulation. It is probably appropriate both from a standpoint of proper use of terminology, as well as from a standpoint of reimbursement, to dispense with the use of the phraseology coma stimulation. Additionally, labeling a program as coma stimulation suggests that this may be the sole or major component of the program. Such implications are a disservice to all parties involved.
There are animal studies that do indicate a beneficial effect of enriched environments relative to sensory deprivation on neurologic recovery processes following experimental brain injury. However, none of the animal protocols in these studies utilized vegetative or comatose subjects. Additionally, the relationship of lower animal nervous system recovery to human recovery in vegetative state can certainly not be assumed to be parallel. Other theories promoting sensory stimulation rationalize that it may facilitate neural recovery following brain injury, promote activation of primitive brain centers, maintain and/or improve tonic arousal pathways and limit the type and extent of afferent input to the central nervous system (CNS).
Many would argue that in a person who was truly comatose or vegetative, here is little to no rationale for sensory stimulation. Although stimulation, sensory or pharmacologic, can increase arousal in such individuals, no one has convincingly shown that it effectuates any change in awareness. The consensus opinion in the neuroscience community is that persons who are comatose and/or vegetative have no awareness of their environment, either internally or externally. One should note, however, there is no methodologically sound evidence to back up this "expert opinion." Additionally, functional brain imaging studies suggest that such individuals may have insufficient cerebral metabolic activity to support cognitive functioning. We are therefore left with some fairly profound arguments that must be countered if we are to defend the use of sensory stimulation as therapeutic.
Most of the studies that are used by proponents of stimulation programs are methodologically poor. These studies are flawed by multiple factors including: small sample size, retrospective nature, lack of control groups, lack of correlationi to functional status/recovery, poor descriptors of potential associated complicating neuromedical factors (e.g. hypoxic ischemic brain injury, lack of scientific peer review and/or inadequate information regarding control group selection criteria). Both Wood and Giacino have written rather comprehensive analyses on the theoretical rationale of sensory stimulation which should be read by anyone interested in this topic. The data as it presently exists, when analyzed according to scientific evidence-based criteria, does not provide any good support that sensory stimulation alters the course of neurologic recovery with regard to either the final neurologic outcome or the rate at which that outcome is achieved. As we should all know too well, the lack of good scientific evidence does not necessarily mean that sensory stimulation does not do what it has been advocated to do. That is - "absence of proof is not proof of absence."
Various professionals have theorized that sensory stimulation, although not empirically validated, might assist in structuring the individual's interaction with the environment, as well as, monitoring progress and response to therapeutic interventions. Theories aside, the evidence to date strongly suggests that as rehabilitation professionals, we need to more closely scrutinize the role of such programs in the greater context of the rehabilitative care of these persons.
Appropriate management of the individual with low level response, whether comatose, vegetative or minimally conscious, should be comprehensive in nature with sensory stimulation being an optional component of such a program as defined by the Aspen Core Workgroup. Interdisciplinary rehabilitative management of this person population involves preventing morbidity, as well as, providing appropriate neuromedical and rehabilitative interventions to maximize neurologic and functional outcome. Briefly, appropriate care should include adequate and ongoing neuromedical management with an emphasis on treating underlying conditions(s) potentially suppressing neural recovery potential and decreasing risk factors for morbidity and/or mortality; good nursing care with an emphasis on skin, respiratory, and bowel/bladder care; and appropriate and timely prescription of adaptive equipment including seating and orthotics. Family involvement, education and counseling should also be an integral part of such a program. The major caveat relative to neurorehabilitative management of individuals in low level neurologic states is "first do no harm."
With appropriate and aggressive interdisciplinary care including timely neuromedical intervention, therapy services (physical therapy, occupational therapy, speech language pathology services, nutritional support services) and most importantly high quality nursing involvement, morbidity will be minimized and potential for longer term survival and recovery optimized.
If sensory stimulation is offered, it should be done in a cost efficient, ethical and responsible fashion and not as the major component of the total program. Sensory stimulation should be considered a treatment option and not a standard. Factors that must be examined as germane to making decisions regarding the duration of sensory stimulation treatment include time post-injury, rate of recovery to date, early prognostic criteria and current neurobehavioral status. For those individuals who remain vegetative beyond one year, becoming "permanently vegetative," we must all take a step back and ask the question, "when is enough, enough?" For those persons in a minimally conscious state, there is clearly a stronger theoretical rationale to defend the use of sensory stimulation given the implicit understanding that the person has at least some level of cognitive awareness.
The controversies surrounding coma and/or sensory stimulation will continue until more definitive studies are available to answer the questions at hand in a methodologically sound manner. Until that time comes, rehabilitation professionals must strive to maintain better uniformity with regards to nomenclature treatment strategies and assessment tools, when working with persons who are in coma or vegetative state. By doing so, we will not only be better able to assess intervention efficacy, but we will also be better able to provide higher quality patient care.
Suggested Reading:
Aspen Workgroup Position Statement. Pending submission for publication.
Ellis DW & Rader MA: Structured sensory stimulation. In: The Coma-Emerging Patient. ME Standel & DW Ellis (Eds.) Hanley & Belfus, Inc., Philadelphia, PA. Pages 465-477, 1990.
Giacino JT: Sensory stimulation: theoretical perspectives and the evidence for effectiveness. NeuroRehabilitation. 6(l): 69-78, 1996.
Giacino JT, Zasler ND: Outcome following severe brain injury: coma, the vegetative state and the minimally responsive state. Journal of Head Trauma Rehabilitation. 10 (1): 40-56, 1995.
LeWinn E and Dimancescu M: Environmental deprivation and enrichment in coma. Letter to the Editor, Lancet. (July 15): 156-157, 1978.
O'Dell MW, Jasin P, Lyons N, et al: Standardized assessment instruments for minimally responsive, brain injured patients. NeuroRehabilitation. 6(l): 45-55, 1996.
O'Dell MW, Riggs RV: Management of the minimally responsive patient. In: Medical Rehabilitation of Traumatic Brain Injury. LJ Horn & ND Zasler (Eds.) Hanley & Belfus, Inc., Philadelphia, PA. Pages 103-132, 1996.
Sandel ME & Ellis DW (Eds.): The Coma-level Emerging Patient. Hanley & Belfus, Inc., Philadelphia, PA. 1990.
Sandel ME: Medical management of the comatose, vegetative or minimally responsive patient. NeuroRehabilitation. 6(l): 9-17, 1996.
Wood RL: Critical analysis of the concept of sensory stimulation for patients in vegetative states. Brain Injury. 5(4): 401-409, 1991.
Wood RL, Winkowski TB, Miller JL et al: Evaluating sensory regulation as a method to improve awareness in: patients with altered states of consciousness: A pilot study. Brain Injury. 6(l):3-8,1996.
Zasler ND: Nomenclature: Evolving trends. NeuroRehabilitation. 6(l),3-8, 1996.
Zasler ND, Kreutzer JS, Taylor D: Coma recovery and coma stimulation : a critical review. NeuroRehabilitation. 1(3): 33-40, 1991.