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Classification of Severe Alterations In Consciousness In Moderate To Severe Traumatic Brain Injury

xray_brainModerate to severe traumatic brain injuries are characterized by varying levels of consciousness, as well as post-traumatic amnesia once the patient is alert. The American Congress of Rehabilitation Medicine (ACRM) points out in the article* under review today that signficant confusion and misdiagnosis exists due to the misunderstanding of terms related to severe alterations of consciousness. In light of these concerns, the ACRM released a position paper a number of years ago, and researchers and professionals were urged to adopt the following classification system of several alterations in consciousness: (1) Coma, (2) Vegetative State, (3) Persistent Vegetative State , (4) Locked-In Syndrome, (5) Minimally Responsive, and (6) Akinetic Mutism. Unfortunately, approximately 30-40% of persons* who sustain a severe alteration of consciousness will remain in one of these stages.

The universal and reliable applications of these 6 terms across disciplines and treatment centers through use of specific behavioral response characteristics were the primary goals of the ACRM. Below is summary of their recommendations:

“Coma” is characterized by the inability to arouse the person and the absence of sleep/wake cycles on an electroencephalogram (EEG). This state rarely last longer than 4 weeks. The following neurobehavioral criteria were established: “The patient’s eyes do not open either spontaneously or to external stimulation; and 2. The patient does not follow any commands; and 3. The patient does not mouth or utter recognizable words; and 4. The patient does not demonstrate intentional movement (may show reflexive movement such as posturing, withdrawal from pain; or involuntary smiling); and 5. The patient cannot sustain visual pursuit movements of the eyes through a 45° arc in any direction when the eyes are held open manually; and 6. The above criteria are not secondary to use of paralytic agents” (pg. 206).

Patients are deemed to be in a “vegetative state” when they lack any signs of conscioness after their eyes open. A vegetative state nearly always follows a coma and the patient is unable to interact with the environment. The following neurobehavioral criteria were adopted: “1. The patient’s eyes open spontaneously or after stimulation; and 2. Criteria 2, 3, 4, 5, and 6 under coma are met” (pg. 206).

“Persistent vegetative states” refers to a chronic state of intact arousal and life-sustaining functions (heart beat, etc.) without environmental interaction. The possible cause may be thalamic lesions with an intact cortex. A study discussed in the ACRM position paper found that approximately 52% of patients emerged from a persistent vegetative state by 12 months postinjury. The ACRM acknowledges that much disagreement exits about the length of time required to be considered “chronic.” Hence, they decided that the best course of action where to simply state the length of time spent in this state and no further neurobehavioral criteria were recommended.

“Locked-in syndrome” describes patients who are alert with a cognitive awareness of the environment and capable of communication but unable to move or speak. The following neurobehavioral criteria were established: “1. Eye opening is well sustained (bilateral ptosis should be ruled out as a complicating factor in patients who do not open their eyes but demonstrate eye movement to command when the eyes are opened manually); and 2. Basic cognitive abilities are evident on examination; and 3. There is clinical evidence of severe hypophonia or aphonia; and 4. There is clinical evidence of quadriparesis or quadriplegia; and 5. The primary mode of communication is through vertical or lateral eye movement or blinking of the upper eyelid” (pg. 207).

“Minimally responsive” is characterized by patients that have emerged from a coma or vegetative state but remain severely disabled. Behavioral responses are inconsistent, but shows signs of definite interaction with the environment. Any form of verbal communication automatically places the patient in a minimally responsive state. The ACRM cites research that suggests that a minimally responsive patient may have suffered bilateral, diffuse cortical damage. The following neurobehavioral criteria were established: “1. A meaningful behavioral response has occurred after a specific command, question, or environmental prompt (eg, attempt to shake examiner’s outstretched hand). The response is considered to be unequivocally meaningful by the observer; or 2. When the evidence for meaningful responsiveness is equivocal, the response can be shown to occur significantly less often when the specific command, question, or prompt associated with it is not present; and 3. The response has been observed on at least one occasion during a period of formal assessment. (Formal assessment consists of regular, structured, or standardized evaluation procedures.)” (pg. 207).

“Akinetic mutism” describes a patient who performs spontaneous visual tracking, but also has severely limited drive or intention and markedly deficient movement and speech. Sometimes akinetic mutism is considered a subcategory of minimally responsive states. The term “abulia” is assigned for less severe forms of akinetic mutism. The ACRM states that the pathophysiology is believed to be attributable to “bilateral mesencephalic, cingulate, third ventricle, and basal or mesial frontal lesions” (pg. 207) and that anecdotal physician experiences suggest a poorer recovery of function for patients in this state, especially for those 3 months post-injury. Neurobehavioral inclusion criteria include “1. Eye opening is well maintained and occurs in association with spontaneous visual tracking of environmental stimuli; and 2. Little to no spontaneous speech or movement is discernible; and 3. Command following and verbalization are elicitable but occur infrequently; and 4. The low frequency of movement and speech cannot be attributed to neuromuscular disturbance (eg, spasticity, hypotonus) or arousal disorder (eg, obtundation) as is typically noted in the minimally responsive state” (pg. 208).

Traumatic brain injury is a very serious condition, and I hope that none of our readers will have family or friends who go on to experience a TBI. But if they do, my hope is that this information will further a better understanding of their loved one’s condition. Of course, this information is also provided to help healthcare providers clarify and properly diagnose severe alterations in consciousness.

Finally, expect to see a plethora of upcoming reviews of traumatic brain injury (TBI) research. I really hope that this topic interests our readers as I am currently on a TBI rotation at a Top 15 rehabilitation hospital in the U.S., and there is much required reading involved. This is actually part of my formal 1 year internship for my doctoral program. I plan to review some of the books and articles that I read for this rotation.


*American Congress of Rehabilitation Medicine (1995). Recommendations for use of uniform nomenclature pertinent to patients with severe alterations in consciousness. Archives of Physical Medicine and Rehabilitaiton, 76, 205-209.

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