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The normal conscious state includes volition, processing of sensory information, and a generalized level of arousal. The brain regions that support these three aspects of consciousness interact extensively with each other. And brain injury at any of these levels can produce disorders of consciousness.
These conditions include a wide range of pathologies, causes, prognoses, and proven treatments. Diagnostic testing can be used to determine the degree of injury and suggest residual capacity for cognitive function.
Studies shows that the pathology responsible for coma and VS is loss of corticothalamic function, while the pathology of MCS represents a low level of residual corticothalamic integrity or an inability to maintain cerebral integrative function. Whereas akinetic mutism and related syndromes represent disorders of goal-directed behavior.
However there are patients with severely damaged motor system that may be miscategorized. These patients are behaviorally in VS or MCS, yet demonstrate imaging evidence of high-level cognitive processes, including command following and, in 2 instances, communication. It is clear that the patients have interacted with their environment; thereby they could be placed in a vague category between high-level MCS and LIS.
The recent studies over the past two decades have progressively changed the spectrum of coma and DOC. while some VS patients will irreversibly remain in this condition; some many actually evolve to MCS.
The bedside examination of consciousness in severely brain damaged patients is extremely challenging because movements can be very small, inconsistent and easily exhausted, leading to diagnostic errors.
This problem was highlighted in a study showing that the clinical consensus diagnosis of VS was incorrect in more than 40% of patients. Locked-in syndrome patients may also be mistakenly considered unconscious.
There are many behavioral assessment tools developed to monitor the recovery of consciousness.
Studies shows that the CRS-R may be used to assess DOC with minor reservations, and the SMART, WNSSP, SSAM, WHIM, and DOCS may be used to assess DOC with moderate reservations. The CNC may be used to assess DOC with major reservations. The FOUR, INNS, Glasgow Lie`ge Coma Scale, Swedish Reaction Level Scale-1985, Loewenstein Communication Scale, and CLOCS are not recommended at this time for bedside behavioral assessment of DOC.
Disentangling VS from MCS with the clinical measurement can be severely compromised when a patient lacks motor responsiveness. Therefore new assessment tools that circumvent the reliance on behavioral output are necessary. A growing body of research addresses this issue by examining a patient‘s brain activity under various conditions, using functional neuroimaging and electrophysiological measures.
Although insufficient population data currently exists, evidence to include the use of such techniques in the formal diagnostic and prognostic procedure in this patient group is accumulating rapidly.
The emerging view is not that brain imaging should replace behavioral assessment, but rather that it should be used, wherever possible, to acquire further information about the patient and their condition. In doing so, the current alarmingly high rate of misdiagnosis in this patient group will undoubtedly fall. Likewise, clinical teams will have the best possible information for planning and monitoring interventions to facilitate recovery.
Detecting pain and depression in severely brain-injured patients with DOC represents a real challenge. Pain assessment is usually based on the patient‘s verbal report, as pain is a subjective first-person experience. However, patients recovering from coma cannot express their feelings. VS patients only show reflexive activity, while patients in MCS demonstrate inconsistent signs of
consciousness, and can sometimes verbalize, but they do not show functional communication that could be used for pain or mood assessment.
Recent studies suggest that MCS patients can experience pain to some extent It is .hence of medical and ethical importance to assess and detect pain in these patients.
Even if pain scales have been developed for different types of noncommunicative populations, none of these are adapted to detect pain in patients recovering from coma. In this context, the Nociception Coma Scale (NCS) has recently been developed and validated to assess pain in patients recovering from coma.
Regarding the intervention option for this population of patients, recent studies shows that transcortical magnetic stimulation and deep brain stimulation can represent useful forms of intervention for persons in VS or MCS as they are for persons with Parkinson‘s motor disorders, pain conditions, and psychiatric problems.
Also the sensory stimulation and music therapy may enhance recovery from brain injury, may reduce the risk of sensory deprivation, and may facilitate alertness while promoting arousal and curbing withdrawal.
There is also studies based on the notion that the use of contingent stimulation (i.e., stimulation occurring in relation to
participant‘s responding) and assistive technology may help the participant acquire/consolidate simple responses as means whereby he or she can independently access preferred environmental stimulation or request caregiver‘s attention and positive mediation.
Although these intervention strategies are clearly different, they should not be seen as alternatives. There may be a number of circumstances, for example, in which the intervention process begins with multisensory stimulation or music therapy and then proceeds with learning setups involving contingent stimulation and assistive technology.
The new technologies and the information they provide raised the possibility of refining understanding of human cognition and awareness in severely brain-injured patients. This is a promising development in terms of enhancing the ability to provide accurate prognostic information and possibly treatment options to patients with severe brain injury. However, it presents a new set of ethical challenges that are variant and multi-faceted. Medical, legal and public controversies that are partly shaped by how different people think about these issues.