Disorders of Consciousness

Author(s): Steven Flanagan, MD

Originally published:11/10/2011

Last updated:09/17/2015

1. DISEASE/DISORDER:

Definition

Definitions of altered consciousness: Coma is a pathological state of unconsciousness in which the eyes remain closed; the patient cannot be aroused by the application of stimulation and there is an absence of sleep-wake cycles. Vegetative state (VS) is manifested by the inability to purposefully interact with others or the environment but with intermittent eye opening and the presence of sleep-wake cycles. The minimally conscious state (MCS) is manifested by minimal but definitive evidence of self- or environmental awareness. Locked-in syndrome (LIS) is not a disorder of consciousness, but is often misdiagnosed as VS or MCS because of paralysis of all 4 limbs and most facial muscles. Posttraumatic confusional state is manifested by profound confusion and posttraumatic amnesia.

Etiology

  1. Trauma
  2. Ischemia
  3. Hypoxia
  4. Toxic/metabolic

Epidemiology including risk factors and primary prevention

The vast majority of individuals who sustain and survive traumatic brain injury (TBI) beyond the acute stage regain consciousness, although reported incidences of those remaining in VS and MCS for prolonged timed periods vary.

Patho-anatomy/physiology

Trauma induced VS is often associated with diffuse axonal injury and severe thalamic degeneration. Limited reports in cases of MCS suggest wide variation in underlying anatomic correlates. Nontraumatic causes of DOC often involve severe bilateral thalamic pathology and diffuse cortical damage. LIS is caused by lesion(s) involving bilateral corticospinal and bilateral corticobulbar tracts.

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

Coma is self limiting, lasting approximately 4 weeks in those who survive. Afterwards, people may emerge into the VS or MCS. Controversy exists regarding the classification of VS in persistent and permanent categories. Persistent VS has been defined as lasting more than one month. Permanent VS is defined as lasting more than 3 months in nontraumatic cases and more than 12 months in traumatic cases.1 “Permanent” VS is a prognostic term based on probability and not an absolute diagnostic one, since numerous reports exist of emergence from the VS more than 12 months post-injury, particularly following TBI. More recent recommendations suggest VS classification be accompanied by the length of time since onset and that the “persistent” and “permanent” descriptors be abandoned.2 Emergence from MCS is signaled by interactive communication or use of functional object(s).

2. ESSENTIALS OF ASSESSMENT

History

See etiology.

Physical examination

Serial bedside evaluations are essential to elicit and distinguish between reflexive and voluntary responses to various forms of stimulation that differentiate VS from MCS. Infrequent responses to complex commands are typically adequate to determine the presence of consciousness, whereas consistent responses to simple commands are required for the same.

Laboratory studies

Presently, no laboratory studies definitively diagnose DOC. Various evoked potentials – for example, somatosensory evoked responses, brainstem auditory evoked responses (BAER), middle latency evoked potentials (MLAEP) – potentially offer prognostic information, while event-related potentials (eg, N100, P300, P400) may offer information regarding the presence of some preserved cognitive functioning.

Imaging

Presently, no imaging studies definitively diagnose DOC. Recent evidence suggests functional magnetic resonance imaging (fMRI) may be useful to detect consciousness in some subjects who clinically appear to be in VS.3Positron emission tomography (PET) and magnetoencephalography (MEG) may offer similar utility.

Supplemental assessment tools

  1. The JFK Coma Recovery Scale (CRS) Revised assists with differential diagnosis, prognosis, and treatment planning.
  2. Western Neuro Sensory Stimulation Profile (WNSSP) assesses patients’ arousal/attention, expressive communication, and response to sensory stimulation.
  3. Coma/Near Coma Scale (CNC) assesses patients who have low-level brain injury.
  4. Sensory Modality Assessment Rehabilitation Technique (SMART) uses both formal and informal components to observe responses to sensory and environmental stimulation.
  5. Wessex Head Injury Matrix assesses patients in and emerging from disorders of consciousness.
  6. Individualized Quantitative Behavioral Assessment (IQBA) investigates the integrity of vision, command following and communication by means of a standardized stimulus presentation and response scoring.
  7. Disorders of Consciousness Scale (DOCS) assesses patient’s response to the administration of sensory stimuli.

