A minimally conscious state (MCS) is a disorder of consciousness distinct from persistent vegetative state and locked in syndrome. Unlike persistent vegetative state, patients with MCS have partial preservation of conscious awareness.
MCS is a relatively new category of disorders of consciousness. The natural history and longer term outcome of MCS have not yet been thoroughly studied. The prevalence of MCS was estimated to be 112,000 to 280,000 in adult and pediatric cases.
Although MCS patients are able to demonstrate cognitively mediated behavior, they occur inconsistently. They are, however, reproducible or can be sustained long enough to be differentiated from reflexive behavior. Because of this inconsistency, extended assessment may be required to determine if a simple response (e.g. a finger movement or a blink) occurred because of a specific environmental event (e.g. a command to move the finger or to blink) or was merely a coincidental behavior.
Distinguishing between VS and MCS is often difficult because the diagnosis is dependent on observation of behavior that show self or environmental awareness and because those behavioral responses are markedly reduced. One of the more common diagnostic errors involving disorders of consciousness is mistaking MCS for VS which may lead to serious repercussions related to clinical management.
Giacino et al. have suggested demonstration of the following behaviors in order to make the diagnosis of MCS.
Following simple commands.
Gestural or verbal yes/no responses (regardless of accuracy).
Purposeful behavior such as those that are contingent due to appropriate environmental stimuli and are not reflexive. Some examples of purposeful behavior include:
appropriate smiling or crying in response to the linguistic or visual content of emotional but not to neutral topics or stimuli.
vocalizations or gestures that occur in direct response to the linguistic content of questions. reaching for objects that demonstrates a clear relationship between object location and direction of reach.
touching or holding objects in a manner that accommodates the size and shape of the object. pursuit eye movement or sustained fixation that occurs in direct response to moving or salient stimuli.
Currently, there is no treatment that has been proven to speed up or improve recovery from the vegetative or minimally conscious state. However, there is general agreement that the primary focus of medical care is to prevent or treat any factors that might hinder recovery (such as hydrocephalus, a build up of fluid on the brain, or use of sedating drugs for other conditions), and to preserve bodily health (such as treating infections or stiffness of joints). Medical facilities and clinicians vary in the extent to which they try various treatments such as medications or sensory stimulation to promote recovery of consciousness. Because the amount of recovery from disorders of consciousness varies so greatly, it is difficult to judge the value of these and other treatments outside of research studies.
Initially, the person with severely impaired consciousness is most likely to be treated in an acute care hospital where the focus is primarily on saving his/her life and stabilizing him/her medically. Once that is achieved, the next focus is on recovery of function to whatever level is possible. Sometimes this happens in an acute rehabilitation hospital, which provides a high intensity program of rehabilitation services, including physical therapy, occupational therapy, speech and language therapy, recreational therapy, neuropsychological services and medical services.
Some patients do not transition from the acute care hospital to an acute rehabilitation program. These people may go directly to a skilled nursing facility, a sub-acute rehabilitation program, a nursing home, or even home with family. Persons discharged from an acute rehabilitation program usually go to one of these places as well. Skilled nursing facilities, sub-acute rehabilitation programs, and nursing homes vary widely in the quantity and quality of medical management, nursing care, and rehabilitation therapy services they provide.
Many factors influence decisions about where a person with severe impairment of consciousness or other severe impairments may go after discharge from the acute care hospital or discharge from the acute rehabilitation program. Some of these factors are the person’s medical condition, health insurance coverage and other benefits, the person’s ability to tolerate rehabilitation therapies, the doctor’s philosophy about where people should go to continue to recover after severe injuries, the family’s ability to care for the person at home, the family’s wishes, and practical matters such as that the distance the family has to travel to visit the person at the facility.
Preventive measures for problems due to immobilization.
Possibly certain drugs
Like people in a coma, people in a minimally conscious state require comprehensive care.
Providing good nutrition (nutritional support) is important. People are fed through a tube inserted through the nose and into the stomach. Sometimes they are fed through a tube (called a percutaneous endoscopic gastrostomy tube, or PEG tube) inserted directly into the stomach through an incision in the abdomen. Drugs may also be given through this tube.
Many problems result from being unable to move, and measures to prevent them are essential (see Problems Due to Bed Rest). For example, the following can happen:
Pressures sores: Lying in one position can cut off the blood supply to some areas of the body, causing skin to break down and pressure sores to form. Caregivers must turn people very frequently.
Contractures: Lack of movement can also lead to permanent stiffening of muscles (contractures) causing joints to become permanently bent.
Blood clots: Lack of movement makes blood clots more likely to form in leg veins.
To prevent these problems, physical therapists gently move the person’s joints in all directions (passive range-of-motion exercises). Therapists may splint joints in certain positions to help prevent contractures. People are also given drugs to prevent blood clots from developing.
If people are incontinent, care should be taken to keep the skin clean and dry. If the bladder is not functioning and urine is being retained, a tube (catheter) may be placed in the bladder to drain urine.
A very few people have improved after treatments such as zolpidem (a sleep aid) or amantadine (a drug used to treat viral infections). However, no treatment has been proved effective.
The aim of a study was to measure the effects of SCS on the EEG of patients in a minimally conscious state (MCS), which would allow them to explore the possible workings underpinning of the approach. Resting state EEG was recorded before and immediately after SCS, using various frequencies (5Hz, 20Hz, 50Hz, 70Hz and 100Hz), for 11 patients in MCS. Relative power, coherence, S-estimator and bicoherence were calculated to assess the EEG changes. Five frequency bands (delta, theta, alpha, beta and gamma) and three regions (frontal, central and posterior) were divided in the calculation. The main findings of this study were that: (1) significantly altered relative power and synchronisation was found in delta and gamma bands after one SCS stimulation using 5Hz, 70Hz or 100Hz; (2) bicoherence showed that coupling within delta was significantly decreased after stimulation using 70Hz, while reduction of coupling between delta and gamma was found when using 5Hz and 100Hz. However, SCS of 20Hz, 50Hz and sham stimulation did not induce changes in any frequency band at any region. This study showed EEG evidence that SCS can modulate the brain function of MCS patients, speculatively by activating the formation-thalamus-cortex network 1).