Consciousness from a medical perspective

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Consciousness from a medical perspective

• 11-02-2008 Blok X.XX (Rob de Vries)
• Brigitte Dahmen, cand. med.

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Overview

• Introduction Consciousness from a medical
  perspective
• Background information
• Anatomy/Neurophysiology of consciousness
• Causes for acute disorders of consciousness
• Acute disorders of consciousness
• Residual states of dysfunctional consciousness
• Imaging consciousness What does it tell us about
  the underlying mechanisms?
• Conclusion and Discussion

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Consciousness from a medical perspective

• The limits of consciousness are
• hard to define satisfactorily
• and we can only infer the
• self-awareness of others by
• their appearance and their acts.
• (Plum and Posner, The Diagnosis
• of Stupor and Coma)

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Consciousness from a medical perspective

• Arousal, Awareness, Selective Attention
• In general, someone is conscious from the medical
  perspective, when
• she/he reacts purposefully to external stimuli
  and
• she/he is awake.
• Different modalities of consciousness
• Consciousness level (quantitative)
• Consciousness content (qualitative)

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Impairments of qualitative consciousness

• Qualitative consciousness equals recognition,
  subjective experience, content
• Impairments are
• Clouded awareness (delirium)
• Narrowing of ones awareness
• Awareness shift

Examples!!
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Impairments of quantitative consciousness

• Quantitative consciousness means objectively
  observable or measureable awareness
• Impairments
• Drowsiness
• Somnolence abnormal sleepiness, but
  acoustically arousable
• Sopor no spontaneous movements, reaction to
  pain stimuli adequate
• Coma no reaction to visual, acoustic or pain
  stimuli
• Afterwards in most cases amnesia

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Background Anatomical structures involved in
being conscious

• Reticular formation (also vegetative functions
  such as breathing)
• Thalamus (gate to consciousness)
• Cerebral Cortex
• (cognitive functions)

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Background Neurophysiology of being conscious

• Dopaminergic system
• Noradrenergic System

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How can we become unconscious? Syndrom of
herniation in the brain

• due to high intracranial pressure
• axial herniation
• lateral herniation
• Different picture!!!

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Causes for becoming unconscious

• High intracranial pressure
• Trauma (cranio-cerebral injury, brain hemorrage)
• Infection (Meningitis, (brainstem-)Encephalitis,
  Cerebellitis)
• Direct harm to brain structures responsible for
  consciousness
• Intoxications (Carbonmono-, -dioxidintoxication,
  hypoxia, medication, drugs)
• Metabolisch (diabetisches/ketoazidotisches,
  urämisches, hepatisches Koma)
• Cardio-vascular (Adam-Stokes-seizure, synkope,
  acute low bloodpressure, heart arrest)
• Infection (Meningitis, (brainstem-)Encephalitis,
  Cerebellitis)
• Psychogenic/Psychiatric
• Neurological causes
• Epileptogenic (e.g. Absence Epilepsy)
• Dementia (neurodegenerative diseases)
• Split-brain
• Medical intervention
• Anaesthesia!
• Physiological
• sleep

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Acute disorders of consciousness

• The symptoms a patient portrays give an idea of
  where in the brain and the regulatory systems of
  consciousness the lesion or the problem lies.
• Diencephale/mesencephale Syndrome
• Sopor to comatose patient, flex- and
• stretch synergisms or stretch cramps to pain
  stimuli,
• different brainstem reflexes are not functioning
  anymore, e.g. okulo-cephale reflex (pictures of
  reflexes?)
• Blood pressure is high with low pulse, arrythmic
  to machine-like breathing pattern

Different pic?
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Acute disorders of consciousness

• Coma
• Patient is comatose, shows only few responses to
  stimuli (evaluated with Glasgow Coma Scale)
• Unarousable and unresponsive, but EEG activity
  visible
• Brain death
• Final breakdown of all brain functions during
  stabilization of circulation and heart via
  machines, no spontaneous breathing, no brain stem
  reflexes
• flat EEG (cave deep anaesthesia or cardiac
  arrest) or no perfusion with perfusion detecting
  ultrasound scan earlier diagnosis possible
• no clinical evidence of brain function as
  evaluated by two neurologists multiple times

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Residual impairments of consciousness I

• vegetative state (transient, persistent)
• Brain functions are reduced to meso-diencephalic
  functions loss of cognitive functions and
  perception with conserved wakefulness
• failure to produce any purposeful voluntary
  behavior
• unconscious, reflexive responses, possibly open
  eyes
• unresponsive to stimuli, except pain, but
  (abnormal) sleep-wake cycles
• normal behavior grinding teeth, smack lips etc
• Recovery, treatment
• possible (after 3 months 35 will continue)
• Pharmacological (Amantadin (Dopamin),
• Methylphenidat), surgery, physical therapy,
• stimulation

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Residual impairments of consciousness II

• Minimally Conscious State (MCS) (recent
  classification!)
• Generally unresponsive patients shows periods of
  deliberate or cognitively mediated behaviour
• requires 1. simple command-following or
• 2. response to yes/no-questions with e.g.
  finger movement,
• 3. episodes of intelligible verbalization,
• 4. specific responses to external stimuli which
  are not reflexive (smiling etc.)
• Separation from vegetative state very difficult
  (see Owen et al. 2006)

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Owen, A.M. et al Detecting awareness in the
vegetative state, Science (2006)
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Residual Impairments of Consciousness III

• Locked-in-Syndrome
• Patient is actually fully conscious, but cannot
  move or make her-/himself clear to his
  environment
• Most of the times can make vertical eye movements
  or close eye lids.

Info diving bell and the butterfly
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New advances Imaging consciousness to validate
diagnosis
E.g. quantify metabolism with PET imaging
Laureys et al., 2004
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New advances Imaging consciousness to validate
diagnosis
Laureys et al., 2004
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Voss et al. Possible axonal regrowth in late
recovery from the minimally conscious state (2006)
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Conclusions from imaging studies

• The brain metabolism in these different
  impairments of consciousness is significantly
  different and can be distinguished from each
  other.
• Even after years, recovery is possible, due to
  plastic changes in the brain.
• Should brain imaging be used to detect
  unconsciousness if the patient isnt able to
  articulate his thoughts in a different way?

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Conclusion and discussion

• In medicine the term conscious describes
  functions which show that the patient can react
  purposeful to her/his environment, functions
  which are vital for surviving on ones own.
• Psychological and neuroscientific advances are
  beginning to influence the medical concept of
  consciousness.
• Still, it is not understood what patients in a
  coma feel or notice from the environment, most
  who wake up say that they felt like they had
  been sleeping or numb.

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Discussion/Questions

• How well do you think does the medical
  terminology system capture the phenomenon of
  consciousness?
• What is included, what is left out?
• What do you think will become of importance in
  consciousness research?

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Video zu vegetative state

• http//video.google.nl/videoplay?docid65695997303
  60593805qvegetativestatetotal50start10num
  10so0typesearchplindex4 ?
• http//video.google.nl/videoplay?docid-8980167825
  088683491qvegetativestatetotal50start30num
  10so0typesearchplindex7 ?