Early predictions of outcomes

Magnetic resonance spectroscopy, diffusion weighted and tensor images, fMRI, brainstem lesions, grey:white matter ratio, evoked potentials, event-related-related responses, electroencephalographic data, time until the reappearance of spontaneous motility, eye-tracking, and oculocephalic reflex and disappearance of oral automatism offer limited predictive utility. Trauma-related DOC has a better prognosis than other etiologies. Individuals in MCS who receive early rehabilitation (the first 6 months after brain injury) may have good outcomes. Individuals emerging from DOC later in recovery typically have poorer outcomes. Severity and type of comorbidities are associated with outcomes. Ischemic or organic heart disease is a strong predictor for mortality while respiratory disease and arrhythmias without ischemic heart disease is a negative predictor of full recovery and functional improvements. (4)

Professional Issues

Limited assessment instruments and high diagnostic error rates complicate ethical and legal decisions regarding care planning, end of life decisions, issues pertaining to intentional trauma and criminal charges, participation in research, resource allocation, and benefits of partially improved function via new treatments, versus increased personal awareness of disability causing despair.

3. REHABILITATION MANAGEMENT AND TREATMENTS

Available or current treatment guidelines

Amantadine hydrochloride was shown to speed recovery of TBI subjects in the VS or MCS when provided in acute inpatient rehabilitation (5). However, there are currently no standardized treatment guidelines for DOC. Multi-modal sensory stimulation provided via either naturally occurring environment exposure or through a structured program is frequently used, although it has very limited proven efficacy. Neuromodulation, either through the provision of pharmacological stimulants other than amantadine (eg, cholinergic, dopaminergic, and/or serotonergic agonists) or the minimization of CNS depressants (eg, anticonvulsants, benzodiazepines) may be helpful, but remains unproven and protocols are not standardized. Overall health maintenance, including skin care, pulmonary hygiene, limb range of motion, spasticity management and bowel/bladder management is an important component of DOC care.

Patient & family education

Family education regarding prognosis, limited data pertaining to treatment efficacy, and long-term planning are essential components of DOC care.

4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE

Cutting edge concepts and practice

Limited evidence suggests deep brain stimulation (DBS) to specific thalamic regions with projections to the cortex may enhance cognitive and physical function. Other potentially efficacious, althoughunproven, treatments include median nerve stimulation, spinal cord stimulation, intrathecal baclofen and extradural cortical stimulation.

5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE

Gaps in the evidence-based knowledge

Treatment effectiveness and definitive assessment tools for accurate diagnosis remain elusive.

REFERENCES

  1. Quality Standards Subcommittee of the American Academy of Neurology. Practice parameters: assessment and management of patients in the persistent vegetative state (summary statement). Neurology. 1995;45(5):1015-1018.
  2. Giacino JT, Katz DI, Schiff N. Assessment and rehabilitative management of individuals with disorders of consciousness. In: Zasler ND, Katz DI, Zafonte RD, eds. Brain Injury Medicine: Principles and Practice. New York, NY: Demos; 2007:423-439.
  3. Monti MM, Vanhaudenhuyse A, Coleman MR, et al. Willful modulation of brain activity in disorders of consciousness. N Engl J Med. 2010;362(7):579-589.
  4. Pistoia F1, Sacco S, Franceschini M, Sarà M, Pistarini C, Cazzulani B, Simonelli I, Pasqualetti P, Carolei A. J Neurotrauma. 2014 Oct 21. [Epub ahead of print]. Comorbidities: a key issue in patients with disorders of consciousness.
  5. Giacino JT1, Whyte J, Bagiella E, Kalmar K, Childs N, Khademi A, Eifert B, Long D, Katz DI, Cho S, Yablon SA, Luther M, Hammond FM, Nordenbo A, Novak P, Mercer W, Maurer-Karattup P, Sherer M. Placebo-controlled trial of amantadine for severe traumatic brain injury. N Engl J Med. 2012 Mar 1;366(9):819-26.

Original Version of Topic

Steven Flanagan, MD. Disorders of Consciousness. 2011/11/10.

Author Disclosures

Steven Flanagan, MD
Spring Publishing: Royalties from text book

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