Disorders of Consciousness (DoC)
10th January 2019
Disorders of Consciousness is an umbrella term used to define patients who are in the state of altered consciousness. It can be broadly classified into three categories :
3.Minimally Conscious State
Coma – It is a state of unconsciousness where individuals are unable to open their eyes or perform any movements either by themselves or to verbal or tactile commands. It typically resolves within 2-4 weeks by itself.
Vegetative State – Vegetative state does not mean someone is a vegetable. It is a state of unconsciousness in which individuals are able to open their eyes either spontaneously or to commands. However, they are not aware of self or environment hence unable to follow any auditory, visual, tactile commands. It is usually the next stage after coma but sometimes the patients can skip this stage.
It is divided into two stages - persistent vegetative state or permanent vegetative state. Persistent vegetative state is when someone is in a vegetative state for 12 months after a traumatic brain injury or 3 months after a non-traumatic brain injury. Permanent vegetative state is when someone is in a vegetative state beyond the time period mentioned above for traumatic and non-traumatic brain injury respectively. However, these definitions are challenged by recent studies as people with traumatic and non-traumatic brain injuries continue to improve even after 1 year after their injury.
Minimally Conscious State – It is a state of altered consciousness where there is minimal but definitive evidence of awareness to self or to the environment. Consequently, they are able to make eye contact, have emotional responses to appropriate stimuli, respond appropriately (excluding any reflexive activity) to verbal, hearing or touch commands but inconsistently. It is also a transitional phase, which comes after the coma and vegetative state.
Emerged State – An individual is said to have emerged from disorders of consciousness when he/she is able to do everything a person in a minimally conscious state is able to do, but consistently. They may also have the ability to functionally use an object when given to them. For example – when a pen is given to them they will hold the pen appropriately as if they are writing.
Rest of the section will use terminology such as unconscious state and conscious state. Unconscious state is Coma or Vegetative State and Conscious state is Minimally Conscious State or Emerged State.
How to assess patients with DoC?
Bedside assessments are traditionally done to determine the state of consciousness. Although these assessments are easy to perform they are inadequate in determining the state of consciousness, which have prognostic implications.
More thorough objective behavioral assessments such as JFK COMA RECOVERY SCALE need to be done serially for accurate diagnosis of the state of consciousness. Otherwise false negative conclusions are highly likely (i.e. the conclusion that someone is unconscious when in fact he/she is conscious).
What are the treatment options for these patients?
The goal is to help them achieve the maximal level of independence as possible. However, the extent to which it can be achieved depends on various factors such as severity of the injury, recovery from coma, onset and intensity of treatment, etc. The treatment options can be divided into three broad categories, sensory stimulation, physical rehabilitation, and neuromodulation.
- Sensory stimulation – A treatment option that provides systematic exposure to various environmental stimulation. The purpose of sensory stimulation is to improve arousal level and increase the frequency of the purposeful behavior.
- Physical Rehabilitation – A treatment option that is focused on improving arms and legs, speech and swallow, bowel and bladder control, through splinting, physical exercises, speech and swallow exercises, use of assistive devices, and strategies to improve physical health and reduce complications.
- Neuromodulation – A treatment option that is focused on improving neural substrates which are damaged through medications, non-invasive measures such as transcranial direct current stimulation (TDCS) and repetitive transcranial magnetic stimulation (rTMS), and invasive measures such as deep brain stimulation and vagal nerve stimulation.
What is the prognosis of patients in DoC?
Prognosis can be divided into three based on the outcome measures. However, the common theme across the outcome measures is that patients with traumatic brain injury have a slightly better prognosis compared to non-traumatic brain injury and patients in a minimally conscious state have a better prognosis than the patients in vegetative state. Prognosis is slightly better for children compared to adults while older adults tend to have the worst prognosis.
- Mortality – According to a study, for patients in the vegetative state or minimally conscious state at 1 year after injury, the mortality rate was 75% for patients in vegetative state and 36% for patients in minimally conscious state, 5 years after injury. According to a recent study, for patients in a vegetative state for 6 months due to traumatic or non-traumatic brain injury, the mortality rate was 42% at a little over 2 years after the injury.
- Recovery of consciousness – According to the same recent study, patients who were in a vegetative state at 6 months, 24% improved to a minimally conscious state and 20% even improved to an emerged state at little over 2 years after the injury. According to a study done in 1994, Patients with traumatic brain injury who are unconscious at 1 month, 33% recovered consciousness at 3 months, 46% at 6 months and 52% at 1 year. Patients with non-traumatic brain injury who are unconscious at 1 month, 11% recovered consciousness at 3 months and 2% at 6 and 12 months.
- Functional outcome – According to the same study from 1994, among patients who regained consciousness, 75% were severely disabled at 12 months. i.e. they were dependent on caregivers to perform activities of daily living. However, they continue to make progress for several years as rehabilitation continued. According to a much larger and recent study, 68% of people regained consciousness at 5years follow up among patients who were in unconscious state during admission to a rehabilitation center (usually anywhere between 1-6 months after their injury), out of which 23% were in emerged state, 21% were independent with day to day activities and 20% were employable.
The statistics mentioned in prognosis should only act as a guideline when attempting to prognosticate. Each patient is different and their recovery pattern depends on lots of factors.
In summary, disorders of consciousness is one of the most complex disabling condition and requires careful objective assessment performed by experienced professionals who can then recommend an integrated comprehensive treatment plan using various options discussed above. The clinician should be able to prognosticate the outcome accurately as much as possible based on plenty of studies available on the same so family members can make informed decisions on the care of their loved ones.